Introduction

Clean water is a fundamental necessity for the coexistence and survival of all living organisms. However, modernization has significantly increased the demand for water resources, leading to a corresponding rise in wastewater production from various activities, including domestic and industrial sources. This growing water demand and wastewater output threatens the availability and quality of clean water. A 2017 UN report states that nearly 80% of all wastewater is discharged into the environment without adequate treatment, posing risks to ecosystems and jeopardizing vital freshwater supplies1. Currently, 3.99 trillion m3 of freshwater is withdrawn annually to meet human needs, encompassing domestic use, industrial applications, and agriculture2. Interestingly, 70% of this entire freshwater withdrawal is due to agriculture alone3. Every year, around 380 billion m3 of wastewater is generated worldwide, primarily from domestic and industrial sources2. However, only about 24% of this wastewater is effectively treated, highlighting a significant gap in sustainable wastewater management1. On the other side, unsustainable wastewater management leads to environmental damage, including water pollution, eutrophication, and loss of biodiversity, while also causing human health risks like diseases, toxic exposure, and antimicrobial resistance4. It exacerbates climate change, depletes freshwater resources, and raises costs for water treatment, impacting agriculture and food security5.

The valorization of wastewater through advanced treatment technologies is essential to address this challenge. Such measures are crucial for increasing water demands, reducing stress on natural resources, and achieving the UN sustainable development goals (SDGs). In particular, this aligns with SDG 6 (clean water and sanitation), ensuring sustainable urban living (SDG 11) and promoting responsible consumption and production (SDG 12). Wastewater originates from various sources, such as domestic, industrial, agricultural, and stormwater runoff, that contain diverse components, including solids, contaminants, and toxins6. Effective wastewater treatment removes a range of contaminants to protect human health and the environment. It targets pollutants like pesticides, surfactants, organic dyes, heavy metals, pathogens like bacteria and viruses, and emerging contaminants like pharmaceuticals and microplastics. By eliminating these substances, treated water can be safely reused or discharged, reducing environmental impact and supporting sustainable water management.

Polymers have become integral to modern wastewater treatment processes, with applications spanning coagulation and flocculation, sludge dewatering, chemical precipitation of contaminants, membrane fouling control, and advanced oxidation and adsorption techniques. Polymers like polyacrylamide/polyacrylic acid (PAM/PAA) copolymer, styrene-acrylonitrile copolymer, polyacrylates, polyacrylamide, polyamines, polyethylene oxides (PEO) and dicyandiamide resins are used in wastewater treatment specifically for flocculation, solid–liquid separation, oil–water separation, and targeted removal of specific contaminants like dyes, pharmaceuticals, etc.7,8,9,10,11,12,13. Synthetic polymers are widely used in wastewater treatment due to their scalability and versatility, as they come in various molecular weights and charge densities (cationic, anionic, or nonionic), making them highly tunable for targeted contaminant removal. However, their use presents significant drawbacks, such as the potential leaching of toxic monomers, reliance on non-renewable fossil resources12,14, unsustainable end-of-life disposal, and greenhouse gas (GHG) emissions during production15.

The use of sustainable biopolymers for wastewater treatment has gained increasing attention due to their advantageous surface characteristics, such as reactive functional groups (amide, carbonyl, carboxyl, and hydroxyl) and exceptional mechanical, chemical, and biological properties, including renewability, environmental compatibility, antibacterial activity, biocompatibility, and biodegradability15,16. Biopolymers are polymers derived from biological resources, such as plants, microorganisms, animals, and marine organisms. They are composed of naturally occurring monomers and are characterized by their renewability, biodegradability, and environmental compatibility. Recently, biopolymers like Chitosan, Cellulose, Alginate, Starch, Pectin, Carrageenan, Chitin, Xanthan Gum, extracellular polymeric substances, and Cyclodextrin have been applied in wastewater treatment. The inherent limitations of biopolymers, such as weak mechanical and chemical properties, are overcome by combining with other materials to form biopolymer composites. These composites integrate biopolymers with organic, inorganic, or nanomaterials to enhance their functionality and performance.

These materials are used to remove heavy metals, dyes, and emerging contaminants via mechanisms, such as adsorption, flocculation, complexation, chelation, membrane filtration, and advanced oxidation processes17,18,19,20,21. Adsorptive removal of contaminants using biopolymers is widely studied and recognized as an effective approach in wastewater treatment. This manuscript reviews various types of biopolymeric materials, their applications in the adsorptive removal of contaminants, and the mechanisms of polymer functionalization. These insights provide an overview of current advancements and highlight knowledge gaps in utilizing biopolymers for wastewater treatment.

Figure 1 presents an overview of various sources for preparing biopolymeric adsorbents, including microbial, plant, seaweed, and animal-based adsorbents. It also outlines preparation techniques, such as physical processing, chemical modification, nanocomposite formation, and hydrogel formation. The figure further illustrates different material forms, including beads, fibers, membranes, and nanoparticles, and their applications in the textile, pharmaceutical, agricultural, mining, and metal processing industries.

Fig. 1: Graphical representation of biopolymer sources and their application.
Fig. 1: Graphical representation of biopolymer sources and their application.The alternative text for this image may have been generated using AI.
Full size image

Schematic representation of biopolymer sources, adsorbent synthesis techniques, adsorbent formulations, and application of biopolymers in wastewater treatment. (Created with BioRender.com)

Method of Literature Search

To study the pollutant removal capacity of biopolymers from wastewater in a tailored aspect, we did a literature search using the “Web of Science” (https://www.webofscience.com/wos). The relevant articles were collected using the keywords “Biopolymer” and “Wastewater treatment”. Segregation of the literature based on the criteria is mentioned below:

The inclusion criteria are as follows:

  1. a.

    Only research and review articles published in English between 2023 and 2024 were considered for this study.

  2. b.

    Research on wastewater treatment using ecofriendly biopolymers was only selected for this study.

The exclusion criteria are as follows:

To analyze the research question, we excluded research articles published in a few countries, such as Bulgaria, Chile, Japan, Malaysia, Denmark, Estonia, Indonesia, Romania, Russia, Singapore, Taiwan, Vietnam, Algeria, Portugal, Iran, Mexico, England, Brazil, and Argentina to gain insights into the relevant literature related to our analysis.

After an initial screening based on keywords, ~504 articles were identified. The list was narrowed down to 37 relevant articles to maintain this review’s objective and scope. The selected studies focused on polymer synthesis and wastewater treatment, emphasizing the removal efficiency of different polymers. Based on the detailed literature survey, the polymer moieties with nanocomposites performed with the highest removal efficiency of around 99%. The parameters such as growth kinetics, adsorption efficiency, pH, and contact time were studied, and the details of articles taken for meta-analysis are shown in Table 1 and the removal percentage of different biopolymers were schematically represented in Fig. 2.

Fig. 2
Fig. 2The alternative text for this image may have been generated using AI.
Full size image

Removal efficiency of different polymers.

Table 1 Polymer with the compound removed and their removal efficiency
Full size table

Biopolymers as effective adsorbents

Removal of pesticides

The chemical pesticides used in agriculture pose acute and severe toxicity to human health based on their quantity and circumstances of exposure. Pesticides can last for several years in both land and water because of their chemical components, and several developed nations have banned the use of pesticides due to their negative ecological consequences22. Since each form of pesticide has unique toxicological effects, hence there exist specific risk factors associated with them. The active ingredients of pesticides include a variety of environmentally hazardous contaminants and impurities22,23. In order to understand the environmental fate, it is necessary to comprehend the physical and chemical characteristics of the pesticide application site and the pesticides that were applied. Once applied to the field, the pesticides start migrating to the surrounding areas, making the zone highly contaminated22. While rapid production is essential for agricultural needs, there is a growing interest in sustainable alternatives like biopolymers over biotechnology-based solutions24. Chitosan-based biopolymers have gained a wider range of applications in agriculture and medicine due to their efficient adsorbent properties for removing pesticides from water25. Studies reported that the adsorption efficiency of pesticides using chitosan-based biopolymers displayed the highest herbicide removal efficiency of 70–90% within an hour at a pH of 3.726. As the treatment is pH sensitive, the highest adsorption efficiency achieved for removing linuron (herbicide) was at the pH of 5.8 by combining chitin and chitosan27. Similarly, better pesticide removal was achieved at different pH values using chitosan, chitin, and activated carbon to eliminate oxadiazon28.

Chitosan, when combined with alginate membranes, removes glyphosate at a higher rate due to the electrostatic interaction between the alginate and pesticides29. Experiments were conducted to investigate the performance efficiency of alginates using a mixture of chitosan and multilayered alginate, which determined that single-layer membranes are significantly more efficient than multilayered membranes30. In a different study, cyclodextrin groups were used to create β-cyclodextrin-based polymers utilizing an aromatic substitution method. It was discovered that the polymer rapidly observed the target molecule when this material was evaluated to remove metolachlor, and the utilized biopolymer could be reused without much loss23. In order to enhance biopolymer-based pollutant removal, the modification of surface functional groups present in the biopolymers significantly improved the removal of specific pollutants. Furthermore, the addition of surface functional groups through various chemical modification methods, such as saponification of ester groups, carboxylation of hydroxyl and amine groups, phosphorylation of hydroxyl groups, halogenation and oxidation, and amination, enhances the functionality of these groups31.

In plants, the cellulose chain is present as microfibrils, which are the source of cellulose nanofibers. Depending on the required application, different functional groups could be added to the cellulose polymer32. For the removal of pesticides from contaminated water, cellulose-based macro, micro, and nanomaterials offer a sustainable and highly adaptable solution (Fig. 3). Cellulose is a biodegradable and renewable resource that can be developed into a variety of forms such as photo-nanocatalysts, activated carbons, functionalized materials, raw biomass, and nanocomposites33,34. Functionalization improves the specificity and effectiveness of adsorption, while pyrolysis of cellulose to produce biochar or activated carbons enhances the surface area and adsorption potential. Hence, they could be a potential adsorbent to remove pesticides and their associated pollutants from different wastewater sources35. Adsorption and degradation capabilities are combined synergistically by nanocomposites that contain graphene oxide or clay, whereas solar-driven pesticide decomposition is made possible by cellulose-metal oxide photo-nanocatalysts. These materials provide a scalable, energy-efficient, and environmentally friendly approach to tackling water contamination36. Enhancing reusability, scaling up for broader implementation and optimizing material performance for targeted pesticides are all necessary to advance this technology further.

Fig. 3: Cellulose-based materials for the removal of pesticides.
Fig. 3: Cellulose-based materials for the removal of pesticides.The alternative text for this image may have been generated using AI.
Full size image

Various cellulose-based materials developed for the removal of pesticides from contaminated water34. (Copyright 2021 Elsevier).

The cellulose nanofibers anchored with hydrocarbons have been demonstrated to remove synthetic herbicides. The modified form of cellulose has the potential to regenerate and be reutilized multiple times. A number of other composite materials fabricated using biopolymers have undergone successful tests against pesticides37,38. Even though many studies have demonstrated effective removal strategies, more investigation is needed to enhance the scale-up procedure. However, polymers are the most environmentally acceptable substitute for pesticides (Table 2), and further investigation is required to confirm their non-toxicity and biodegradability.

Table 2 Different polymers and pesticides treated
Full size table

Dye removal

Biopolymer-based materials engineered for removing dyes exhibit environmental sustainability across their entire life cycle, encompassing raw material extraction, production, and utilization phases. These materials offer distinct advantages, including optimized properties such as surface area, pore size, pore volume, ease of handling, and a commitment to environmental responsibility. The versatility of these materials allows for the fabrication of various configurations, such as hydrogels, aerogels, microspheres, beads, sponges, polymeric composites, and nanofibrils39. Their efficacy can be augmented through co-doping with metal oxides, carbon-based nanomaterials, and activated carbons. Moreover, the facile incorporation of functional groups like hydroxyl (–OH), amine (–NH2), carboxyl (–COO−), and amide (–NHCOCH3) enables uncomplicated surface functionalization without compromising the biological and physicochemical integrity of the materials40. This results in materials characterized by robust adsorption capabilities, making them promising candidates for applications in dye removal. Dye removal employing biopolymer-based materials encompasses three primary mechanisms: adsorption, advanced oxidation processes (AOPs), and membrane filtration. Adsorption, characterized as a surface phenomenon, represents a straightforward, safe, cost-effective, and sludge-free methodology41. Moreover, this process does not yield toxic by-products, and the adsorbent can be regenerated multiple times, contingent upon the adsorption mechanism. Physisorption and chemisorption are the two principal categories of adsorption processes distinguished by their mode of interaction42. Physisorption, a reversible phenomenon, can be tailored for mono or multi-layer absorption, relying on weak intermolecular forces28,42. In contrast, chemisorption, an irreversible process, is mediated by robust chemical bonds such as covalent and ionic bonds31,32. Physisorption interactions involve various mechanisms, including electrostatic forces, π–π interactions, hydrophobic interactions, dipole–dipole interactions, Van der Waals forces, and hydrogen bonding between the adsorbate and adsorbent39.

Advanced oxidation processes (AOPs), recognized as chemical oxidation, emerge as the preferred technology for removing dyes in groundwater treatment43. These processes facilitate the in situ generation of potent oxidants, including peroxides (O22−), superoxide (O2−), hydroxyl radicals (OH−), and sulphatic radicals (SO4–), resulting in the comprehensive degradation of intricate organic compounds such as dyes44,45. AOP technologies encompass various methodologies such as photocatalytic, Fenton-like, ozonation, semiconductor photocatalysis, catalytic oxidation, ultrasound irradiation, and electronic beam irradiation44,46. The radicals produced through these processes induce the thorough degradation of large and complex organic compounds like dyes, transforming them into intermediates and ultimately into the water, simple inorganic compounds, and ions, including carbon dioxide (CO2), sulfates (SO42–), chloride (Cl-), nitrates(NO3–), and other simple inorganic substances47,48. Biopolymers possessing surface hydroxyl groups, such as cellulose, chitin, and chitosan, exhibit remarkable efficacy as potent reducing and stabilizing agents, rendering them highly valuable for applications in AOPs39. Membrane filtration, another advanced and sustainable dye removal technology, operates efficiently and cheaply at low costs. The efficiency of the membrane depends on factors such as pore size, mechanical strength, surface charge, and resistance to cleaning chemicals49. In this process, wastewater is directed through a membrane featuring small pores that act as a selective barrier, allowing only particles smaller than the pore size to pass through. The solutes retained on the membrane are termed permeate, while the water and extracted solutes are referred to as concentrate or reject. The driving force for water in this process is the transmembrane pressure (TMP), which represents a pressure gradient across the membrane. Pressure-driven membrane filtration relies on the sieving effect and the physio-chemical interactions of separated components with the membrane. Common membrane filtration techniques include low-pressure processes like microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF), and high-pressure-driven processes such as reverse osmosis (RO)50. In RO, the separation process is based on the differences in the sorption or solubility of solutes during the solution-diffusion process, while MF and UF primarily operate on the sieving effect51. In contrast, NF or UF techniques involve physical interactions, including electrostatic repulsions between charged solutes like divalent ions, charged colloids, and amino acids with the charged membrane39. Conventional membranes are typically constructed from synthetic organic polymers like polysulfone, polyethersulfone, polypropylene52, polytetrafluoroethylene (PTFE), and polyethylene (PE)53,54. However, membrane fouling, which results from particles, molecules, or colloids deposition onto the membrane surface via chemical, physical, and mechanical processes, limits their effectiveness. Biopolymers, such as functionalised chitosan and cellulose-based nanofiltration membranes, are recognized for their antifouling properties due to the presence of hydroxyl groups and the ability to modify the surface55. Because of their improved surface nature, charge, and hydrophilicity, functionalised biopolymers are very useful for membrane filtering in the removal of dyes, either individually or in combination. The types, forms, and efficacy of different biopolymers utilized for dye removal application against different colors are described in Table 3.

Table 3 Biopolymer type and formulations used for dye removal
Full size table

Removal of heavy metal ions

Biosorption, a process utilizing biopolymer composites offers a promising approach to the sequestration of heavy metals. c. Biosorbent materials are essential to this endeavor, which wield a pivotal role in the chelation and complexation of sorbent materials, affecting the purification of metal ions from aqueous solutions, even when present in small concentrations56. These biomaterials boast diverse functional groups, showcasing superior selectivity for water pollutants when added with commercially activated carbon. Biopolymeric biosorbents, delineated by their chemical structures, fall into three distinct categories: polysaccharides, proteins, and microbial polymers57. Natural polysaccharides, such as starch, chitin/chitosan, pectin, cellulose, alginate, and gum, emerge as environmentally amicable, sustainable, abundant, and non-toxic substances amenable to facile modification for applications in water purification. Notably, cellulose, alginate, and chitosan enjoy widespread utilization in this context58. Cellulose, an abundant biopolymer, finds its presence in the primary cell walls of plants, is synthesized by microbes, and abounds in marine fauna and flora. Cellulosic materials sourced from fibers, leaves, roots, shells, barks, husks, stems, seeds, and other botanical components prove efficacious as discerning adsorbents59. Furthermore, cellulose materials derived from grasses, aquatic plants, and agricultural remnants are held in esteem. The presence of hydroxyl functional groups in cellulosic biomaterials augments their adsorptive capabilities, endowing them with considerable value in addressing challenges related to water purification60.

Agricultural residues, abundant in cellulose content, exhibit remarkable activity for metal removal through adsorption61. The chemically treated waste adsorbent, distinguished by an augmented adsorption capacity for heavy metals and pollutants, surpasses its untreated counterparts. This enhancement can be ascribed to the heightened presence of functional groups on the chemically treated adsorbent’s surface62. Leveraging agricultural remnants for wastewater treatment presents benefits such as facile regeneration, cost-effectiveness, wide availability, and exceptional selective adsorption of heavy metals63. Another kind of biomass with significant metal biosorption properties is wood bark. The bark contains Tannins, which have polyhydroxy polyphenol moieties that drive the metal ion absorption, and the property of water discoloration has been overcome by acid, alkali or acidified formaldehyde treatments without disturbing the adsorption properties. However, the utilization of untreated biomass waste as biosorbents presents challenges, including constrained adsorption efficiency, elevated chemical oxygen demand (COD) and biochemical oxygen demand (BOD), and increased total organic carbon (TOC) due to the release of soluble organic compounds from plant materials62. In addressing this, a cellulose-driven adsorbent derived from sugarcane was engineered to target metallic pollutants such as Pb (II), Zn (II), and Cu(II) in both singular and binary pollutant systems. The application of Langmuir isotherm in kinetic investigations unveiled maximum adsorption removal capacities of 558.9, 446.2, and 363.3 mg/g, respectively31. Nevertheless, the efficiency of this adsorbent experienced a significant reduction in the presence of binary pollutant systems. This decrease underscores the imperative for more resilient biosorbent designs capable of co-adsorbing pollutants or selectively adsorbing pollutants with heightened efficacy, regardless of the concurrent presence of co-pollutants31,63.

Alginate, a naturally occurring anionic and hydrophilic biopolymer with metal ion removal potential, is obtained through the aqueous alkali treatment of brown seaweed algae, specifically Phaeophycean, whose principal constituent is alginic acid64. In contrast, sodium alginate (SA) represents the sodium salt of alginic acid, characterized by numerous free hydroxyl and carboxyl groups distributed along the backbone chain. This linear, anionic polysaccharide comprises two types of 1,4-linked hexuronic acid residues: β-d-mannuronopyranosyl and α-1-guluronopyranosyl (G). These residues are organized into blocks of repeating M residues (MM blocks), blocks of repeating G residues (GG blocks), and blocks of mixed M and G residues (MG-blocks)65. Adsorbents from SA have exhibited noteworthy rates of adsorption and elimination for ions through surface grafting and cross-linking. The SA’s carboxyl and hydroxyl functional groups electrostatically adsorb and chelate ions, inducing gelation66. The link strengthens as the covalently bonded ions interact with the polymeric alginate chains, causing polymer agglomeration and gel formation. Nevertheless, the utilization of sodium alginate-based polymers in commercial applications has been significantly restricted by their inherent lack of physical strength and uncomplicated thermostability. Lately, the emergence of the possibility of theoretical studies has enabled the designing of more sophisticated biopolymer-based adsorption matrices for a wide range of metal pollutants like using diethylaminoethyl cellulose (DMC) and quaternary ammonium cellulose (QC) biopolymer matrices toward CrO42−, Cr2O72−, SeO32−, and SeO42−67. Various biopolymers and their composite form used to remove heavy metal ions are summarized in Table 4.

Table 4 Metal ion removal efficiency of biopolymers and their composites
Full size table

Biopolymers, in their natural state, exhibit weak chemical and mechanical properties. Therefore, treatments involving organic, inorganic, metal oxides, layered double hydroxides (LDHs), and other substances are employed to enhance their adsorption efficiency68. The synthesis of nanocomposite materials, achieved through the hybridization of diverse polymer backbones, proteins, and polysaccharides, has gained popularity due to the significantly enhanced properties compared to isolated entities. These nanocomposites exhibit excellent biocompatibility, multiple functionalities, low toxicity, and biodegradability, making them highly desirable. The most commonly employed polysaccharides for creating nanohybrids include cellulose, chitosan, and alginate. Nanocomposites can be produced by hybridizing polymers with various materials, including inorganic materials, polymers, carbonaceous materials, and other encapsulation processes. This approach offers a versatile means of tailoring the properties of biopolymers for specific applications, contributing to advancements in adsorption technologies and environmental remediation69.

Removal of other contaminants

Biopolymers exhibit exceptional adaptability in the field of water purification, serving a variety of purposes, including the elimination of microplastics, emerging contaminants, desalination and oil–water separation. Other contaminants encompass pharmaceutical and personal hygiene products, endocrine disruptors, priority chemicals, and various organic pollutants. These contaminants arise from the routine use of everyday products and the indiscriminate application of chemicals on a large scale, including pharmaceuticals, fertilizers, pesticides, aerosols, and surface coatings. Their concentrations range from ng L−1 to g L−1, featuring pharmaceuticals but not restricted to such as erythromycin, metronidazole, sulfamethoxazole, trimethoprim, ciprofloxacin, amoxicillin, and tetracycline. These substances pose significant threats to both human health and the environment. Table 5 provides a compilation of biopolymers and their composites employed to remove diverse emerging contaminants. The biopolymers that act as platforms for catalysts and adsorbents remove pollutants in various modes, such as biosorption, photocatalytic degradation, and adsorption.

Table 5 Biopolymers and their composites are employed for the removal of diverse emerging contaminants
Full size table

Microplastics have gained recent attention due to their potential to cause chronic toxicity in organisms exposed to them over extended periods. Wastewater treatment plants (WWTPs) are significant contributors to microplastic release, originating from microbeads in facial cleansers, toothpaste and microfibers shedding from synthetic textiles in daily activities. Microplastic concentrations in WWTP influents vary from 1 to 10044 particles/L, but those in effluents range from while that form effluent ranges from 0 to 447 particle L−1 70. These concentrations are higher than the typical atmospheric deposition rate of 118 particles m−2 day−1 71. Research has been done on the retention of microplastics in sludge and different treatment techniques where the wastewater treatment process greatly influences microplastic concentrations. WWTPs using tertiary treatment processes have effluent microplastic concentrations of 0–51 particles/L, while those using only primary or secondary treatment processes have concentrations of (9 × 10−4–447 particles/L)70,72. The median total daily discharge of microplastics was estimated at 2 × 106 particles per day, and WWTPs with high microplastic discharges had annual effluxes exceeding 1 × 107 cubic meters. More than 30 types of microplastic exhibiting various shapes have been identified to date. The most abundant microplastics are polyester (PES, ∼28–89%), polyethylene (PE, ∼4–51%), polyethylene terephthalate (PET, ∼4–35%), and polyamide (PA, ∼3–30%)70,73. Fibers, primarily released from domestic washing, constitute the largest proportion, accounting for up to 52.7% of observed microplastics in wastewater70,74,75,76. Interestingly, more than 90% of effluent microplastics have a size of <500 μm, with ~60% measuring <100 μm. Recent findings indicate that microplastics measuring <25 μm are more abundant than previously estimated70,77,78. The detection of microplastics in size <20 μm is still a challenge, and advanced detection techniques like attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) are being actively employed to identify and detect these small particles from WWTP71. Recently, the adsorption and removal of microplastics have seen the usage of biopolymers in the form of composites and micro biopolymers, where these functionalized nanoparticles work as membrane filters, flocculants, catalysts, and adsorbents. Adsorption is an exothermic surface phenomenon; flocculants result in the agglomeration of microplastics and remove them as flocs, catalysts aid in degradation, and membranes filter out microplastics79,80.

Jalvo and co-authors reported on designing a water filtration membrane with the efficiency to filter microplastics as small as 500 nm. The membrane was prepared using various biopolymer nanocrystals, namely cellulose nanocrystals (CNCs), 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibers (T-CNF), and chitin nanocrystals (ChNCs) employing a cast coating technique. Among this, T-CNF demonstrated a remarkable ability to segregate particles as small as 2 μm in size81. The bioflocculation of microplastics mediated by lysozyme amyloid fibrils produced removal efficiencies of 97.9–98.2% for both polystyrene microplastics and humic acids, indicating that this nano-sized flocculant can be efficiently used to remove the microplastic contaminant82. In addition, it has recently been determined that these algal biopolymers and bacterial extracellular polymeric substances83 as potential resources for the removal of microplastics. EPS from the freshwater Cyanothece sp. strain effectively flocculated micro and nano plastics at low to higher concentrations of MPs resulting in a negative effect on microalgae growth84. Pectin resulted in efficient microplastic removal by flocculation when pectin in a concentration of 15 mg L−1 was added to a suspension of polystyrene nanoplastic (size: 110 ± 0.67 nm, 10 mg L−1) in the presence of Fe(III) (0.10 mM) resulted in removal 97.3% of microplastics in a span of 2 days85. Oyster filtration mechanism-based, bioinspired ultralight chitosan-glutaraldehyde nanofiber sponge (chitosan NF sponge) was prepared from Chitosan/polyethylene oxide (PEO) nanofibers (NF) through a series of processes like electrospinning, casting, freeze-drying and crosslinking. The sponge efficiently removed up to 80.1% of polyester microplastics86.

Biopolymers find their use in desalination; notably, the integration of carbon nanotubes (CNTs) derived from biopolymers or modified biopolymer–CNT composites, when applied as coatings on reverse osmosis membranes, has been observed to enhance the pore characteristics and hydrophobicity of the membranes. This augmentation correlates with a substantial increase in salt rejection, reaching approximately 87% for Na2SO4, aiding in enhanced desalination87. Desalination, a process predominantly facilitated by pressure-driven modified membrane technology, has seen widespread use of polyamide membranes. These conventional membranes exhibit remarkable desalination potential, surpassing 99% efficiency for seawater. Additionally, alternative membranes such as polysulfone-functionalized membranes and polyvinylidene fluoride hollow fiber membranes have gained attention due to their distinctive features, including high hydrophobicity, catalytic properties, ion exchange capabilities, and applications in the biomedical field. Polyvinylidene fluoride hollow fibers, for instance, have proven effective in removing dissolved volatile species from water88. Furthermore, advancements in biopolymeric membranes, including cellulose acetate, acetylated cellulose ether, cellulose acetate membranes with MIL-53(Fe) additive, cellulose acetate propionate, and cellulose acetate butyrate membranes, have demonstrated potential in desalination processes. Studies have shown that these membranes have improved anti-fouling activity and contribute to the desalination process89,90,91.

Oil contamination in water imposes serious threats to the environment and surrounding ecosystem, like reducing the dissolved oxygen, causing the death of aquatic organisms, and contaminating soil when used for irrigation, causing a loss in harvests41. Oil is versatile and finds its use in various daily activities, resulting in water pollution from various routes, including residential sewage, oil refineries, crude oil production, and transportation, forming oil-water emulsion. Hence, it is important to separate oil from wastewater for effective water treatment. The traditional method includes the usage of ultrafiltration membranes made of unprocessed or modified polymers, but in recent times, hydrophobic adsorbents have been used to remove oil. Recent advancements include using copolymers, carbon compounds, inexpensive organic matter and organoclays in the form of fiber, powder or other porous structures as sorbents. Membrane filtration of forms line nanofiltration, ultrafiltration and microfiltration are currently employed. Guar gum-based92 adsorbents have recently been explored as biopolymeric sources for remediation of oil-contaminated waterbodies due to their adsorptive nature towards oil and antibacterial properties93. GG Hydrogel with metaborate crosslinkers has been identified to efficiently separate water from various oil/ water mixtures, including cyclohexane, canola, silicone, and crude oil. GG hydrogel-coated membranes or materials are identified to separate crude oil/ water mixture with selective separation efficiency of >99.6% and water flux of 2850 L m−2 h−1 93,94.

Factors affecting the efficiency of biopolymers

The effectiveness of liquid-phase adsorption and wastewater treatment relies on several factors, encompassing the adsorbate’s nature, the adsorbent characteristics, and properties specific to the wastewater composition. Biopolymer optimization in wastewater treatment is influenced by both common and specific components. Regardless of their mechanism or kind of action, common obstacles collectively known as shared attributes have an impact on biopolymers efficiency everywhere. These common characteristics are listed in Table 6 and are essential in controlling the effectiveness of biopolymers. On the other hand, distinctive factors include characteristics unique to particular modes of application, such as flocculation, adsorption, membrane filtration, and the utilization of algal polymers. The primary limitation of biopolymers in their native form lies in their inefficiency, which significantly restricts their adsorption capacity. Hence, they are modified or co-polymerized to enhance efficiency, which adds up to the cost of these adsorbents59. Biopolymer modifications can be broadly classified into chemical modifications, physical modifications, composite formation, inorganic incorporation, and nanomaterial integration, each designed to enhance their adsorption properties40. Chemical modifications include grafting, which introduces functional groups or polymer chains to alter surface properties, and cross-linking, which forms interconnections between polymer chains to improve structural stability63. Physical modifications involve blending biopolymers with other materials to synergize their properties or applying thermal treatment to induce changes that enhance adsorption characteristics. Composite formation focuses on integrating biopolymers with materials such as graphene oxide to increase surface area and adsorption sites or with zeolites to improve ion exchange and pollutant removal capabilities15. Inorganic incorporation includes the addition of metal oxides like Fe3O4 or TiO2 to enhance adsorptive affinity and functionalization with layered double hydroxides (LDHs) to boost contaminant removal efficiency59. Finally, nanomaterial integration involves embedding nanoparticles such as silver or gold to introduce unique adsorptive and antimicrobial properties or incorporating carbon nanotubes to enhance mechanical strength and adsorption performance. Together, these strategies address the limitations of native biopolymers, enabling their effective use in applications such as wastewater treatment.

Table 6 Factors affecting the efficiency of biopolymers
Full size table

While these modifications are essential and can be carefully tailored to optimize biopolymer performance, external factors such as environmental conditions and chemical interactions can also influence their effectiveness. In some instances, these external factors may degrade or alter the modified biopolymer or its composites, diminishing its adsorption capacity and limiting its long-term applicability95. In biopolymer membrane-based wastewater treatment, membrane biofouling presents a significant challenge, resulting from the accumulation of organic pollutants, soluble microbial products (SMP), or extracellular polymeric substances83. Organic fouling occurs due to the buildup of organic contaminants, while the growth and metabolism of bacterial cells or flocs on the membrane causes membrane biofouling. The effectiveness of biopolymer membranes in resisting fouling, although relatively higher, can be further improved by enhancing the hydrophobicity of the membranes. Factors contributing to fouling include the size and shapes of pollutants concerning membrane pores, membrane porosity, and the functionality and charge of the membrane surface. Notably, alginate-based films are prone to clogging due to their affinity towards calcium ions, leading to adsorptive binding with polysaccharide functional groups, resulting in the formation of clogs and a subsequent reduction in filtration efficiency96. The efficacy of dye removal through flocculation is significantly influenced by molecular factors, particularly the structural characteristics (branched vs. linear) and charge density. Branched molecules exhibit higher removal efficiency due to the robust resistance, large size, and loose structure of the flocs they produce. However, if a grafted polymer has an increased and denser branching structure, the efficiency of dye removal through flocculation may be impeded by steric hindrance. Notably, a higher charge density corresponds to increased dye flocculation efficiency97.

Specific controlling factors come into play when considering microalgae-based biopolymers for wastewater treatment. These include the utilization of live/dead biomass, the species of microalgae, resistance to water treatment processes, and the management of the culture. Metal precipitation may occur as a result of these factors. Additionally, common and major factors affecting the efficiency of biopolymers in this context are listed in Table 6, including temperature, pH, salinity, contaminants, and biopolymer concentration21. In the realm of biopolymer membrane filters, the swelling ratio is influenced by factors such as cross-link density (CLD), pH, temperature, and the nature of functionalities or groups constituting the materials. These groups' hydrophilic or hydrophobic nature also affects swelling, with a higher hydrophilic nature contributing to increased swelling. Furthermore, the addition of bio-nanocomposites enhances the adsorption efficiency of hydrogels98.

Bio-polymer-based materials for wastewater treatment show significant promise when modified through techniques such as grafting, co-doping, composite preparation, bio-nanocomposite integration, and the addition of carbon nanotubes, graphene oxide, and nano clays. These modifications enhance their potential as effective resources for wastewater treatment. However, to fully capitalize on the commercial viability of these materials, several challenges must be addressed. Scalability and cost-effectiveness in large-scale production are critical considerations for the practical application of bio-polymer-based wastewater treatment materials. Achieving enhanced stability in the preparation of biopolymeric materials is another challenge that needs attention, ensuring their reliability and performance over time. Additionally, addressing the issue of reusability is crucial for the prolonged and sustainable use of these materials in wastewater treatment processes. Environmental sustainability is a key aspect that requires careful consideration in the design and utilization of bio-polymer-based materials. This includes developing strategies for regenerating nanocomposites and establishing safe disposal methods for used adsorbents. By addressing these challenges, the full potential of bio-polymer-based materials in wastewater treatment can be realized, contributing to both effective pollution control and environmentally responsible practices99.

Regeneration and reuse of spent biopolymer

Historically, adsorbents were discharged into the environment after recovering the pollutants to enhance their efficiency. However, the release of adsorbents into the environment causes secondary pollution and is also toxic to all life forms on Earth because they still contain adsorbed toxic compounds. There is a risk of pollutants leaching, migrating, or bioaccumulating over time, which can lead to the reintroduction of these pollutants back into the environment100. The regeneration and reuse of spent biopolymer adsorbents involve restoring the adsorbent’s ability to capture pollutants, extending its lifecycle and enhancing sustainability. To minimize the toxicity of adsorbents after recovery, they should be reused in other applications (Table 7), which helps reduce the environmental toxicity in the surrounding area. This approach not only maximizes the utility of the adsorbents but also contributes to a more sustainable and environmentally friendly waste management strategy.

Table 7 Regeneration and reusability applications of spent adsorbents in various processes
Full size table

Reusing biopolymers from wastewater treatment extends the life cycle, enhances the recyclability and acts as a more sustainable mode of biopolymer application. The regeneration and reuse of spent biopolymers in industry is a cost-efficient process, reduces treatment costs, enables the release of adsorbed molecules in biopolymers via chemical, physical, or biological processes, and has important environmental applications. Figure 4 shows an overview of the life cycle analysis of different biopolymer feedstocks, biocomposite preparation methods, regeneration, and the possible fate of spent adsorbents. Discharging used materials into the environment without prior removal of pollutants contributes to secondary environmental pollution101. Although regeneration and reuse are promising technologies, it is imperative to assess the environmental consequences and the operational efficiency of regeneration. Various methods have been used to retain the contaminant removal efficiency of biopolymers for several cycles, such as ultrasound, chemical regeneration, oxidation, biological degradation, and thermal treatment63. The chemical treatment method is most commonly applied to regenerate the biopolymers due to their rapid recovery and low energy consumption63. Various acid and alkaline treatments using chemicals, including NaOH, HCl, EtOH, and HNO3, are effectively used to regenerate spent biopolymers.

Fig. 4: Graphical representation of biopolymers preparation, regeneration and reuse.
Fig. 4: Graphical representation of biopolymers preparation, regeneration and reuse.The alternative text for this image may have been generated using AI.
Full size image

Diagrammatic representation of sources of biopolymers, preparation of biocomposites, and their regeneration and reuse for pollutant removal applications (Created with BioRender.com)

Introducing acid-desorbing eluents such as HNO3 into the adsorbent material generates a substantial amount of H3O+, facilitating the desorption of the adsorbate. This occurs through ion exchange, which weakens the adsorbent sites, promoting the removal of adsorbate from the adsorption sites and leading to a clean surface suitable for the next adsorption cycle63,71,102. The adsorption and desorption of Cu(II), Cd(II), and Pb(II) ions in aqueous solution were examined by103 using chitosan (CTS) that had been crosslinked covalently and ionically with epichlorohydrin and triphosphate (TPP). The maximum adsorption capacities for Cu (II), Cd(II) and Pb(II) ions of 130.72, 83.75 and 166.94 mg g−1, respectively, were achieved as predicted by the Langmuir isotherm model. The eluents HNO3 and HCl exhibited the highest levels of ion desorption for Cu (II), Cd(II), and Pb(II) with respective rates of 88.7%, 89.9% and 79.2%. According to Laus et al. good desorption results were obtained in 0.1 mol L−1 HNO3, HCl and EDTA solutions; however, KCl and NH4Cl were inefficient eluents for Cu(II) and Cd(II) ion desorption104. In another study, Ngah and co-workers used crosslinked Chitosan beads with glutaraldehyde (GLA), epichlorohydrin (ECH), and ethylene glycol diglycidyl ether (EGDE) to adsorb and desorb Cu(II) ions. They have used various concentrations (10−2–10−6 mol L−1) of EDTA and obtained 97.7%, 95.4%, and 82.3% for Cu(II) ions desorption values in chitosan-ECH, chitosan-GLA, and chitosan-EGDE, respectively104.

The HSAB principle by Pearson was applied in an experiment involving the absorption and desorption of heavy metals, namely Pb2+ and Cd2+, utilizing a hydrogel composed of chitosan/poly(ethylene glycol)/poly(acrylic acid) (CS/PEG/PAA)105. The selective adsorption of Pb2+ and Cd2+ was achieved through the glow-discharge electrolysis plasma (GDEP) technique, creating an adsorbent with hard Lewis base adsorption sites such as amino groups, hydroxyl groups, ether links, and carboxylate ions. Successful Pb2+ and Cd2+ ions desorption was demonstrated in CS/PEG/PAA composites using EDTA-4Na (0.015 M) as the eluent, with respective values of 495.0 and 201.7 mg g−1. Chitosan-coated perlite beads were employed for the adsorption of Cd2+ ions, subsequently undergoing three desorption cycles using 0.1 N HCl. The introduction of 0.5 M ethylenediamine tetra acetate (EDTA) during the removal of a Cd2+ solution (100 mg L−1) and beads led to the complete elimination of Cd2+ ions from the beads, showcasing a robust desorption capability and allowing for effective reuse106. Ge and co-workers107 prepared a novel carbon-chitosan complex adsorbent (ACCA) by microwave crosslinking glutaraldehyde and activated carbon-(NH2-protected) chitosan complex. The ACCA demonstrated the highest desorption efficiency in the fifth cycle, with 78% and 88% desorption capacity of Cd2+ and Pb2+ ions, respectively. Commercial adsorbents should be capable of regeneration and desorption, and these capabilities should be employed to remove pollutants from the wastes107.

In a study employing cross-linked magnetic modified chitosan (CMMC) for the adsorption of Zn2+ from water, it was observed that the quantitative desorption efficiencies using 0.1 mol L −1 HCl, 0.1 mol L−1 HNO3, and 0.5% acetic acid were 97.2%, 82.1%, and 70%, respectively108. The desorption efficiencies using HCl, HNO3, and acetic acid were found to be 97.2%, 82.1%, and 70%, respectively. Notably, no loss of activity was observed even after five cycles of the desorption process. An alternative cellulose-based polymer hydrogel, known as C-g-AA, demonstrates remarkable efficacy in removing environmental contaminants, especially metal ions. The desorption of metal ions from the C-g-AA hydrogel was studied using 0.1 mol L-1 HNO3 and 0.1 mol L-1 NaOH. The reusability of the hydrogel was evaluated through three cycles after adsorption, employing 0.1 M HNO3. The C-g-AA hydrogel had sufficient removal ability, with 95% and 87% removal recorded in the first and fourth cycles, respectively109. Pb2+, Cd2+, Ni2+, Cu2+, and Zn2+ ions were removed from aqueous solutions using a Fe3O4@SiO2@PEI-NTDA adsorbent made from polyethyleneimine and 1, 4, 5, 8-naphthalenetetracarboxylic-dianhydride (NTDA) with Fe3O4@SiO2 nanoparticles109. Due to electrostatic interactions, the adsorbent exhibited an adsorption capacity of 285.3 mg g-1 for Pb2+ from water at pH 6. The Fe3O4@SiO2@PEI-NTDA nanoparticles displayed high stability and prolonged reusability, demonstrating effectiveness through six cycles of desorption-adsorption using 2 M HCl over a period of 144 h109.

Brião and co-workers110 used a reusable zeolite produced from biopolymer chitin using a hydrothermal process to study cationic dye adsorption. The adsorption capacities of zeolite for various dyes, such as basic fuchsin (BF), methylene blue (MB), and crystal violet (CV), were assessed at adsorbent concentrations of 2.0 g L–1 and pH values of 7.5, 8.0, and 9.0. The study concludes that zeolite is suitable for fifteen adsorption cycles, achieving an 85% color removal rate110. Regenerating biocomposite material has both economic and environmental significance. Many researchers have studied the desorption process by using different acids and repeating the process a few times. Most of these studies have been conducted on a laboratory scale. Conde Cid and co-workers111 conducted a study on the repetitive adsorption tests for tetracycline and oxytetracycline (OTC), focusing on the reusability of CAMIL-MMT and CAMIL-SEP hydrogels using 0.1 M methanol (MeOH) as a desorbing agent. The adsorption capacity for TC showed a slight decrease, with CAMIL-MMT reducing from 25.02 to 21.01 mg/g, and CAMIL-SEP from 17.14 to 13.87 mg/g over multiple cycles (Fig. 5 A and B). For OTC, CAMIL-MMT’s adsorption capacity decreased slightly from 28.89 to 26.01 mg/g, while CAMIL-SEP capacity reduced from 19.76 to 17.98 mg/g. CAMIL-MMT retained over 90% of its adsorption capacity for OTC after five cycles, indicating strong chemical stability and suitability for repeated use in water treatment applications. This stability suggests that CAMIL-MMT and CAMIL-SEP hydrogels are promising materials for effectively removing TC and OTC from water, maintaining performance even after multiple cycles. According to Pan et al.112, the study highlights the regeneration and reuse of chitosan for uranium recovery (Fig. 5C and D). The study found that acidic eluents (HCl) play a significant role in this process. While higher concentrations of these eluents improve uranium recovery, they also lead to a decrease in adsorption capacity over successive cycles and can damage the biopolymer structure (due to the biodegradability and dissolution tendency of chitosan) (Fig. 5A and B). Despite these challenges, the study found that the fourth adsorption-desorption cycle recovered ~73% of uranium using 0.05 M of HCl. In addition to previous studies113, adsorption-desorption trends and structural analyses of pAAm-g-XG/HKUST-1@Fe3O4 biopolymer nanocomposite hydrogel for chlorpyrifos (CPF) and diazinon (DZ) from wastewater. The desorption study showed that the desorption efficiency (0.1 M HCl) for chlorpyrifos (CPF) and diazinon (DZ) decreased slightly over four cycles. Specifically, the desorption efficiency for CPF decreased from 83.11% to 75.01%, while DZ decreased from 88.84% to 80.01% (Fig. 5E and F). The results indicate that the hydrogel remains effective for additional cycles. Its porous nature and functional groups are preserved even after multiple regeneration cycles, supporting its durability and reusability. Table 8 summarizes different biopolymers used for pollutant removal and their regeneration studies with potential eluents. Several authors have regenerated the biopolymers from a minimum of 2 to a maximum of 10 times in order to achieve the efficacy of adsorbents’ reusability. Besides this, suitable regeneration techniques influence the cost of fabricating adsorbents. In addition, the table exhibits that each adsorbent has its own unique recyclability cycles, such as several times, and it shows that selecting suitable materials is important. However, considering economic factors, investigations in real-time environments become imperative. Additionally, it is crucial to incorporate analyses of chemical, structural, and mechanical changes in the adsorbent during the desorption process.

Fig. 5: Regeneration and reusability of biopolymers.
Fig. 5: Regeneration and reusability of biopolymers.The alternative text for this image may have been generated using AI.
Full size image

Effects of biopolymer regeneration capacity for removing TC and OTC using CAMIL-MMT and CAMIL-SEP (A and B)202, Copyright 2023 Elsevier. Regeneration capacity for uranium separation from FTW using chitosan (C and D)203, Copyright 2020 Elsevier. Regeneration and reusability of spent adsorbents (OPPs and DZ) loaded with pAAm-g-XG/HKUST-1@Fe biopolymer (E and F)113, Copyright 2024 Elsevier.

Table 8 Performance of biopolymer-based composites for diverse pollution removal and regeneration
Full size table

Application of spent absorbent material

The reuse of spent adsorbents is of paramount importance to prevent secondary pollution, and this area of research is gaining significant attention. Recent literature highlights the following discussions regarding reuse applications. Conventionally, various techniques such as biodeterioration, depolymerization, assimilation, and mineralization have been used to degrade spent biopolymers; however, these methods create sequential environmental pollution. In recent decades, efforts have been made to create value-added products from spent adsorbents using methods such as steam treatment, catalyst applications, cement applications, fertilizers and soil conditioners, and latent fingerprint detection. Figure 6 illustrates the implementation of various strategies for regeneration techniques and their associated challenges in maintaining the eco-friendliness of spent adsorbents. The aim is to reduce toxicity and mitigate adverse environmental effects, highlighting their potential application sectors in spent adsorbents.

Fig. 6: Graphical representation of regeneration techniques and associated challenges.
Fig. 6: Graphical representation of regeneration techniques and associated challenges.The alternative text for this image may have been generated using AI.
Full size image

Schematic representation of adsorption and desorption of pollutant removal, various regeneration techniques, regeneration challenges, and applications of saturated adsorbents. (Created with BioRender.com)

The study conducted by He and his co-workers focused on the removal of Cr(VI) from wastewater114. They observed that the disposal of Cr(VI) adsorbents in landfills led to significant Cr contamination in the surrounding environment. This draws attention to the environmental issues surrounding the management of adsorbents after the end of their useful lives, highlighting the necessity of sustainable disposal or regeneration methods to mitigate contamination risks114. The author explored the potential of repurposing spent Cr adsorbents as catalysts for the removal of sulfur-containing volatile organic compounds (VOCs), with a focus on CH3SH gas. The study found that Cr(III) is significantly less toxic than Cr(VI), being 100 times less harmful. This reduction in toxicity is attributed to the immobilization of Cr(VI) in the form of a Cr2S3 solid phase, effectively reducing its environmental impact. This innovative approach not only addresses the disposal issues associated with spent adsorbents but also provides a sustainable method for VOC removal.

Likewise, Verbinnen and colleagues developed ceramics by incorporating 3% of the adsorbent spent into the production process. They successfully stabilized hazardous elements by heating a mixture of 3% spent adsorbent and industrial sludge at 1100 °C. This process also reduced the initial leaching values of these elements by 0.5–1%115. Furthermore, heating industrial sludge to 1100 °C successfully stabilizes heavy metals and cation-forming elements like Cr, Ni, Cu, Zn, As, Cd, and Pb, allowing them to be integrated into the sludge without exceeding regulatory limitations in the leachate115. Phosphate can be effectively reclaimed and reused from aqueous solutions using an engineered biochar made from magnesium-enriched tomato tissues. This biochar demonstrates a maximum sorption capacity exceeding 100 mg g−1, which is primarily due to precipitation and surface deposition mechanisms. It has the potential to serve as a tool for the controlled and sustained slow release of fertilizer into the soil environment116

Another notable approach for reusing spent adsorbents is latent fingerprint detection, which can aid in crime resolution. Fouda-Mbanga and colleagues have extensively reviewed this method100 in order to successfully identify people, forensic science utilizes a variety of chemicals and procedures such as powder dusting, silver nitrate soaking, iodine fuming, and ninhydrin spraying in latent fingerprinting to successfully identify individuals100. The iodine fuming, silver nitrate and ninhydrin methods are frequently employed for latent fingerprint detection. However, they exhibit significant limitations, including low contrast and selectivity, poor sensitivity, and notable background interference117. Researchers have explored the use of nanoparticles, fluorescent nanomaterials, and rare-earth up-conversion fluorescent nanomaterials to overcome these shortcomings100.

Economic analysis and life cycle assessment

Biopolymers have emerged as sustainable alternatives to conventional polymers, addressing critical environmental concerns associated with non-biodegradable plastics. However, their widespread adoption faces economic hurdles stemming from high production costs. For instance, recent market analysis revealed that while the cost of Polyethylene (PE) and Polypropylene (PP) averages around US$2.5/kg, the production of PHAs can exceed US$25/kg. This variation is completely based on the application and quality of the biopolymer118,119. Biopolymers utilized in the food industry are priced at ~US$8/kg, with a market size of US$25 million, whereas those in the biomedical sector command prices as high as $12/kg due to stringent quality standards, representing a $15 million market120. These elevated costs primarily occur from factors such as high-energy demands, expensive carbon substrates, and downstream processing121.

The economic barriers associated with biopolymer production underscore the need for innovative cost-reduction strategies. The utilization of a mixed microbial community capable of producing biopolymers like chitosan and cellulose could be a possible solution to lower the cost of production. Notably, carbon sequestration through polymer production offers a dual benefit: reducing carbon dioxide emissions while creating high-value bioproducts122. However, achieving commercial viability requires a comprehensive approach that optimizes yield, productivity, and raw material utilization. Recent studies have identified productivity and global yield as the most significant cost determinants, emphasizing the need for process innovations and advanced biotechnological interventions123. Based on the available economic analysis, future research should focus on raw materials, yield, and productivity.

Life cycle assessment is a tool that can be used to evaluate the environmental impacts of biopolymers and wastewater treatment technologies. By evaluating the cradle-to-grave impacts of biopolymers, including raw material extraction, production, usage, and disposal, LCA can identify cost drivers and areas for improvement. According to LCA, feedstocks sourced from waste, such as agricultural leftovers or by-products of food processing, not only save expenses but also improve environmental performance by reducing waste124. Hence, using biopolymers for wastewater treatment serves as a carbon source contribution. The synthesis of PHA involves significant energy needs from fermentation and downstream processing. The carbon footprint and operating expenses are greatly reduced when renewable energy sources are used during these phases125. The synthesis of PHA involves significant energy needs from fermentation and downstream processing. The carbon footprint and operating expenses are greatly reduced when renewable energy sources are used during these phases. The optimization strategies identified via LCA could mitigate the major environmental impact caused by petroleum-based plastics126. The circular economy benefits of incorporating PHA into biorefineries and wastewater treatment technologies could potentially improve the economic feasibility by utilizing secondary by-products such as bioenergy127. Although bioplastics have great potential, obstacles like elevated production expenses and varying life cycle assessment (LCA) methods impede their implementation. Tackling these challenges through innovation and expanded research collaboration is crucial for optimizing their ecological advantages.

Conclusion

This review examines the critical role of biopolymer-based adsorbents in addressing environmental pollution and wastewater remediation. Effective wastewater treatment is fundamental for containing environmental contamination, ensuring equitable access to clean water for drinking and agriculture, and advancing sustainable resource management practices. These objectives are integral to promoting circularity and achieving sustainable water management. Biopolymers offer a promising, sustainable alternative to conventional polymers due to their renewability, environmental compatibility, and exceptional adsorption properties. Despite these advantages, their native mechanical and chemical limitations necessitate modifications to enhance their efficiency for diverse applications, including removing pesticides, dyes, heavy metals, microplastics, and emerging contaminants. The literature highlights the positive impact of biopolymer applications while emphasizing the need to address certain research gaps. There is broad consensus on the benefits of chemical and physical modifications, composite formation, and nanomaterial integration in enhancing adsorption efficiency. However, challenges remain in achieving scalability, ensuring cost-effectiveness, and understanding the environmental implications of these modification techniques.

While laboratory studies highlight the efficacy of biopolymers, challenges such as regeneration, reuse, and real-time applicability remain significant barriers to their widespread adoption. Furthermore, gaps in understanding the long-term environmental impacts and potential toxicity of products loaded onto spent adsorbents underscore the need for comprehensive toxicity analyses. Addressing these gaps necessitates advancements in biopolymer production methods to improve scalability and cost-effectiveness. This includes leveraging renewable feedstocks and developing innovative regeneration strategies alongside sustainable end-of-life management techniques to enhance reusability and responsible disposal of spent biopolymers. Future research should also prioritize long-term studies to evaluate environmental impacts and refine biopolymer-based technologies for broader implementation. Collaborative efforts between academia, industry, and policymakers are crucial to overcoming these barriers and facilitating the integration of biopolymer-based wastewater treatment systems into global sustainable development frameworks. By addressing current challenges and prioritizing advancements, biopolymers can significantly contribute to sustainable water management.