Hydrochar Production and Adsorption Applications

Hydrochar production via hydrothermal carbonisation offers a sustainable pathway to transform diverse biomass feedstocks into stable carbonaceous materials with controllable porosity and surface chemistry. Under moderate temperatures (typically 180–250 °C) and autogenous pressure, water facilitates hydrolysis, dehydration and polymerisation, yielding hydrochar enriched in oxygen- and nitrogen-containing functional groups. The resulting material exhibits enhanced specific surface area and hierarchical micro- to mesoporosity, which underpin its efficacy in adsorbing contaminants. Applications encompass the removal of heavy metals, dyes, pharmaceuticals and emerging organic pollutants, with adsorption governed by electrostatic attraction, complexation, hydrogen bonding and π–π interactions. Recent research has emphasised heteroatom doping, chemical activation and process optimisation to boost uptake capacity and selectivity. Interdisciplinary studies now integrate hydrochar production with circular-economy strategies, highlighting low-cost wastewater treatment, resource recovery and valorisation of agricultural residues on a global scale.

Research from Nature Portfolio

Optimised production of alkali-modified hydrochar from sugarcane bagasse demonstrates that reaction parameters can be fine-tuned for maximal heavy-metal removal. Using response surface methodology, conditions of 180 °C, 11.5 h residence time and a ZnCl₂ : biomass ratio of 3.5 : 1 yielded activated hydrochar with a Langmuir maximum capacity of 90 mg g⁻¹ for Pb(II). Adsorption follows a pseudo-second-order kinetic model and spontaneous, exothermic thermodynamics. In another instance, nitrogen-enriched hydrochar derived from Salix biomass features an open, molecular-sieve-type pore network and abundant heteroatom functionality, achieving near-complete removal of Cr(VI) at pH 1. Rapid uptake kinetics and a Langmuir-type isotherm highlight the benefit of heteroatom doping for targeted pollutant capture.

Hydrochar Production and Adsorption Applications publication trend

The graph below shows the total number of articles in hydrochar production and adsorption applications across all publications each year (not limited to Nature Index journals).

Technical terms

Hydrothermal carbonisation: A thermochemical conversion of wet biomass into hydrochar under elevated temperature and pressure in aqueous media.

Hydrochar: The carbon-rich solid product of hydrothermal carbonisation, characterised by porous morphology and surface functional groups.

Adsorption isotherm: An equation describing the relationship between adsorbate concentration in solution and the amount bound to the adsorbent at equilibrium.

Pseudo-second-order kinetics: A model assuming adsorption rate is proportional to the square of the number of available binding sites.

Langmuir model: An adsorption isotherm describing monolayer coverage of adsorbate on a surface with uniform energy sites.

Functional groups: Specific chemical moieties (e.g. –OH, –COOH, –NH₂) on the adsorbent surface that interact with contaminants.

Specific surface area: The total surface area of a material per unit mass, determining the number of accessible adsorption sites.

References

1. Adsorption of endocrine disrupting compounds and other emerging contaminants using lignocellulosic biomass-derived porous carbons: A review. Journal of Water Process Engineering (2020).
2. Optimized production, Pb(II) adsorption and characterization of alkali modified hydrochar from sugarcane bagasse. Scientific Reports (2021).
3. A Novel Nitrogen Enriched Hydrochar Adsorbents Derived from Salix Biomass for Cr (VI) Adsorption. Scientific Reports (2018).
4. Evaluation of Adsorption Efficiency on Pb(II) Ions Removal Using Alkali-Modified Hydrochar from Paulownia Leaves. Processes (2023).
5. Low Temperature One-Pot Hydrothermal Carbonization of Corn Straw into Hydrochar for Adsorbing Cadmium (II) in Wastewater. Energies (2021).