Polymer-Enhanced Membrane Filtration for Heavy Metal Removal

Polymer-enhanced membrane filtration is an emerging approach for selective removal of heavy metal ions from aqueous streams. In this process, functional polymers are introduced into the feed solution to form complexes or aggregates with target metal cations. The polymer–metal assemblies are then retained by pressure-driven membranes such as ultrafiltration, nanofiltration or reverse osmosis, effecting high rejection rates under mild operating conditions. Compared with conventional treatments—precipitation, ion exchange or adsorption—polymer-enhanced systems combine chelation, size exclusion and electrostatic repulsion in a single stage, allowing fine tuning of removal efficiency via polymer chemistry, membrane pore architecture and process parameters such as pH and ionic strength. Commonly employed polymers include polyacrylonitrile derivatives, chelating biopolymers such as chitosan and functionalised polyacrylates, which can be crosslinked or grafted onto membrane surfaces to enhance fouling resistance and selectivity. This hybrid strategy offers low energy consumption, minimal secondary waste and adaptability to diverse heavy metals including chromium, cadmium, lead and nickel. Industrial effluent treatment, potable water purification and recovery of valuable metals represent key applications, with ongoing efforts directed at scale-up, membrane longevity and environmental compatibility.

Research from Nature Portfolio

Recent studies have demonstrated the potential of hydrolysed polyacrylonitrile ultrafiltration membranes to remove chromium oxyanions from drinking water sources. By exploiting Donnan exclusion rather than size sieving, these membranes achieved over 90% rejection of chromate ions at neutral to alkaline pH, while retaining high permeate flux. Detailed transport modelling using a steric-partitioning pore and dielectric exclusion framework enabled optimisation of operating pressure and cross-flow velocity, identifying concentration polarisation as a limiting factor at elevated feed concentrations. These fundamental insights into polymer-membrane interactions and ion transport have informed design principles for next-generation heavy metal removal membranes.

Polymer-Enhanced Membrane Filtration for Heavy Metal Removal publication trend

The graph below shows the total number of articles in polymer-enhanced membrane filtration for heavy metal removal across all publications each year (not limited to Nature Index journals).

Technical terms

Polymer-Enhanced Ultrafiltration (PEUF): A technique wherein water-soluble polymers bind metal ions and the resulting complexes are retained by ultrafiltration membranes.

Donnan Exclusion Principle: Electrostatic repulsion of charged ions by a membrane bearing fixed charges, leading to selective ion rejection.

Concentration Polarisation: Localised accumulation of rejected solutes near the membrane surface, reducing permeate flux and efficiency.

Permeate Flux: Volume of fluid passing through a membrane per unit area per unit time, often expressed in L h⁻¹ m⁻².

Rejection Rate: Percentage of target solute retained by the membrane, calculated from feed and permeate concentrations.

References

1. Water-Soluble and Insoluble Polymers, Nanoparticles, Nanocomposites and Hybrids With Ability to Remove Hazardous Inorganic Pollutants in Water. Frontiers in Chemistry (2018).
2. Ultrafiltration membrane for effective removal of chromium ions from potable water. Scientific Reports (2017).
3. A Review on Promising Membrane Technology Approaches for Heavy Metal Removal from Water and Wastewater to Solve Water Crisis. Water (2021).
4. Pressure-Driven Membrane Process: A Review of Advanced Technique for Heavy Metals Remediation. Processes (2021).
5. Micellar-Enhanced Ultrafiltration to Remove Nickel Ions: A Response Surface Method and Artificial Neural Network Optimization. Water (2020).