Electrically tuning low-pressure membrane surface charge for highly efficient Cr(VI) removal from drinking water

Area of Science:

• Environmental Science
• Materials Science
• Electrochemistry

Background:

• Ionic contaminants, particularly heavy metals like hexavalent chromium (Cr(VI)), pose significant risks to drinking water safety and quality.
• Conventional electrosorption and membrane separation technologies face limitations due to high energy consumption and poor selectivity.
• Developing advanced materials for selective contaminant removal is crucial for effective water treatment.

Purpose of the Study:

• To develop a low-pressure membrane with an electrically tunable surface charge for selective and efficient removal of Cr(VI) from water.
• To investigate the use of poly(vinyl ferrocene) (PVF) on an activated carbon felt (ACF) substrate for creating an electro-responsive interface.
• To demonstrate the membrane's capacity for regeneration without chemical additives.

Main Methods:

• Fabrication of an electro-responsive adsorptive membrane (PERAM) using PVF and ACF.
• Characterization of the membrane's redox properties and surface charge tunability using fluorescence spectroscopy.
• Evaluation of Cr(VI) removal efficiency, selectivity, and regeneration performance under varying electrical potentials.
• Computational analysis using density functional theory (DFT) and molecular dynamics (MD) simulations to elucidate the adsorption-desorption mechanism.

Main Results:

• The PVF-based electro-responsive adsorptive membrane (PERAM) demonstrated excellent adsorption capacity and selectivity for Cr(VI) during single-pass filtration.
• Regeneration of the membrane was successfully achieved by applying a reversed electric potential, eliminating the need for chemical additives.
• Cr(VI) levels were reduced to below 0.05 mg/L at a high flux of 424 L/m²·h.
• The membrane exhibited a high treatment capacity exceeding 5140 L/m² due to efficient activation and regeneration cycles.
• DFT and MD simulations confirmed that changes in electrostatic forces between PVF and Cr(VI) at different potentials drive the reversible adsorption-desorption process.

Conclusions:

• The developed PERAM offers a promising solution for selective and efficient removal of hexavalent chromium from water.
• The electrically tunable surface charge and facile regeneration mechanism provide a sustainable and cost-effective approach to water purification.
• This technology addresses the limitations of conventional methods, paving the way for advanced water treatment applications.