Advancing wastewater treatment from cadmium contamination via functionalized graphene nanosheets

A Khalajiolyaie and CY Jian, JOURNAL OF WATER PROCESS ENGINEERING, 63, 105491 (2024).

DOI: 10.1016/j.jwpe.2024.105491

The study investigates using graphene nanosheets to remove cadmium from water with machine learning and molecular simulation. Customized graphene pores, modified with hydrogen or hydroxyl groups, selectively filter heavy metal ions from contaminated water, improving purification. Machine learning shows the heavy metal to water ratio governs ion distribution and clustering. Moreover, we applied external pressure to augment the efficiency of the removal process. The study reveals that the clustering of Cd2+ in water depends on the water-toion ratio, with notable clustering observed in a system with 1700 water molecules, while increased water content in systems with 8500 and 17,000 water molecules diminishes clustering due to enhanced solvation, dilution, and increased entropy. Furthermore, potential of mean force (PMF) difference analysis reveals a pressure-dependent interplay between functional groups and effective pore radius. At lower pressures, functional groups, particularly OH-, significantly influence water molecule interactions with the membrane. However, at higher pressures, the positive PMF difference indicates that effective pore radius becomes dominant, reducing energy barriers and facilitating water molecule passage through the membrane. This provides nuanced insights into the pressuredependent mechanisms governing water transport across membranes. Through comprehensive assessments encompassing water permeability, heavy metal rejection rate, radial distribution function, and potential of mean force of water molecules, we evaluated the performance of the functionalized graphene membrane with varying pore sizes and under diverse applied pressures. Our findings demonstrated that the optimization of applied pressure, pore size, and functional group type substantially enhances the efficacy of the graphene membrane in separating heavy metals.

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