A high-performance nanofiltration membrane synthesized by embedding amino acids and ionic liquids in cellulose acetate for heavy metal separation

Abstract

Water reclamation is necessary to meet the potable water demand. Heavy metals such as iron, zinc, lead, and copper, particularly in water, pose significant toxicity risks to humans and other biological life. Over the last few years, the contamination level of these heavy metals in water and soils has increased alarmingly. Correspondingly, membrane systems have emerged as a prominent approach to water reclamation. In this study, cellulose acetate (CA) membranes incorporating amino acids (AAs) and ionic liquids (ILs) were fabricated using phase inversion technique and effectively utilized for metal separation. The characterizations of these membranes using FTIR, SEM, TGA, and DSC revealed the presence of various functional groups, changes in surface morphologies, and improvements in thermal stabilities due to AA–IL. The pure water flux (PWF) was increased to 98 L m⁻² h⁻¹ at 4 bar pressure owing to the enhancement of hydrophilicity. The rejection percentage of heavy metal ions for AA–IL (0.5%) incorporated CA membranes was 94%. The rejection rates for ions of the heavy metals copper, zinc, iron, and lead present in the industrial effluent were studied and found to be 89%, 91%, 84%, and 90%, respectively. The rejection capacity of the AA–IL (0.5) incorporated CA membrane was the highest for all the metals. The AA–IL incorporated CA membranes are efficient and effective for nanofiltration to treat heavy metal ion solutions.