Health hazardous heavy metals separation from water resources using a modified polysulfone (PSf) membrane by covalent organic framework-polyamidoamine dendrimer as a novel nanocomposite

Abstract

In this study, a novel COF/CS@PAMAM (CCD) dendrimer nanocomposite was synthesized and applied as a functional additive to enhance the performance of polysulfone (PSf) membranes. The CCD nanocomposite was prepared via a stepwise method, starting with covalent organic framework (COF) nanoparticles, followed by chitosan coating and PAMAM dendrimer grafting. FTIR, SEM, and EDS analyses confirmed the successful formation of CCD, revealing characteristic shifts in N–H functional groups, morphological evolution from spherical COF to tree-like CCD structures, and increased nitrogen content, indicating abundant hydrophilic amine groups. The CCD nanocomposite was incorporated into PSf membranes using the non-solvent induced phase separation (NIPS) technique. Membrane characterization demonstrated enhanced porosity, enlarged finger-like structures, reduced thickness, smoother surfaces, and increased hydrophilicity. Among various loadings, 0.50 wt.% CCD yielded the optimum membrane, exhibiting the highest water flux of 275.3 LMH (255% enhancement over bare PSf) while maintaining high BSA rejection (≈99%). Also, the modified membrane displayed superior antifouling performance and reduced total fouling resistance properties due to presence of the CCD nanocomposite. In addition, 0.50 CCD membranes achieved excellent removal efficiencies for heavy metals, including Hg²⁺ (99.3%), Pb²⁺ (98.6%), Th³⁺ (97.6%), As³⁺ (96.7%), Cr³⁺ (96.1%), and Ni²⁺ (95.6%), significantly higher than those of unmodified PSf membranes. The enhanced rejection of organic dyes and antibiotics was also observed, driven by electrostatic repulsion, hydrophobic/hydrophilic interactions, and specific binding of contaminants to functional groups in CCD. Comparison with the literature highlighted the effectiveness of amine-functionalized nanocomposites in improving membrane performance. Overall, this study demonstrates that incorporating CCD nanocomposites is a highly effective strategy for enhancing membrane performance, providing a versatile platform for next-generation water and wastewater treatment applications. The optimum 0.50 wt.% CCD dosage successfully balances permeability, selectivity, antifouling, and contaminant removal.