REMOVAL OF CHROMIUM (VI) AND COBALT IONS FROM AQUEOUS SOLUTION USING HYPERBRANCHED POLYETHYLENEIMINE IMPREGNATED AG-GO MIXED MATRIX MEMBRANE

Abstract

The current study looks at the synthesis and optimization of performance of polyamide nanofiltration membranes engineered with silver-graphene oxide (Ag -GO) and hyperbranched polyethyleneimine (HPEI) to selectively remove hexavalent chromium (Cr(VI)) and cobalt(II) (Co²⁺⁾ ions on aqueous media. The treatment of Ag - GO into the polyamide layer was aimed at polishing membrane surface chemistry, expanding hydrophilic regions, and controlling the electrostatic characteristics so as to increase rejection rates within pH variation. Extensive characterization involving measurement of water contact angle and zeta potential established that incorporation of nanoparticles had a great effect on the wettability of surfaces and distribution of charges, thus making interactions between ions and the membrane more responsive. The performance testing showed that the B4 with an optimized level of Ag+GO had the most favorable trade-off between the permeate flux and the selectivity, having 91 percent removal of Cr(VI) and up to 99 per cent rejection of Co 2 + at neutral pH. The latter was explained by a well-balanced system between an increase in hydrophilicity, robustness of electrostatic repulsion or attraction (depending on ion charge), and a less unfavorable pore framework. Though water flux was slightly higher on the B5 membrane, its selectivity was worse, which is related to the agglomeration of nanoparticles, and, thus, to the importance of controlled loading of nanomaterials. Taken together, the findings substantiate the fact that prudent nanoscale engineering has the potential of fundamentally transforming the functionality of membranes which is a feasible option in regard to the effective treatment of industrial effluents that might have toxic heavy metals. Not only does the study highlight the prospect of Ag -GO-modified membranes in environmental cleanup, but also provides a conceptual foundation of the next-generation nanofiltration systems that can be described as having higher adaptability, stability and separation efficiency.