Polysulfone-highly uniform activated carbon sphere mixed-matrix membrane intended for efficient purification of dye wastewater

In this study, membrane technology is adopted as a promising technique for dye wastewater purification. Highly uniform carbon spheres (CSs) with high surface area of 1791.5 m² g⁻¹ were synthesized through modified Stöber method using resorcinol and formaldehyde as precursors. The synthesized CSs were activated using CO₂ to produce highly uniform activated CSs (HUACSs) with negative charges as demonstrated by zeta potential measurements. Polysulfone-HUACS mixed-matrix membranes (PSf-HUACS MMMs) with different HUACS contents, i.e. 0.5, 1, 3, 5 and 7% with respect to the PSf weight, were produced through wet casting of PSf/Dimethylformamide (DMF)/HUACS dope. The potential of the produced MMMs to efficiently purify methylene blue wastewater with relatively high concentration of 200 ppm was investigated. It was demonstrated that regardless of ACS content, all MMMs exhibit enhanced water flux compared to the PSf pristine membrane by at least 80%. The enhancement in water flux increased up to 105% and 527.87% when HUACS content increased to 1% and 5%, respectively. Furthermore, using PSf-HUACS MMMs with HUACS content as low as 0.5%, methylene blue rejection efficiency of 99.9% was achieved. This high dye rejection efficiency can be explained based on the synergistic contribution of size exclusion and adsorption mechanisms involved in nanofiltration applications. The best antifouling performance with flux recovery ratio of ∼90%, was observed for MMM with HUACS content of 7% by which dye rejection efficiency of 91.13% and water flux enhancement of 209.84% was achieved. Overall, PSf membrane morphology and performance can be best engineered by adjusting HUACS content. (paper)