Oil palm residue-based cellulose acetate membranes enhanced with zinc oxide and n-methyl pyrrolidinone for batik wastewater treatment

As the world's top producers of oil palm (Elaeis guineensis), Indonesia and Malaysia are urged to propose a value-added valorization of its lignocellulosic biomass, oil palm empty fruit bunches (OPEFB). Meanwhile, the nations' signature 'batik' textile industries are in dire need of optimum remediation treatments of their wastewater high in harmful dyes and chemicals. Organic-inorganic hybrid systems of mixed matrix membranes (MMMs) for heavy metals removal were prepared using OPEFB-based cellulose acetate (CA) and zinc oxide (ZnO; 0.5, 0.75, 1%, w/v) in N-methyl pyrrolidinone (NMP; 89, 90, 91%, v/v). The high crystallinity (62.42%) and fibrils' web-like structure of OPEFB-CA were confirmed. Microscopic observation of OPEFB CA-NMP-ZnO membranes evidenced the porous yet smooth surface due to the use of plasticizing NMP, as well as uniform dispersion of ZnO particles. MMM 2 (0.75%ZnO; 90%NMP) was the best-performing membrane mechanically with excellent tensile strength (1.78 MPa), Young's modulus (0.13 GPa), and elongation-at-break (2.59%), while thermal stability (T_d,5%, 291 °C) improvement was also highlighted. Pores characteristics on size, volume, and surface area were discussed, too. Remediation performance was excellent even at high (20%) effluent concentration reaching 28% and 65% removal of Cu and Pb, respectively, by MMM 1 (0.5%ZnO; 89%NMP). These findings confirmed the promising prospect of the developed membranes as a wastewater remediation treatment, including in textile industries.