A hydrophilic and antifouling nanofiltration membrane modified by citric acid functionalized tannic acid (CA-f-TA) nanocomposite for dye removal from biologically treated baker's yeast wastewater

The aim of this study was to remove non-biodegradable colored compounds from biologically treated baker's yeast effluent using an antifouling membrane in order to facilitate reuse of the wastewater. To get this purpose, in a facile effort, a new nanofiller, citric acid functionalized tannic acid (CA-f-TA), was synthesized by employing a simple, economical and green method. The produced nanofiller was used in the fabrication of polyethersulfone (PES) nanofiltration (NF) membranes. The influence of CA-f-TA on the cross section morphology, pore size, porosity, water content, hydrophilic properties, and roughness of the modified PES/NF membrane was evaluated. The performance of the fabricated membranes was analyzed as pure water flux (PWF), antifouling and dye rejection capacity. Based on obtained results, incorporation of the CA-f-TA nanofiller resulted in an increase in the PWF from 23.5 to 23.6 and 34.4 kg m-2 h-1 for the membranes blended with CA-f-TA-1, CA-f-TA-0.5 and CA-f-TA-0.1, respectively, in contrast to 16.4 kg m-2 h-1 for the reference membrane. The antifouling characteristics of the prepared membranes dramatically raised owing to improvement in smoothness and hydrophilicity of membrane surface. The synthesized NF membrane with 1 wt% CA-f-TA nanofiller had the highest flux recovery ratio (FRR, 93.2%) and dye rejection (95.7% for Direct Red 16 (DR 16) and 97% for biologically treated baker's yeast wastewater), and the lowest irreversible fouling resistance (6.8%). Furthermore, PWF of 34 kg m-2 h-1, FRR of 97%, TSS and turbidity removal efficiencies of 100%, and COD removal efficiency of 80% were obtained using the 1 wt% CA-f-TA membrane after filtration of a field sample i.e. biologically treated baker's yeast wastewater over a 1-h filtration.