Green approach for the synthesis of ultrafiltration photocatalytic membrane for tannery wastewater: modeling and optimization

Abstract

A novel polyvinylidene fluoride/titanium dioxide solar active photocatalytic membrane with excellent rejection and reduction ability was prepared by phase inversion technique. The ex situ formed titanium dioxide nanoparticles using extract of Cajanus cajan of average size 10.5 nm were immobilized in the polymer matrix to enhance the performance of polyvinylidene fluoride membrane. This paper explores the innovation of synthesizing a cost-effective bifunctional membrane to eliminate toxic heavy metal: hexavalent chromium from wastewater using a synergistic approach of separation to reject hexavalent chromium and further reducing the toxicity by photocatalytic reduction of concentrated hexavalent chromium. The purpose of this work is to optimize the process condition that governs the process, namely pH, transmembrane pressure (Pa) and chromium concentration (mg/l), to maximize the rejection and reduction percentage using the same material. A quite high value of 97.59% rejection and 91.733% reduction values were suggested by response surface methodology at the predicted value of parameters: pH 5.55, 3.608 × 10⁵ Pa and at 26.652 mg/l. Real industry was also treated and could achieve > 90% rejection and > 85% reduction of Cr.