A novel photocatalytic self-cleaning PES nanofiltration membrane incorporating triple metal-nonmetal doped TiO2 (K-B-N-TiO2) for post treatment of biologically treated palm oil mill effluent

Biologically treated palm oil mill effluent (POME) still has a dark-brown color and contains residual organic matter. In this paper, a novel self-cleaning mixed matrix K-B-N triple doped-TiO2/PES nanofiltration membrane at three weight fractions (0.1, 0.5 and 1 wt%) was prepared by the phase inversion method. The performance of the prepared membranes was investigated in terms of permeability, fouling resistance and capability for post treatment of the biologically treated POME. The prepared membranes were characterized by contact angle measurement, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The obtained results indicated that the pure water flux of the modified membranes improved significantly by addition of K-B-N-TiO2 nanoparticles up to 0.5 wt% which could be attributed to the hydrophilic nature of the nanoparticles and induced photocatalytic ability. Also, flux recovery ratio (FRR) of the optimized membrane was increased from 48 to 95.4% relative to unfilled membrane that confirmed antifouling and self-cleaning capability of the nanocomposite. This behavior was ascribed to the photocatalytic role of the nanoparticles resulting mineralization of organic matter from surface of the modified membrane that enhanced reusability of the prepared membranes. Maximum permeation flux, dye and COD removal efficiencies were obtained about 27 kg/m2 h, 98% and 90%, respectively for treating the biologically treated POME.