Effect of nano-TiO₂ loading in polysulfone membranes on the removal of pollutant following natural-rubber wastewater treatment

The natural-rubber processing industry produces large amounts of wastewater. The treatment of this wastewater to produce clean water has potential as an alternative source of process water for natural-rubber production. In this study, we modified a polymeric membrane by nanoparticle blending to enhance its mechanical and separation properties. In this study, we processed natural-rubber wastewater using polysulfone membranes doped with nano-TiO₂ particles. SEM characterization shows that the nano-TiO₂ loading caused enlargement of the finger-like micro-voids in the membrane sublayer and localization of the TiO₂ nanoparticles at the membrane surface. The addition of nano-TiO₂ also improved the hydrophilicity by reducing the water contact angle from 61.83 to 41.67° and the mechanical strength of the membrane from 4.1–7.2 MPa. However, at higher nano-TiO₂ loadings (>1.5 wt.%), the tensile strength and hydrophilicity both decreased slightly. Due to its greater porosity and pore size, the highest PWF (4.65 L.m⁻² h^-1) was achieved using a membrane with 2.0-wt.% TiO₂. The best pollutant removal efficiency was exhibited by the PSf-TiO₂ 1.0-wt.% membrane with TDS, COD, NH₃, and turbidity rejections of 14.03 %, 87.88 %, 88.79 %, and 99 %, respectively. Due to the improved hydrophilicity of the 0.5-wt.% TiO₂ loading membrane, it achieved the lowest reversible fouling resistance R_rf (6.90 × 10¹⁵ m^–1) for natural-rubber wastewater treatment. The developed membranes have the potential for application in industrial rubber wastewater treatment to produce clean water for reuse.