Novel green hybrid processes for oily water photooxidation and purification from merchant ship

Abstract

Two hybrid photooxidation systems consisting of two different reactors; photocatalytic reactor-ultrafiltration (PR-UF) and photocatalytic membrane reactor (PMR) have been investigated and compared for photolysis and separation of oily water. In both, oily water was irradiated by ultraviolet (UV) light. In PR, UV irradiation was made on the TiO2 photocatalyst suspended in oily water, followed by ultrafiltration (UF) to remove TiO2 particles and hydrocarbon residues. On the other hand, TiO2 was immobilized on the halloysite nanotube (HNT) and embedded in the UF membrane in PMR. In both systems, hydrocarbon concentration, chemical oxygen demand (COD), total dissolved solid (TDS), and hydrocarbon concentration were measured at each step of photooxydation and filtration. In UF, membrane flux, reduction in solute concentration, flux decline and flux recovery by backwashing were investigated. The experimental results showed that the reduction in TOC by PR-UF was ~10% higher than PMR. On the other hand, reduction in hydrocarbon concentration, COD and TDS was higher for PMR. The TiO2 concentration in UF permeate was 8 ppm and 0.2 ppm, respectively, for PR-UF and PMR.