Investigation of Naphthalene Removal from Aqueous Solutions in an Integrated Slurry Photocatalytic Membrane Reactor: Effect of Operating Parameters, Identification of Intermediates, and Response Surface Approach

A laboratory scale indigenous integrated slurry photocatalytic membrane reactor (PMR), coupling TiO₂/UV-C photocatalysis and ultrafiltration (UF) membrane process was evaluated for the removal of naphthalene (NAP)—one of the low molecular weight polycyclic aromatic hydrocarbons (PAHs), frequently detected in municipal and industrial wastewaters. The different operational parameters such as initial NAP concentration (5–25 mg/L), catalyst dosage (0.1–0.9 g/L), and feed solution pH (3–9) were investigated for NAP and total organic carbon (TOC) removal. The experimental results obtained from the batch study of the integrated process showed 92.8% and 90.2% of NAP and TOC removals while the individual processes; UV-TiO₂ (76.8% NAP and 56.4% TOC removals) and UF membrane separation process (49.1% NAP removal) exhibited low removal rates for the same experimental conditions. The NAP and TOC removals obtained during continuous flow studies were 93.1% and 91.4% at 180 min and thereafter remained constant up to 560 min of reactor running time. This study also includes the identification of intermediates that are formed after 30 min of operation of PMR. The photocatalytic degradation of NAP followed pseudo-first-order kinetics and the obtained experimental data were analyzed with response surface methodology (RSM) using design expert software.