Employing UV/peroxydisulphate (PDS) activated by ferrous ion for the removal of toluene in aqueous environment: electrical consumption and kinetic study

The main purpose of this project was to explore the removal of toluene (TOL) from a typical synthetic wastewater by peroxydisulfate (PDS) activated by ferrous ion and ultra violet (UV) light. The effect of various factors such as PDS and ferrous ion concentration and pH on the removal of TOL was studied. Three-level full factorial design of experiments was employed for experimental design and statistical analysis. It was revealed that the studied variables and quadratic terms were statistically significant while the interactions were insignificant. Increasing the PDS and ferrous concentration enhanced the TOL removal efficiency, but it was decreased with increase in pH. The most significant term was ferrous ion concentration which influenced greatly on TOL removal efficiency. The optimum condition was obtained at pH of 4, ferrous ion concentration at 0.7 mM and PDS concentration of 1.5 mM. The maximum removal of TOL and COD were achieved as 97.6 and 65%, respectively, after 45 min of reaction. Besides, the kinetic study showed pseudo-first-order reaction for the removal of TOL. So, as a figure-of-merit, the ‘electrical energy per order’ was determined at 7.39 kWhm−3 order−1, showing little electrical energy intake and high economical income.