Degradation of a Toxic Molecule o-Toluidine in Industrial Effluents using UV254 / PS System

The study aimed to determine the effect of UV254 activated PS on the removal of OT and its byproducts. The experimental setup consisted of six 400 mL borosilicate reactors, each fitted with a quartz insert and a commercial 11 watts low-pressure mercury lamp. The reactors were placed in a temperature-controlled water bath fixed at 20°C. The results showed significant degradation of OT and its byproducts upon exposure to UV, however only in the presence of PS. The oxidation mechanism was attributed to sulfate and hydroxyl radicals. Several initial conditions were assessed to reach optimal OT degradation, including [PS]0, [OT]0, and pHinitial. OT degradation under saline conditions was also investigated. The results indicated that OT undergoes pseudo-first order degradation kinetics under controlled conditions, with a maximum degradation extent of 90% over a period of 1 hour in a UV 254/PS system. The study also investigated the effect of pH on OT degradation, with results showing that degradation was enhanced only under neutral pH conditions. OT removal was partially inhibited in saline and strongly saline media. The transformation products of OT were not recalcitrant, as they disappeared along with OT as the treatment time was extended to 1 hour and as PS was actively present in the reaction system. The role of sulfate radicals (SRs) in the degradation process was determined by monitoring OT and its byproducts removal in UV only systems and UV254/PS spiked systems. The polymers formed as a result of the oxidative reaction between OT and SRs were visually observed by color development in the reaction mixture and later characterized by FTIR and SEM. The study's findings have significant implications for the treatment of industrial effluents containing OT. The use of UV254/PS system for OT degradation offers a promising approach for the removal of this toxic molecule and its byproducts. The results of this study can be used to inform the development of more effective treatment technologies for industrial effluents. The degradation of OT was found to be influenced by several factors, including the concentration of PS, OT, and pH. The study's results showed that the optimal conditions for OT degradation were achieved at a PS concentration of 15 mM, an OT concentration of 0.2332 mM, and a pH of 7. Under these conditions, the degradation of OT was found to be pseudo-first order, with a rate constant of 0.027 min-1. The study's findings also highlighted the importance of pH in OT degradation. The results showed that OT degradation was enhanced only under neutral pH conditions, with a maximum degradation extent of 90% achieved at a pH of 7. In contrast, OT removal was partially inhibited in saline and strongly saline media, with a maximum degradation extent of 60% achieved at a pH of 9. The transformation products of OT were found to be non-recalcitrant, as they disappeared along with OT as the treatment time was extended to 1 hour and as PS was actively present in the reaction system. The polymers formed as a result of the oxidative reaction between OT and SRs were visually observed by color development in the reaction mixture and later characterized by FTIR and SEM.