Optimising the parameters affecting degradation of Cypermethrin in an aqueous solution using TiO2/H2O2 mediated UV photocatalysis: RSM-BBD, kinetics, isotherms and reusability

Abstract

ABSTRACT TiO2/H2O2 mediated UV photocatalysis was studied for estimating the degradation of cypermethrin in a synthetic aqueous solution. All the experiments were performed in a laboratory scale photo-reactor under UV-A (~365 nm) irradiation. Optimisation of the process parameters was done to achieve maximum degradation of cypermethrin. The process parameters chosen for this investigation were concentration of TiO2 (0.5 to 2 g/L), concentration of H2O2 (50 to 350 mg/L) and initial pH of the reaction mixture (2 to 10). A three-level Box-behnken factorial design (BBD) in combination with Response Surface Methodology (RSM) was adopted to perform the optimisation process. Further, thermal treatment method was adopted to regenerate the TiO2 particles and their reusability was assessed. The findings of this analysis revealed that after 3 h of reaction time and at optimised conditions (i.e., concentration of TiO2 = 0.65 g/L; concentration of H2O2 = 179 mg/L and pH = 3.9), 48.30% of cypermethrin was degraded and subsequent biodegradability index, of the reaction mixture, improved from 0.55 to 0.3. Also, it was estimated that the adsorption and photocatalytic degradation processes followed Langmuir isotherm and first-order kinetics, respectively. The TiO2 particles were observed to be reusable as, after five cycles only 12.6% reduction was observed in its degradation efficiency. The findings of this study may prove beneficial for treating the pesticides’-contaminated water bodies, in the tropical countries, where sunlight is intense and pesticides are continuously entering into the water bodies from nearby agricultural fields.