Adsorption kinetics and degradation mechanism study of water persistent insecticide quinalphos: for heterogeneous photocatalysis onto TiO2

Abstract

AbstractThe kinetics of adsorption and photodecomposition of the water polluting insecticide quinalphos (QP), in aqueous suspensions of TiO2 were evaluated under laboratory conditions. Langmuir and Freundlich models were applied to describe the adsorption process and the model proposed by Langmuir–Hinshelwood was used to illustrate the kinetics of the photodecomposition reactions of QP. The adsorption capacity of TiO2 observed to increase from 7.86 to 20.04 mg g−1 with the increase in initial QP concentration from 5 to 25 mg L−1, respectively. About 45.8% adsorption of 20 mg L−1 QP was observed in just 60 min at pH 6 with 5 g L−1 TiO2 loading and 25 ± 1°C temperature. TiO2 was found to have a maximum adsorption capacity of 23.7 mg g−1 for QP. Photocatalytic treatment of 200-mL solution (20 mg L−1) under least harmful UV-A radiations (365 nm/30 W m−2) with 0.5 g L−1 TiO2 loading gives nearly 89.67% degradation in 3 h. The photodecomposition rate of QP was significantly higher at slightly acidic conditions ...