β-Cyclodextrin-chitosan biocomposites for synergistic removal of imazethapyr and imazamox from soils: Fabrication, performance and mechanisms

Abstract

The present study delineates to develop and explore the possibility of using chitosan-β-cyclodextrin biocomposites as environmentally friendly decontamination agent for removal of imazethapyr and imazamox from soils. The biocomposites were synthesised using ultrasonic assisted technique and characterised by UV–Visible spectrophotometer. The quantification of imazethapyr and imazamox was done using liquid chromatography tandem mass spectrometry. The adsorption capacity for imazethapyr and imazamox ranged from 0.12 to 1.22 and 0.02 to 1.01 μg1−ng−1mLn, respectively in studied soils (p < .05) indicating strong influence of soil properties on adsorption. Desorption studies indicated that distilled water could desorb only 1.23 to 5.48 and 3.11 to 8.63% of adsorbed imazethapyr and imazamox, respectively at high concentrations (1.0 and 10 μg mL−1) whereas herbicides were not desorbed at low concentrations (0.01 and 0.1 μg mL−1). The removal of imazethapyr and imazamox from soils were carried out with β-cyclodextrin, chitosan and their biocomposites and the influence of various parameters such as type and concentration of extractant, contact time, liquid to soil ratio, temperature and sequential extraction cycle was investigated. Under optimum conditions, herbicides were successfully desorbed from studied soils using low molecular weight chitosan-β-cyclodextrin biocomposite (LCD) and removal rate varied from 59.42 to 99.44% at initial herbicide concentration of 0.01 to 10 μg mL−1. The highest removal rate of imazethapyr and imazamox was observed for inceptisol 3 followed by entisol, inceptisol 2, aridisol, inceptisol 1, vertisol and alfisol probably due to differential physico-chemical properties of soil which affected the herbicide-soil interactions. Based on these results, LCD can be regarded as effective and environmentally friendly in situ green extracting agent for remediating soils contaminated with imazethapyr and imazamox.