Adsorption of organochlorinated pesticides: Adsorption kinetic and adsorption isotherm study

Abstract

Adsorption of organochlorine pesticides (OCPs) on 4 contrasted activated carbons (ACs) and biochars (BCs) and 5 different basic substances of soil organic matter (SOM) in aqueous media was investigated using adsorption kinetic and isotherm study. This study was performed with emphasis on relationship between adsorption capabilities and physical-chemical properties of the OCPs and above-mentioned sequestration materials (SMs). A kinetic batch study revealed that adsorption efficiency of the SMs-OCPs is time-and dose dependent. Adsorption process between different OCPs and SMs showed diverse fitting to Freundlich isotherm model (R2 ranked between 0.587 and 0.995). Interestingly, that Freundlich constants such as adsorption capacity and adsorption intensity of all SMs revealed a very similar uptake behavior for dichlorodiphenyltrichloroethane (DDT) metabolites (P < 0.0001). The principal component analysis (PCA) demonstrated that adsorption of porous SMs was driven by high carbon content and surface porosity, and adsorption of non-porous SOM-type samples was explained by richness of elemental composition and functional groups. In addition, DDT and metabolites, hexachlorocyclohexane isomers (HCHs) and chlordecone (CLD) showed a different degree of affinity and adsorption to the SMs indicating on an obvious molecular effect, which in case was explained by difference in molecular weight, stereochemistry and hydrophobicity. Generally, results of this study revealed the list of adsorbents which could be effectively applied in further investigations focused on sequestration of OCPs in environmental matrices.