Kinetics and isotherms of dichlorodiphenyltrichloroethane (DDT) adsorption using soil–zeolite mixture

Abstract

Soil contaminated by organic pollutants such as dichlorodiphenyltrichloroethane (DDT) is an environmental concern due to the strong sorption of organochlorine pesticide onto the soil matrix and persistence in the environment. The remediation of contaminated soils with organochlorine pesticide using nanotechnology is an innovative technology for speeding up this process. This work presents a study of adsorption of DDT onto the zeolite surface. Experiments were conducted using batch adsorption procedures at different DDT concentrations, from 5 to 50 mg/L, and the amount of the zeolite used was 0.1, 0.5, 0.8, and 1.2 g. Results show that the zeolite has a moderate adsorption capacity for the DDT, and the highest adsorption capacity obtained from this study was about 30%. However, the percentage of adsorption can be increased significantly with the increase in the amount of the zeolite in samples. Also, adsorption kinetics and adsorption isotherms were applied. Five different kinetic models, i.e., pseudo-first-order kinetic model, the pseudo-second-order kinetic model, intraparticle diffusion model, Elovich kinetic model, and Bangham kinetic model were used to fit the kinetic data. The result shows that the pseudo-second-order model represented the best fits to the experiments. The adsorption isotherms were determined using three different models as well, i.e., Freundlich, Langmuir, and Temkin. The best-fitted adsorption isotherm models were found to be in both Langmuir and Freundlich. Moreover, results show that the effectiveness of treatment process is highly affected by pH. Increasing the pH has a negative effect on the adsorption process, and best uptake of DDT was noted in acidic media at pH 3.