Adsorption study of low-cost and locally available organic substances and a soil to remove pesticides from aqueous solutions

- The adsorption/desorption behavior of four pesticides onto three unmodified organic residues and a soil was studied.
- The pseudo-second-order kinetic model was suitable in all cases.
- The sorption capacity increased with the hydrophobic character of the pesticides.
- Sorption capacity was high but weak, and it was inversely related with desorption.

SummarySorption and desorption of chlorfenvinphos, chlorpyrifos, simazine and trifluralin on sunflower seed shells, rice husk, composted sewage sludge and an agricultural soil was studied. Film diffusion and sorption pointed to be related with pesticide physicochemical characteristics. Trifluralin and chlorpyrifos were the pesticides which showed the fastest sorption kinetics and the best sorption capacities when sorbed on all organic wastes. Rice husk revealed as the best adsorbent for simazine. Chlorfenvinphos showed comparable adsorption levels for all sorbents. Koc and Kf values suggested that not only the organic matter content but also the nature of the organic matter and other factors, such as physicochemical characteristics of the surface could be play a significant role in pesticide adsorption. Low desorption percentages were detected; nevertheless Kfd and H values reveal a weak and reversible adsorption. The studied organic residues can be used as an effective and alternative adsorbent for removing pesticides, because of their high adsorption capacity, being natural and economic.