Removal of some commercial pesticides containing α-Cypermethrin, Deltamethrin and Mancozeb as active ingredients by chitosan solution

Abstract

Removal of some commercial pyrethroid (F and Dc) and dithiocarbamate (Dt) pesticides from model wastewaters by chitosan was investigated by UV–Vis spectroscopy in dependence on some external parameters, namely polycation dose, pH and pesticide concentration. The active ingredients for the pesticides under investigation are α-Cypermethrin for F, Deltamethrin for Dc and Mancozeb for Dt. The results show similar values for the maximum removal efficiency (around 90 %), irrespective of the pesticide type. Slightly higher optimum chitosan doses (doseop, mg L−1) were found for higher pesticides concentrations (%v/v), namely 1.4–2.8 for c = 0.04 against 1 for c = 0.01 in case of F, 1.3–1.6 for c = 0.04 against 0.6 for c = 0.01 in case of Dc and 2.8–3.4 for c (%w/w) = 0.02 against 2–2.2 for c = 0.01 in case of Dt. The pH increase of pesticide emulsion F from 4.4 to 8 has also led to the optimum polycation dose increase (from around 1.2 to 2). The supernatant zeta potential dependence on the chitosan dose and particle aggregates size measurements at optimum polycation dose plead for the charge neutralization as the dominant mechanism for the flocculation of pesticide particles. The flocculation efficiency of chitosan solution for mixtures of pyrethroid pesticides of different composition has been also evaluated.