Sorption of organophosphorous pesticides onto chickpea husk from aqueous solutions

The sorption efficiency of chickpea husk of black gram variety (BGH), for the removal of organophosphorous pesticides (OPPs), i.e. triazophos (TAP) and methyl parathion (MP) from aqueous media has been investigated. Optimization of operating sorption parameters, i.e. particle size, sorbent dose, agitation time, pH, initial concentration of sorbates, and temperature has been studied. The sorption data fitted well to Freundlich, Langmuir and Dubinin–Radushkevich (D–R) sorption isotherms. The maximum sorption capacities of BGH for TAP and MP were calculated to be 3.5 ± 0.45 and 10.6 ± 0.83 mmol g−1 by Freundlich, 0.0077 ± 0.021 and 0.025 ± 0.0094 mmol g−1 by Langmuir and 0.48 ± 0.037 and 0.15 ± 0.077 mmol g−1 by D–R isotherms respectively, employing 0.2 g of sorbent, at pH 6, 90 min agitation time and at 303 K. Application of first order Lagergren and Morris–Weber equations to the kinetic data yielded correlation coefficients, close to unity and showed partial intra-particle diffusion. The negative values of thermodynamic parameters, i.e. ΔH (kJ mol−1), ΔS (J mol−1 K−1) and ΔG (kJ mol−1) indicate the exothermic and spontaneous nature of the sorption process. The sorbed pesticides were recovered by sonication with methanol, making the regeneration and reutilization of the sorbents promising. The investigated sorbent exhibited potential applications in water decontamination, treatments of industrial and agricultural waste waters and thus productively demonstrated viable use of agricultural waste material.