Low cost sorbents for the removal of methyl parathion pesticide from aqueous solutions

Sorptive potential of selected agricultural waste materials i.e. rice (Oryza sativa) bran (RB), bagasse fly ash (BFA) of sugarcane (Saccharum officinarum), Moringa oleifera pods (MOP) and rice husk (RH) for the removal of methyl parathion pesticide (MP) from surface and ground waters has been investigated. Optimization of operating parameters of sorption process, i.e. sorbent dose, agitation time, pH, initial concentration of sorbate, and temperature have been studied. The sorption data fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms. The maximum capacities of RB, BFA, MOP and RH for MP were calculated to be 3.6 ± 0.8, 5.3 ± 1.4, 5.2 ± 1.5 and 4.7 ± 1.0 mmol g−1 by Freundlich, 0.39 ± 0.009, 0.39 ± 0.005, 0.36 ± 0.004 and 0.35 ± 0.008 mmol g−1 by Langmuir and 0.9 ± 0.08, 1.0 ± 0.10, 1.0 ± 0.10 and 0.9 ± 0.07 mmol g−1 by D-R isotherms respectively, employing 0.1 g of each 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. Thermodynamic parameters of sorption process, i.e. ΔH, ΔS and ΔG were computed and their negative values indicated the exothermic and spontaneous nature of sorption process. The pesticide may be stripped by sonication with methanol, making the regeneration and reutilization of sorbents promising. The sorbents investigated exhibited their potential applications in water decontamination, treatment of industrial and agricultural waste waters.