Adsorption of Chlorpyrifos From Pesticide Wastewater With Activated Bentonite Clay Adsorbent

Abstract

Chlorpyrifos is an organophosphate insecticide that reaches water sources for multiple reasons, and people who use water from nearby sources are exposed to chlorpyrifos. The adsorption of chlorpyrifos insecticides by using the low-cost 5% sodium bicarbonate activated bentonite was investigated at different adsorbent dose, pH, contact time, contaminant concentration and regenerative ability via batch experiment method. The raw and activated bentonite were characterized by fourier transform infrared spectrometry (FT-IR), X-Ray Diffractometer (XRD), differential thermal gravimetry (DTG), X-ray fluorescence spectrometer (XRF) and scanning electron microscopy (SEM). The results of the XRD showed that the raw bentonite is composed of montmorillonite, quartz, muscovite, hematite, feldspar and cristobalite. X-ray and FTIR data confirmed that 5% sodium bicarbonate activation affects both the octahedral and the tetrahedral sheets. The results of the analysis by X-ray fluorescence spectrometer (XRF), showed that, presence of silica, alumina, magnesium, calcium and iron as major constituents, along with traces of sodium, potassium, titanium, sulfur and phosphorus in the form of impurities. The differential thermal analysis curve confirms that the sample did not undergo phase changes and is thermally stable up to 500 ℃. High performance liquid chromatography (HPLC) was used to identify and analyze the chlorpyrifos insecticides. The activated bentonite demonstrated a 99.1% chlorpyrifos removal efficiency, a capacity of 49.3 mg/g, at an optimum condition at pH 6, 100 ml/L initial concentration, 40 minutes contact time and 2 g/L adsorbent dose and excellent reusability for four cycles. The Langmuir's isotherm model was found the best fit, with the high value 0.9894 of correlation coefficient (R2) and with the monolayer adsorption capacities 3.659 mg/g of chlorpyrifos. The amount of adsorbed at equilibrium was (Qe, cal) obtained for first and second order kinetics were (19.49 and 36.65 mg/g) respectively. The kinetic result obtained at the equilibrium of (Qe, cal) and high correlation coefficient (R2 = 0.9976) value of pseudo second order model was suggesting that more of the adsorption process might be chemical sorption. The findings outlined the potential of the newly developed AB was able to reduce chlorpyrifos in the adami tulu pesticides processing factory wastewater pond from 0.974 mg/L to 0.09 mg/L with 90.76% removal efficiencies.