Methomyl removal from synthetic water using natural and modified bentonite clays

Abstract

Abstract The removal of methomyl from synthetic aqueous solutions by using Ecuadorian bentonite clays was studied. A natural clay was purified (P-C) and modified by three methods: thermal activation at 200°C for 2 h, acid activation with a 3N sulfuric acid solution for 1 h, and saline activation with hexadecyltrimethyl ammonium bromide (HDTMA) for 12 h. Clays were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and the BET method. The removal was performed with the natural and modified bentonites considering three particle size ranges and three operating temperatures (20, 30 and 40°C). For this purpose, 0.5 g of clay were added to 50 mL of a 100 µg L−1 synthetic methomyl wastewater. Pesticide removal was quantified using ultraperformance liquid chromatography - tandem mass spectrometry. It was found that the adsorption process can be relatively efficient, particularly with thermally activated clays being used at 40°C. In this case, removal efficiencies between 66 and 76% were achieved. The highest efficiency was observed for a relatively large particle size (106-150 µm). The adsorption curves obtained were fitted to the Langmuir model. The analysis of variance for the removal of methomyl showed a significant effect for the temperature x clay x particle size interaction with a confidence level of 95% (p = 0.004).