Adsorption of methomyl on marine sediments

The adsorption behaviors of polar carbamate pesticide methomyl [(CH3S)(CH3)CNO(CO)NHCH3 or S-methyl-N-(methylcarbamoyloxy) thioacetimidate] on marine sediments treated by different methods were investigated. Ten hours were required for adsorption equilibrium of methomyl on sediments. The adsorption isotherms of methomyl on all sediments could be described by Freundlich equation very well. Adsorption of methomyl was completed mainly via the surface H-bond forces between function groups of organic constituents and methomyl molecules. In addition, microporosity action of clays and the van der Waals forces between clays and methomyl molecules might also play important roles in the adsorption of methomyl on sediments. Some external factors which could affect adsorption behaviors of methomyl were also investigated in the present study. Our results showed that the adsorption capacity of methomyl on the sediment decreased with increasing temperature and pH value. Moreover, the adsorption capacity of methomyl on the sediment appeared to be lower in natural seawater than in diluted seawater.