Adsorption behaviour of methyl parathion on synthetic goethite

Methyl parathion (MP), a typical organophosphorus pesticide widely used in agriculture, can cause a variety of late onset multiple neuropathy and permanent damage to nerve cells with irreversibility. Therefore, the study on... [ view full abstract ]

Methyl parathion (MP), a typical organophosphorus pesticide widely used in agriculture, can cause a variety of late onset multiple neuropathy and permanent damage to nerve cells with irreversibility. Therefore, the study on its environmental fate and transport has aroused extensive concern of researchers. The adsorption behavior of MP on synthetic goethite was investigated in our study given the ubiquity of goethite in soils and aquatic sediments. It was found that the adsorption behaviour of MP on goethite could be expressed well using pseudo-second-order kinetic models, including the fast surface diffusion process and the slow formation stage of aggregates or oxidation of by-products. The adsorption behaviour of MP on geothite was strong pH dependent and related to other adsorbents such as humus acid, montmorillonite and modified geothite with humus acid. At the same time, other factors including the initial concentration of MP, the dosage of geothite, solution ionic strength and temperature were also discussed. Not only there exist different adsorption capicity, but the desorption process of MP on modified geothite and humus acid present obvious hysteresis phenomenon than that on montmorillonite attributed to their various adsorption mechanisms of MP. According to the characterization of adsorbed geothite and the identification of by-products in solution, the adsorption mechanism of MP by geothite was also discussed.