The Sorption Behavior Of Organotin Compounds In The Soil And Black Carbon

Organotins, especially tributyltin (TBT) is one of the most toxic compounds that man has ever introduced in the environment on purpose. Therefore, TBT and other organotins represent a very high risk for the aquatic and terrestrial ecosystem. Black carbon which is produced by the combustion of fossil fuels and biomass, is found widely present in soils and sediments. Due to its high adsorptivity, black carbon sorption of pollutants has been a main subject of environmental research. In this study, the organotin sorption behavior and mechnisms on black carbon and soil were evaluated by the batch equilibrium method, the black carbon samples were derived from pyrolysis of pine. The study consists mainly of the following two parts:First, under various pH conditions, triphenyltin(TPT) sorption onto five soils with different characters was evaluated. The results showed that all sorption isotherms of TPT could be well fitting by linear equation in the five soil samples. At the same pH conditions, the sorption of TPT increased with the increase of the organic carbon content and CEC content on soils. In addition, higher sand content of the soil could also enhance the sorption strength. TPT forms presented in aqueous solution were changed with pH change, resulting in the sorption capacity of TPT in soil increased first and then decreased with increase of pH, and TPT maximum sorption occurred at pH5.27(the pKa rules). Therefore, the sorption of TPT on soil was probably a combined effect of the distribution, electrostatic interaction and physical adsorption.Second, under various pH conditions, organotins sorption onto black carbon with different characters was evaluated. The results showed that organotins forms presented in aqueous solution were changed with pH change, resulting in the sorption capacity of organotins in black carbon increased first and then decreased with increase of pH. All sorption isotherms of organotins could be well fitting by Langmuir equation in the black carbon, therefore, proposed model assumes that black carbon sorption of organotin. As TPT sorption onto soils, the sorption of organotins on black carbon was probably also a combined effect of the distribution, electrostatic interaction and physical adsorption. In addition, the competitive sorption show that the black carbon sorption of TBT was decrease with the affinity increase of the added of organtion with the black carbon, except tetrabutyltin (TeBT) and monobutyltin (MBT). In addition, the results also showed that the presence of black carbon in the soil has a significant impact for soil adsorption of organotin.