Interactions Of Sulfamethazine With Selected Heavy Metals And The Influence On Cd(?) Sorption Onto Goethite

Antibiotics are widely used in humans as medicine or in livestock as means of enhancing production recently.However,more than 80% of these compounds are discharged into the environment as active parent compounds or their metabolites.Thus,Soil would be contaminated through irrigation by sewage manure.Besides antibiotics,other pollutants also coexist in the environment,such as heavy metals.Many antibiotics possess strong capability to form complexes with inorganic ions,the presence of these chemicals could facilitate leaching and transport of inorganic pollutants in aquatic systems.In this study,sulfamethazine?SMT?was chosen because of the high concentration in polluted soils,and common metal ions(Cd²⁺ and Pb²⁺)were chosen as target pollutants,goethite was chosen as a representative of typical mineral in soil to investigate the complexation ability of SMT with metal and the influence of SMT on the sorption of cadmium on goethite.Through the research we found that:1.SMT could complex with Cd and Pb.The complexation constant at neutral environment revealed higher than acid environment.The covalent bond was the dominant mechanism at neutral environment,the complexation site was at the N of pyrimidine ring and the attached –NH-.The cation-? interaction was the dominate interaction at acid environment.2.The sorption of SMT on goethite was linear,FTIR revealed that SMT was absorbed by surface complex interaction.While the sorption of Cd²⁺ was nonlinear,solution p H is one of the most important factors affecting Cd²⁺ adsorption,while ionic strength has little effect on the sorption.Indicating Cd²⁺ was absorbed by inner sphere complexation and ion exchange interaction.3.The existence of SMT would decrease the positive charge of goethite and complex with Cd²⁺,thus promoting the of sorption capacity of Cd²⁺ on goethite.The synergic adsorption of co-contaminants should be considered to assess the risk of antibiotic drugs and heavy metal pollution in the environment.