Effects Of Low Molecular Organic Acids On Immobilazition Of Soil Heavy Metals By Apatites

Low molecular organic acids (LMOAs) are commonly present and become an important factor in affecting transformation and transfer of heavy metals in environment. Batch and leach experiments were conducted to investigate desorption of heavy metals in soils by LMOAs. Additionally, the effects of LMOAs on immobilization of heavy metals in water and soil by four types of apatite (USP, TNP, HBP, KYP) was also studied by using simulated experiment. The main results were summarized as following:1.In batch experiment, Pb, Cd, Cu and Zn in the soil were partly dissolved by four LMOA solutions under different concentrations . The desorption sequence of each LMOA for different heavy metals were in the order of citric > tratric succinic > oxalic (for Pb and Cd), citric > oxalic > tratric succinic (for Cu), tratric > citric succinic > oxalic (for Zn). The concentration of heavy metals in solution were inhanced with the increasing of LMOAs density and the decreasing of pH..2.The behavior of desorption of heavy metals in leach experiment was similar to batch experiment. Results of sequential extration procedure showed that heavy metals dissolved by LMOAs mainly came from water soluble, exchangeable and carbonate fractions. The chemical fractions made effects on the desorption procedure, the varition tendency of desorption curve was fast-slow. Desorptin was restrained when HPO42- be added into solution.3.Immobilization of Pb from aqueous solution by apatites could be inhibited by adding of LMOAs, and the effects sequence of four LMOAs was in the order of citric > tratric > succinic, restrain of oxalic was not showed. The immobilization sequence of four apatites was in the order of TNP > USP > KYP > HBP.4.Immobilization of heavy metals from soil by apatites was inhibited for the adding of LMOAs, and the ability of restrain was related to desorption efficiency of each LMOA. The amount of Pb, Cd, Cu and Zn in solution were obviously increased with increasing of concentration of LMOAs. TNP was priority to USP on the ability of immobilization for Pb , but degree of effects by LMOAs on immobilization of heavy metals using TNP was little than USP.Author: Pan Jie (Environmental Science and Engineering)Directed by: Professor Zeng Qingru...