Synthesis Of Biomimetic Materials And Their Application To The Removal Of Heavy Metals

In recent years, the treatment of heavy metals especially for low concentration of heavy metals become a hot topic. For example, both industrial wastewater and Chinese herbal medicine contain heavy metals with different content. They have affected human health directly or indirectly. Nowadays, in the developed materials for the removal of heavy metals, there exist many issues, such as high costs, poor removal effect, bad change of efficacy after separation, serious pollution in the regeneration process, and so on. So it is necessary to develop a new type of material for removing heavy metals. It should be low cost, friendly to environment and highly efficient in the aspect of removing heavy metals.Firstly, the hydroxyapatite (Ca10(PO4)6(OH)2, HAP) was prepared by chemical precipitation at pH 7⁷.5, near the condition of the fluid. It was characterized by ICP, XRD, EDS, IR, TG and SEM, and its removal capacity for Pb²⁺, Cd²⁺, Hg²⁺, Cr³⁺ and Cr₂O₇^2-, AsO₃^3- were investigated. The results showed that the shape of the synthesized HAP was similar with human bone. It has some positive effect in removing Pb²⁺, Cd²⁺ , Hg²⁺ and Cr³⁺, but no adsorption for Cr₂O₇^2- and AsO₃^3-.Then, various inorganic salts imitating bone were synthesized, simulating the elements and ions contained in the bone. The impact of temperature, pH and operating methods on the final product were investigated, and their application to the removal of heavy metals were studied. The results suggested that all kinds of imitation bone salts have a certain capacity on the removal of heavy metals. The adsorbing ability of the compound cotaining strontium and fluorinated apatite are not better than HAP. The HCO₃^--AP showed the best removal effect. It can remove 0.02mM Pb²⁺, Cd²⁺, Cr³⁺ and 1ppm Hg²⁺ thoroughly. It also works in a mixed solution of Cr₂O₇^2- and AsO₃^3-. In addition, their removal mechanism were studied preliminarily by XPS and EDS.Based on the said studies, the composite materials were prepared by coprecipitation, with chitosan and polyaspartic acid as the sugar composition and protein components of bone. The effect of experiment conditions on the sedimentation results and partical shape of the product were investigated. These conditions included solvents, crosslinkers dosage and organic components. Their removal capacity for the heavy metals were also studied. The results showed that the composite materials exhibited excellent removal performance for the heavy metal cations (Pb²⁺, Cd²⁺, Hg²⁺, Cr³⁺). They also have some adsorption for Cr₂O₇^2- and AsO₃^3-.