Heavy Metal Ion Absorption Materials And Their Application Research

At present, commonly used methods to remove heavy metals in water are as follows: Ferrite method, ion exchanging method, biology flocculation and so on. All this methods could wipe off the heavy metal in water, but they cost too much and can make second water pollution. In resent years, hydrotalcite and modified silica gel as new absorption materials become a research hotspot in environmental science because of its lower cost and less pollution to the environment.Hydrotalcite-like compounds is a sort of anionic clays with double-layer structure. It is layered mixed hydroxides containing exchangeable anions. The anionic clays were found application in agriculture, industry, medicine and other field. The characters and effects on using of hydrotalcite are closely related to its composition, crystal structure and synthesis methods. The study of the hydrotalcite synthesis conditions can guide the applications of HTLCs. It has large specific surface area, and the calcinations ones have unique memory effect. It can remake the structure of hydrotalcite. During the whole process, the ions come into this structure. Thus hydrotalcite and its calcination one become an extremely valuable adsorbent.In this paper, we synthesize Mg₃Al-CO₃^2- hydrotalcite and compound metal oxide layer. XRD, TEM, TG-DSC, FT-IR, BET and TPD are used to characterize the structure and physicochemical properties of the samples. Hydrotalcite and its calcination can both remove the Pb²⁺ and Ni²⁺. While the calcinations possess larger surface area and can release a lot of hydroxyl ions, it absorbs more.Thiol-functionalized silica has been prepared by cheaper chloropropyl trichlorosilane and NaSH successfully instead of expensive mercaptosilylating agent. The silica-SH and its precursor are characterized by BET, FT-IR, TOC and element analysis. Surface coverage density of silica-chloropropyl and silica-SH is 2.5mmol/g and1.56mmol/g, respectively. The silica-SH is used as sorbent to fix heavy metal ions, and the saturated adsorption capacity for Hg²⁺,Pd²⁺,Au³⁺ were 47mg/L,87mg/g,120mg/g respectively, so it is an excellence material for fixation of mercury from wastewater and waste solid. It is proved that the Sulfhydryl silica gel cost less and has high efficiency in absorbing the heavy metal. It can be used as heavy metal remover in the environmental emergency event.