DEVELOPMENT OF LAYERED DOUBLE HYDROXIDE MANUFACTURING PROCESS USING STEELMAKING SLAG AS RAW MATERIALS

摘要

The metal elements that are the metal source of layered double hydroxides (LDHs) are leached from steelmaking slag with HC1. LDHs that act as inorganic anion exchangers can be prepared from the slag leachate. LDHs are synthesized from the slag leachate at various pHs by a co-precipitation method. Their physical and chemical properties, including the crystal structure and chemical composition, are investigated. The behavior of the dissolution and precipitation of metal components in the leachate were researched by considering the mass balance in an LDH manufacturing process. The reaction products obtained from slag leachate include Mg-Al and Ca-Al LDHs. Mg-Al LDH is predominant at pH11 and below, whereas the mixtures of Mg-Al and Ca-Al LDHs are mainly formed at pH12 and above. The anion exchange capacity of LDH varies by type of LDH. As a result of the mass balance in the LDH manufacturing process, more than 90% of all metal elements except for Ca are contained in the product at precipitation pH10. The chemical composition of LDHs varies remarkably with the precipitation pH. In synthesizing LDHs from slag, the control of the precipitation percentage of Ca in the slag leachate by adjusting the synthesis pH is an important factor in determining the kind of produced LDH.