Research progress of chromium solidification mechanism and preparation of inorganic materials by Cr-containing solid wastes from stainless steel industry

In recent years, with the rapid development of the stainless steel industry in China, a large number of Cr-containing solid wastes are produced. Chromium resources in China are very scarce, and China mainly dependent on imported chromium. In the current situation of a limited supply of chromium ore in the world, determining the efficient utilization of chromium resources will become very important. The recovery of chromium in various solid wastes produced by the stainless steel industry has practical economic significance. In addition, an uncontrolled emission of Cr-containing solid wastes will endanger the ecological environment and hamper biological safety. Further, the large scale of China’s stainless steel industry has caused urgent environmental problems, i.e., the whole manufacturing process has produced a large number of Cr-containing solid wastes, including stainless steel slag, stainless steel dust, stainless steel rolled iron scale, and pickling sludge. The detoxification/solidification of Cr to obtain long-term safety performance is an important factor that must be considered in the development of a comprehensive utilization process technology for a large amount of Cr-containing solid wastes generated by the stainless steel industry. This paper reviewed the previous research work in this field, including the work regarding the chemical and phase compositions of the stainless steel industrial solid waste, the existing forms of chromium in different Cr-containing solid wastes, the cycle enrichment rule, and the toxicity of chromium in the environment. The evolution law of Cr-bearing mineral phases and the solidification mechanism of Cr in different mineral phases were discussed. The research progress of various inorganic materials such as cement, glass ceramics, and sintered ceramics prepared using Cr-containing solid wastes in the stainless steel industry was summarized. Bottleneck problems in the preparation of various inorganic materials from chromium-containing solid wastes in the stainless steel industry were analyzed to provide a basis for the future harmless, high-value, resource-based treatment of stainless steel Cr-containing solid wastes and the realization of industrial applications in China.