Wastes and Effluents Containing Calcium; Turning Environmental Challenges into Opportunities

In this lecture, the industries that produce wastes or effluents containing calcium are briefly introduced. These industries include steel industry, construction industry (construction waste), gas purification industry (gas desulfurization), phosphoric acid production industry, paper industry and soda ash industry. Although calcium wastes and effluents are not highly toxic, their high volume that accumulates as waste in nature is worrying. In recent years, due to the increase in carbon dioxide gas in the atmosphere, which has led to global warming; the issue of fixing carbon dioxide is at the top of the list of environmental challenges. In this regard, a lot of research has been done to use wastes and effluents containing calcium to stabilize carbon dioxide. Undoubtedly, the best solution proposed by the researchers is to inject excess carbon dioxide gas into calcium-containing wastewater and producing precipitate calcium carbonate (PCC) as a product. In fact, in this process, three goals are acheived. First, stabilization of excess carbon dioxide gas as a solid mineral. Second, the removal of calcium from the wastewater, which allows the reuse of the brine wastewater in the Solvay process and saves water, energy, and raw materials. The third, is the production of a valuable product called precipitated calcium carbonate or precipitated lime (PCC). Although this product is cheap, it is used in high volume as a filler in paper, plastic, glue, paint, and resin industries, and it reduces the price of finished products. With this method and by stabilizing carbon dioxide using calcium-containing wastewater, it can be claimed that environmental challenges can be turned into opportunities.