Chemical conversion of carbon dioxide via target metal separation using seawater-derived wastewater

This study investigated the capture of carbon dioxide (CO2) and its chemical conversion to high-purity calcium carbonate salt, which has potential uses in a range of industrial sectors. Indirect inorganic aqueous carbonation methods were used, with seawater-based industrial wastewater as the source of metal ions. The alkanolamine absorbent solutions of monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA) were used at typical industrial concentrations of 30 wt%. Calcium ions from industrial wastewater were extracted in the form of gypsum. Subsequently, a carbonation reaction afforded high-purity calcium carbonate salt. The conversion yields of 33.16% for monoethanolamine, 33.86% for diethanolamine, and 55.18% for methyldiethanolamine were achieved. Thermogravimetric analysis demonstrated the purity of the product to be 93.6, 95.2 and 92.8 wt%, respectively. X-ray diffraction and scanning electron microscopy showed the crystal structure of the products to be aragonite mixed with vaterite. Furthermore, the CO2 capture capacity of each absorbent and the amount of CO2 desorbed by the carbonation reaction were investigated. The results may support the design of carbon capture and utilization plants and potential market research.