This technology is a method for the fractional production of metal carbonates. It involves the staged addition of pH adjusters to industrial wastewater containing mixed metal ions to sequentially precipitate and recover magnesium hydroxide and calcium hydroxide, which are then reacted with an aqueous amine-based absorbent solution that has captured carbon dioxide to obtain calcium carbonate and magnesium carbonate separately.
Existing wet-absorption-based CCS processes designed to reduce CO2 from fossil fuel use face limitations: the desorption stage, where CO2 is stripped from the absorbent, consumes 70–80% of total operating energy, and many countries lack sufficient storage space for captured CO2. Methods that convert CO2 into organic chemicals have also struggled with commercialization due to high energy requirements or the need for expensive catalysts.
This technology is configured to filter out magnesium hydroxide at pH 7.0–10.0 in the first stage and calcium hydroxide at pH 11.0–13.0 in the second stage, then react them with CO2 saturated in an amine-based absorbent, such as monoethanolamine, to produce carbonates. After removing calcium and magnesium, the remaining wastewater can also be reacted with the same absorbent solution to produce additional sodium bicarbonate. It can be applied to seawater desalination brine, desulfurization wastewater from steel mills and power plants, carbon capture facilities in the cement and lime industries, and the production of calcium carbonate filler raw materials. This allows for the fixation of captured CO2 into marketable minerals without desorption energy, while simultaneously recycling metals from wastewater without separate separation processes.
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