Mg–Al layered double hydroxide intercalated with CO3 2− (CO3•Mg–Al LDH) was investigated for treating HCl gas generated from industrial plants. Specifically, we compared the performance of CO3•Mg–Al LDH and highly reactive Ca(OH)2, and they showed approximately the same HCl removal capacity in conventional methods. For HCl gas (300 ppm, linear velocity 1.0 m/min) at 170 °C, the removals by CO3•Mg–Al LDH at Mg/Al = 2.0 and 4.0 were 93.5% and 93.1% after 90 min, respectively, while that by Ca(OH)2 was 93.3%. This indicates that CO3•Mg–Al LDH could be used in place of slaked lime to treat HCl. After the reaction, the CO3•Mg–Al LDH could be regenerated from Cl•Mg–Al LDH in a CO3 2− anion exchange reaction. Finally, we studied the cyclic use of CO3•Mg–Al LDH by combining HCl treatment with regeneration in Na2CO3 solution. At least 3 adsorption-desorption cycles could be carried out for CO3•Mg–Al LDH at Mg/Al = 2.0 and 4.0, with the final performance being 86% and 94% of the initial value, respectively.
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