Treatment of HCl gas by cyclic use of Mg-Al layered double hydroxide intercalated with CO32-

Mg-Al layered double hydroxide intercalated with CO32- (CO3 center dot Mg-Al LDH) was investigated for treating HCl gas generated from industrial plants. Specifically, we compared the performance of CO3 center dot 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 degrees C, the removals by CO3 center dot 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 center dot Mg-Al LDH could be used in place of slaked lime to treat HCl. After the reaction, the CO3 center dot Mg-Al LDH could be regenerated from Cl center dot Mg-Al LDH in a CO32-- anion exchange reaction. Finally, we studied the cyclic use of CO3 center dot Mg-Al LDH by combining HCl treatment with regeneration in Na2CO3 solution. At least 3 adsorption-desorption cycles could be carried out for CO3 center dot Mg-Al LDH at Mg/Al = 2.0 and 4.0, with the final performance being 86% and 94% of the initial value, respectively.