New Treatment Method for Dilute Hydrochloric Acid Using Magnesium-Aluminum Oxide

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Abstract
Magnesium-aluminum oxide (Mg-Al oxide) was shown to be superior to CO32- intercalated hydrotalcite (CO3-HT) for removing dilute hydrochloric acid. Cl- in a 0.5 M HCl solution could be quantitatively removed by adding 1.75-times the stoichiometric quantity of Mg0.70Al0.20O at 60 °C for 1 h. The solution after the reaction was weakly alkaline. This reaction could be adequately described as being first order for the HCl concentration, and the apparent activation energy was 49.3 kJ mol-1. The amount of Cl- removal per 1 g of Mg-Al oxide in the first use was 3.08 meq at a Mg/Al molar ratio of 2.0 and 2.89 meq at a ratio of 3.5.