Treatment of hydrochloric acid with magnesium-aluminum oxide at ambient temperatures

Our results demonstrate that magnesium-aluminum oxide (Mg-Al oxide) can be advantageous in treating hydrochloric acid waste at temperatures between 10 and 30 °C, by acting as both a neutralizer and fixative for Cl^-. The Mg-Al oxide was prepared by the thermal decomposition of a hydrotalcite-like compound. The extent of Cl^- removal by Mg-Al oxide increased with increases of temperature, oxide quantity and Mg/Al molar ratio. The initial pH had little effect on Cl^- removal; the pH increased rapidly from the start of the reaction and attained a nearly constant value. The reaction involved in Cl^- removal from HCl by Mg-Al oxide proceeded under surface chemical reaction control, with apparent activation energy of 65.6 kJ mol^-1.