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.