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A green route to synthesize layered double hydroxides



This article demonstrates a green route for synthesis of Ca-doped [Mg3Al(OH)8]Cl from a reaction of AlCl3·6H2O, Mg(OH)2, Ca(OH)2, and NH3·H2O in water, which produces only the desired solid product and a by-product NH4Cl in the mother solution; therefore, they can be separated easily by filtration or centrifugation. Being carefully designed, enough NH4Cl can be crystallized from the mother solution, which could be used as a fertilizer; while the distilled water be used to wash the products for the last time; the mother solution that still contains some NH4Cl and filtrate from the first time washing of the product can be used to prepare the LDH again. By using cheaper Mg(OH)2 and Ca(OH)2 instead of MgCl2·6H2O and CaCl2·2H2O, the process is more economic and produces less NH4Cl. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 234–239, 2015