Effect of synthesis method on selective adsorption of thiosulfate by calcined MgAl-layered double hydroxides

• Calcined MgAl-LDHs could separate S2O32- from mixed SCN− by selective adsorption.
• The synthesis method of calcined MgAl-LDHs influenced their adsorption performance.
• Calcined MgAl-LDH obtained using urea decomposition method presented the better adsorption selectivity for S2O32-.
• Different adsorption behaviors over the two calcined MgAl-LDH were studied.

Calcined MgAl-layered double hydroxides (CLDH-U) derived from layered double hydroxide (LDH) precursors synthesized by urea decomposition, had the higher adsorption selectivity for thiosulfate (S2O32-) in aqueous solutions mixed with thiocyanate (SCN−) than the counterpart (CLDH-C) obtained by co-precipitation method. The adsorption rates for S2O32- over CLDH-U with diameter in 2 μm and CLDH-C with diameter in 50 nm were respectively about 98.00% and 94.80%, and those for SCN− were only about 0% and 6.84%. The results revealed that the selective adsorption was realized over these CLDH materials and the synthesis method influenced the adsorption behavior. The reason for the better selectivity over CLDH-U could be probably related to these mini sheets growing perpendicularly to the lamellate surface, which completely differed to the adsorption process over the small-sized counterpart. The different adsorption mechanisms of two CLDH materials were respectively proposed.