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Gold recovery from secondary resources has been an interesting topic due to its high market prices and vast industrial applications. Reductive adsorption is a new promising technique that provides a cost-effective, efficient and eco-friendly way for gold recovery. In this study, we prepared a gallic acid-functionalised Mg/Al hydrotalcite (Mg/Al HT-GA) as well as first and second refunctionalised calcined Mg/Al hydrotalcite (Mg/Al CHT-GA_1 and Mg/Al CHT-GA_2) for reductive adsorption of AuCl 4−  in aqueous solution. The as-prepared adsorbents were characterised using a Fourier transform infrared (FTIR) spectrometer, an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). Adsorption test showed that Mg/Al HT-GA, Mg/Al CHT-GA_1 and Mg/Al CHT-GA_2 were effective in adsorbing AuCl 4–  at pH 3 with adsorption capacities ( b ) according to Langmuir isotherm model were 175.43, 112.36 and 86.20 mg g –1 , respectively. Kinetics study showed that all adsorbents followed pseudo-second order with rate constant ( k p2) of 9.81 × 10 –4 , 33.17 × 10 –4  and 9.80 × 10 –4  g/(mg.min) for Mg/Al HT-GA, Mg/Al CHT-GA_1 and Mg/Al CHT-GA_2, respectively. The characterisation of the spent adsorbent by using an XRD showed that Au(0) was formed. It was revealed that phenolic – OH groups of gallic acid played a key role for the reduction mechanism of Au(III).

international journal of environmental analytical chemistry

Functionalisation of Mg/Al hydrotalcite and calcined Mg/Al hydrotalcite with gallic acid for reductive adsorption of tetrachloroaurate(III) ion in aqueous solution