Efficient gold(III) detection, separation and recovery from urban mining waste using a facial conjugate adsorbent

Abstract

This study developed an efficient fine-tuning conjugate adsorbent for simultaneous gold (Au(III)) detection and recovery from urban mining waste. The adsorbent was prepared by indirect and dense immobilization of 6-((2-(2-hydroxy-1-naphthoyl)hydrazono)methyl) benzoic acid (HMBA) onto fine-tuned surface patterning of nanostructure inorganic silica. This adsorbent has the large surface area-to-volume ratios and uniformly shaped pores in nanostructures in its cage cavities. Therefore, the conjugate adsorbent permitted to fast and specific Au(III) ions capturing via a colorimetric naked-eye visualization based on the stable complexation [Au(III)–HMBA]n+ mechanism. The small energy gap for the complex compared with the HMBA suggested the easily excitation of electrons according to the electron transfer or energy transferred mechanism, which results in the intense color of the stable complexation mechanism. The influence of several variables such as solution acidity, initial concentrations and the addition of diverse ions for Au(III) detection and recovery has also been considered and evaluated. The detection limit of the conjugate adsorbent at optimum conditions was 0.11μg/L. The Au(III) sorption forms a monolayer on the interior pore surfaces of the conjugate adsorbent and showed high sorption capacity (203.42mg/g). In addition, the sorption uptake on the adsorbent reaching equilibrium was rapid and adsorbent was also exhibited high Au(III) ion selectivity in ionic competition. Acidified thiourea was used in the elution of the Au(III) and conjugate adsorbent exhibited in terms of reproducibility and versatility over a number of analysis/regeneration cycles. Therefore, the present conjugate adsorbent offered a low-cost material for potential application of ultra-trace Au(III) detection and recovery from urban mining waste scraps.