Gengwei Zhang

Selective recovery of Au(III) from aqueous solutions by nano-silica grafted with 4-(aminomethyl) pyridine

A new adsorbent was synthesized via functionalizing nano-silica with 4-(aminomethyl) pyridine for selective recovery of gold. The adsorbent was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and transmission electron microscopy, and BET (surface area and porosimetry analyzer). The results indicated that the maximum adsorption capacity of Au(III) was 55.5 mg/g at pH 4.0 and room temperature. The adsorption reaction was fairly rapid and reached equilibrium within 30 min. The adsorption processes of Au(III) were fitted well to the Langmuir isotherm model and adsorption kinetics of Au(III) followed the pseudo-second-order rate equation. The adsorption mechanism lies on the chelation and ion exchange between gold ions and amines/hydroxyl groups. The adsorbent had good reusability after five cycles. Moreover, 4-(aminomethyl) pyridine-Silica nanoparticles has a good selectivity in the adsorption of Au(III) from the coexisting ions. Therefore, 4-(aminomethyl) pyridine functionalized nano-silica could be of great potential as new adsorbent for the selective recovery of Au(III) from industrial effluents and waste e-products.Graphical Abstract

Ultra fast ultrasound-assisted decopperization from copper anode slime

An ultra fast decopperization method from the anode slime has been developed based on the ultrasound-assisted leaching. The effects of parameters such as ultrasound power, leaching time, sulfuric acid concentration and liquid/solid ratio were investigated. Under optimum conditions, the concentration of Cu in residue was only 2.64%. The removal efficiency increases considerably and the decopperization time was significantly shortened comparing with conventional method (>10%, 24h). Se and Te have not been detected in lixivium, indicating the selective leaching of Cu. In addition, the mineralogical characteristics of the untreated anode slime and the residues after ultrasound-assisted decopperization are investigated. The results revealed that the increasing of decopperization efficiency was attributed to the change of the phase composition and the morphology and size of samples during ultrasound-assisted decopperization.

Nanosilica-supported thiosemicarbazide–glutaraldehyde polymer for selective Au(III) removal from aqueous solution

A new adsorbent thiosemicarbazide/nanosilica composite was synthesized via a facile two-step reaction, including the functionalization of silica nanoparticles via amino groups, and crosslinking the thiosemicarbazide with glutaraldehyde onto the amino functionalized silica nanoparticles. The adsorption capability of the adsorbent for Au(III) ions was investigated. Fourier transform infrared, X-ray photoelectron spectroscopy and thermogravimetric analysis were used to characterize the adsorbent. Experimental results indicated that nanocomposites exhibited highly selective and efficient adsorption for Au(III). The equilibrium data fitted well with the Langmuir isotherm and the obtained kinetic data obeyed the pseudo-second-order kinetics model. The maximum adsorption capacity was 4.3 mmol g−1 at pH 2. The adsorbent can still keep high adsorption capability after five recycling rounds. The adsorption mechanisms were proposed as the synergistic effect of ionic interaction and chelation.