Modification of activated carbon by chemical vapour deposition through thermal decomposition of thiourea for enhanced adsorption of gold thiosulfate complex

• Published in: Separation and purification technology 2020-06, Vol.241, p.116632, Article 116632
• Main Authors: Wang, Chaowu, Chen, Shuliang, Chen, Yunlong, Zi, Futing, Hu, Xianzhi, Qin, Xuecong, Zhang, Yan, Yang, Peng, He, Yi, He, Puqiang, Lin, Yue, Zhang, Guifen
• Format: Article
• Language: English
• Subjects: Chemical vapour deposition; Gold thiosulfate complex recovery; Modified activated carbon; Thiocyanate
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2020.116632

•Activated carbon was modified with thiourea for the enhanced adsorption of gold.•Up to 85% gold could be recovered over a wide range of pH.•The adsorption mechanism between the modifier and the adsorbent is proposed.•SCN could effectively recover gold from the Cu2+-NH3/en-Na2S2O3 system. Modified activated carbon (SCN-AC) was prepared by chemical vapour deposition through the thermal decomposition of thiourea. Compared with the AC-modified by impregnation, the benefits of SCN-AC were a simpler modification process and a shorter modification time. The Au(I) ion adsorption performance of SCN-AC in thiosulfate solution was systematically studied. The adsorbent was well characterised by scanning electron microscopy–energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The effects of contact time, pH, temperature, and gold concentration were investigated, and the gold adsorption performances in Cu2+-NH3-Na2S2O3 and Cu2+-en-Na2S2O3 systems were also evaluated. More than 85% of Au(I) could be recovered over a wide pH range, and the adsorption capacity increased with decreasing adsorption temperature, reaching a maximum of 11.86 kg/t-AC. The adsorption followed pseudo-second order kinetics and was well explained by the Freundlich model. Analysis of the thermodynamic parameters indicated that the adsorption of Au(I) on SCN-AC was exothermic and spontaneous. The adsorption of Au(I) on SCN-AC was attributed to the strong affinity between the soft acid and soft base, the formation of a π-π conjugated system, and the electrostatic interaction between the adsorbent and adsorbate. Additionally, SCN-AC showed good adsorption properties in the Cu2+-NH3-Na2S2O3 system and the Cu2+-en-Na2S2O3 system. This strategy could be used as a green and environmentally friendly method for gold recovery.