Pilot-scale, cost-effective waste resource recovery: Efficient reduction of trace Au(I) from industrial wastewater via an adsorption and electrodeposition coupling process

The efficient and cost-effective recovery of trace gold from industrial wastewater is essential for the sustainable use of gold resources. Herein, an innovative adsorption and electrodeposition coupling (AEDC) process utilizing activated carbon coated titanium (AC/Ti) electrodes was proposed to recover trace gold from industrial wastewater. The AEDC process achieved a remarkable gold recovery of 99.82 % at an initial concentration of 0.424 ppm, outperforming conventional methods of activated carbon adsorption and electrodeposition by 34.47 % and 81.66 %, respectively. Pilot-scale tests and technoeconomic analyses demonstrated that the AEDC process consistently maintains over 99 % gold recovery after 10 cycles using the same AC/Ti electrode, yielding a significant profit of $65.99/g(Au). The high efficiency in recovering trace gold is mainly due to the synergistic effects of the porous structure and low charge transfer resistance of the AC/Ti cathode, which facilitate the effective adsorption and rapid reduction of trace Au(CN)2- ions. Furthermore, the efficient reduction of Au(CN)2- generates a concentration gradient at the AC/Ti cathode surface, accelerating the diffusion of Au(CN)2- ions toward the cathode within the electrolyzer, as verified by COMSOL simulation. This work presents an efficient and industrially viable method for trace gold recovery, highlighting its potential to promote a circular economy and enhance the sustainability of gold resources.