Ultrasound-Assisted Activated Carbon Adsorption Au(CN)2−

Ultrasound is introduced into the gold adsorption process by activated carbon to improve the adsorption efficiency. The effects of ultrasonic equipment, initial pH value, amount of activated carbon, initial CN^- concentration, and temperature on the Au(CN)2- adsorption onto activated carbon were investigated. The adsorption results show that the water bath ultrasonic generator is more beneficial to promote the gold adsorption onto activated carbon than the probe ultrasonic equipment. With the introduction of ultrasound, the gold adsorption capacity of activated carbon is obviously improved, and the gold balance loading is increased by about 37%. The Freundlich model can describe well the adsorption behavior of Au(CN)2- onto activated carbon with or without ultrasound, which indicates that the Au(CN)2- adsorption onto activated carbon belongs to multi-molecular chemisorption. Compared with the pseudo-first-order equation and intra-particle diffusion equation, the pseudo-second-order equation can better fit dynamic data. Through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR), BET specific surface area, SEM, and particle size distribution analysis, it is proved that the enhancement of the gold adsorption onto activated carbon by ultrasound is due to the continuous action of ultrasound, which reduces the particle size and ultrasonication increases specific surface area through physical fragmentation effects and improves active site accessibility by reducing mass transfer resistance of activated carbon, rather than changing the adsorption mechanism of gold onto activated carbon.