Recycling of residual valuable metals in cyanide-leached gold wastewater using the N263-TBP system

Abstract

In this study, the synergistic extraction system of trioctylmethyl ammonium chloride (N263)-tributyl phosphate (TBP)-n-octanol-sulfonated kerosene was used to enrich and recover valuable metals from cyanide gold extraction of wastewater. The effects of the proportion of N263 and TBP, contact time, initial pH of water phase, temperature, and phase ratio (O/A) on the extraction percentage of metal cyanide complex ions and the synergistic extraction reaction mechanism were mainly investigated. Results showed that the single-stage extraction percentages of Cu, Zn, and Fe ions in wastewater were 99.87%, 99.8%, and 96.2%, respectively, and the saturated extraction capacity was 4356.4 mg/L under the conditions of N263 (20 vol%)-TBP (20 vol%)-n-octanol (10 vol%)-sulfonated kerosene system at 25 °C, O/A of 1:1, pH of 10, and contact time of 5 min. Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS) analyses showed that metals entered the organic phase in the form of metal cyanide complex ions during extraction. Metal cyanide complex ions preferentially combined with TBP to lose hydrophilicity and then reacted with N263 cations to enter the organic phase. The saturated organic phase was stripped by NaOH and NaSCN mixed solution, and the total concentration of metal ions in the stripping solution reached 11,996.6 mg/L.