Treatment of cyanide-bearing wastewater by the N263-TBP synergistic extraction system.

In this study, a trioctylmethylammonium chloride (N263)- tributyl phosphate (TBP)- n -octanol-sulfonated kerosene (N263-T) synergistic extraction system and an N263- n -octanol-sulfonated kerosene (N263–O) system were used to treat cyanide (CN)-bearing wastewater. The extraction saturation capacity of the two systems was measured. The influences of the initial pH and phase ratio (O/A) of the two systems on extraction were compared and analyzed. Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, and slope methods were used to analyze the characteristic functional groups in the loaded organic phase, the compositions of the extracted compounds in the extraction reactions and the reaction mechanism. The results indicated that the saturated extraction capacity of the N263-T system, which was much larger than that of the N263–O system, for metal CN complex ions was 4354.31 mg/L. In addition, the N263-T system operated over a wider pH range. The extraction rates of copper (Cu), zinc (Zn), and iron (Fe) ions at pH 14 were 97.4%, 99.1%, and 87.2%, respectively. There was a strong compatibilization effect of TBP on the extraction system. The extraction efficiency of the N263-T system for metal CN complex ions was higher than that of the N263–O system when O/A = 0.4. The saturated loaded N263-T and N263–O systems were stripped by 1 mol/L NaOH +2 mol/L NaSCN solution at O/A = 3. The metal ion concentration in the stripping solution could be enriched to 11996.6 and 8913.3 mg/L for the N263-T and N263–O systems, respectively. During the extraction process, the binding ratios of N263 cations to Cu(CN) 3 2−, Zn(CN) 4 2−, and Fe(CN) 6 3− were 2:1, 2:1, and 3:1, respectively. The binding ratios of TBP to Cu(CN) 3 2−, Zn(CN) 4 2−, and Fe(CN) 6 3− in wastewater were 3:1, 4:1, and 6:1, respectively. The P O group in TBP was linked to the C N group of the metal CN complex ion by hydrogen bonds using the water molecule as a bridge to form a supramolecular anion group, which entered into the organic phase and combined with the N263 cation under the action of ion association. [Display omitted] • An approach for valuable metals recovery from cyanide wastewater is developed. • The N263-T was more effective at O/A of 0.4, N263 and TBP concentration of 10 vol%. • TBP is attached to the C N group of the metal complex ion by hydrogen bonding. • The binding ratios of TBP to Cu, Zn and Fe are 3:1, 3:1 and 6:1. • N263 binds to anionic groups in ratios of 2:1(Cu), 2:1(Zn), 3:1(Fe). [ABSTRACT FROM AUTHOR]