Synergistic extraction of valuable metals from cyanide tailings slurry electrolyte and preparation of ferrous oxalate.

A cyanide tailings slurry electrolyte (CTSE) was treated using a synergistic extraction system (P204-T) composed of di(2-ethylhexyl)phosphate (P204, (C 8 H 17 O) 2 PO 2 H, H 2 A 2), trioctylamine (TOA, ([CH 3 (CH 2) 7 ] 3 N), R 3 N), and iso-alkanes, and a collaborative extraction technique involving oxalic acid stripping and photocatalysis was developed to separate and recover valuable metals and prepare ferrous oxalate. The results show that at a pH of 1.5, the P204 concentration of 15 vol%, TOA concentration of 10 vol%, O/A of 1:1, an oscillation time of 10 min, and an oscillation frequency of 190 rpm, the single-stage Fe(III) and Zn(II) extraction efficiencies of P204-T were 99.25% and 99.02%, respectively, and the saturated extraction capacities were 25.01 g•L⁻¹ and 1.20 g•L⁻¹, respectively. TOA destroyed the dimer structure of P204 and promoted the –OH bond and –O P group in P204 to combine with TOA through hydrogen bonding to form N–H⁺···O–P and N–H⁺···O P bonds, resulting in the R 3 NHA·(HA) composite structure. During the collaborative extraction process, ion exchange with FeSO 4 ⁺ resulted in the formation of FeSO 4 A·(HA) 3 and ion exchange with the intermediate product (R 3 NH) 2 SO 4 and Zn(SO 4) 2 ^2- formed (R 3 NH) 2 Zn(SO 4) 2 , which improves the extraction efficiency of metal ions. In addition, some amount of P204 underwent ion exchange with free Fe³⁺ and Zn²⁺ to produce FeA 3 (HA) 3 and ZnA 2 (HA) 2 , respectively. At oxalic acid concentration of 1 mol•L⁻¹, an O/A of 1:3, the efficiencies of Fe(III) and Zn(II) stripped from the saturated organic phase reached 99.65% and 99.41%. Zn(II) formed the ZnC 2 O 4 ·2 H 2 O precipitate and Fe(III) separation. FeC 2 O 4 ·2 H 2 O was successfully synthesized by ultraviolet photocatalysis using iron oxalate complex as the stock solution. [Display omitted] • Process of synergistic extraction, oxalic acid stripping and photocatalysis was developed. • Technical parameters of iron enrichment and value-added utilization are determined. • Ferrous oxalate was prepared from cyanide tailings slurry electrolyte. • The reaction mechanism of P204-T synergistic extraction process has been explore. [ABSTRACT FROM AUTHOR]