Efficient recovery of Sb(V) by hydrated electron reduction followed by cathodic deposition in a photoelectrochemical process

Recovery of antimony (Sb) from wastewater is desired. Deposition of Sb(III) to metal Sb can occur via cathodic reduction, which is limited for Sb(V) reduction. Herein, a UV/sulfite-assisted electrodeposition (UV/sulfite/E) system was developed for the recovery of Sb(V) as metal Sb. The hydrated electron (e_aq⁻) generated from UV/sulfite process reduced Sb(V) to Sb(III), which was simultaneously reduced to metal Sb via cathodic reduction. Results indicated that as high as 95% of Sb(V) with a concentration of 50 mg/L can be deposited onto the cathode as metal Sb within 6 h. The reduction of Sb(V) to Sb(III) by e_aq⁻ was confirmed by laser flash photolysis tests. More importantly, the OH⁻ generated at cathode increased the pH of the UV/sulfite/E system and enabled the e_aq⁻ generation even at pH = 4, which was beneficial for Sb(V) reduction at a wide pH range. The optimal conditions for Sb(V) recovery were found to be at a sulfite concentration of 10 mM and an applied potential of −1.2 V (vs. SCE). The recovery of Sb(V) from practical Sb-containing wastewater was finally carried out and the results indicated that more than 60% of Sb was recovered as metal Sb.