Arsenic Removal and Recovery from Copper Smelting Wastewater Using TiO2

Removal and recovery of high levels of arsenic (As) in copper smelting wastewater present a great environmental challenge. A novel approach was investigated for the first time using TiO2 for As adsorptive removal from wastewater and subsequent spent adsorbent regeneration and As recovery using NaOH. EXAFS results demonstrate that As(III), as the only As species present in the raw water, does not form an aqueous complex with other metal ions. An average of 3890 +/- 142 mg/L As(III) at pH 1.4 in the wastewater was reduced to 59 +/- 79 mu g/L in the effluent with final pH at 7 in the 21 successive treatment cycles using regenerated TiO2. Coexisting heavy metals including Cd, Cu, and Pb with concentrations at 369 mg/L, 24 mg/L, and 5 mg/L, respectively, were reduced to less than 0.02 mg/L. As(III) adsorption followed pseudosecond-order rate kinetics, and the adsorption behavior was described with the charge distribution multisite surface complexation model. Approximately 60% As(III) in the waste solution after the TiO2 regeneration process was recovered by therm.) vaporization and subsequent precipitation of sodium arsenite, as suggested by the EDX and XPS analysis. This zero sludge process sheds new light on successful As remediation technology for acidic metallurgical industry wastewater.