Utilization of the dilute acidic sulfate effluent as resources by coupling solvent extraction-oxidation-hydrolysis

The pollution risk of dilute acidic sulfate effluent (DASE),which is discharged from titanium dioxide factories heavily every year, has sparked the recycling of sulfuric acid, iron and water. In this study, a new green recovery process for the DASE is proposed based on coupling solventextraction-oxidation-hydrolysis. Compared to the conventional ways, this innovative method allows the effective extraction of sulfuric acid and the precipitation of FexOy·nH2O in onestep without adding inorganic neutralizer or precipitant. Trioctylamine (TOA) in kerosene (20-50%) was used as an organic phase for solvent extraction. The hydrolytic productions and the raffinate purified by a cation exchange were evaluated using XRD and ICP-OES, respectively. The initial pH of 0.63 and Fe(II) concentration of 0.1 mol/L in the DASE, the volume ratio of organic toaqueous phase (O/A) of 3/1, and reaction temperature of 25 °C were determined as the optimal conditions. Under this conditions, Fe(II) was transformed as yellow precipitation which was characterized as α-FeOOH, and pH of raffinate was in the range of 3.6-3.8.