Mechanism for the synergistic removal of Sb(Ⅲ) and Sb(V) from printing and dyeing wastewater by polyferric sulfate

Abstract

Herein, the synergistic removal of Sb(Ⅲ) and Sb(Ⅴ) from wastewater by polymeric ferric sulfate (PFS) and the oxidation process were investigated. The results showed that PFS exhibited superior performance on Sb(Ⅲ) removal in terms of coagulant dosage, applied pH, and anti-interference properties than Sb(V) removal. For the Sb liquid in pure water matrix (Sb=1000 μg/L), when the dose was 60 mg/L and the final pH was 5.0, the independent removal of Sb(Ⅲ) and Sb(V) was 95% and 90%, respectively. Meanwhile, Sb(Ⅲ) removal in the PFS coagulation system remained stable within a wider pH range (pH=3–9). Sb(Ⅲ) could be preferentially removed in the solution column and had an inhibitory effect on the adsorption of Sb(V). Sb(Ⅲ) was also partially oxidized to Sb (V) during the coagulation process, which was influenced by the coagulant dosage and the solution pH. The results of the actual printing and dyeing wastewater (PDW) treatment indicated that the pre-reduction of Sb(V) to Sb(Ⅲ) could significantly increase the total Sb removal from 72.0% to 97.5%. The characterization results, such as Zeta potential and x-ray photoelectron spectroscopy (XPS), indicated that the Sb(Ⅲ) removal by PFS was achieved mainly through chemical adsorption. While the Sb(V) removal was realized by both chemical adsorption and electrostatic adsorption, the electrostatic adsorption contributed more than the chemical adsorption. This study provides a new idea for understanding the synergistic removal of Sb(Ⅲ) and Sb(V) using PFS in PDW advanced treatment.