Efficient Sb(Ⅲ) removal from printing and dyeing wastewater using TiCl4 as a potential coagulant instead of polyferric sulfate

Abstract

With increasing health concerns and the tightening of discharge standards, there is growing demand for more efficient Sb(Ⅲ) removal from printing and dyeing wastewater (PDW). Currently, the most common coagulant used in Sb removal in industry is polyferric sulfate (PFS). However, the residual Fe ions in the effluent cause colorimetric problems and irreversibly damage the membrane components during the subsequent reverse osmosis treatment process. Therefore, identifying novel coagulants to replace PFS in the removal of Sb(Ⅲ) is necessary. In this study, TiCl4 was employed for in-situ hydrolysis to produce flocs for Sb(Ⅲ) removal in simulated and real PDW. TiCl4 exhibited an excellent performance compared to PFS in terms of dosage, turbidity, application pH, and anti-interference properties. Sb(Ⅲ) removal of 97.3 % was realized at a dosage of 30 mg/L and a final pH of 5.0 in slightly contaminated PDW, whereas PFS required a higher dosage, resulting in higher disposal costs. Furthermore, the application of TiCl4 led to lower turbidity and reduced secondary contamination. An investigation of the co-existing ions revealed that TiCl4 was considerably more tolerant than PFS toward PO43–, humic acid, and silicate at a lower concentration. Simultaneously, Sb(Ⅲ) was partially oxidised to Sb(Ⅴ) during removal, but TiCl4 exhibited lower oxidative properties. The results of PDW treatment indicated that TiCl4 could realize 85.6 % Sb(Ⅲ) removal at a dosage of 30 mg/L, and the pre-reduction of Sb(Ⅴ) to Sb(Ⅲ) was a safe, effective treatment. The results of zeta potential measurements and X-ray photoelectron spectroscopy revealed that Sb(Ⅲ) removal was mainly realised via chemical adsorption. Overall, this study provides a promising alternative material for use in practical Sb(Ⅲ) removal from PDW, particularly for reducing coagulation sludge, operational costs, and damage during the possible subsequent reverse osmosis process.