Synergistic process using Fe hydrolytic flocs and ultrafiltration membrane for enhanced antimony(V) removal

Antimony (Sb) is harmful to human health, and Sb(V) is much more difficult to remove from water than other toxic elements such as arsenic (As). Theoretical studies have suggested that in situ flocs have stronger adsorption ability toward heavy metals than pre-made adsorbents. We believe that rational design of in situ flocs and the associated device structure will enable a floc-based device to be utilized in the removal of heavy metals. Based on this concept, we developed an integrated process taking advantage of the strong adsorption abilities of in-situ Al or Fe hydrolytic flocs and excellent separation properties of ultrafiltration (UF) membranes. We found that flocs could be well dispersed in a membrane tank with aeration from the bottom, and Fe-based flocs performed better in removing Sb(V) and alleviating membrane fouling than Al-based flocs. We also demonstrated that higher Sb(V) removal efficiency was induced with continuous injection, and lower solution pH. By controlling the aeration rate, injection frequency and the solution pH, membrane fouling was alleviated, especially under weakly acidic conditions. Additionally, owing to the higher rejection efficiency of the UF membrane, the effluent quality was improved, including the iron concentration, turbidity, and chromaticity. This innovative separation method shows promising potential for application in removing heavy metals in water treatment.