Efficient Removal of Fluoride From Water by Polymeric Aluminum Zirconium Chloride: Performance and Mechanism From Flocculation Aspects

In this work, polymeric aluminum zirconium chloride (PAZC), a defluoridating flocculant, was prepared using calcium aluminate and zirconium tetrachloride as the main materials, and its defluoridation performance was evaluated. At pH 7 and PAZC dosage (Zr) of 50 mg•L −1 , the flocculation and defluorination rates of PAZC in simulated fluorinated wastewater with initial fluoride ion concentrations of 10, 8, and 5 mg•L −1 were 90.90%, 89.38%, and 92.2%, respectively, and the residual fluoride ion concentration in the solution was reduced to 0.91, 0.85, and 0.39 mg•L −1 , respectively. The degree of the effects of the same concentration of anions on the flocculation and fluoride removal performance of PAZC was in the order of SiO 3 2− >PO 4 3− >CO 3 2− >NO 3 − >Cl − >SO 4 2− . Characterization results indicated that PAZC was a polymer containing hydroxyl bonds of zirconium–aluminum metal ions, and the surface of PAZC had a tight, dense, porous nature. Under optimum flocculation conditions, the average particle size of the flocs obtained after fluoride removal by PAZC flocculation was 2.54 μm, and the flocculation mechanism was dominated by adsorption, electro-neutralization, and ion exchange when the dosage of the PAZC was 40–50 mg•L −1 and the pH was 5–7. It is proved that the composite flocculant PAZC has good application prospects and can provide guidance for the treatment of actual fluorine-containing wastewater.