A polymeric al/La chloride coagulant for fluoride removal

A new type of composite coagulant, polyaluminum lanthanum chloride (PALC), was prepared using AlCl 3 ·6H 2 O and LaCl 3 ·7H 2 O as the main raw materials. The optimal preparation conditions were determined with the removal rate of fluoride ions as the evaluation index, which were a basicity degree B value of 1.00 and an Al/La molar ratio of 10:5. Under the optimal preparation conditions, the particle size of PALC was 121 nm and the Zeta potential was 35.3 mV, significantly larger than the corresponding values of 21 nm and 6.9 mV for polyaluminum chloride (PAC), indicating an enhanced particle size and positive charge carrying capacity. The FTIR spectrum of PALC exhibits a La–O-related band at ∼846 cm −1 and a weak feature near 1041 cm −1 attributed to metal–oxygen/metal–hydroxyl (M–O(H)) vibrations in the hydrolyzed Al/La framework, suggesting La incorporation and structural perturbation of the Al-hydroxo polymer network. EDS analysis indicated that the weight percentages of La and Al in PALC were 21.51% and 9.95%, respectively, suggesting that La ions had stronger competitiveness and preferentially combined with –OH to form high-polymer lanthanide products.SEM-EDS analysis suggested a heterogeneous hierarchical distribution of La and Al within the PALC aggregates, with La-enriched inner regions and Al-enriched outer regions. Characterizations by DLS, FTIR, SEM, and EDS demonstrated the successful preparation of PALC, which exhibited stronger adsorption bridging and electro-neutralization capabilities.