Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

Abstract

a b s t r a c tThis study investigates the effects of aluminum (Al) and F interactions on the coagulation behaviors of Al salts, i.e., AlCl 3 and polymer aluminum chloride (PACl) at different basicity (B) towards fluoride. These coagulants achieve the optimum fluoride removal over pH 6-7, and PACl exhibits higher removal efficiency than AlCl 3 does over pH 4-9. The removal of fluoride is positively correlated with the content of either Al 13 or Al b in Al-based coagulants over pH 4-9 and increases in the order: PACl 2 > PACl 1 > AlCl 3 . As for PACl, the increased B from 0 to 2.4 improves fluoride removal owing to the elevated ratios of Al b . However, at further increased B to 2.8, the formation of colloidal Al species

Optimum parameters for humic acid removal and power production by Al–air fuel cell electrocoagulation in synthetic wastewater

“…Al species are crucial in the EC process as they determine the behavior and efficiency of Al-based coagulants (He et al 2016;Kong et al 2021). Equations ( 1)-(3) show that the anode dissolves to generate Al 3þ into the solution, and Al 3þ is hydrolyzed to form various forms of compounds or polymers.…”

Physico‐Chemical Processes

“…The coagulationflocculation control of pollutants was closely related to the state of hydrolysate species (Jiao et al, 2016;Zhu, Wang, Liu, et al, 2016;Shirasaki et al, 2016). For example, fluoride removal was found to be positively correlated with Al b or Al 13 content (He, Lan et al, 2016). The preparation should be preferentially considered so as to create the best species formation thus assisting the enhanced coagulation for treatment of pollutants.…”

Aggregation and Dissociation of Aqueous Al13 Induced by Fluoride Substitution

“…21 The ε-K Al 13 7+ polymer has been reported to be an effective component for coagulation and complexation of contaminants in water purification and soil remediation, 22−24 and exhibits especially superior aqueous fluoride (F − ) removal efficiency compared to other aluminum species. 25 Therefore, the investigation on the interaction mechanism of ε-K Al 13 7+ and F − would be helpful not only to understanding the transformation and migration of Al 13 and F in the geological environment but also to provide a basis for the application and regulation of Al polymers in water treatment, which has attracted wide attention from environmental researchers. According to previous research, the hydroxyl coordination on the Keggin structure is divided into three types with different activities according to the configuration: outer binding water (η-OH 2 ), hydroxyl between two trimers (μ-OH a ), and hydroxyl between two Al in one trimer (μ-OH b ), which are the binding sites for ligands.…”