Removal of Sb(III) and Sb(V) by Ferric Chloride Coagulation: Implications of Fe Solubility

Abstract

Coagulation and precipitation appear to be the most efficient and economical methods for the removal of antimony from aqueous solution. In this study, antimony removal from synthetic water and Fe solubility with ferric chloride (FC) coagulation has been investigated. The effects of pH, FC dosage, initial antimony loading and mixed Sb(III), Sb(V) proportions on Fe solubility and antimony removal were studied. The results showed that the Sb(III) removal efficiency increased with the increase of solution pH particularly due to an increase in Fe precipitation. The Sb(V) removal was influenced by the solution pH due to a change in Fe solubility. However, the Fe solubility was only impaired by the Sb(III) species at optimum pH 7. The removal efficiencies of both Sb species were enhanced with an increase in FC dose. The quantitative analysis of the isotherm study revealed the strong adsorption potential of Sb(III) on Fe precipitates as compared to Sb(V). Furthermore, the removal behavior of antimony was inhibited in mixed proportion with high Sb(V) fraction. In conclusion, this study contributes to better understanding the fate of Sb species, their mobilities, and comparative removal behavior, with implications for Fe solubility using ferric chloride in different aqueous environments.

Influence of pH and Contaminant Redox Form on the Competitive Removal of Arsenic and Antimony from Aqueous Media by Coagulation

“…Moreover, Sb(III) demonstrated strong adsorption potential irrespective of pH in the presence of coexisting As and Sb species [36]. Our previous study [13] has shown the significant inhibition of Sb removal under coexisting Sb(III, V) conditions with higher Sb(V) fraction using FC coagulation. The higher adsorption capacity of poorly crystalline coagulant has been also reported [34].…”

“…The coagulation experiments were conducted to study the effect of pH (4-10) on Fe solubility and As, Sb removal, where 0.1 mM (27.029 mg/L) FC dose was used for solutions with 1 mg/L As(III, V) and Sb(III, V), respectively [13]. The experiments were also performed to study the competitive interactions of either As and Sb species in various binary systems over a broad pH range, where solutions contain single As and Sb species.…”

“…They are both mostly found in inorganic forms, that is, trivalent (As(III) and Sb(III)) under naturally reducing environment and pentavalent (As(V) and Sb(V)) species under toxic surroundings [12]. The trivalent species predominantly exist as As(OH) 3 and Sb(OH) 3 under the most natural water pH conditions [13,14]. Furthermore, the inorganic As(V) species occur in the forms of H 2 AsO 4 − , HAsO 4 2− at pH (2.20-9.22) and Sb(V) is in the deprotonated form of antimonic acid as Sb(OH) 6 − at pH > 2.72 [15,16].…”

“…A recent study [27] has reported that NOM might enhance Fe(III) oxide dissolution, due to the formation of surface complexes. In our earlier study [13], the dissolution of Fe(III) precipitates in the presence of inorganic ligand like Sb(OH) 6 − under alkaline conditions was intensively investigated. The complete dissolution of Fe(III) precipitates was observed due to the complexation of Fe with Sb(OH) 6 − and strong electron transfer from Sb(OH) 6 − to Fe(III), resulting in the breaking of Fe-O bond in the mineral lattice [13].…”

“…In our earlier study [13], the dissolution of Fe(III) precipitates in the presence of inorganic ligand like Sb(OH) 6 − under alkaline conditions was intensively investigated. The complete dissolution of Fe(III) precipitates was observed due to the complexation of Fe with Sb(OH) 6 − and strong electron transfer from Sb(OH) 6 − to Fe(III), resulting in the breaking of Fe-O bond in the mineral lattice [13]. In other words, this significantly influences the Fe(III) stability, thereby affecting the fate and mobility, as well as the removal behavior, of pollutants in natural waters [28,29].…”