Abstract
The process of coagulation and precipitation affect the fate and mobility of antimony (Sb) species in drinking water. Moreover, the solubility and physico-chemical properties of the precipitates may be affected by the media chemistry. Accordingly, the present study aimed to investigate the removal of Sb(III, V) species by ferric chloride coagulation under various water chemistry influences with a particular focus on the role of the properties of the precipitates. The results indicated that the amount of Sb(III) removed increased with increasing solution pH, showing the insignificant effects of the hydrodynamic diameter (HDD) and ζ-potential of the precipitates. However, no Sb(V) removal occurred at alkaline pH values, while a highly negative ζ-potential and the complete dissolution of precipitates were observed in the aqueous solution. The solution pH was also useful in determining the dominant coagulation mechanisms, such as co-precipitation and adsorption. The Fe solubility substantially affects the Sb removal at a certain pH range, while the HDD of the precipitates plays an insignificant role in Sb removal. The presence of divalent cations brings the ζ-potential of the precipitates close to point of zero charge (pzc), thus enhancing the Sb(V) removal at alkaline pH conditions. Pronounced adverse effects of humic acid were observed on Sb removal, ζ-potential and HDD of the precipitates. In general, this study may provide critical information to a wide group of researchers dealing with environmental protection from heavy metal pollution.
Highlights
Antimony (Sb) and its compounds are ubiquitous in the environment due to natural processes and the consequences of modern industrial activities [1,2]
Our findings suggested that the redox Sb species may influence the ζ-potential, hydrodynamic diameter (HDD) and stability of ferric chloride (FC) precipitates, thereby affecting the overall Sb removal during the chemical coagulation process
We systematically examined the properties and solubility of FC precipitates and their respective Sb(III, V) removal under the influence of various solution chemistries
Summary
Antimony (Sb) and its compounds are ubiquitous in the environment due to natural processes and the consequences of modern industrial activities [1,2]. High levels of Sb pollution, that is, 1000, 239 and 2–6384 μg/L, have been found in water bodies near Sb mines in Slovakia, the Kantishna Hills mining district (Alaska, USA) and Sb mine at Xikuangshan in Hunan Province (China), respectively [3,4,5]. The adverse health effects of the oral uptake of water-soluble Sb in the human body may lead to abdominal cramps, cardiac toxicity, vomiting and diarrhea [7]. In order to minimize the toxicological risks of Sb to humans, the USEPA, EU, Korea and the World Health Organization (WHO) have set Sb regulatory standards limited to 6, 10, 20 and 5 μg/L respectively [9,10]
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