Removal of antimony (III) and antimony (V) from drinking water by ferric chloride coagulation: Competing ion effect and the mechanism analysis

• Published in: Separation and purification technology 2010-12, Vol.76 (2), p.184-190
• Main Authors: Wu, Zhijun, He, Mengchang, Guo, Xuejun, Zhou, Ruijing
• Format: Article
• Language: English
• Subjects: Adsorption; Antimony; Applied sciences; Chemical engineering; Coagulation-Flocculation-Sedimentation (CFS); Competing ion; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; Global environmental pollution; Liquid-liquid and fluid-solid mechanical separations; Pollution; Removal; Settling; Water treatment and pollution
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2010.10.006

▶ Competing ions significantly affect antimony removal. ▶ Sb(III) removal involves adsorption and coprecipitation. ▶ Internal and surface adsorption explains Sb(V) removal. Antimony, a pollutant of priority interest by United States Environment Protection Agency (USEPA) and Europe Union (EU), is detected in soil and water with elevated concentration due to its extensive use in a variety of industries. However, antimony purification from liquid system is yet poorly documented. In this study, effect of competing ions on antimony (III/V) removal by ferric chloride (FC) coagulation was comprehensively investigated. At lower FC dose (2× and 4 × 10 −4 mol/L of Fe), the percentage of Sb(V) removal showed a significant and continued decrease with the increasing presence of competing ions, including bicarbonate, sulfate, phosphate, and humic acid (HA). In contrast to Sb(V), Sb(III) removal remained highly effective, and was only slightly affected by the presence of HCO 3 − and SO 4 2−. Phosphate and HA considerably decreased Sb(III) removal at lower coagulant dose. However, with coagulant dose reaching 6 × 10 −4 mol/L of FC, Sb(III) removal became independent of phosphate and HA effect. The mechanism of antimony (III) adsorption onto hydrous ferric oxide (HFO) formed during FC coagulation, combined with a coprecipitation approach of anomalous incorporation of Sb(III) into HFO nanocrystaline, was proposed to interpret the effective Sb(III) removal under various suboptimal conditions. The predominance of Sb(V) adsorption onto HFO, including both surface and internal adsorption, can satisfactorily explain the Sb(V) removal with high sensitivity to competing ion effect.