Adsorption of Sb(III) and Sb(V) on Freshly Prepared Ferric Hydroxide (FeOxHy)

Abstract

This study prepared fresh ferric hydroxide ( FeOxHy) by the enhanced hydrolysis of Fe ions, and investigates its adsorptive behaviors toward Sb(III) and Sb(V) through laboratory and pilot-scale studies. A contact time of 120-min was enough to achieve adsorption equilibrium for Sb(III) and Sb(V) on the FeOxHy, and the Elovich model was best to describe the adsorption kinetics of Sb(III) and Sb(V). The Freundlich model was better than Langmuir model to describe the adsorption of Sb(III) and Sb(V) on the FeOxHy, and the maximum adsorption capacity of Sb(III) and Sb(V) was determined to be 12.77 and 10.21 mmol/g the FeOxHy as Fe, respectively. Adsorption of Sb(V) decreased whereas that of Sb(III) increased with elevated pH over pH 3-10, owing to the different electrical properties of Sb(III) and Sb(V). Adsorption of Sb(III) and Sb(V) was slightly affected by ionic strength, and thus indicated the formation of inner sphere complexes between Sb and the adsorbent. Sulfate and carbonate showed little effect on the adsorption of Sb(III) and Sb(V). Phosphate significantly inhibited the adsorption of Sb(V), whereas slightly effected that of Sb(III) due to its similar chemical structure to Sb(V). Pilot-scale continuous experiment indicated the feasibility of using FeOxHy to remove Sb(V), and equilibrium adsorption capacity at the equilibrium Sb(V) concentration of 10 μg/L was determined to be 0.11, 0.07, 0.07, 0.11, and 0.12 mg/g the FeOxHy as Fe at equilibrium pH of 7.5-7.7, 6.9-7.0, 6.3-6.6, 5.9-6.4, and 5.2-5.9, respectively.

Synergistic process using Fe hydrolytic flocs and ultrafiltration membrane for enhanced antimony(V) removal

“…To remove trace concentrations of Sb in drinking water, Fe hydrolytic flocs were freshly prepared and the removal efficiency of Sb (V) was significantly increased after filtration. The maximal adsorption capacity of Sb(V) is as high as 10.2 mM/g Fe at pH 5.0 [1].…”

“…Antimony (Sb), which is similar to arsenic (As), has received great attention due to its high toxicity and carcinogenicity towards humans after long-time exposure [1][2][3]. The maximum contaminant level (MCL) in drinking water for Sb is 5.0 and 6.0 µg/L in the USA and Europe, respectively [4,5].…”

“…In China, the MCL is 5.0 µg/L [6]. Sb(III) and Sb(V) are the two main species, of which Sb(III) is dominant under anoxic conditions with the main species of Sb(OH) 3 , while Sb(V) is dominant in oxic surface waters with the main species of Sb(OH) 6 − over a wide pH range [1,3]. In comparison with As, the removal of Sb is much more difficult.…”

“…In fact, the synthetic adsorbents always showed reduced adsorption abilities after drying and granulation procedures [1]. To overcome this problem, the freshly prepared adsorbents may be advantageous regarding their adsorption capability due to maintaining the activity of adsorption sites as much as possible.…”

“…Here, a noticeable problem is that the corresponding loading efficiency is always lower due to the properties of the carriers [1]. As a result, the flocs have a large potential to release during filtration, leading to higher concentrations of Al or Fe in the effluent.…”