2025-05-14 ワシントン大学セントルイス校
＜関連情報＞
- https://source.washu.edu/2025/05/removing-selenium-from-water-takes-iron-strength/
- https://pubs.acs.org/doi/10.1021/acs.est.4c12305
- https://pubs.acs.org/doi/10.1021/acsestengg.5c00068
連続フロースルー鉄電気凝集による6価セレン除去： 運転条件と残留固体中のセレンの安定性の影響 Selenium(VI) Removal by Continuous Flow-Through Iron Electrocoagulation: Effects of Operating Conditions and Stability of Selenium in Residual Solids
Xicheng He,Elaine D. Flynn,Jeffrey G. Catalano,and Daniel E. Giammar
Environmental Science & Technology Published: March 6, 2025
DOI:https://doi.org/10.1021/acs.est.4c12305
Abstract
Selenium (Se) contamination is widespread, and Se(VI) removal from water is particularly challenging. This study evaluated Se(VI) removal using iron electrocoagulation (EC) in a flow-through reactor under various water chemistry and operating conditions. Effective Se(VI) removal (>98% from 1000 μg/L Se) was achieved under anoxic conditions with an iron dose as low as 30 mg/L and an EC reactor residence time as short as 11 s that was followed by a 1-h settling period. The removal remained stable over an extended operating time (24 h) and involved the generation of reactive Fe(II)/Fe(III) solids (green rust and magnetite). Oxic conditions were less effective for Se removal because of limited Se adsorption at the elevated pH of the effluent. The immobilized Se in the solids was in a reduced form (-II or 0), but about 70% of Se was oxidized after air exposure. Despite the reduced forms of Se being oxidized, very little Se was released from the solids and the toxicity characteristic leaching procedure indicated that EC-generated solids can be classified as nonhazardous. This study highlights the potential of flow-through iron EC to produce iron-containing adsorbents and reductants that can be tailored for Se(VI) and other oxyanion removal. It also offers practical insights into designing effective treatment systems and ensuring the safe disposal of EC-generated residual solids in real-world applications.
鉄電気凝集による六価セレン除去の進展： 水化学と運転条件の役割 Advancing Selenium(VI) Removal by Iron Electrocoagulation: Roles of Water Chemistry and Operating Conditions
Yihang Yuan,Maya Mehrotra,Xicheng He,Elaine D. Flynn,Jeffrey G. Catalano,and Daniel E. Giammar
ACS ES&T Engineering Published: April 13, 2025
DOI:https://doi.org/10.1021/acsestengg.5c00068
Abstract
Selenium(VI) (Se(VI)) is a challenging contaminant to remove from water due to its high solubility and limited adsorption affinity. Elevated Se concentrations pose adverse effects to both aquatic ecosystems and human health. Iron electrocoagulation (EC) is a promising method for Se removal by generating iron-containing solids that act as adsorbents and reductants. This study systematically investigated the effects of water chemistry and operating conditions on the rates and extents of Se(VI) removal in batch reactors. A reaction-based model for Se(VI) removal under oxic conditions (DO: 7.5–9 mg/L) was developed to enhance mechanistic understanding. Under oxic conditions, Se(VI) removal occurred through adsorption onto Fe(III) (oxy)hydroxides, with enhanced removal at acidic pH (pH 4–6). Under anoxic conditions (DO ≤ 0.1 mg/L), Se(VI) removal proceeded through chemical reduction on mixed-valence iron-containing solids, achieving better removal at neutral-alkaline pH. Three optimal conditions were identified (1 – pH 4, oxic; 2 – pH 7, anoxic; 3 – pH 8, anoxic). Se(VI) removal rates and extents increased with increasing charge loading rates but were independent of current density. EC demonstrated superior or similar Se(VI) removal extents compared to chemical coagulation at the three optimal conditions. These findings provide valuable insights for the optimal deployment of iron EC to achieve Se(VI) removal from waters.
