Electrochemical Cr(VI) removal from aqueous media using titanium as anode: Simultaneous indirect electrochemical reduction of Cr(VI) and in-situ precipitation of Cr(III). (December 2020)

• Record Type: Journal Article
• Authors: Yao, Fubing; Jia, Maocong; Yang, Qi; Luo, Kun; Chen, Fei; Zhong, Yu; He, Li; Pi, Zhoujie; Hou, Kunjie; Wang, Dongbo; Li, Xiaoming
• Is Part Of: Chemosphere. Volume 260(2020)
• Publication Date: 2020-12
• Subjects: Indirect electrochemical Cr(Ⅵ) reduction -- In-situ Cr(Ⅲ) precipitation -- Titanium anode -- Reaction mechanism; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.127537
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: In this work, a novel method for complete Cr(Ⅵ) removal was achieved in a single-chamber cell with titanium (Ti) as anode via simultaneous indirect electro-reduction of Cr(Ⅵ) and in-situ precipitation of Cr(Ⅲ). The Cr(Ⅵ) and total Cr removal, and electric energy consumption were optimized as a function of electrochemical reactor, current density, initial Cr(Ⅵ) and chloride (Cl − ) concentration, and initial solution pH. The maximum Cr(Ⅵ) and total Cr removal efficiency reached 80.5 and 79.4% respectively within 12 h at current density of 10 mA cm −2 as initial Cr(Ⅵ) concentration was 0.078 mM. Decreasing the initial solution pH was beneficial to Cr(Ⅵ) reduction, but Cr(Ⅲ) precipitation was inhibited, resulting in the poor total Cr removal. The suitable Cl − concentration guaranteed sufficient reducing agents (Ti 3+ and Ti 2+ ) for Cr(Ⅵ) removal. The reaction mechanism demonstrated that Ti anode could be corroded to produce Ti 3+ and Ti 2+, which provided the electrons for reduction of Cr(Ⅵ) to Cr(Ⅲ). Simultaneously, the solid products ( Ti 2 O ( 6 x − y − z + 5 2 ) Cl 2 y Cr 2 x ( OH ) 2 z ( s ) ) were in-situ formed and precipitated from the solution due to the continuous generation of hydroxyl ion (OH − ) from cathode. This study might provide a new electrochemical method with non-precious metal as the electrode for complete Cr(Ⅵ) removal from aqueous media. Graphical abstract: Image 1 Highlights: Simultaneous Cr(Ⅵ) reduction and in-situ Cr(Ⅲ) deposition was achieved by using Ti anode. The Cr(Ⅵ) and total Cr removal efficiency were highly pH-dependent. The suitable Cl − concentration ensured sufficient Ti 3+ and Ti 2+ for Cr(Ⅵ) reduction. The Ti 2 O ( 6 x − y − z + 5 / 2 ) Cl 2 y Cr 2 x ( OH ) 2 z ( s ) precipitate was formed. The possible mechanisms involved in the reaction process were proposed.