One-time removal of V(V) and Cr(VI) from aqueous solution of different pH by sulphate green rust: The overlooked adsorption and reactivity of Fe (III)-Cr(III) oxides

• Published in: Separation and purification technology Vol. 354; p. 128722
• Main Authors: Li, Haidong, Song, Han, Yang, Yuankun, Wang, Haitao, Fan, Beibei, Zheng, Juncheng, Tu, Weiguo, Luo, Xuemei, Chen, Shu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 19.02.2025
• Subjects: Chromium; Reduction; Sorption; Sulphate green rust; Vanadium; Sorption; Chromium; Reduction; Sulphate green rust; Vanadium
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2024.128722

[Display omitted] •V(V) and Cr(VI) could be rapidly removed by sulphate green rust (GRSO4);•In the single system, Cr(VI) is removed at a faster rate than V(V) by GRSO4;•The addition of Cr(VI) reduces the reaction equilibrium time of V(V) by 30%;•GR-Cr(III) is the key to the GRSO4 enhanced V(V) adsorption reaction process. Efficient and economical reduction and elimination of co-pollution of vanadium (V) and chromium (Cr) from water sources is a major challenge. In this study, sulphate green rust (GRSO4) was successfully prepared by co-precipitation method and used for the removal of V(V) and Cr(VI). The findings from batch adsorption experiments indicated that the adsorption capacity of GRSO4 for V(V) and Cr(VI) individually was 30.66 mg⋅g−1 and 39.48 mg⋅g−1, respectively, with equilibrium reached in 25 min and 10 min. Intriguingly, in a binary system with both V(V) and Cr(VI) present, the time to reach adsorption equilibrium for V(V) removal by GRSO4 was 30 % shorter comparison to the single system under identical conditions. By analyzing the surface characteristics, crystal structure and elemental valence changes of GRSO4 minerals before and after the reaction, it can be obtained that: i) Direct adsorption mainly drives the removal of V(V) by GRSO4, whereas the removal of Cr(VI) is preceded by reduction and followed by adsorption. ii) In a binary coexistence system, the formation of Fe(III)-Cr(III) oxide (GR-Cr(III)) during the removal of Cr(VI) by GRSO4 formed during the removal of Cr(VI) by GRSO4 creates additional adsorption sites for V(V), which shortens the equilibrium time of the V(V) removal reaction by GRSO4 and reduces the amount of V(V) leached. These findings are of great practical significance for understanding the mechanism and practical application of GRSO4 in the synergistic removal of V(V) and Cr(VI) heavy metals and provide valuable insights into their geophysical-chemical cycling.