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Tian H, Wang X, Pan R, Qin J, Xu N, Huang X. Decreasing dissolved oxygen enhances in situ curtailment of intermediate Cr(VI) during photo-oxidative decomplexation of Cr(III)-EDTA. Environ Sci Pollut Res Int 2023; 30:62733-62743. [PMID: 36949374 DOI: 10.1007/s11356-023-26594-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 03/18/2023] [Indexed: 05/10/2023]
Abstract
Cr(III)-organic complexes are stably presented in tanning, electroplating, and other industrial wastewaters, and their safe and efficient removal remains a current challenge. Available oxidation processes can remove Cr(III) complexes but readily result in highly toxic Cr(VI) accumulation. Herein, negligible Cr(VI) accumulation was achieved during photo-oxidation of Cr(III) complexes using a simple strategy of decreasing dissolved oxygen (DO). At the DO concentration of 5.0 mg·L-1 or less, the in-process formation of intermediate Cr(VI) was totally abated by in situ formed reductive species, and total Cr was reduced from 9.0-11.0 mg·L-1 to below 1.0 mg·L-1. A complete curtailment of Cr(VI) was observed after 30-60 min at pH 6.0-9.0. Increasing Cr(III)-EDTA concentration and decreasing pH value facilitated the in situ reduction of intermediate Cr(VI). Based on the identification of intermediates and additional Cr(II) and quenching experiments, the possible key species involved in intermediate Cr(VI) reduction were the photogenerated Cr(II) and some C-centered radicals from Cr(III)-EDTA decomplexation, and the possible mechanisms of Cr(III)-EDTA decomplexation and intermediate Cr(VI) reduction were thus proposed. The process also showed efficient treatment on other Cr(III) complexes (citrate, oxalate, and tartrate) and realistic Cr(III) complexed wastewater. This study would provide an insignificant Cr(VI)-accumulated alternative for efficient and safe removal of Cr(III) complexes from contaminated water.
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Affiliation(s)
- Hailong Tian
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, School of Life and Environmental Science, Wenzhou University, Wenzhou, 325035, China
| | - Xuehui Wang
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, School of Life and Environmental Science, Wenzhou University, Wenzhou, 325035, China
| | - Rubin Pan
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, School of Life and Environmental Science, Wenzhou University, Wenzhou, 325035, China
| | - Jialu Qin
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, School of Life and Environmental Science, Wenzhou University, Wenzhou, 325035, China
| | - Nuo Xu
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, School of Life and Environmental Science, Wenzhou University, Wenzhou, 325035, China
| | - Xianfeng Huang
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, School of Life and Environmental Science, Wenzhou University, Wenzhou, 325035, China.
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Chen C, Liu P, Li Y, Tian H, Zhang Y, Zheng X, Liu R, Zhao M, Huang X. Electro-peroxone enables efficient Cr removal and recovery from Cr(III) complexes and inhibits intermediate Cr(VI) generation in wastewater: Performance and mechanism. Water Res 2022; 218:118502. [PMID: 35490457 DOI: 10.1016/j.watres.2022.118502] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 03/31/2022] [Accepted: 04/21/2022] [Indexed: 06/14/2023]
Abstract
Available oxidation processes for removing Cr(III) complexes from water/wastewater usually encounter the formation of highly toxic Cr(VI) and the generation of Cr enriched waste sludge, posing challenges on the subsequent disposal. Herein, we achieve efficient removal of Cr(III)-organic complexes and simultaneous recovery of Cr from wastewater with enhanced curtailment of intermediate Cr(VI), by using an electrochemically driven peroxone (i.e., electro-peroxone) process with activated carbon fiber (ACF) electrodes. For Cr(III)-EDTA, electro-peroxone could remove ∼90% total Cr from 11.50 mg/L to 1.20 mg/L and ∼80% total organic carbon, with a strong curtailment of Cr(VI) to less than 0.2 mg/L. Additionally, the process could obtain a complete recovery of the removable Cr, of which 78.3% are enriched at ACF cathode as amorphous Cr(OH)3 deposits and the remaining 21.7% are adsorbed at the anode, thus avoiding the generation of Cr laden sludge. Mechanism studies show the electro-generated H2O2 reacts with O3 to generate abundant HO· for decomplexation, which sequentially oxidizes Cr(III) to Cr(VI), and degrades the released EDTA via stepwise decarboxylated process, as confirmed by HPLC analysis. Multiple pathways including electro-reduction, H2O2 reduction and electro-adsorption synergistically curtail and immobilize the formed intermediate Cr(VI). ACF characterizations and continuous 5-cycle experiments substantiate the excellent reusability of the ACF electrodes. Moreover, this process exhibits satisfactory effectiveness to Cr(III) complexed with other ligands (e.g., citrate and oxalate), and complexed Cr(III) in the real electroplating wastewater. We believe this study would provide an efficient and eco-friendly alternative for Cr(III) complexes removal from wastewater.
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Affiliation(s)
- Cong Chen
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Pengfei Liu
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Yubao Li
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Hailong Tian
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Yanyang Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
| | - Xiangyong Zheng
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Renlan Liu
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Min Zhao
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
| | - Xianfeng Huang
- National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
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