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Liu H, Li X, Lu S, Li X, Zhang G, Feng C. Overlooked competition and promotion effects in electrochemical oxidation of humic acid and ammonia in landfill leachate. JOURNAL OF HAZARDOUS MATERIALS 2024; 474:134732. [PMID: 38805814 DOI: 10.1016/j.jhazmat.2024.134732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 05/07/2024] [Accepted: 05/23/2024] [Indexed: 05/30/2024]
Abstract
Electrochemical oxidation (EO) can effectively reduce the degree of humification and toxicity of landfill leachate by generating highly active oxidative species in situ. However, the selective and competitive oxidation of humic acid (HA) and ammonia (NH4+) and the role of different oxidative species during the EO process in complex aqueous conditions remain unclear. In this study, a nanostructured tin-antimony electrode (Ti/Sb-SnO2 NFs) was prepared and compared with three types of commercial electrodes (Ti/Ir-RuO2, Ti4O7, Ti/Sb-SnO2) in terms of electrochemical properties and electrocatalytic oxidation of HA and NH4+. The de-humification capacity, interactive effects of HA and NH4+ on each other's oxidation by different oxidative species, as well as the related oxidation byproducts were investigated. The differences in pollutant electrooxidation among the different electrodes were found to be insignificant. The presence of HA was found to be detrimental to NH4+ degradation while reducing the N2 conversion rate. Interestingly, NH4+ initially inhibited the degradation rates of HA while promoted the degradation and reduced the accumulation of organic chlorine during the later EO process. A proposed mechanism accounts for both competitive and promotional effects for simultaneous HA and NH4+ oxidation during the EO process.
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Affiliation(s)
- Huiyuan Liu
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen (HITSZ), Shenzhen 518055, PR China
| | - Xuechuan Li
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen (HITSZ), Shenzhen 518055, PR China
| | - Sen Lu
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen (HITSZ), Shenzhen 518055, PR China
| | - Xiao Li
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen (HITSZ), Shenzhen 518055, PR China
| | - Guan Zhang
- State Key Laboratory of Urban Water Resource and Environment, Shenzhen Key Laboratory of Organic Pollution Prevention and Control, School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen (HITSZ), Shenzhen 518055, PR China.
| | - Chunhua Feng
- The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
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Hu P, Li H, Tan Y, Adeleye AS, Hao T. Enhanced electrochemical treatment of humic acids and metal ions in leachate concentrate: Experimental and molecular mechanism investigations. JOURNAL OF HAZARDOUS MATERIALS 2024; 462:132774. [PMID: 37839382 DOI: 10.1016/j.jhazmat.2023.132774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/26/2023] [Accepted: 10/11/2023] [Indexed: 10/17/2023]
Abstract
Membrane technologies are effective for treating leachate, but they generate leachate concentrates (LCs), which contain elevated humic acids (HAs) and metals. LCs are very challenging and expensive to treat; but in-situ coagulation-electrochemical oxidation (CO-EO) treatment is promising. We previously hypothesized and proved that substituting the widely used graphite cathode with an Al cathode will generate Al(OH)3 floccules that would enhance HAs removal in CO-EO systems. However, the fundamental mechanisms are unclear. Here, we examined this hypothesis using laboratory experiments (using an Al cathode and a Ti/Ti4O7 anode CO-EO system) and performed molecular dynamics (MD) simulation to investigate the underlying mechanisms. Up to 84.2% HAs was removed by the Al-cathode system, which is ∼10% higher than a graphite cathode-based system. Based on MD simulation we found that enhanced HAs removal occurred via two steps: (1) degradation by oxidants produced at the anode, and (2) subsequent coagulation with the Al(OH)3 generated from the Al cathode. This finding challenges the current belief that whole HAs and Al(OH)3 directly flocculate. Meanwhile, metal removal efficiency by the graphite cathode system was only 0.8-13.9%, which increased up to 13-folds at most when in the Al cathode system. This work provides new molecular-level insights into an efficient electrochemical treatment of LC.
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Affiliation(s)
- Peng Hu
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau, China
| | - Huankai Li
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau, China
| | - Yunkai Tan
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau, China
| | - Adeyemi S Adeleye
- Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175, USA
| | - Tianwei Hao
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau, China.
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Electrochemical oxidation of phenol in chloride containing electrolyte using a carbon-coated Ti4O7 anode. Electrochim Acta 2023. [DOI: 10.1016/j.electacta.2023.142233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
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A facile synthesis of a novel Ti4O7 anode rich in oxygen defects and its electrochemical oxidation of florfenicol: Performance and mechanism. Sep Purif Technol 2023. [DOI: 10.1016/j.seppur.2023.123134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Maqbool T, Sun M, Chen L, Zhang Z. Molecular-level characterization of natural organic matter in the reactive electrochemical ceramic membrane system for drinking water treatment using FT-ICR MS. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 846:157531. [PMID: 35870579 DOI: 10.1016/j.scitotenv.2022.157531] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/18/2022] [Accepted: 07/17/2022] [Indexed: 06/15/2023]
Abstract
Applications of electrochemical advanced oxidation processes are rising in drinking water treatment for effective mitigation of refractory organic compounds. This study explored the fate of natural organic matter (NOM) (lake water and standard NOM (SRNOM solution)) at molecular-level in the reactive electrochemical membrane (REM) system utilizing Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Fluorescence spectroscopy showed above 90 % removal of the humic-like component in both lake water and SRNOM solution in 10 min of REM operation compared to 70-80 % removal of the fulvic-like component after 30 min. REM-based treatment effectively eliminated (>70 %) the disinfection byproduct precursors. The lake water, sharing ~70 % of similar compounds with SRNOM, displayed a different propensity toward electrochemical oxidation, and its finished water was characterized with relatively lower double-bond equivalent (DBE), nominal oxidation state of carbon (NOSC), and aromaticity compared to that of SRNOM. The chloride ions in the water matrix of lake water impacted the electrochemical oxidation and generated significantly different transformation products than SRNOM solution. The heteroatoms (N and S) containing compounds (CHON and CHOS) were preferentially degraded in lake water; however, CHOS compounds were removed fewer in SRNOM. The electrosorption and electrochemical oxidation on the REM surface were the significant contributors for NOM removal. The newly formed compounds were mostly retained on the REM surface and fewer were released in finished water. This study is believed to help understand the fate of NOM in real source drinking water during electrochemical treatment.
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Affiliation(s)
- Tahir Maqbool
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China; Department of Civil, Construction and Environmental Engineering, University of Alabama, Tuscaloosa, AL 35487, USA
| | - Mingming Sun
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China
| | - Li Chen
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China
| | - Zhenghua Zhang
- Institute of Environmental Engineering & Nano-Technology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; Guangdong Provincial Engineering Research Centre for Urban Water Recycling and Environmental Safety, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, Guangdong, China; School of Environment, Tsinghua University, Beijing 100084, China.
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Abstract
Humic acid (HA) has complex molecular structure and is capable of adsorption, ion exchange, and chelation with organic and inorganic pollutants in water bodies, worsening water quality and jeopardizing human health and ecological environment. How to effectively remove HA from water is one of the research focuses of this paper. In this study, the UV-activated sodium perborate (SPB) synergistic system (UV/SPB) was established to eliminate HA in water. The effects of initial HA concentration, SPB dose, and initial pH value on the HA elimination were determined, and the main mechanisms of the synergy and HA degradation were explored. The outcomes show that the HA elimination ratio by the sole UV and only SPB system were only 0.5% and 1.5%, respectively. The HA removal of UV/SPB reached 88.8%, which can remove HA more effectively than other systems. Free radical masking experiment proved that hydroxyl radical produced by SPB activation is the main active substance for HA removal. The results of UV-vis absorption spectrum, absorbance ratio, specific UV absorbance, and excitation–emission matrix spectroscopy verified that the UV/SPB system can effectively decompose and mineralize HA.
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