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Yu W, Liu L, Yan N, Zheng X. Groundwater denitrification enhanced by a hydrogel immobilized iron/solid carbon source: impact on denitrification and substrate release performance. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2024. [PMID: 38712385 DOI: 10.1039/d3em00444a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Encapsulating a solid carbon source and zero-valent iron (ZVI) within a hydrogel can prevent direct contact with groundwater, thereby extending the lifespan of their released active substrates. It is currently unclear whether the solid carbon source and ZVI will mutually influence each other's active substrate release process and the corresponding denitrification patterns, necessitating further investigation. In this study a hydrogel encapsulating different weight ratios of micron-sized zero-valent iron (mZVI, as ZVI) and polyhydroxybutyrate (PHB, as a solid carbon source) was synthesized. The aim was to investigate the influence of PHB on the release of dissolved iron from mZVI and denitrification mechanism. Results indicated that PHB was consumed at a higher rate than mZVI, and more mZVI active sites could be exposed after PHB consumption. Meanwhile, PHB increased the porosity of the hydrogel, allowing more active sites of mZVI to be exposed and thus releasing more dissolved iron. Furthermore, PHB enhanced the rate of microbial corrosion of mZVI, which further increased the release of dissolved iron. Higher PHB content in the hydrogel reduced the oxidation of the released dissolved iron, resulting in a microbial community dominated by heterotrophic microorganisms. Conversely, lower PHB content led to significant Fe(II) oxidation and a considerable relative abundance of mixotrophic microorganisms in the microbial community. Microorganisms with iron reduction potential were also detected. This study provides theoretical support for the precise control of mixed nutrient denitrification based on hydrogel immobilization and lays the foundation for its further practical application in groundwater.
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Affiliation(s)
- Wenhao Yu
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P. R. China.
- Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
| | - Lecheng Liu
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P. R. China.
- Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
| | - Ni Yan
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P. R. China.
- Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
| | - Xilai Zheng
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P. R. China.
- Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
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Yu W, Zheng T, Guo B, Tao Y, Liu L, Yan N, Zheng X. Coupling of polyhydroxybutyrate and zero-valent iron for enhanced treatment of nitrate pollution within the Permeable Reactive Barrier and its downgradient aquifer. WATER RESEARCH 2024; 250:121060. [PMID: 38181646 DOI: 10.1016/j.watres.2023.121060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 12/18/2023] [Accepted: 12/22/2023] [Indexed: 01/07/2024]
Abstract
Permeable Reactive Barriers (PRBs) have been utilized for mitigating nitrate pollution in groundwater systems through the use of solid carbon and iron fillers that release diverse nutrients to enhance denitrification efficiency. We conduct laboratory column tests to evaluate the effectiveness of PRBs in remediating nitrate pollution both within the PRB and in the downgradient aquifer. We use an iron-carbon hydrogel (ICH) as PRB filler, which has different weight ratios of polyhydroxybutyrate (PHB) and microscale zero-valent iron (mZVI). Results reveal that denitrification in the downgradient aquifer accounts for at least 19.5 % to 32.5 % of the total nitrate removal. In the ICH, a higher ratio of PHB to mZVI leads to higher contribution of the downgradient aquifer to nitrate removal, while a lower ratio results in smaller contribution. Microbial community analysis further reveals that heterotrophic and mixotrophic bacteria dominate in the downgradient aquifer of the PRB, and their relative abundance increases with a higher ratio of PHB to mZVI in the ICH. Within the PRB, autotrophic and iron-reducing bacteria are more prevalent, and their abundance increases as the ratio of PHB to mZVI in the ICH decreases. These findings emphasize the downgradient aquifer's substantial role in nitrate removal, particularly driven by dissolved organic carbon provided by PHB. This research holds significant implications for nutrient waste management, including the prevention of secondary pollution, and the development of cost-effective PRBs.
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Affiliation(s)
- Wenhao Yu
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, PR China; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
| | - Tianyuan Zheng
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, PR China; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China.
| | - Bo Guo
- Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA.
| | - Yiheng Tao
- Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ08544, USA
| | - Lecheng Liu
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, PR China; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
| | - Ni Yan
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, PR China; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
| | - Xilai Zheng
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, PR China; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China
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Pei H, Chen D, Jiang H, Xiao Z. Development of a mathematical model for a microbial denitrification co-culture system comprising acetogenic bacterium Sporomusa ovata and denitrifying bacterium Pseudomonas stutzeri. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2023; 87:2043-2060. [PMID: 37119171 DOI: 10.2166/wst.2023.110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Previous study has shown that co-culturing acetogenic bacterium Sporomusa ovata (SO), with denitrifying bacterium Pseudomonas stutzeri (PS), is a promising strategy to enhance the microbial denitrification for nitrate-contaminated groundwater remediation. However, the mutual effects and reaction kinetics of these two bacteria in the co-culture system are poorly understood. In this study, a mathematical model for this co-culture system was established to fill this knowledge gap. Model simulation demonstrated that SO had a significant effect on the kinetics of denitrification by PS, while PS slightly affected the kinetics of acetate production by SO. The optimal initial HCO3-/NO3- ratio and SO/PS inoculation ratio were 0.77-1.48 and 67 for the co-culture system to achieve satisfied denitrification performance with less acetate accumulation. Finally, the minimum hydrogen supply was recommended when the initial bicarbonate and nitrate concentrations were assigned in the range of 2-20 mM and 2-4 mM for simulating the natural nitrate-contaminated groundwater treatment. These findings could provide useful insights to guide the operation and optimization of the denitrification co-culture system.
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Affiliation(s)
- Haoyi Pei
- College of Urban Construction, Nanjing Tech University, Nanjing 211816, China E-mail:
| | - Dan Chen
- College of Urban Construction, Nanjing Tech University, Nanjing 211816, China E-mail:
| | - Hongxia Jiang
- College of Urban Construction, Nanjing Tech University, Nanjing 211816, China E-mail:
| | - Zhixing Xiao
- College of Urban Construction, Nanjing Tech University, Nanjing 211816, China E-mail:
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Zhou Y, Chen L, Wang J, Lu L, Liu F, Chen C, Qin X. Solution, exchangeable and fixed ammonium in natural diatomite as a simulated PRB material: effects of adsorption and bioregeneration processes. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:52433-52445. [PMID: 36840872 DOI: 10.1007/s11356-023-26058-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Accepted: 02/17/2023] [Indexed: 06/18/2023]
Abstract
Ammonia nitrogen (NH4+-N) is widely found in aquifers with strong reducibility or poor adsorptivity as a dissolved inorganic nitrogen pollutant. The application of adsorbents with effective long-term in situ bioregeneration as permeable reactive barrier (PRB) media for nitrogen removal has raised concern. In this study, the advantage of natural diatomite as a PRB material was investigated by exploring its NH4+-N adsorption and desorption characteristics, and the ability of diatomite and zeolite to be loaded nitrifying bacteria was also compared. The results showed that the exchangeable ammonium from chemical-monolayer adsorption was the main form of NH4+-N and was adsorbed by diatomite. Moreover, the adsorption process was limited with a maximum adsorption capacity of 0.677 mg g-1. However, diatomite demonstrated an excellent loading of aerobic-heterotrophic microorganisms, even stronger than zeolite. Compared with zeolite reactors, a higher OD600 value of nitrifiers, a faster NH4+-N degradation rate and more abundant functional genes were observed during the bioregeneration process of diatomite. Both the solution and exchangeable ammonium forms were bioavailable, and the regeneration of diatomite was more than 80.0% after two days. Moreover, desorption-biodegradation was systematically analysed to determine the bioregeneration mechanism of diatomite. Diatomite with good regeneration ability can be used as a competitive alternative to address sudden nitrogen pollution.
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Affiliation(s)
- Yang Zhou
- MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
- Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
| | - Linpeng Chen
- MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
- Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
| | - Jialin Wang
- MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
- Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
| | - Li Lu
- Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin, 541004, Guangxi, China
- Guangxi Karst Resources and Environment Research Center of Engineering Technology, Guilin, 541004, Guangxi, China
| | - Fei Liu
- MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
- Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China
| | - Cuibai Chen
- MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China.
- Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, People's Republic of China.
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China.
| | - Xiaopeng Qin
- Technical Centre for Soil, Agricultural and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing, 100012, People's Republic of China.
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Chu L, Zhang C, Yu J, Sun X, Zhou X, Zhang Y. Adsorption of nitrate from interflow by the Mg/Fe calcined layered double hydroxides. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2022; 86:511-529. [PMID: 35960834 DOI: 10.2166/wst.2022.224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Nitrate loss in interflow caused serious nitrate pollution of neighboring water bodies in the purple soil region of China's Sichuan Province. In this study, Mg/Fe(Al)-calcined layered double hydroxides (Mg/Fe(Al)-CLDHs) with varied Mg/Fe(Al) ratios were synthesized for nitrate removal from interflow, and 3:1 Mg/Fe CLDH exhibited the best adsorption performance. The effects of initial pH, adsorbent dosage and co-existing anions on the adsorption performance were investigated by batch experiments. The best-fitting kinetic and isothermal models for nitrate adsorption were the pseudo-second-order model and Freundlich model, respectively, indicating that the adsorption process was a physical-chemical multilayer process. The maximum adsorption capacity of nitrate was 73.36 mg/g, which was higher than that of many other commonly used adsorbents. The adsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) techniques, and the XRD and FT-IR results revealed that the adsorption mechanism involved original layered structure reconstruction and ion-exchange interaction. Under the coexistence of SO42- and Cl-, 75.63% nitrate in interflow could be removed after 6 h of adsorption. Overall, the synthesized Mg/Fe CLDH is an effective and low-cost nitrate adsorbent for in-situ nitrate removal.
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Affiliation(s)
- Liquan Chu
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China E-mail: ; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Chaojie Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China E-mail: ; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Jing Yu
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China E-mail: ; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Xu Sun
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China E-mail: ; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Xuefei Zhou
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China E-mail: ; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Yalie Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China E-mail: ; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
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Wang W, Gong T, Li H, Liu Y, Dong Q, Zan R, Wu Y. The multi-process reaction model and underlying mechanisms of 2,4,6-trichlorophenol removal in lab-scale biochar-microorganism augmented ZVI PRBs and field-scale PRBs performance. WATER RESEARCH 2022; 217:118422. [PMID: 35413559 DOI: 10.1016/j.watres.2022.118422] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 03/31/2022] [Accepted: 04/04/2022] [Indexed: 06/14/2023]
Abstract
This work developed calcium alginate (CA) embedded zero-valent iron (ZVI@CA) and CA embedded biochar (BC) immobilized microorganism (BC&Cell@CA) gel beads as alternative to conventional Fe0 permeable reactive barriers for treating groundwater contaminated with 2,4,6-trichlorophenol (2,4,6-TCP). Lab-scale and field-scale biochar-microorganism augmented PRBs (Bio-PRBs) were constructed and tested. The underlying mechanisms were revealed by a multi-source data calibrated multi-process reaction model, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-throughput sequencing. Moreover, calibrated advection-dispersion (a) coupled with the two-site sorption (Kd) and chemical-biological multi-process reaction (λ) model were used for revealing 2,4,6-TCP transport behavior and optimizing Bio-PRBs. Compared to that in the ZVI@CA (0.004 h-1) system, the reaction rate (0.011 h-1) of 2,4,6-TCP increased by 175% in the combined chemical-biological batch system. Moreover, chemical-biological augmentation significantly improved the retardation effect of Bio-PRBs for 2,4,6-TCP. It came from that chemical-biological augmentation significantly decreased the dispersivity a (0.53 to 0.20 cm), and increased the distribution coefficient Kd (2.20 to 19.00 cm3 mg-1), the reaction rate λ (2.40 to 3.60 day-1), and the fraction (30% to 80%) of first-order kinetic sorption of 2,4,6-TCP in the lab-scale one-dimensional Bio-PRBs. Moreover, versatile functional bacteria Desulfitobacterium was crucial in the transformation of Fe (III) iron oxides. The diversity and richness of archaea in the reaction solution were improved by ZVI@CA gel beads addition. Furthermore, the field-scale reaction system was designed to remediate the chlorinated organic compounds and Benzene Toluene Ethylbenzene & Xylene contaminated groundwater in a pesticide factory site. The field test results demonstrated it is a promising technology to construct vertical reaction columns or horizontal Bio-PRBs for the efficient remediation of actually contaminated groundwater.
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Affiliation(s)
- Wenbing Wang
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai, 200444, China
| | - Tiantian Gong
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai, 200444, China
| | - Hui Li
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai, 200444, China.
| | - Yiming Liu
- Department of Geography, McGill University, Montreal, QC H3A 0G4, Canada
| | - Qianling Dong
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai, 200444, China
| | - Rixia Zan
- School of Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Yulin Wu
- Shanghai Geotechnical Investigations and Design Institute (SGIDI) Engineering Consulting (Group) Co. Ltd., China
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Zhu F, Tan X, Zhao W, Feng L, He S, Wei L, Yang L, Wang K, Zhao Q. Efficiency assessment of ZVI-based media as fillers in permeable reactive barrier for multiple heavy metal-contaminated groundwater remediation. JOURNAL OF HAZARDOUS MATERIALS 2022; 424:127605. [PMID: 34741938 DOI: 10.1016/j.jhazmat.2021.127605] [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: 07/04/2021] [Revised: 10/11/2021] [Accepted: 10/23/2021] [Indexed: 05/27/2023]
Abstract
Four zero valent iron-based composites were prepared and applied as the reactive media of permeable reactive barriers. Batch tests and continuous-flow column experiments were conducted to assess the long-term performance of these composites for possible utilization as fillers for PRB. The experimental results of the batch tests revealed that in single-metal systems, the removal efficiency of Cu(Ⅱ), Co(Ⅱ), Cr(Ⅵ) and As(Ⅲ) could reach 98% at equilibrium. Equilibrium data showed that composites displayed different selectivity values in binary and quaternary-component systems. For the continuous tests, column filled with chitosan-zero valent iron-based composites, exhibited optimal removal efficiency and achieved average removal values of 98.84%, 88.28%, 95.65% and 87.10% for Cu(Ⅱ), Co(Ⅱ), Cr(Ⅵ) and As(Ⅲ) during the whole 30-day operation, respectively. Dynamic removal improvement of multiple metals was observed with further assembly media, with average removal of 99.11%, 90.05% and 87.34% for Cu(Ⅱ), Co(Ⅱ) and As(Ⅲ), respectively. Combined with superficial characteristic analysis, the functional groups distributed on the surface of composites played a key role in metal sorption. Moreover, the adsorbed Cu(Ⅱ), Co(Ⅱ) and Cr(Ⅵ) gradually transferred to the mobile phase when the operational periods were prolonged, while As(Ⅲ) became more stable.
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Affiliation(s)
- Fengyi Zhu
- School of Environment, Harbin Institute of Technology, Harbin 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Harbin Institute of Technology, Harbin 150090, China
| | - Xuefei Tan
- College of Materials and Chemical Engineering, Heilongjiang Institute of Technology, Harbin 100050, China
| | - Weixin Zhao
- School of Environment, Harbin Institute of Technology, Harbin 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Harbin Institute of Technology, Harbin 150090, China
| | - Likui Feng
- School of Environment, Harbin Institute of Technology, Harbin 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Harbin Institute of Technology, Harbin 150090, China
| | - Shufei He
- School of Environment, Harbin Institute of Technology, Harbin 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Harbin Institute of Technology, Harbin 150090, China
| | - Liangliang Wei
- School of Environment, Harbin Institute of Technology, Harbin 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Harbin Institute of Technology, Harbin 150090, China.
| | - Lin Yang
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150090, China
| | - Kun Wang
- School of Environment, Harbin Institute of Technology, Harbin 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Harbin Institute of Technology, Harbin 150090, China
| | - Qingliang Zhao
- School of Environment, Harbin Institute of Technology, Harbin 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), Harbin Institute of Technology, Harbin 150090, China
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The Suitability of Hybrid Fe0/Aggregate Filtration Systems for Water Treatment. WATER 2022. [DOI: 10.3390/w14020260] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Metallic iron (Fe0) corrosion under immersed conditions (Fe0/H2O system) has been used for water treatment for the past 170 years. Fe0 generates solid iron corrosion products (FeCPs) which are known to in situ coat the surface of aggregates, including granular activated carbon (GAC), gravel, lapillus, manganese oxide (MnO2), pyrite (FeS2), and sand. While admixing Fe0 and reactive aggregates to build hybrid systems (e.g., Fe0/FeS2, Fe0/MnO2, Fe0/sand) for water treatment, it has been largely overlooked that these materials would experience reactivity loss upon coating. This communication clarifies the relationships between aggregate addition and the sustainability of Fe0/H2O filtration systems. It is shown that any enhanced contaminant removal efficiency in Fe0/aggregate/H2O systems relative to the Fe0/H2O system is related to the avoidance/delay of particle cementation by virtue of the non-expansive nature of the aggregates. The argument that aggregate addition sustains any reductive transformation of contaminants mediated by electrons from Fe0 is disproved by the evidence that Fe0/sand systems are equally more efficient than pure Fe0 systems. This demonstration corroborates the concept that aqueous contaminant removal in iron/water systems is not a process mediated by electrons from Fe0. This communication reiterates that only hybrid Fe0/H2O filtration systems are sustainable.
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