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Konadu-Amoah B, Ndé-Tchoupé AI, Hu R, Gwenzi W, Noubactep C. Investigating the Fe 0/H 2O systems using the methylene blue method: Validity, applications, and future directions. CHEMOSPHERE 2022; 291:132913. [PMID: 34788675 DOI: 10.1016/j.chemosphere.2021.132913] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 11/12/2021] [Accepted: 11/13/2021] [Indexed: 06/13/2023]
Abstract
An innovative approach to characterize the reactivity of metallic iron (Fe0) for aqueous contaminant removal has been in use for a decade: The methylene blue method (MB method). The approach considers the differential adsorptive affinity of methylene blue (MB) for sand and iron oxides. The MB method characterizes MB discoloration by sand as it is progressively coated by in-situ generated iron corrosion products (FeCPs) to deduce the extent of iron corrosion. The MB method is a semi-quantitative tool that has successfully clarified some contradicting reports on the Fe0/H2O system. Moreover, it has the potential to serve as a powerful tool for routine tests in the Fe0 remediation industry, including quality assurance and quality control (QA/QC). However, MB is widely used as a 'molecular probe' to characterize the Fe0/H2O system, for instance for wastewater treatment. Thus, there is scope to avoid confusion created by the multiple uses of MB in Fe0/H2O systems. The present communication aims at filling this gap by presenting the science of the MB method, and its application and limitations. It is concluded that the MB method is very suitable for Fe0 material screening and optimization of operational designs. However, the MB method only provides semi-quantitative information, but gives no data on the solid-phase characterization of solid Fe0 and its reaction products. In other words, further comprehensive investigations with microscopic and spectroscopic surface and solid-state analyses are needed to complement results from the MB method.
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Affiliation(s)
- Bernard Konadu-Amoah
- School of Earth Science and Engineering, Hohai University, Fo Cheng Xi Road 8, Nanjing 211100, China.
| | - Arnaud Igor Ndé-Tchoupé
- School of Earth Science and Engineering, Hohai University, Fo Cheng Xi Road 8, Nanjing 211100, China.
| | - Rui Hu
- School of Earth Science and Engineering, Hohai University, Fo Cheng Xi Road 8, Nanjing 211100, China.
| | - Willis Gwenzi
- Biosystems and Environmental Engineering Research Group, Department of Agricultural and Biosystems Engineering, University of Zimbabwe, P.O. Box MP167, Mount Pleasant, Harare, Zimbabwe.
| | - Chicgoua Noubactep
- Centre for Modern Indian Studies (CeMIS), Universität Göttingen, Waldweg 26, 37073 Göttingen, Germany; Department of Applied Geology, University of Göttingen, Goldschmidtstraße 3, D-37077 Göttingen, Germany; Department of Water and Environmental Science and Engineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania; Faculty of Science and Technology, Campus of Banekane, Université des Montagnes, P.O. Box 208, Bangangté, Cameroon.
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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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Cao V, Alyoussef G, Gatcha-Bandjun N, Gwenzi W, Noubactep C. The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe 0/MnO 2/sand systems. Sci Rep 2021; 11:12069. [PMID: 34103590 PMCID: PMC8187491 DOI: 10.1038/s41598-021-91475-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/26/2021] [Indexed: 11/20/2022] Open
Abstract
Metallic iron (Fe0) has shown outstanding performances for water decontamination and its efficiency has been improved by the presence of sand (Fe0/sand) and manganese oxide (Fe0/MnOx). In this study, a ternary Fe0/MnOx/sand system is characterized for its discoloration efficiency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 days. The objective was to understand the fundamental mechanisms of water treatment in Fe0/H2O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO2 and sand delay MB discoloration by avoiding the availability of free iron corrosion products (FeCPs). Results clearly demonstrate no monotonous increase in MB discoloration with increasing contact time. As a rule, the extent of MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (test-tubes). The presence of MnOx and sand enabled the long-term generation of iron hydroxides for MB discoloration by adsorption and co-precipitation. Results clearly reveal the complexity of the Fe0/MnOx/sand system, while establishing that both MnOx and sand improve the efficiency of Fe0/H2O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe0-based systems with reactive MnOx.
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Affiliation(s)
- Viet Cao
- Faculty of Natural Sciences, Hung Vuong University, Nguyen Tat Thanh Street, Viet Tri, Phu Tho, 35120, Vietnam
| | - Ghinwa Alyoussef
- Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, 37077, Göttingen, Germany
| | - Nadège Gatcha-Bandjun
- Department of Chemistry, Faculty of Science, University of Maroua, BP 46, Maroua, Cameroon
| | - Willis Gwenzi
- Biosystems and Environmental Engineering Research Group, Department of Agricultural and Biosystems Engineering, University of Zimbabwe, P.O. Box MP167, Mt. Pleasant, Harare, Zimbabwe
| | - Chicgoua Noubactep
- Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, 37077, Göttingen, Germany.
- Centre for Modern Indian Studies (CeMIS), Universität Göttingen, Waldweg 26, 37073, Göttingen, Germany.
- Department of Water and Environmental Science and Engineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania.
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Cao V, Alyoussef G, Gatcha-Bandjun N, Gwenzi W, Noubactep C. Characterizing the impact of MnO 2 addition on the efficiency of Fe 0/H 2O systems. Sci Rep 2021; 11:9814. [PMID: 33963252 PMCID: PMC8105408 DOI: 10.1038/s41598-021-89318-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/21/2021] [Indexed: 11/23/2022] Open
Abstract
The role of manganese dioxide (MnO2) in the process of water treatment using metallic iron (Fe0/H2O) was investigated in quiescent batch experiments for t ≤ 60 d. MnO2 was used as an agent to control the availability of solid iron corrosion products (FeCPs) while methylene blue (MB) was an indicator of reactivity. The investigated systems were: (1) Fe0, (2) MnO2, (3) sand, (4) Fe0/sand, (5) Fe0/MnO2, and (6) Fe0/sand/MnO2. The experiments were performed in test tubes each containing 22.0 mL of MB (10 mg L−1) and the solid aggregates. The initial pH value was 8.2. Each system was characterized for the final concentration of H+, Fe, and MB. Results show no detectable level of dissolved iron after 47 days. Final pH values varied from 7.4 to 9.8. The MB discoloration efficiency varies from 40 to 80% as the MnO2 loading increases from 2.3 to 45 g L−1. MB discoloration is only quantitative when the operational fixation capacity of MnO2 for Fe2+ was exhausted. This corresponds to the event where adsorption and co-precipitation with FeCPs is intensive. Adsorption and co-precipitation are thus the fundamental mechanisms of decontamination in Fe0/H2O systems. Hybrid Fe0/MnO2 systems are potential candidates for the design of more sustainable Fe0 filters.
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Affiliation(s)
- Viet Cao
- Faculty of Natural Sciences, Hung Vuong University, Nguyen Tat Thanh Street, Viet Tri, Phu Tho, 35120, Vietnam
| | - Ghinwa Alyoussef
- Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, 37077, Göttingen, Germany
| | - Nadège Gatcha-Bandjun
- Faculty of Science, Department of Chemistry, University of Maroua, BP 46, Maroua, Cameroon
| | - Willis Gwenzi
- Biosystems and Environmental Engineering Research Group, Department of Agricultural and Biosystems Engineering, University of Zimbabwe, P.O. Box MP167, Mt. Pleasant, Harare, Zimbabwe
| | - Chicgoua Noubactep
- Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, 37077, Göttingen, Germany. .,Centre for Modern Indian Studies (CeMIS), Universität Göttingen, Waldweg 26, 37073, Göttingen, Germany. .,Department of Water and Environmental Science and Engineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania.
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The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System. Processes (Basel) 2021. [DOI: 10.3390/pr9030548] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The typical time-dependent decrease of the iron corrosion rate is often difficult to consider while designing Fe0-based remediation systems. One of the most promising approaches is the amendment with manganese dioxide (Fe0/MnO2 system). The resulting system is a very complex one where characterization is challenging. The present communication uses methylene blue discoloration (MB method) to characterize the Fe0/MnO2 system. Shaken batch experiments (75 rpm) for 7 days were used. The initial MB concentration was 10 mg L−1 with the following mass loading: [MnO2] = 2.3 g L−1, [sand] = 45 g L−1, and 0 < [Fe0] (g L−1) ≤ 45. The following systems where investigated: Fe0, MnO2, sand, Fe0/MnO2, Fe0/sand, and Fe0/MnO2/sand. Results demonstrated that MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the test-tubes. Results confirm the complexity of the Fe0/MnO2/sand system, while establishing that both MnO2 and sand improve the efficiency of Fe0/H2O systems in the long-term. The mechanisms of water decontamination by amending Fe0-based systems with MnO2 is demonstrated by the MB method.
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Gheju M, Balcu I. Sustaining the efficiency of the Fe(0)/H 2O system for Cr(VI) removal by MnO 2 amendment. CHEMOSPHERE 2019; 214:389-398. [PMID: 30268895 DOI: 10.1016/j.chemosphere.2018.09.129] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 09/18/2018] [Accepted: 09/20/2018] [Indexed: 06/08/2023]
Abstract
This study aims to provide new knowledge regarding the effect of MnO2 co-presence on efficiency of Cr(VI) removal with Fe(0). Non-disturbed batch experiments (≤40 days) were conducted using two types of Fe(0) (milli- and micro-sized), two Cr(VI) concentrations (5 and 100 mg/L), in three different systems ("Fe(0) only", "MnO2 only", and "Fe(0) + MnO2"), at an initial pH value of 6.9. Compared to "Fe(0) only" system, the efficiency and rate of Cr(VI) removal were highly promoted in "Fe(0) + MnO2" system; moreover, while for the "Fe(0) only" system removal of Cr(VI) was severely hindered by increasing Cr(VI) concentration, in "Fe(0) + MnO2" system comparable high efficacies were noticed both at low and high concentration. Recycling experiments indicated that total Cr(VI) removal capacity of "Fe(0) + MnO2" system was up to 48.1 times greater than of the "Fe(0) only" system. Enhanced removal of Cr(VI) with Fe(0) was achieved at low doses of MnO2, with an optimal mass ratio Fe(0):MnO2 of 4:1. The favorable synergistic effect observed in "Fe(0) + MnO2" system was ascribed to capacity of MnO2 to accelerate Fe(0) oxidative dissolution, and to generate supplementary amounts of secondary adsorbents/reductants with removal ability towards Cr(VI). This study provides compelling evidence that "Fe(0) + MnO2" system could represent a highly efficient and cost-effective alternative for the abatement of Cr(VI) aqueous pollution.
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Affiliation(s)
- Marius Gheju
- Politehnica University Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, Bd. V. Parvan Nr. 6, 300223, Timisoara, Romania.
| | - Ionel Balcu
- National Institute for Research and Development in Electrochemistry and Condensed Matter, Str. Dr. Aurel Paunescu Podeanu Nr. 144, 300587, Timisoara, Romania
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Bilardi S, Calabrò PS, Greco R, Moraci N. Selective removal of heavy metals from landfill leachate by reactive granular filters. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 644:335-341. [PMID: 29981981 DOI: 10.1016/j.scitotenv.2018.06.353] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Revised: 06/28/2018] [Accepted: 06/28/2018] [Indexed: 06/08/2023]
Abstract
The pre-treatment of landfill leachate prior to its co-treatment in the municipal plants of waste water processing could represent an appropriate and cost-effective solution for its management. Pre-treatment is necessary especially to remove heavy metals, which may be transferred to the excess sludge preventing its valorisation. In the present paper, we propose a chemical-physical pre-treatment of leachate using four different granular reactive media able to selectively remove the contaminants present in the leachate. The efficiency of these materials was investigated using synthetic leachate through batch tests and a column test. In the latter case the four materials were placed in two columns connected in series and fed an under constant upward flow (0.5 mL/min). The first column was filled half (50 cm) with a granular mixture of zero valent iron (ZVI) and pumice and half (50 cm) with a granular mixture of ZVI and granular activated carbon (GAC). The second column, which was fed with the effluent of the first column, was filled half with zeolite (chabazite) and half with GAC. Heavy metals were mainly removed by the ZVI/pumice and ZVI/GAC steps with a removal efficiency that was higher than 98, 94 and 90% for copper, nickel and zinc, respectively, after 70 days of operation. Ammonium was removed by zeolite with a removal efficiency of 99% up to 23 days. The average reduction of the chemical oxygen demand (COD) was of 40% for 85 days, whereas chloride and sulphate removal was negligible.
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Affiliation(s)
- Stefania Bilardi
- Department of Civil, Energy, Environment and Materials Engineering (DICEAM), Mediterranea University of Reggio Calabria, Reggio Calabria, Italy.
| | - Paolo S Calabrò
- Department of Civil, Energy, Environment and Materials Engineering (DICEAM), Mediterranea University of Reggio Calabria, Reggio Calabria, Italy.
| | - Rosa Greco
- Department of Civil, Energy, Environment and Materials Engineering (DICEAM), Mediterranea University of Reggio Calabria, Reggio Calabria, Italy
| | - Nicola Moraci
- Department of Civil, Energy, Environment and Materials Engineering (DICEAM), Mediterranea University of Reggio Calabria, Reggio Calabria, Italy.
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Heimann S, Ndé-Tchoupé AI, Hu R, Licha T, Noubactep C. Investigating the suitability of Fe 0 packed-beds for water defluoridation. CHEMOSPHERE 2018; 209:578-587. [PMID: 29957518 DOI: 10.1016/j.chemosphere.2018.06.088] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 06/08/2018] [Accepted: 06/11/2018] [Indexed: 06/08/2023]
Abstract
A commercial granular metallic iron (Fe0) specimen was used to evaluate the suitability of Fe0 materials for removing aqueous fluoride (F-) (water defluoridation). Experiments were performed to characterize the defluoridation potential of the tested Fe0 as influenced by the presence of chloride (Cl-) and bicarbonate (HCO3-) ions using tap water (H2O) as operational reference system. Duplicate column studies were conducted for 120 days (4 months) using an initial F- concentration of 22.5 mg L-1, columns flow rates were about 17 mL h-1. Each column contained a reactive layer (11 cm) made up of 100 g of Fe0 in a 1:1 volumetric Fe0:sand mixture. The reactive layer was sandwiched between two layers of the same sand. A pure sand column was used as control system. After the F- removal experiments, the columns were flushed by methylene blue (MB) and Orange II for 21 days. Removal studies revealed (i) no F- removal in the control system, (ii) no F- significant removal on the Cl- system, (iii) limited F- removal in the HCO3- system, and (iv) the best F- removal efficiency in tap water (H2O). Dye flushing studies confirmed the ion-selective nature of the Fe0/H2O system and demonstrated the relatively low efficiency of the same for F- removal. The overall results challenge the prevailing perception that water defluoridation using granular Fe0 is not possible and suggest that effective water defluoridation in Fe0 packed-beds is pure a site-specific design issue.
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Affiliation(s)
- Svenja Heimann
- Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, D-37077, Göttingen, Germany
| | - Arnaud Igor Ndé-Tchoupé
- University of Douala, Faculty of Sciences, Department of Chemistry, B.P. 24157 Douala, Cameroon
| | - Rui Hu
- School of Earth Science and Engineering, Hohai University, Fo Cheng Xi Road 8, 211100 Nanjing, PR China
| | - Tobias Licha
- Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, D-37077, Göttingen, Germany
| | - Chicgoua Noubactep
- Angewandte Geologie, Universität Göttingen, Goldschmidtstraße 3, D-37077, Göttingen, Germany.
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Avoiding the Use of Exhausted Drinking Water Filters: A Filter-Clock Based on Rusting Iron. WATER 2018. [DOI: 10.3390/w10050591] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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