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This communication is motivated by recent publications discussing the affordability of appropriate decentralized solutions for safe drinking water provision in low-income communities. There is a huge contrast between the costs of presented technologies, which vary by a factor of up to 12. For example, for the production of 2000 L/d of treated drinking water, the costs vary between about 1500 and 12,000 Euro. A closer look at the technologies reveals that expensive technologies use imported manufactured components or devices that cannot yet be locally produced. In the battle to achieve the United Nations Sustainable Development Goal for safe drinking water (SDG 6.1), such technologies should be, at best, considered as bridging solutions. For a sustainable self-reliance in safe drinking water supply, do-it-yourself (DIY) systems should be popularized. These DIY technologies include biochar and metallic iron (Fe0) based systems. These relevant technologies should then be further improved through internal processes.
Zhe Huang; Esther Laurentine Nya; Viet Cao; Willis Gwenzi; Mohammad Azizur Rahman; Chicgoua Noubactep. Universal Access to Safe Drinking Water: Escaping the Traps of Non-Frugal Technologies. Sustainability 2021, 13, 9645 .
AMA StyleZhe Huang, Esther Laurentine Nya, Viet Cao, Willis Gwenzi, Mohammad Azizur Rahman, Chicgoua Noubactep. Universal Access to Safe Drinking Water: Escaping the Traps of Non-Frugal Technologies. Sustainability. 2021; 13 (17):9645.
Chicago/Turabian StyleZhe Huang; Esther Laurentine Nya; Viet Cao; Willis Gwenzi; Mohammad Azizur Rahman; Chicgoua Noubactep. 2021. "Universal Access to Safe Drinking Water: Escaping the Traps of Non-Frugal Technologies." Sustainability 13, no. 17: 9645.
There is escalating salinity levels on small islands due to uncontrolled groundwater extraction. Conventionally, this challenge is addressed by adopting optimal groundwater pumping strategies. Currently, on Unguja Island (Zanzibar), urban freshwater is supplied by desalination, which is expensive and energy-intensive. Hence, desalinization cannot be afforded by rural communities. This study demonstrates that the innovative Kilimanjaro Concept (KC), based on rainwater harvesting (RWH) can remediate seawater intrusion in Unguja, while enabling a universal safe drinking water supply. The reasoning is rooted in the water balance of the whole island. It is shown that if rainwater is systematically harvested, quantitatively stored, and partly infiltrated, seawater intrusion will be reversed, and a universal safe drinking water supply will be secured. Water treatment with affordable technologies (e.g., filtration and adsorption) is suggested. The universality of KC and its suitability for small islands is demonstrated. Future research should focus on pilot testing of this concept on Unguja Island and other island nations.
Zuleikha Pembe-Ali; Tulinave Mwamila; Mesia Lufingo; Willis Gwenzi; Janeth Marwa; Mwemezi Rwiza; Innocent Lugodisha; Qinwen Qi; Chicgoua Noubactep. Application of the Kilimanjaro Concept in Reversing Seawater Intrusion and Securing Water Supply in Zanzibar, Tanzania. Water 2021, 13, 2085 .
AMA StyleZuleikha Pembe-Ali, Tulinave Mwamila, Mesia Lufingo, Willis Gwenzi, Janeth Marwa, Mwemezi Rwiza, Innocent Lugodisha, Qinwen Qi, Chicgoua Noubactep. Application of the Kilimanjaro Concept in Reversing Seawater Intrusion and Securing Water Supply in Zanzibar, Tanzania. Water. 2021; 13 (15):2085.
Chicago/Turabian StyleZuleikha Pembe-Ali; Tulinave Mwamila; Mesia Lufingo; Willis Gwenzi; Janeth Marwa; Mwemezi Rwiza; Innocent Lugodisha; Qinwen Qi; Chicgoua Noubactep. 2021. "Application of the Kilimanjaro Concept in Reversing Seawater Intrusion and Securing Water Supply in Zanzibar, Tanzania." Water 13, no. 15: 2085.
Rainwater harvesting (RWH) is generally perceived as a promising cost-effective alternative water resource for potable and non-potable uses (water augmentation) and for reducing flood risks. The performance of RWH systems has been evaluated for various purposes over the past few decades. These systems certainly provide economic, environmental, and technological benefits of water uses. However, regarding RWH just as an effective alternative water supply to deal with the water scarcity is a mistake. The present communication advocates for a systematic RWH and partial infiltration wherever and whenever rain falls. By doing so, the detrimental effects of flooding are reduced, groundwater is recharged, water for agriculture and livestock is stored, and conventional water sources are saved. In other words, RWH should be at the heart of water management worldwide. The realization of this goal is easy even under low-resource situations, as infiltration pits and small dams can be constructed with local skills and materials.
Zhe Huang; Esther Nya; Mohammad Rahman; Tulinave Mwamila; Viet Cao; Willis Gwenzi; Chicgoua Noubactep. Integrated Water Resource Management: Rethinking the Contribution of Rainwater Harvesting. Sustainability 2021, 13, 8338 .
AMA StyleZhe Huang, Esther Nya, Mohammad Rahman, Tulinave Mwamila, Viet Cao, Willis Gwenzi, Chicgoua Noubactep. Integrated Water Resource Management: Rethinking the Contribution of Rainwater Harvesting. Sustainability. 2021; 13 (15):8338.
Chicago/Turabian StyleZhe Huang; Esther Nya; Mohammad Rahman; Tulinave Mwamila; Viet Cao; Willis Gwenzi; Chicgoua Noubactep. 2021. "Integrated Water Resource Management: Rethinking the Contribution of Rainwater Harvesting." Sustainability 13, no. 15: 8338.
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.
Viet Cao; Ghinwa Alyoussef; Nadège Gatcha-Bandjun; Willis Gwenzi; Chicgoua Noubactep. The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems. Scientific Reports 2021, 11, 1 -11.
AMA StyleViet Cao, Ghinwa Alyoussef, Nadège Gatcha-Bandjun, Willis Gwenzi, Chicgoua Noubactep. The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems. Scientific Reports. 2021; 11 (1):1-11.
Chicago/Turabian StyleViet Cao; Ghinwa Alyoussef; Nadège Gatcha-Bandjun; Willis Gwenzi; Chicgoua Noubactep. 2021. "The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems." Scientific Reports 11, no. 1: 1-11.
The growing demands for affordable and applicable technologies for decentralized safe drinking water provision have instigated technical innovations in the water filtration industry. Adsorptive filtration appears to be the most affordable, resilient, and socially acceptable solution for households and small communities worldwide. However, water filtration devices have not yet been widely implemented due to lack of awareness for the efficiency of such systems using locally available materials. Water filtration has the potential to secure universal access to safe drinking water by 2030. This special issue has elucidated the applicability, benefits, constraints, effectiveness, and limitations of metallic iron as filter material for safe drinking water provision. Tools to make rainwater a primary water source are also presented together with ways to transform existing centralized water management systems into decentralized ones (sectorization). The knowledge is applicable to a wide variety of situations on a global scale.
Chicgoua Noubactep. Special Issue on Planning, Designing and Managing Decentralized Drinking Water Supply System—Editorial. Processes 2021, 9, 930 .
AMA StyleChicgoua Noubactep. Special Issue on Planning, Designing and Managing Decentralized Drinking Water Supply System—Editorial. Processes. 2021; 9 (6):930.
Chicago/Turabian StyleChicgoua Noubactep. 2021. "Special Issue on Planning, Designing and Managing Decentralized Drinking Water Supply System—Editorial." Processes 9, no. 6: 930.
The global effort to mitigate the impact of environmental pollution has led to the use of various types of metallic iron (Fe(0)) in the remediation of soil and groundwater as well as in the treatment of industrial and municipal effluents. During the past three decades, hundreds of scientific publications have controversially discussed the mechanism of contaminant removal in Fe(0)/H2O systems, with the large majority considering Fe(0) to be oxidized by contaminants of concern. This view assumes that contaminant reduction is the cathodic reaction occurring simultaneously with Fe0 oxidative dissolution (anodic reaction). This view contradicts the century-old theory of the electrochemical nature of aqueous iron corrosion and hinders progress in designing efficient and sustainable remediation Fe(0)/H2O systems. The aim of the present communication is to demonstrate the fallacy of the current prevailing view based on articles published before 1910. It is shown that properly reviewing the literature would have avoided the mistake. Going back to the roots is recommended as the way forward and should be considered first while designing laboratory experiments.
Viet Cao; Arnaud Igor Ndé-Tchoupé; Rui Hu; Willis Gwenzi; Chicgoua Noubactep. The mechanism of contaminant removal in Fe(0)/H2O systems: The burden of a poor literature review. Chemosphere 2021, 280, 130614 .
AMA StyleViet Cao, Arnaud Igor Ndé-Tchoupé, Rui Hu, Willis Gwenzi, Chicgoua Noubactep. The mechanism of contaminant removal in Fe(0)/H2O systems: The burden of a poor literature review. Chemosphere. 2021; 280 ():130614.
Chicago/Turabian StyleViet Cao; Arnaud Igor Ndé-Tchoupé; Rui Hu; Willis Gwenzi; Chicgoua Noubactep. 2021. "The mechanism of contaminant removal in Fe(0)/H2O systems: The burden of a poor literature review." Chemosphere 280, no. : 130614.
Keeping up-to-date with the literature is a great challenge for all scientists because analyzing and sorting published data can be very laborious and time-consuming. With the use of metallic iron (Fe0) in environmental remediation, scientists are facing such a challenging situation. Without an appropriate background, it can be very difficult to discern which information is plausible and which one is not. This communication demonstrates how the chemistry of aqueous iron corrosion (Fe0/H2O system) facilitates a critical assessment of the literature on the decontamination of waters polluted with metals and metalloids. It is reiterated that the pH-dependent solubility of iron and the extent of the oxidation from FeII to FeIII species determine the extent of contaminant mitigation in Fe0/H2O systems. Future remediation Fe0/H2O systems should be designed based on the science of iron corrosion under aqueous conditions.
Chicgoua Noubactep. Metallic iron for the removal of metals and metalloids from aqueous solutions: an old-timer view. Current Opinion in Environmental Science & Health 2021, 22, 100256 .
AMA StyleChicgoua Noubactep. Metallic iron for the removal of metals and metalloids from aqueous solutions: an old-timer view. Current Opinion in Environmental Science & Health. 2021; 22 ():100256.
Chicago/Turabian StyleChicgoua Noubactep. 2021. "Metallic iron for the removal of metals and metalloids from aqueous solutions: an old-timer view." Current Opinion in Environmental Science & Health 22, no. : 100256.
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.
Viet Cao; Ghinwa Alyoussef; Nadège Gatcha-Bandjun; Willis Gwenzi; Chicgoua Noubactep. The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System. Processes 2021, 9, 548 .
AMA StyleViet Cao, Ghinwa Alyoussef, Nadège Gatcha-Bandjun, Willis Gwenzi, Chicgoua Noubactep. The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System. Processes. 2021; 9 (3):548.
Chicago/Turabian StyleViet Cao; Ghinwa Alyoussef; Nadège Gatcha-Bandjun; Willis Gwenzi; Chicgoua Noubactep. 2021. "The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System." Processes 9, no. 3: 548.
The role of pyrite (FeS2) in the process of water treatment using metallic iron (Fe0) was investigated. FeS2 was used as a pH-shifting agent while methylene blue (MB) and methyl orange (MO) were used as an indicator of reactivity and model contaminant, respectively. The effect of the final pH value on the extent of MB discoloration was characterized using 5 g L−1 of a Fe0 specimen. pH variation was achieved by adding 0 to 30 g L−1 of FeS2. Quiescent batch experiments with Fe0/FeS2/sand systems (sand loading: 25 g L−1) and 20 mL of MB were performed for 41 days. Final pH values varied from 3.3 to 7.0. Results demonstrated that MB discoloration is only quantitative when the final pH value was larger than 4.5 and that adsorption and co-precipitation are the fundamental mechanisms of decontamination in Fe0/H2O systems. Such mechanisms are consistent with the effects of the pH value on the decontamination process.
Rui Hu; Xuesong Cui; Minhui Xiao; Willis Gwenzi; Chicgoua Noubactep. Characterizing the impact of pyrite addition on the efficiency of Fe0/H2O systems. Scientific Reports 2021, 11, 1 -13.
AMA StyleRui Hu, Xuesong Cui, Minhui Xiao, Willis Gwenzi, Chicgoua Noubactep. Characterizing the impact of pyrite addition on the efficiency of Fe0/H2O systems. Scientific Reports. 2021; 11 (1):1-13.
Chicago/Turabian StyleRui Hu; Xuesong Cui; Minhui Xiao; Willis Gwenzi; Chicgoua Noubactep. 2021. "Characterizing the impact of pyrite addition on the efficiency of Fe0/H2O systems." Scientific Reports 11, no. 1: 1-13.
Biological and chemical contamination of natural water bodies is a global health risk for more than one billion people, mostly living in low-income countries. Innovative, affordable, and efficient decentralized solutions for safe drinking water supply are urgently needed. Metallic iron (Fe0)-based filtration systems have been described as such an appropriate solution. This communication focuses on the Kanchan arsenic filter (KAF), presented in the early 2000s and widely assessed during the past decade. The KAF contains iron nails as the Fe0 source and is primarily designed to remove As from polluted tube well waters. Recent independent works assessing their performance have all reported on a high degree of variability in efficiency depending mostly on (1) the current operating conditions, (2) the design, and (3) the groundwater chemistry. This communication shows that the major problems of the KAF are twofold: (1) a design mistake as the Fe0 units disturb the operation and functionality of the biosand filter, and (2) the use of poorly characterized iron nails of unknown reactivity. This assertion is supported by the evidence that the very successful community filter designed by the Indian Institute of Technology Bombay works with iron nails and has been efficient for many years. Replacing iron nails by more reactive Fe0 materials (e.g., iron fillings and steel wool) should be tested in a new generation KAF. It is concluded that a methodological or systematic approach in introducing and monitoring the efficiency of KAF should be used to test and disseminate the next generation KAF worldwide. Moreover, better characterization of the Fe0 materials including their intrinsic reactivity is required.
Zhe Huang; Viet Cao; Esther Laurentine Nya; Willis Gwenzi; Chicgoua Noubactep. Kanchan Arsenic Filters and the Future of Fe0-Based Filtration Systems for Single Household Drinking Water Supply. Processes 2020, 9, 58 .
AMA StyleZhe Huang, Viet Cao, Esther Laurentine Nya, Willis Gwenzi, Chicgoua Noubactep. Kanchan Arsenic Filters and the Future of Fe0-Based Filtration Systems for Single Household Drinking Water Supply. Processes. 2020; 9 (1):58.
Chicago/Turabian StyleZhe Huang; Viet Cao; Esther Laurentine Nya; Willis Gwenzi; Chicgoua Noubactep. 2020. "Kanchan Arsenic Filters and the Future of Fe0-Based Filtration Systems for Single Household Drinking Water Supply." Processes 9, no. 1: 58.
There is growing interest in using pyrite minerals (FeS2) to enhance the efficiency of metallic iron (Fe0) for water treatment (Fe0/H2O systems). This approach contradicts the thermodynamic predicting suppression of FeS2 oxidation by Fe0 addition. Available results are rooted in time series correlations between aqueous and solid phases based on data collected under various operational conditions. Herein, the methylene blue method (MB method) is used to clarify the controversy. The MB method exploits the differential adsorptive affinity of MB onto sand and sand coated with iron corrosion products to assess the extent of Fe0 corrosion in Fe0/H2O systems. The effects of the addition of various amounts of FeS2 to a Fe0/sand mixture (FeS2 method) on MB discoloration were characterized in parallel quiescent batch experiments for up to 71 d (pH0 = 6.8). Pristine and aged FeS2 specimens were used. Parallel experiments with methyl orange (MO) and reactive red 120 (RR120) enabled a better discussion of the achieved results. The results clearly showed that FeS2 induces a pH shift and delays Fe precipitation and sand coating. Pristine FeS2 induced a pH shift to values lower than 4.5, but no quantitative MB discoloration occurred after 45 d. Aged FeS2 could not significantly shift the pH value (final pH ≥ 6.4) but improved the MB discoloration. The used systematic sequence of experiments demonstrated that adsorption and coprecipitation are the fundamental mechanisms of contaminant removal in Fe0/H2O systems. This research has clarified the reason why a FeS2 addition enhances the efficiency of Fe0 environmental remediation.
Minhui Xiao; Xuesong Cui; Rui Hu; Willis Gwenzi; Chicgoua Noubactep. Validating the Efficiency of the FeS2 Method for Elucidating the Mechanisms of Contaminant Removal Using Fe0/H2O Systems. Processes 2020, 8, 1162 .
AMA StyleMinhui Xiao, Xuesong Cui, Rui Hu, Willis Gwenzi, Chicgoua Noubactep. Validating the Efficiency of the FeS2 Method for Elucidating the Mechanisms of Contaminant Removal Using Fe0/H2O Systems. Processes. 2020; 8 (9):1162.
Chicago/Turabian StyleMinhui Xiao; Xuesong Cui; Rui Hu; Willis Gwenzi; Chicgoua Noubactep. 2020. "Validating the Efficiency of the FeS2 Method for Elucidating the Mechanisms of Contaminant Removal Using Fe0/H2O Systems." Processes 8, no. 9: 1162.
The technology of using metallic iron (Fe0) for in situ generation of iron oxides for water treatment is a very old one. The Fe0 remediation technology has been re-discovered in the framework of groundwater remediation using permeable reactive barriers (PRBs). Despite its simplicity, the improvement of Fe0 PRBs is fraught with difficulties regarding their operating modes. The literature dealing with Fe0 remediation contains ambiguities regarding its invention and its development. The present paper examines the sequence of contributions prior to the advent of Fe0 PRBs in order to clarify the seemingly complex picture. To achieve this, the current paper addresses the following questions: (i) What were the motivations of various authors in developing their respective innovations over the years?, (ii) what are the ancient achievements which can accelerate progress in knowledge for the development of Fe0 PRBs?, and (iii) was Fe0 really used for the removal of organic species for the first time in the 1970s? A careful examination of ancient works reveals that: (i) The wrong questions were asked during the past three decades, as Fe0 was premised as a reducing agent, (ii) credit for using Fe0 for water treatment belongs to no individual scientist, and (iii) credit for the use of Fe0 in filtration systems for safe drinking water provision belongs to scientists from the 1850s, while credit for the use of Fe0 for the removal of aqueous organic species does not belong to the pioneers of the Fe0 PRB technology. However, it was these pioneers who exploited Fe0 for groundwater remediation, thereby extending its potential. Complementing recent achievements with the chemistry of the Fe0/H2O system would facilitate the design of more sustainable Fe0-remediation systems.
Viet Cao; Huichen Yang; Arnaud Igor Ndé-Tchoupé; Rui Hu; Willis Gwenzi; Chicgoua Noubactep. Tracing the Scientific History of Fe0-Based Environmental Remediation Prior to the Advent of Permeable Reactive Barriers. Processes 2020, 8, 977 .
AMA StyleViet Cao, Huichen Yang, Arnaud Igor Ndé-Tchoupé, Rui Hu, Willis Gwenzi, Chicgoua Noubactep. Tracing the Scientific History of Fe0-Based Environmental Remediation Prior to the Advent of Permeable Reactive Barriers. Processes. 2020; 8 (8):977.
Chicago/Turabian StyleViet Cao; Huichen Yang; Arnaud Igor Ndé-Tchoupé; Rui Hu; Willis Gwenzi; Chicgoua Noubactep. 2020. "Tracing the Scientific History of Fe0-Based Environmental Remediation Prior to the Advent of Permeable Reactive Barriers." Processes 8, no. 8: 977.
The ambitious United Nations Sustainable Development Goal for 2030 to “leave no one behind” concerning safe drinking water calls for the development of universally applicable and affordable decentralized treatment systems to provide safe drinking water. Published results suggest that well-designed biological sand filters (BSFs) amended with metallic iron (Fe0-BSFs) have the potential to achieve this goal. Fe0-BSFs quantitatively remove pathogens and a myriad of chemical pollutants. The available data were achieved under various operating conditions. A comparison of independent research results is almost impossible, especially because the used Fe0 materials are not characterized for their intrinsic reactivity. This communication summarizes the state-of-the-art knowledge on designing Fe0-BSFs for households and small communities. The results show that significant research progress has been made on Fe0-BSFs. However, well-designed laboratory and field experiments are required to improve the available knowledge in order to develop the next generation of adaptable and scalable designs of Fe0-BSFs in only two years. Tools to alleviate the permeability loss, the preferential flow, and the use of exhausted filters are presented.
Huichen Yang; Rui Hu; Arnaud Igor Ndé-Tchoupé; Willis Gwenzi; Hans Ruppert; Chicgoua Noubactep. Designing the Next Generation of Fe0-Based Filters for Decentralized Safe Drinking Water Treatment: A Conceptual Framework. Processes 2020, 8, 745 .
AMA StyleHuichen Yang, Rui Hu, Arnaud Igor Ndé-Tchoupé, Willis Gwenzi, Hans Ruppert, Chicgoua Noubactep. Designing the Next Generation of Fe0-Based Filters for Decentralized Safe Drinking Water Treatment: A Conceptual Framework. Processes. 2020; 8 (6):745.
Chicago/Turabian StyleHuichen Yang; Rui Hu; Arnaud Igor Ndé-Tchoupé; Willis Gwenzi; Hans Ruppert; Chicgoua Noubactep. 2020. "Designing the Next Generation of Fe0-Based Filters for Decentralized Safe Drinking Water Treatment: A Conceptual Framework." Processes 8, no. 6: 745.
Metallic iron (Fe0) has been demonstrated as an excellent material for decentralized safe drinking water provision, wastewater treatment and environmental remediation. An open issue for all these applications is the rational material selection or quality assurance. Several methods for assessing Fe0 quality have been presented, but all of them are limited to characterizing its initial reactivity. The present study investigates H2 evolution in an acidic solution (pH 2.0) as an alternative method, while comparing achieved results to those of uranium removal in quiescent batch experiments at neutral pH values. The unique feature of the H2 evolution experiment is that quantitative H2 production ceased when the pH reached a value of 3.1. A total of twelve Fe0 specimens were tested. The volume of molecular H2 produced by 2.0 g of each Fe0 specimen in 560 mL H2SO4 (0.01 M) was monitored for 24 h. Additionally, the extent of U(VI) (0.084 mM) removal from an aqueous solution (20.0 mL) by 0.1 g of Fe0 was characterized. All U removal experiments were performed at room temperature (22 ± 2 °C) for 14 days. Results demonstrated the difficulty of comparing Fe0 specimens from different sources and confirmed that the elemental composition of Fe0 is not a stand-alone determining factor for reactivity. The time-dependent changes of H2 evolution in H2SO4 confirmed that tests in the neutral pH range just address the initial reactivity of Fe0 materials. In particular, materials initially reacting very fast would experience a decrease in reactivity in the long-term, and this aspect must be incorporated in designing novel materials and sustainable remediation systems. An idea is proposed that could enable the manufacturing of intrinsically long-term efficient Fe0 materials for targeted operations as a function of the geochemistry.
Arnaud Igor Ndé-Tchoupé; Rui Hu; Willis Gwenzi; Achille Nassi; Chicgoua Noubactep. Characterizing the Reactivity of Metallic Iron for Water Treatment: H2 Evolution in H2SO4 and Uranium Removal Efficiency. Water 2020, 12, 1523 .
AMA StyleArnaud Igor Ndé-Tchoupé, Rui Hu, Willis Gwenzi, Achille Nassi, Chicgoua Noubactep. Characterizing the Reactivity of Metallic Iron for Water Treatment: H2 Evolution in H2SO4 and Uranium Removal Efficiency. Water. 2020; 12 (6):1523.
Chicago/Turabian StyleArnaud Igor Ndé-Tchoupé; Rui Hu; Willis Gwenzi; Achille Nassi; Chicgoua Noubactep. 2020. "Characterizing the Reactivity of Metallic Iron for Water Treatment: H2 Evolution in H2SO4 and Uranium Removal Efficiency." Water 12, no. 6: 1523.
The general suitability of water treatment systems involving metallic iron (Fe0) is well-established. Various attempts have been made to improve the efficiency of conventional Fe0 systems. One promising approach combines granular Fe0 and an iron sulfide mineral to form Fe0/Fe-sulfide/H2O systems. An improved understanding of the fundamental principles by which such systems operate is still needed. Through a systematic analysis of possible reactions and the probability of their occurrence, this study establishes that sulfide minerals primarily sustain iron corrosion by lowering the pH of the system. Thus, chemical reduction mediated by FeII species (indirect reduction) is a plausible explanation for the documented reductive transformations. Such a mechanism is consistent with the nature and distribution of reported reaction products. While considering the mass balance of iron, it appears that lowering the pH value increases Fe0 dissolution, and thus subsequent precipitation of hydroxides. This precipitation reaction is coupled with the occlusion of contaminants (co-precipitation or irreversible adsorption). The extent to which individual sulfides impact the efficiency of the tested systems depends on their intrinsic reactivities and the operational conditions (e.g., sulfide dosage, particle size, experimental duration). Future research directions, including the extension of Fe0/Fe-sulfide/H2O systems to drinking water filters and (domestic) wastewater treatment using the multi-soil-layering method are highlighted.
Minhui Xiao; Rui Hu; Xuesong Cui; Willis Gwenzi; Chicgoua Noubactep. Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment. Processes 2020, 8, 409 .
AMA StyleMinhui Xiao, Rui Hu, Xuesong Cui, Willis Gwenzi, Chicgoua Noubactep. Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment. Processes. 2020; 8 (4):409.
Chicago/Turabian StyleMinhui Xiao; Rui Hu; Xuesong Cui; Willis Gwenzi; Chicgoua Noubactep. 2020. "Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment." Processes 8, no. 4: 409.
A critical survey of the abundant literature on environmental remediation and water treatment using metallic iron (Fe0) as reactive agent raises two major concerns: (i) the peculiar properties of the used materials are not properly considered and characterized, and, (ii) the literature review in individual publications is very selective, thereby excluding some fundamental principles. Fe0 specimens for water treatment are typically small in size. Before the advent of this technology and its application for environmental remediation, such small Fe0 particles have never been allowed to freely corrode for the long-term spanning several years. As concerning the selective literature review, the root cause is that Fe0 was considered as a (strong) reducing agent under environmental conditions. Subsequent interpretation of research results was mainly directed at supporting this mistaken view. The net result is that, within three decades, the Fe0 research community has developed itself to a sort of modern knowledge system. This communication is a further attempt to bring Fe0 research back to the highway of mainstream corrosion science, where the fundamentals of Fe0 technology are rooted. The inherent errors of selected approaches, currently considered as countermeasures to address the inherent limitations of the Fe0 technology are demonstrated. The misuse of the terms “reactivity”, and “efficiency”, and adsorption kinetics and isotherm models for Fe0 systems is also elucidated. The immense importance of Fe0/H2O systems in solving the long-lasting issue of universal safe drinking water provision and wastewater treatment calls for a science-based system design.
Rui Hu; Huichen Yang; Ran Tao; Xuesong Cui; Minhui Xiao; Bernard Konadu Amoah; Viet Cao; Mesia Lufingo; Naomi Paloma Soppa-Sangue; Arnaud Igor Ndé-Tchoupé; Nadège Gatcha-Bandjun; Viviane Raïssa Sipowo-Tala; Willis Gwenzi; Chicgoua Noubactep. Metallic Iron for Environmental Remediation: Starting an Overdue Progress in Knowledge. Water 2020, 12, 641 .
AMA StyleRui Hu, Huichen Yang, Ran Tao, Xuesong Cui, Minhui Xiao, Bernard Konadu Amoah, Viet Cao, Mesia Lufingo, Naomi Paloma Soppa-Sangue, Arnaud Igor Ndé-Tchoupé, Nadège Gatcha-Bandjun, Viviane Raïssa Sipowo-Tala, Willis Gwenzi, Chicgoua Noubactep. Metallic Iron for Environmental Remediation: Starting an Overdue Progress in Knowledge. Water. 2020; 12 (3):641.
Chicago/Turabian StyleRui Hu; Huichen Yang; Ran Tao; Xuesong Cui; Minhui Xiao; Bernard Konadu Amoah; Viet Cao; Mesia Lufingo; Naomi Paloma Soppa-Sangue; Arnaud Igor Ndé-Tchoupé; Nadège Gatcha-Bandjun; Viviane Raïssa Sipowo-Tala; Willis Gwenzi; Chicgoua Noubactep. 2020. "Metallic Iron for Environmental Remediation: Starting an Overdue Progress in Knowledge." Water 12, no. 3: 641.
Studies were undertaken to characterize the intrinsic reactivity of Fe0-bearing steel wool (Fe0 SW) materials using the ethylenediaminetetraacetate method (EDTA test). A 2 mM Na2-EDTA solution was used in batch and column leaching experiments. A total of 15 Fe0 SW specimens and one granular iron (GI) were tested in batch experiments. Column experiments were performed with four Fe0 SW of the same grade but from various suppliers and the GI. The conventional EDTA test (0.100 g Fe0, 50 mL EDTA, 96 h) protocol was modified in two manners: (i) Decreasing the experimental duration (down to 24 h) and (ii) decreasing the Fe0 mass (down to 0.01 g). Column leaching studies involved glass columns filled to 1/4 with sand, on top of which 0.50 g of Fe0 was placed. Columns were daily gravity fed with EDTA and effluent analyzed for Fe concentration. Selected reactive Fe0 SW specimens were additionally investigated for discoloration efficiency of methylene blue (MB) in shaken batch experiments (75 rpm) for two and eight weeks. The last series of experiments tested six selected Fe0 SW for water defluoridation in Fe0/sand columns. Results showed that (i) the modifications of the conventional EDTA test enabled a better characterization of Fe0 SW; (ii) after 53 leaching events the Fe0 SW showing the best kEDTA value released the lowest amount of iron; (iii) all Fe0 specimens were efficient at discoloring cationic MB after eight weeks; (iv) limited water defluoridation by all six Fe0 SW was documented. Fluoride removal in the column systems appears to be a viable tool to characterize the Fe0 long-term corrosion kinetics. Further research should include correlation of the intrinsic reactivity of SW specimens with their efficiency at removing different contaminants in water.
Benjamin Hildebrant; Arnaud Igor Ndé-Tchoupé; Mesia Lufingo; Tobias Licha; Chicgoua Noubactep. Steel Wool for Water Treatment: Intrinsic Reactivity and Defluoridation Efficiency. Processes 2020, 8, 265 .
AMA StyleBenjamin Hildebrant, Arnaud Igor Ndé-Tchoupé, Mesia Lufingo, Tobias Licha, Chicgoua Noubactep. Steel Wool for Water Treatment: Intrinsic Reactivity and Defluoridation Efficiency. Processes. 2020; 8 (3):265.
Chicago/Turabian StyleBenjamin Hildebrant; Arnaud Igor Ndé-Tchoupé; Mesia Lufingo; Tobias Licha; Chicgoua Noubactep. 2020. "Steel Wool for Water Treatment: Intrinsic Reactivity and Defluoridation Efficiency." Processes 8, no. 3: 265.
This study characterizes the decrease of the hydraulic conductivity (permeability loss) of a metallic iron-based household water filter (Fe0 filter) for a duration of 12 months. A commercial steel wool (SW) is used as Fe0 source. The Fe0 unit containing 300 g of SW was sandwiched between two conventional biological sand filters (BSFs). The working solution was slightly turbid natural well water polluted with pathogens (total coliform = 1950 UFC mL−1) and contaminated with nitrate ([NO3−] = 24.0 mg L−1). The system was monitored twice per month for pH value, removal of nitrate, coliforms, and turbidity, the iron concentration, as well as the permeability loss. Results revealed a quantitative removal of coliform (>99%), nitrate (>99%) and turbidity (>96%). The whole column effluent depicted drinking water quality. The permeability loss after one year of operation was about 40%, and the filter was still producing 200 L of drinking water per day at a flow velocity of 12.5 L h−1. A progressive increase of the effluent pH value was also recorded from about 5.0 (influent) to 8.4 at the end of the experiment. The effluent iron concentration was constantly lower than 0.2 mg L−1, which is within the drinking-water quality standards. This study presents an affordable design that can be one-to-one translated into the real world to accelerate the achievement of the UN Sustainable Development Goals for safe drinking water.
Raoul Tepong-Tsindé; Arnaud Igor Ndé-Tchoupé; Chicgoua Noubactep; Achille Nassi; Hans Ruppert. Characterizing a Newly Designed Steel-Wool-Based Household Filter for Safe Drinking Water Provision: Hydraulic Conductivity and Efficiency for Pathogen Removal. Processes 2019, 7, 966 .
AMA StyleRaoul Tepong-Tsindé, Arnaud Igor Ndé-Tchoupé, Chicgoua Noubactep, Achille Nassi, Hans Ruppert. Characterizing a Newly Designed Steel-Wool-Based Household Filter for Safe Drinking Water Provision: Hydraulic Conductivity and Efficiency for Pathogen Removal. Processes. 2019; 7 (12):966.
Chicago/Turabian StyleRaoul Tepong-Tsindé; Arnaud Igor Ndé-Tchoupé; Chicgoua Noubactep; Achille Nassi; Hans Ruppert. 2019. "Characterizing a Newly Designed Steel-Wool-Based Household Filter for Safe Drinking Water Provision: Hydraulic Conductivity and Efficiency for Pathogen Removal." Processes 7, no. 12: 966.
Metallic iron (Fe0) materials have been industrially used for water treatment since the 1850s. There are still many fundamental challenges in affordably and reliably characterizing the Fe0 intrinsic reactivity. From the available methods, the one using Fe0 dissolution in ethylenediaminetetraacetic acid (EDTA—2 mM) was demonstrated the most applicable as it uses only four affordable chemicals: Ascorbic acid, an ascorbate salt, EDTA and 1,10-Phenanthroline (Phen). A careful look at these chemicals reveals that EDTA and Phen are complexing agents for dissolved iron species. Fe3-EDTA is very stable and difficult to destabilize; ascorbic acid is one of the few appropriate reducing agents, therefore. On the other hand, the Fe2-Phen complex is so stable that oxidation by dissolved O2 is not possible. This article positively tests Fe0 (0.1 g) dissolution in 2 mM Phen (50 mL) as a characterization tool for the intrinsic reactivity, using 9 commercial steel wool (Fe0 SW) specimens as probe materials. The results are compared with those obtained by the EDTA method. The apparent iron dissolution rate in EDTA (kEDTA) and in Phen (kPhen) were such that 0.53 ≤ kEDTA (μg h−1) ≤ 4.81 and 0.07 ≤ kPhen (μg h−1) ≤ 1.30. Higher kEDTA values, relative to kPhen, are a reflection of disturbing Fe3 species originating from Fe2 oxidation by dissolved O2 and dissolution of iron corrosion products. It appears that the Phen method considers only the forward dissolution of Fe0. The Phen method is reliable and represents the most affordable approach for characterizing the suitability of Fe0 for water treatment.
Mesia Lufingo; Arnaud Igor Ndé-Tchoupé; Rui Hu; Karoli N. Njau; Chicgoua Noubactep. A Novel and Facile Method to Characterize the Suitability of Metallic Iron for Water Treatment. Water 2019, 11, 2465 .
AMA StyleMesia Lufingo, Arnaud Igor Ndé-Tchoupé, Rui Hu, Karoli N. Njau, Chicgoua Noubactep. A Novel and Facile Method to Characterize the Suitability of Metallic Iron for Water Treatment. Water. 2019; 11 (12):2465.
Chicago/Turabian StyleMesia Lufingo; Arnaud Igor Ndé-Tchoupé; Rui Hu; Karoli N. Njau; Chicgoua Noubactep. 2019. "A Novel and Facile Method to Characterize the Suitability of Metallic Iron for Water Treatment." Water 11, no. 12: 2465.
A survey of the literature on using metallic iron (Fe0) for environmental remediation suggests that the time is ripe to center research on the basic relationship between iron corrosion and contaminant removal. This communication identifies the main problem, which is based on the consideration that contaminant reductive transformation is the cathodic reaction of iron oxidative dissolution. Properly considering the inherent complexities of the Fe0/H2O system will favor an appropriate research design that will enable more efficient and sustainable remediation systems. Successful applications of Fe0/H2O systems require the collective consideration of progress achieved in understanding these system. More efforts should be made to decipher the long-term kinetics of iron corrosion, so as to provide better approaches to accurately predict the performance of the next generation Fe0-based water treatment systems.
Rui Hu; Chicgoua Noubactep; Hu. Redirecting Research on Fe0 for Environmental Remediation: The Search for Synergy. International Journal of Environmental Research and Public Health 2019, 16, 4465 .
AMA StyleRui Hu, Chicgoua Noubactep, Hu. Redirecting Research on Fe0 for Environmental Remediation: The Search for Synergy. International Journal of Environmental Research and Public Health. 2019; 16 (22):4465.
Chicago/Turabian StyleRui Hu; Chicgoua Noubactep; Hu. 2019. "Redirecting Research on Fe0 for Environmental Remediation: The Search for Synergy." International Journal of Environmental Research and Public Health 16, no. 22: 4465.