Papers by Chicgoua Noubactep
Environmental chemistry letters, Apr 18, 2024
Water pollution is calling for a sustainable remediation method such as the use of metallic iron ... more Water pollution is calling for a sustainable remediation method such as the use of metallic iron (Fe 0) to reduce and filter some pollutants, yet the reactivity and hydraulic conductivity of iron filters decline over time under field conditions. Here we review iron filters with focus on metallic corrosion in porous media, flaws in designing iron filters, next-generation filters and perspectives such as safe drinking water supply, iron for anaemia control and coping with a reactive material. We argue that assumptions sustaining the design of current Fe 0 filters are not valid because proposed solutions address the issues of declining iron reactivity and hydraulic conductivity separately. Alternatively, a recent approach suggest that each individual Fe 0 atom corroding within a filter contributes to both reactivity and permeability loss. This approach applies well to alternative iron materials such as bimetallics, composites, hybrid aggregates, e.g. Fe 0 /sand, and nano-Fe 0. Characterizing the intrinsic reactivity of individual Fe 0 materials is a prerequisite to designing sustainable filters. Indeed, Fe 0 ratio, Fe 0 type, Fe 0 shape, initial porosity, e.g. pore size and pore size distribution, and nature and size of admixing aggregates, e.g. pumice, pyrite and sand, are interrelated parameters which all influence the generation and accumulation of iron corrosion products. Fe 0 should be characterized in long-term experiments, e.g. 12 months or longer, for Fe dissolution, H 2 generation and removal of contaminants in three media, i.e., tap water, spring water and saline water, to allow reactivity comparison and designing field-scale filters.
Volume 3: Hazardous Waste; Engineered/Geological Barriers in Disposal Systems; L/ILW; Radioactive Waste From Research/Industries; Spent Fuel/HLW Disposal; Public Involvement; Remediation of Uranium Mining/Milling; LL/ILW; Clearance/Exemption Levels; Mgmt. of Fissile Material; HLW; Dismantling; Re..., 2001
This study was conducted to investigate the influence of iron corrosion products on the removal p... more This study was conducted to investigate the influence of iron corrosion products on the removal precipitation of uranium (VI) from aqueous solutions by zero valent iron (ZVI). Batch experiments were conducted with solutions containing 20 mg /L U(VI) (0.084 mM) at room temperature with washed and untreated scrap iron. The results show significant decrease of the immobilization efficiency of ZVI for uranium in the presence of both atmospheric corrosion products and those generated in situ. Among the relevant groundwater components, those who promote the iron corrosion e.g. SO42−, Cl− produce more corrosion products and have a stronger negative effect on the immobilization process. Carbonate ions also have a negative effect on the immobilization efficiency since they form stable complexes with uranium and reduce the adsorption on the iron surface which is the first step to immobilization. Humic substances didn’t show any negative effect but rather a slight enhancement of the immobiliza...
Fresenius Environmental Bulletin, 2012
In the mining industry, the separation of economically valuable metals from gangue materials is a... more In the mining industry, the separation of economically valuable metals from gangue materials is a well established process. As part of this field, hydrometallurgy uses chemical fluids (leachates) of acidic or basic pH to dissolve the target metal(s) for subsequent concentration, purification and recovery. The type and concentration of the leach solution is typically controlled to allow selective dissolution of the target metal(s), and other parameters such as oxidation potential, temperature and the presence of complexing/chelating agents. In the remediation industry the use of elemental metals (M0) for the removal of aqueous contaminant species is also a well established process. Removal is achieved by the oxidative corrosion of the M0 and associated pH and/or redox potential change. Whilst the two processes are directly opposed and mutually exclusive they both stem from the same theoretical background: metal dissolution/precipitation reactions. In the mining industry, with each prospective ore deposit physically and chemically unique, a robust series of tests are performed at each mine site to determine optimal hydrometallurgical fluid composition and treatment conditions (e.g. fluid temperature, flow rate) for target metal dissolution/yield. In comparison, within the remediation industry not all such variables are typically considered. In the present communication a comparison of the processes adopted in both industries are presented. The consequent need for a more robust empirical framework within the remediation industry is outlined.
Geoscience frontiers, Jul 1, 2023
Chemosphere, Mar 1, 2019
h i g h l i g h t s The Fe(0)/H 2 O system is not really efficient for water defluoridation. Fe(0... more h i g h l i g h t s The Fe(0)/H 2 O system is not really efficient for water defluoridation. Fe(0) filtration is potentially the system of choice for decentralized water supply. Blending using harvested rainwater is an applicable tool to achieve defluoridation. Avoiding technical defluoridation increases the potential of Fe(0)/H 2 O systems. RWH coupled to Fe(0) filtration could solve the worldwide fluorisis crisis.
Chemical Engineering Journal, Jun 1, 2023
Chemosphere, Oct 1, 2021
The global effort to mitigate the impact of environmental pollution has led to the use of various... more 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.
Chemosphere, Oct 1, 2018
A commercial granular metallic iron (Fe 0) specimen was used to evaluate the suitability of Fe 0 ... more A commercial granular metallic iron (Fe 0) specimen was used to evaluate the suitability of Fe 0 materials for removing aqueous fluoride (F −) (water defluoridation). Experiments were performed to characterize the defluoridation potential of the tested Fe 0 as influenced by the presence of chloride (Cl −) and bicarbonate (HCO 3 −) ions using tap water (H 2 O) 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 Fe 0 in a 1:1 volumetric Fe 0 :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 HCO 3 − system, and (iv) the best F − removal efficiency in tap water (H 2 O). Dye flushing studies confirmed the ion-selective nature of the Fe 0 /H 2 O 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 Fe 0 is not possible and suggest that effective water defluoridation in Fe 0 packed-beds is pure a site-specific design issue.
Environmental Science & Technology, Oct 15, 2009
In a recent study, Chiew et al. (1) reported on the performance of Kanchan arsenic filter (KAF) f... more In a recent study, Chiew et al. (1) reported on the performance of Kanchan arsenic filter (KAF) for arsenic and pathogen removal in rural Cambodia. As-contaminated groundwater sources were spiked with lab cultured E. coli and MS2 and filtered through KAF devices. The KAF, designed and distributed in Nepal by Ngai et al. (2), is rigorously a conventional
Journal of Hazardous Materials, Jun 15, 2009
This letter presents an improved discussion of the data provided in a recent article on EDTA remo... more This letter presents an improved discussion of the data provided in a recent article on EDTA removal from aqueous solutions using elemental iron (Fe 0) by O. Gyliene and his co-workers. It is shown that the authors have furnished a brilliant validation of the concept that dissolved contaminants are primary removed in Fe 0 /H 2 O systems by adsorption onto iron corrosion products and co-precipitation with iron corrosion products. It is reiterated that "contaminant removal" and "contaminant reduction" should not be interchanged randomly.
Journal of Radioanalytical and Nuclear Chemistry, 2006
The removal of uranium (VI) in zerovalent iron permeable reactive barriers and wetlands can be ex... more The removal of uranium (VI) in zerovalent iron permeable reactive barriers and wetlands can be explained by its association with iron oxides. The long term stability of this immobilized U is yet to be addressed. The presented study investigates the remobilization of U(VI) from iron oxides via diverse reaction pathways (acidification, reduction, complex formation) in the laboratory. Prior uranium co-precipitation experiments were conducted under various conditions. The addition of various amounts of a pH-shifting agent (pyrite), an iron complexing agent (EDTA) or an iron (III) reduction agent (TiCl 3) yielded in uranium remobilisation to concentrations above the US EPA maximum allowed contaminant level (MCL = 30 µg/L). This study demonstrates that U(VI) release in nature will strongly depend on the conditions and the mechanism of its fixation by geological materials.
Current Opinion in Environmental Science & Health, Aug 1, 2021
Abstract Keeping up-to-date with the literature is a great challenge for all scientists because a... more Abstract 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.
Corrosion Reviews, Aug 1, 2013
The science of metallic iron for environmental remediation is yet to be established. The prevaili... more The science of metallic iron for environmental remediation is yet to be established. The prevailing theory of the Fe 0 /H 2 O system is characterized by its inability to fully rationalize the concept that holds up the technology. The present article demonstrates that Fe 0 technology was introduced by altering the course of mainstream science and by distorting the work of corrosion scientists. The Fe 0 research community is now facing the consequences of this initial " forcing ". The technology is still innovative despite two decades of commercialization.
Carbon, 1997
In this study, activated carbon prepared from hazelnut husk (HHAC) using zinc chloride as chemica... more In this study, activated carbon prepared from hazelnut husk (HHAC) using zinc chloride as chemical activating agent was characterized by FT-IR spectroscopy, BET surface area, Boehm titration, SEM and elemental analyses. During adsorption from aqueous solution of methylene blue (MB) studied by the batch method, effects of many variables, including solution pH, agitation time, temperature and initial concentration were investigated. It was established that MB adsorption reached equilibrium at 120 min at pH 7.0 as the appropriate value and is more compatible with Langmuir adsorption isotherm with respect to Freundlich. MB adsorption capacity of HHAC was found to be 476.2 mg g −1 and MB adsorption kinetics corresponds well with pseudo second order model. Thermodynamic studies revealed that MB adsorption is a spontaneous and endothermic process.
Environmental Technology and Innovation, Nov 1, 2017
The influence of iron corrosion products (FeCPs) on the efficiency of metallic iron (Fe 0) for aq... more The influence of iron corrosion products (FeCPs) on the efficiency of metallic iron (Fe 0) for aqueous contaminant removal is characterized. Quiescent batch experiments were conducted for four weeks with solutions containing about 30 M of either methylene blue (MB) or methyl orange (MO) at room temperature. Before dye (MB or MO) addition, used Fe 0 (iron fillings) was allowed to equilibrate with demineralized water for 0 to 45 days (pre-corrosion). This operation enabled the in-situ generation of various amounts FeCPs. Results clearly demonstrated the crucial importance of freshly precipitated FeCPs for the decontamination process. The differential behaviour of MB and MO confirmed the ion-selective nature of Fe 0 /H 2 O systems. A significant pH increase was observed in the MO system relative to the MB system. This was attributed to increased iron corrosion by virtue of formation of soluble Fe 2+-MO complexes. The overall result questions the usefulness of pre-treating (e.g. acid washing) Fe 0 materials before testing in short term experiments and reiterates the importance of longer lasting experiments with Fe 0 materials.
Processes, Sep 14, 2019
Researchers and engineers using metallic iron (Fe 0) for water treatment need a tutorial review o... more Researchers and engineers using metallic iron (Fe 0) for water treatment need a tutorial review on the operating mode of the Fe 0 /H 2 O system. There are few review articles attempting to present systematic information to guide proper material selection and application conditions. However, they are full of conflicting reports. This review seeks to: (i) Summarize the state-of-the-art knowledge on the remediation Fe 0 /H 2 O system, (ii) discuss relevant contaminant removal mechanisms, and (iii) provide solutions for practical engineering application of Fe 0-based systems for water treatment. Specifically, the following aspects are summarized and discussed in detail: (i) Fe 0 intrinsic reactivity and material selection, (ii) main abiotic contaminant removal mechanisms, and (iii) relevance of biological and biochemical processes in the Fe 0 /H 2 O system. In addition, challenges for the design of the next generation Fe 0 /H 2 O systems are discussed. This paper serves as a handout to enable better practical engineering applications for environmental remediation using Fe 0 .
Research Square (Research Square), Mar 24, 2021
Metallic iron (Fe 0) has shown outstanding performances for water decontamination and its e cienc... more Metallic iron (Fe 0) has shown outstanding performances for water decontamination and its e ciency has been improved by the presence of sand (Fe 0 /sand) and manganese oxide (Fe 0 /MnO x). In this study, a ternary Fe 0 /MnO x /sand system is characterized for its discoloration e ciency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 d. The objective was to understand the fundamental mechanisms of water treatment in Fe 0 /H 2 O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO 2 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 in uenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (testtubes). The presence of MnO x 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 Fe 0 /MnO x /sand system, while establishing that both MnO x and sand improve the e ciency of Fe 0 /H 2 O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe 0-based systems with reactive MnO x .
Tous droits réservés © Revue des sciences de l'eau, 2012 Ce document est protégé par la loi sur l... more Tous droits réservés © Revue des sciences de l'eau, 2012 Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne.
Journal of Hydrology, Sep 1, 2022
Chemosphere, 2022
Over the past three decades, groundwater remediation using permeable reactive barriers (PRBs) has... more Over the past three decades, groundwater remediation using permeable reactive barriers (PRBs) has proven to be effective. The majority of installed PRBs uses metallic iron (Fe(0)) as a reactive material. However, the success of implemented Fe(0) PRBs is yet to be rationalized as Fe(0) is a generator of iron oxides (contaminant scavengers) and secondary reducing agents (e.g. Fe(II), Fe3O4, H2, green rust), This communication demonstrates that Fe(0) is not an environmental reducing agent. Therefore, more science-based investigations are needed to optimize the operation of Fe(0) PRBs. In particular, Fe(0) PRBs and Fe(0)-based water filters should be regarded as particular cases of "metal corrosion in porous media". A key feature of such systems is that the extent of Fe0 corrosion temporally depends on the residual porosity (capillarity). Thus, the functionality of any Fe0 PRB should be monitored in a way that the time-dependent variation of the kinetic of iron corrosion is discussed.
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Papers by Chicgoua Noubactep