scholarly journals Metallic Iron for Environmental Remediation: Starting an Overdue Progress in Knowledge

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 641 ◽  
Author(s):  
Rui Hu ◽  
Huichen Yang ◽  
Ran Tao ◽  
Xuesong Cui ◽  
Minhui Xiao ◽  
...  
Keyword(s):  
Water Treatment ◽  
Literature Review ◽  
Metallic Iron ◽  
Environmental Remediation ◽  
Isotherm Models ◽  
Critical Survey ◽  
Root Cause ◽  
Water Provision ◽  
Adsorption Kinetics And Isotherm

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.

scholarly journals Redirecting Research on Fe0 for Environmental Remediation: The Search for Synergy

2019 ◽  
Vol 16 (22) ◽  
pp. 4465 ◽  
Author(s):  
Hu ◽  
Noubactep
Keyword(s):  
Water Treatment ◽  
Metallic Iron ◽  
Environmental Remediation ◽  
Cathodic Reaction ◽  
Contaminant Removal ◽  
Iron Corrosion ◽  
Basic Relationship ◽  
Kinetics Of ◽  
Center Research

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.

scholarly journals Characterizing the Reactivity of Metallic Iron for Water Treatment: H2 Evolution in H2SO4 and Uranium Removal Efficiency

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1523 ◽  
Author(s):  
Arnaud Igor Ndé-Tchoupé ◽  
Rui Hu ◽  
Willis Gwenzi ◽  
Achille Nassi ◽  
Chicgoua Noubactep
Keyword(s):  
Metallic Iron ◽  
Environmental Remediation ◽  
Material Selection ◽  
H2 Production ◽  
H2 Evolution ◽  
Solution Ph ◽  
Neutral Ph ◽  
Uranium Removal ◽  
Initial Reactivity

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.

scholarly journals Tracing the Scientific History of Fe0-Based Environmental Remediation Prior to the Advent of Permeable Reactive Barriers

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 977 ◽  
Author(s):  
Viet Cao ◽  
Huichen Yang ◽  
Arnaud Igor Ndé-Tchoupé ◽  
Rui Hu ◽  
Willis Gwenzi ◽  
...  
Keyword(s):  
Water Treatment ◽  
Environmental Remediation ◽  
Groundwater Remediation ◽  
Permeable Reactive Barriers ◽  
Careful Examination ◽  
Organic Species ◽  
Operating Modes ◽  
Complex Picture ◽  
Reactive Barriers ◽  
Water Provision

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.

scholarly journals Reforestation is Not a Mitigation of Climate Change in All Situations – A Literature Review

2019 ◽  
pp. 1-8
Author(s):  
Shen Jia Jing
Keyword(s):  
Climate Change ◽  
Literature Review ◽  
Root Cause ◽  
Co2 Levels ◽  
Change Climate ◽  
Mitigate Climate Change ◽  
Carbon Dioxide Co2 ◽  
Mitigation Methods ◽  
Do So

Background: Environmental issues have gained widespread attention from all around the world and most of them originate from the root cause of climate change. Climate change occurs when there is increased concentrations of greenhouse gases in the environment, reflecting less heat back to space. In view of extreme weather and consequences, afforestation is now seen as one of the most effective methods in mitigating the effects of climate change. Increasing popularity of using forests as mitigation methods, however, does not translate to forests being effective solutions in all situations. Being part of our ecosystem, processes of forests are easily altered by climate change itself. Aims: To ascertain if afforestation can effectively mitigate the effects of climate change in consideration that the processes of trees are affected by climate change itself. Study Design:  Literature review. Methods: Data sources include Nature, Science Direct and environmental journals. Results: Climate change currently increases the ability of forests to mitigate climate change but long-term exposure to increased temperatures and carbon dioxide (CO2) levels reduce their abilities to do so. Location of where afforestation is carried out also affects the extent of effectiveness in reducing CO2 levels and climate change. Conclusion: Afforestation can mitigate climate change if implemented appropriately, especially where it is effective. However, the primary solution will still be cutting carbon emissions since trees have a biological limit in response to climate change.

scholarly journals Water Treatment Using Metallic Iron: A Tutorial Review

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 622 ◽  
Author(s):  
Hu ◽  
Gwenzi ◽  
Sipowo-Tala ◽  
Noubactep
Keyword(s):  
Water Treatment ◽  
Metallic Iron ◽  
Environmental Remediation ◽  
Material Selection ◽  
Engineering Application ◽  
Operating Mode ◽  
Contaminant Removal ◽  
Removal Mechanisms ◽  
Practical Engineering ◽  
Proper Material

Researchers and engineers using metallic iron (Fe0) for water treatment need a tutorial review on the operating mode of the Fe0/H2O 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 Fe0/H2O system, (ii) discuss relevant contaminant removal mechanisms, and (iii) provide solutions for practical engineering application of Fe0-based systems for water treatment. Specifically, the following aspects are summarized and discussed in detail: (i) Fe0 intrinsic reactivity and material selection, (ii) main abiotic contaminant removal mechanisms, and (iii) relevance of biological and bio-chemical processes in the Fe0/H2O system. In addition, challenges for the design of the next generation Fe0/H2O systems are discussed. This paper serves as a handout to enable better practical engineering applications for environmental remediation using Fe0.

scholarly journals Evaluation and characterisation of metal sorption and retention by drinking water treatment residuals (WTRs) for environmental remediation

2021 ◽  
Author(s):  
K. A. H. Arab ◽  
D. F. Thompson ◽  
I. W. Oliver
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Environmental Remediation ◽  
Drinking Water Treatment ◽  
Water Remediation ◽  
Isotherm Models ◽  
Water Treatment Residuals ◽  
Drinking Water Treatment Residuals ◽  
Contaminant Metals ◽  
Sorption Mechanisms

AbstractDrinking water treatment residuals (WTRs) are wastes generated when water is clarified using aluminium or iron salts. They are increasingly being considered as a resource with potential reuse value, particularly in relation to soil or water remediation. Adsorption–desorption capacity of Al-based (Al-WTR) and Fe-based (Fe-WTR) materials was investigated here for Pb and Zn, both separately and in combination, as a preliminary trial to assess their utility for immobilising contaminant metals in environmental settings. Maximum adsorption observed at the highest test solution concentrations imposed (400 mg/L) was similar for each WTR type and each metal; Al-WTRs sorbed Zn at 3579 mg/kg and Pb at 4025 mg/kg, while Fe-WTRs sorbed Zn and Pb at 3579 mg/kg and 3980 mg/kg, respectively. Equilibrium adsorption data were tested against Langmuir, Freundlich, and Temkin isotherm models, which indicated a substantial reserve capacity for further Pb sorption and that multiple sorption mechanisms were involved. Subsequent desorption tests with 0.001 M CaCl2 solution indicated that > 89.76% of sorbed metal remained sorbed. When in solution together, both metals were strongly sorbed by WTRs, but a slight preference for Pb was observed. The results indicate that WTRs would be very effective immobilising agents if placed in contaminated soil or if used to treat contaminated waters.

A Review on Recent Trends in Nanomaterials and Nanocomposites for Environmental Applications

2020 ◽  
Vol 16 ◽  
Author(s):  
Kannappan Panchamoorthy Gopinath ◽  
Malolan Rajagopal ◽  
Abhishek Krishnan ◽  
Shweta Kolathur Sreerama
Keyword(s):  
Environmental Pollution ◽  
Environmental Remediation ◽  
Carbon Capture ◽  
Potential Applications ◽  
Important Challenge ◽  
Term Basis ◽  
Short And Long Term ◽  
Recent Trends ◽  
Water And Soil Pollution

Background: Depletion and contamination of environmental resources such as water, air and soil caused by human activities is an increasingly important challenge faced around the world. The consequences of environmental pollution are felt acutely by all living beings, both on a short and long-term basis, thereby making methods of remediation of environmental pollution an urgent requirement. Objectives: The objective of this review is to dissect the complications caused by environmental degradation, highlight advancements in the field of nanotechnology and to scrutinize its applications in environmental remediation. Furthermore, the review aims to concisely explain the merits and drawbacks of nanotechnology compared to existing methods. Conclusion: The current and potential applications of nanomaterials and nanocomposites in the prevention, control and reduction of air, water and soil pollution and the mechanisms involved have been elucidated, as have their various merits and demerits. The applications of nanotechnology in the fields of carbon capture and agriculture have also received attention in this review.

scholarly journals Suitability of Different Titanium Dioxide Nanotube Morphologies for Photocatalytic Water Treatment

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 708
Author(s):  
Clayton Farrugia ◽  
Alessandro Di Mauro ◽  
Frederick Lia ◽  
Edwin Zammit ◽  
Alex Rizzo ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Titanium Dioxide ◽  
Water Treatment ◽  
Environmental Remediation ◽  
Survival Rates ◽  
Bacterial Survival ◽  
Nanotubular Structure ◽  
Excellent Activity ◽  
Uva Light ◽  
High Degree

Photocatalysis has long been touted as one of the most promising technologies for environmental remediation. The ability of photocatalysts to degrade a host of different pollutants, especially recalcitrant molecules, is certainly appealing. Titanium dioxide (TiO2) has been used extensively for this purpose. Anodic oxidation allows for the synthesis of a highly ordered nanotubular structure with a high degree of tunability. In this study, a series of TiO2 arrays were synthesised using different electrolytes and different potentials. Mixed anatase-rutile photocatalysts with excellent wettability were achieved with all the experimental iterations. Under UVA light, all the materials showed significant photoactivity towards different organic pollutants. The nanotubes synthesised in the ethylene glycol-based electrolyte exhibited the best performance, with near complete degradation of all the pollutants. The antibacterial activity of this same material was similarly high, with extremely low bacterial survival rates. Increasing the voltage resulted in wider and longer nanotubes, characteristics which increase the level of photocatalytic activity. The ease of synthesis coupled with the excellent activity makes this a viable material that can be used in flat-plate reactors and that is suitable for photocatalytic water treatment.

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