9 research outputs found
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Investigation of the mechanisms controlling chromate and arsenate removal from water using zerovalent iron media
This research investigated the mechanisms controlling chromate and arsenate removal by zerovalent iron media. The removal kinetics of aqueous Cr(VI) and As(V) were studied in batch experiments for initial concentrations ranging from 100 to 10,000 μg/L. Removal kinetics were also studied in columns packed with zerovalent iron filings over this same concentration range. Electrochemical analyses were used to investigate the electron transfer reactions occurring on the iron surface, and to determine the effect of chromate and arsenate on the iron corrosion behavior. The removal mechanism for chromate involved reduction to Cr(III) and the formation of hydroxide precipitates. Increasing chromate concentrations resulted in decreasing removal rates due to iron surface passivation. Even at low concentrations, chromate acts as a corrosion inhibitor and decreases iron corrosion rates. The condition of the iron surface prior to exposure to chromate determined the chromium removal kinetics. Air-formed oxides significantly inhibited chromate removal, whereas oxides formed in anaerobic, chromate-free water resulted in higher removal rates. Although direct reduction of chromate at cathodic sites on the iron surface was observed at early elapsed times, chromate removal eventually became limited by the rate at which Fe²⁺ could be generated at anodic sites. The removal mechanism for arsenate did not involve reduction and was due to the formation of inner-sphere, bidentate complexes with iron corrosion products. At low arsenate concentrations the rate of arsenate removal was limited by diffusion to adsorption sites. At high concentrations the rate of arsenate removal was limited by the rate of adsorption site generation resulting from iron corrosion. Adsorbed arsenate blocked electroactive sites on the iron surface and decreased iron corrosion rates. Arsenate is expected to remain as the principal adsorbed species in iron filter media because electrochemical reduction of As(V) to As(III) is not favorable under the conditions relevant to freely corroding iron
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When the fourth water and digital revolution encountered COVID-19.
The ongoing COVID-19 pandemic is, undeniably, a substantial shock to our civilization which has revealed the value of public services that relate to public health. Ensuring a safe and reliable water supply and maintaining water sanitation has become ever more critical during the pandemic. For this reason, researchers and practitioners have promptly investigated the impact associated with the spread of SARS-CoV-2 on water treatment processes, focusing specifically on water disinfection. However, the COVID-19 pandemic impacts multiple aspects of the urban water sector besides those related to the engineering processes, including sanitary, economic, and social consequences which can have significant effects in the near future. Furthermore, this outbreak appears at a time when the water sector was already experiencing a fourth revolution, transitioning toward the digitalisation of the sector, which redefines the Water-Human-Data Nexus. In this contribution, a product of collaboration between academics and practitioners from water utilities, we delve into the multiple impacts that the pandemic is currently causing and their possible consequences in the future. We show how the digitalisation of the water sector can provide useful approaches and tools to help address the impact of the pandemic. We expect this discussion to contribute not only to current challenges, but also to the conceptualization of new projects and the broader task of ameliorating climate change
Recommended from our members
When the fourth water and digital revolution encountered COVID-19.
The ongoing COVID-19 pandemic is, undeniably, a substantial shock to our civilization which has revealed the value of public services that relate to public health. Ensuring a safe and reliable water supply and maintaining water sanitation has become ever more critical during the pandemic. For this reason, researchers and practitioners have promptly investigated the impact associated with the spread of SARS-CoV-2 on water treatment processes, focusing specifically on water disinfection. However, the COVID-19 pandemic impacts multiple aspects of the urban water sector besides those related to the engineering processes, including sanitary, economic, and social consequences which can have significant effects in the near future. Furthermore, this outbreak appears at a time when the water sector was already experiencing a fourth revolution, transitioning toward the digitalisation of the sector, which redefines the Water-Human-Data Nexus. In this contribution, a product of collaboration between academics and practitioners from water utilities, we delve into the multiple impacts that the pandemic is currently causing and their possible consequences in the future. We show how the digitalisation of the water sector can provide useful approaches and tools to help address the impact of the pandemic. We expect this discussion to contribute not only to current challenges, but also to the conceptualization of new projects and the broader task of ameliorating climate change