Hexavalent chromium reduction by zero-valent magnesium particles in column systems. 2021

Alessio Siciliano, and Giulia Maria Curcio, and Carlo Limonti
Laboratory of Sanitary and Environmental Engineering, Department of Environmental Engineering, University of Calabria, P. Bucci, 87036, Arcavacata di Rende, CS, Italy. Electronic address: alessio.siciliano@unical.it.

The discharge of hexavalent chromium in aquatic environments represents an issue of great concern. The chemical reduction of Cr6+ to Cr3+, which is less mobile and harmful, is a suitable approach for chromium removal. In this regard, in comparison to other reactive metals, the use of zero-valent magnesium (ZVM) has several advantages. Nevertheless, this element has been scarcely investigated in the decontamination of water and wastewater. In particular, no studies have been conducted by applying Mg0 particles fixed in column systems for Cr6+ reduction. In the present study, a wide experimental investigation was carried out to analyse the chromium abatement through zero valent magnesium particles in a packed batch column. The effects of pH, initial Cr6+ concentration and temperature were investigated. The experimental results proved that the process performances were mainly affected by pH values. High efficiencies were detected at pH 3, while unsatisfactory abatements were observed at pH 5 and under uncontrolled pH conditions. At pH 3, the process performance worsened with the rise in the initial chromium concentration. In particular, a complete abatement was detected in 180 min by treating solutions with initial Cr6+ concentrations up to 40 mg/L. The effect of temperature was negligible at pH 3 and under uncontrolled pH, while the increase from 20 to 30 and 40 °C produced a significant improvement in the removal yields at pH 5. By means of a kinetic analysis a theoretical law able to accurately describe the experimental removal trends was identified. Furthermore, a mathematical relation between the observed kinetic constants and the magnesium to initial chromium amount ratio was defined. Finally, the reaction pathways were proposed, and the reaction products identified.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008274 Magnesium A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D002857 Chromium A trace element that plays a role in glucose metabolism. It has the atomic symbol Cr, atomic number 24, and atomic weight 52. According to the Fourth Annual Report on Carcinogens (NTP85-002,1985), chromium and some of its compounds have been listed as known carcinogens.
D014874 Water Pollutants, Chemical Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water. Chemical Water Pollutants,Landfill Leachate,Leachate, Landfill,Pollutants, Chemical Water

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