Characterisation of zinc bearing-ferrites obtained as by-products of hydrochemical waste-water purification processes (original) (raw)
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Industrial & Engineering Chemistry Research, 2003
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Diyala Journal For Pure Science, 2021
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Electrochimica Acta, 2002
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Zero-valent iron has received considerable attention for its potential application in the removal of heavy metals from water. This paper considers the possibility of removal of zinc ions from water by causing precipitates to form on the surface of iron. The chemical states and the atomic concentrations of solids which have formed on the surface of zero-valent iron as well as the type of the deposited polycrystalline substances have been analyzed with the use of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The BET surface area, the pH at point of zero charge (pH PZC), the ORP of the solutions, and the pH and chemical concentrations in the solutions have also been measured. Furthermore, the paper also considers the possibility of release of zinc from the precipitates to demineralised water in changing physicochemical and chemical conditions. In a wide range of pH values, Zn x Fe 3−x O 4 (where x≤1) was the main compound resulting from the removal of zinc in ionic form from water. In neutral and alkaline conditions, the adsorption occurred as an additional process. Keywords Zero-valent iron. Zinc. X-ray photoelectron spectroscopy. Diffraction. Surface charge 1 Introduction Zinc is a metal which finds its application in multiple industries. The minerals most commonly exploited for the purposes of zinc production are sphalerite, smithsonite, and calamine. Zinc is essential for human metabolism, but may also pose certain risks. Free zinc ions in solutions are highly toxic to bacteria, plants, invertebrates, and even vertebrate fish (Ronald 1993). Wastes resulting from the mining of non-ferrous metal ores and hard coal as well as from the manufacturing process of non-ferrous metals accumulated at industrial waste disposal sites contain zinc minerals and, as a result, may affect the quality of ground and surface waters in the southern provinces of Poland. Meanwhile, the Water Framework Directive (Directive 2000/60/EC of the European Parliament and of the Council) issued in October 2000 commits European Union members states to achieve a good qualitative and quantitative status of all water bodies by 2015. Therefore, the problem associated with waste dumps in Silesia, Poland, and their impact on ground and surface waters must be solved as soon as possible. The pH of the groundwater under the waste disposal sites for wastes resulting from the mining of hard coal and non-ferrous metal ores and from the manufacture of non-ferrous metals is slightly acidic and rather neutral or alkaline, respectively. Permeable reactive barrier technology with the use of zero-valent iron (ZVI) as a reactive material may be applied to remove free zinc ions from groundwater and thus to protect the surface waters. In this technology, the contaminants are removed from the aquifer during the
Journal of hazardous materials, 2009
Data are presented which evaluate the performance of a pilot-scale treatment system using pelletised hydrous ferric oxide (HFO; a waste stream from coal mine water treatment) as a high surface area sorbent for removing zinc (Zn) from a metal mine water discharge in the North Pennines Orefield, UK. Over a 10-month period the system removed Zn at mean area- and volume-adjusted removal rates of 3.7 and 8.1 g m−3 day−1, respectively, with a mean treatment efficiency of 32% at a low mean residence time of 49 min. There were seasonal effects in Zn removal owing to establishment and dieback of algae in the treatment tank. This led to increased Zn uptake in early summer months followed by slight Zn release upon algae senescence. In addition to these biosorptive processes, the principal sinks for Zn appear to be (1) sorption onto the HFO surface, and (2) precipitation with calcite-dominated secondary minerals. The latter were formed as a product of dissolution of portlandite in the cement binder and calcium recarbonation. Further optimisation of the HFO pelletisation process holds the possibility for providing a low-cost, low footprint treatment option for metal rich mine waters, in addition to a valuable after-use for recovered HFO from coal mine water treatment facilities.