Abstract
Sulfuric acid-based leaching is a promising cleaner method to produce chromium salts, but its feasibility for treating low Fe(II)-chromite still remains to be proven. A Box–Behnken design (BBD)-based set of experiments for sulfuric acid leaching of low Fe(II)-chromite was utilized in this work for generating an experimental dataset for revealing the functional relationships between the processing parameters and the extraction yields of Cr and Fe. The dependent variables were found to exhibit strong intercorrelations and the models developed on the basis of statistical criteria showed excellent prediction accuracy. The optimum process conditions of leaching treatment were found to be a temperature of 176 °C, a dichromic acid/chromite mass ratio of 0.12, and a sulfuric acid concentration of 81%. Furthermore, the dissolution behavior of chromite in the leaching process and the effect of dichromic acid were experimentally investigated. It was found that the decomposition efficiency was highly dependent on the Fe(II) content of chromite, and that the dichromic acid acted both as an oxidant and a catalyst in the leaching process. On the basis of the results of this study, a novel process for treating low-Fe(II) chromite was proposed.
Highlights
Chromium (Cr) and its oxides have been widely applied in manufacturing tanning agents, pigments, stainless steel, alloys, and refractory materials [1,2,3]
With the aim of extracting Cr from low Fe(II)-chromite, sulfuric acid leaching treatment with the help of dichromic acid was investigated in the current work following an experimental plan, i.e., the Box–Behnken design (BBD), which is widely employed in different research fields to produce, in an optimal way, experimental data for response surface modeling [35,36,37,38]
On the basis of the FeO content, the three ores were referred to as low Fe(II)-chromite (LFC), medium Fe(II)-chromite (MFC), and high Fe(II)-chromite (HFC), respectively, in the current study
Summary
Chromium (Cr) and its oxides have been widely applied in manufacturing tanning agents, pigments, stainless steel, alloys, and refractory materials [1,2,3]. With the aim of extracting Cr from low Fe(II)-chromite, sulfuric acid leaching treatment with the help of dichromic acid was investigated in the current work following an experimental plan, i.e., the Box–Behnken design (BBD), which is widely employed in different research fields to produce, in an optimal way, experimental data for response surface modeling [35,36,37,38]. By these methods, the combined effects of sulfuric acid concentration (C), dichromic acid/chromite ratio (r), and processing temperature (T) on the Cr and Fe extracting behavior were studied. Three chromites with various Fe(II) contents were employed as comparison samples to investigate the dissolution behavior of chromite in the sulfuric acid-based leaching process
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