Rapid chromite dissolution using manganese dioxide-lithium-sulphate-sulphuric acid mixture-estimation of alumina in chromite for quality control assessment

Abstract

Abstract. Proposed in this paper is a less labour-intensive method involving a mixture (0.3 g MnO 2 + 1.0 g Li2SO~; + 10 mL H20 + 20 mL of 36 M H2SO 4 for 0.2 g sample) to decompose chromites for accurate and precise estimation of alumina in chromite matrices for quality control (QC) assessment. Several international chromite samples, namely, CHR-BKg, CHR-Pt, IGS-30 and BCS-308 were analysed. Intermethod comparison studies reveal that the probability of results being different is less than (slight variation in case of CHR-BKg) 99 % when two methods l-ethylenediamine tetraacetic acid (EDTA) titration and spectrophotometry using ammonium aurinitricarboxylate (aluminon)] were compared. It also shows that the proposed method yields better results than the most conventional route involving HCIO 4 decomposition used for similar purpose; hence can be used for QC programme and in the evaluation of reference materials.Key words: chromite dissolution, MnO2-H2SO4-Li2SO 4 mixture, alumina estimation, quality control.Chromite or chrome ore is the sole commercial source of chromium metal, its alloys and compounds. It is also the major ingredients of an entire group of refractories. The mineral chromite is a spinel with the theoretical formula FeCr20r and the general formula (Fe +2, Mg) (Cr, A1, Fe + 3)20 4. There are wide variation in the composition of chromite because of this isomorphous replacement. The commercial ore is normally admixed with small amount of gangue which is principally a magnesium silicate. Commercial ores fall into three major classes: metallurgical ores, having chromic oxide content of 48%, a Cr/Fe ratio in the excess of 3 and A1/Mg ratio over 1; refractory ores, in which the Cr20 3 content is usually about 30-35%,

Mineral processing: leaching process of chromium and recovery of platinum group elements from Northwestern Saudi Arabian Ophiolitic chromite

“…Different methods have been used for the dissolution of chromite, e.g. lithium tetraborate flux [23], sodium peroxide fusion and mixtures of HNO 3 , HF and HClO 4 [21], MnO 2 -LiSO 4 -sulphuric acid mixtures [24]. In this study, four Saudi Arabian chromite ore samples collected from Wadi Al Hawanet (samples I-III) and Jabal Al Wasq (sample IV) areas were digested in the acid mixture of HClO 4 -HNO 3 Antony et al [26] and Zhang et al [27] have been processed chromite ore by roasting with sodium carbonate, limestone and dolomite at 1000-1200 °C [27].…”

A New Method for Low‐Temperature Decomposition of Chromites and Dichromium Trioxide using Bromic Acid Evaluated by Chromium Isotope Measurements

“…Recently, the isotope composition of chromium (Cr) has become an integral part of many studies in metallurgy (Mandal et al . , , Chattopadhyay and Mistry ) and in biogeochemistry and geomedicine (Ellis et al . , Bullen , Izbicki et al .…”