Microwave radiation leaching of colemanite in sulfuric acid solutions

Two leaching methods were used to study colemanite leaching reactions. First, the conventional acid leaching method was performed using a glass reactor at atmospheric pressure, leaching in a water bath. Second, microwave acid leaching was carried out using the glass reactor in a modified microwave oven. The characterization of ground colemanite was determined by X-ray diffraction (XRD) analysis, X-ray Fluorescence (XRF) analysis and chemical analysis. An investigation was made of the influence of the solid/liquid ratio, stirring speed, acid concentration, microwave power, reaction time and reaction temperature on the leaching recovery of boron oxide. The results of the conventional acid leaching (CVAL) method were compared to the microwave leaching (MWAL) method. The crystallization of gypsum was investigated with regard to obtaining high-purity boric acid at different acid concentrations using microwave leaching, in which all of the calcium ions in the liquid phase were incorporated into the gypsum crystals. The optimum leaching efficiency for the CVAL and MVAL methods was 99.82% and 99.9% respectively. (c) 2012 Elsevier B.V. All rights reserved.