The effect of pretreatments on the dissolutions of impurities from Indonesian cassiterite mineral

Abstract

The purpose of this research was to purify cassiterite from associated minerals (impurities) and to investigate the effects of pretreatment on the dissolution of impurities from Indonesian cassiterite mineral. The steps of this research are as follows: characterization, pretreatment and leaching processes by dilute hydrochloric acid (HCl) solution. Firstly, cassiterite was characterized by X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) techniques, and then pretreatments were carried out including washing, roasting at 700 o C and both combinations of washing and roasting at 700 o C. Cassiterite obtained from the processes of pretreatment and without pretreatment was then leached using 10% HCl solution with temperature variations of 35 o C-150 o C for 2 hours in atmospheric condition. The results showed that the chemistry composition of cassiterite was as follows: 57.82% Sn, 0.45% Si, 1.45% Ti, 1.79% Fe, 3.43% La, 3.37% Ce and 31.69 % others. The best condition for purification of cassiterite was leaching without pretreatment that has the highest dissolution of associated mineral from cassiterite than other processes (pretreatment) for leaching at 110 o C for 2 hours. This research was able to purify cassiterite with a chemical composition as follows: 66.14% Sn, 0.27% Si, 1.38% Ti, 1.18% Fe, 2.12% La, 2.03% Ce and 26.88% others. These results are quite satisfactory because this technology is quite simple and economical. 1. Introduction One type of mineral that is widely available in Indonesia, particularly in Bangka Belitung island is cassiterite. Cassiterite or tin oxide which has the molecular formula (SnO 2) is the primary mineral producing tin and is quite abundant in the earth's crust [1][2][3]. The cassiterite found in hard-rock deposits is associated with granitic host rock that needs further processes for separating associated minerals from SnO 2. Numerous techniques were developed such as classification, gravity concentration, and flotation techniques; however the minerals associated with such types of cassiterite deposits are harder to be seperated because of its fine liberation size [3]. The hydrometallurgical processes were also applied to obtain SnO 2 high grade of cassiterite. Some researchers used a hydrometallurgical route were as follows: Gerald et al. [4] tried to recover SnO 2 from cassiterite ore by microwave pretreatment, leaching and precipitation. Microwave treatment was selected due to the presence of associated minerals which behave differently and could be separated by microwave energy. The leaching processes conducted using-212 m particle size of cassiterite, 1-8 M potassium hydroxide (KOH) solution and a temperature at 35 o C, 55 o C, 85 o C and 103 o C. The result showed the SnO 2 recovery by the microwave assisted process was 53%. It was higher than SnO 2 obtained by the untreated conventional method that was about 28%.