The Evaluation of Starch-Based Flocculant on the Thickener Operation in the Molybdenum Processing Plant and Competency of Molybdenite Flotation

The type and dosage of flocculants used in the middle thickener of the copper-molybdenum plant, in addition to adjusting the quality of recycled process water, is very effective on the floatability of molybdenite. In this study, the effect of starch-based flocculant (wheat starch) was investigated on the efficiency of middle thickener and molybdenite flotation, in the molybdenum processing plant. First, sampling from overflow and underflow of the middle thickener in Mo processing circuit (in industrial scale), in the presence and absence of starch, were collected. The polished sections of samples from the overflow and underflow of the thickener were studied in order to determine the effect of starch on particles settling with different shapes. Microscopic studies show that molybdenite plate-like coarse particles are transferred to the thickener overflow (process water) in the presence of starch flocculant, whereas molybdenite fine particles present in the underflow are often needle-shaped. In addition, in terms of grade distribution, the grade of molybdenum in the thickener overflow is higher than that of copper and iron. Then, after sedimentation tests (in laboratory scale) with different concentrations of flocculant, flotation tests were performed on test samples. According to the results from laboratory studies, increasing the dosage of starch from 0 to 1000 g/t increased the recovery of molybdenite flotation and reduced the access of copper minerals to molybdenite concentrate. In this case, molybdenum recovery (in lab tests) is increased by about 5% compared to the case of not using starch. While the increase in the recovery of molybdenum by adding starch to the middle thickener in the industrial scale is about 10%. In higher dosages of starch (2000 g/t), the trend is reversed (in the lab and industrial scale) and molybdenum recovery decreased sharply due to the decrease in contact angle and depression, whereas the amount of copper transferred to the molybdenum concentrate increased.

Automated summary

This study investigated the effect of starch-based flocculant on the efficiency of middle thickener and molybdenite flotation. The results showed that at an appropriate dosage, the addition of starch increased the recovery of molybdenite and reduced the access of copper minerals to the molybdenite concentrate. However, at higher dosages, the trend was reversed.