Application of Taguchi method for optimization of process parameters in preparation of high-purity molybdenum disulfide

A new purification method for molybdenum disulfide via NaNO 3 –HCl–HNO 3 synergistic leaching at 80 °C was developed. The effects of the concentration of NaNO 3 , HCl, and HNO 3 , and liquid–solid ratio and the leaching time on the purification of molybdenum disulfide were investigated by orthogonal array design methodology. The results of Taguchi method utilizing L 25 (5 5 ) orthogonal array indicated that the NaNO 3 concentration had the greatest impact on the purification of molybdenum disulfide. The optimum conditions for the purification of molybdenum disulfide were as follow: concentration of NaNO 3 = 2.5%, concentration of HCl = 11%, concentration of HNO 3 = 1.0%, liquid–solid ratio = 3, and the leaching time = 10 h. Under optimum conditions, the content of molybdenum increased from 55.1 to 59%, and the contents of iron, copper, lead, and calcium decreased from 0.35 to 0.21%, 0.027 to 0.008%, 0.054 to < 0.005%, and 0.27 to 0.035%, respectively. Based on molecular formula of molybdenum disulfide, the content of molybdenum disulfide increased from 91.93 to 98.44%. XRD and SEM indicated that this method removed only the impurities and did not affect the phase and particle size of molybdenum disulfide. The results show that the new purification method avoids the roasting process and will achieve the “green” production. The new method based on orthogonal array is effective for the purification of molybdenum disulfide via acid leaching.