Study On The Extraction Of Molybdenum From Low-grade Molybdenite Concertrate

Currently, molybdnite is the main raw material used to produce molybdenum in the world. The content of Mo in standard molybdenum concentrate is not less than45percent, low grade molybdenum concentrate mainly refers to the concentrate containing20～40%Mo and a large amount impurities of SiO2, CaO, Mg as well as a small amount of Cu, Fe, Pb, W, V, etc. Highly grade and easily leaching molybdenum ore is continuously decreased with the development of Mo smelting technique and the consumption of Mo resource. As a result, low grade and complex molybdenum ore are increasingly concerned. Therefore, it is necessary to study and develop a treatment proc-ess aming to the low-grade molybdnite.This paper adopted a process of roasting-leaching-residue alkali leach ing to extract Mo from skarn type low-grade (sulfide molybdate) molybden-um concentrate, and the recovery reached98.49%. The ammonium molybdate solution obtained from this process was deeply purified using anion exchange resin, and then the purified solution was treated using the methods of evaporation and acid precipitation respectively to produce ammonium molybdate crystal.In the process of roasting, the effects of roasting temperature and treating time on the desulfurization rate, yield rate of Mo, weight loss rate and Mo leaching rate were invistaged using single factor experiment. The experimental results showed that the optium conditions were that the roasting temperature was600℃and the roasting time was2.Oh. Under these conditions, the desulfurization rate was86.40%and the yield rate of Mo was up to98.06%.In the ammonia leaching stage, the influences of leaching temperature, leaching time, liquid-solid ratio,ammonia dosage and Na2CO3dosage on Mo leaching rate were studied.The results indicated that the optium conditions were as follows:the leaching temperature was80℃, the leaching time was1.0h, the liquid-solid ratio was4:1, the ammonia excessed1.4times and Na2CO3dosage (concentration) was18%. Under these conditions, the Mo leaching rate reached84.38%. The ammonia leaching residues were treated using sodium carbonate and sodium hydroxide. The optium conditions were as follows:leaching temperature was90℃, leaching time was2.0h,liquid-solid ratio was4:1, dosages of Na2CO3and NaOH were500kg·t-1and400kg-t-1, respectively. Under these conditons, the leaching rate of Mo reached90.38%. In this leaching stage, the recovery rate of Mo was98.5%.The experimental results indicated that that the resin had the optium adsorption behavior when the pH value of the original feed solution reached10.2,Mo content was11.46g/L and feed velocity was4mL/min during the stage of resin purification. A solution containing NH4Cl and NH4OH was adopted to elute Mo from resin, which had the properties of high elution speed and high desorption rate. The content of Mo in the elution solution reached as high as167.72g/L and the desorption rate reached99.86%.The methods of evaporation and acid precipitation were used to crystallize ammonium molybdate. Structure and morphologies of the crystal were studied by X-ray diffraction(XRD) and scanning electron microscopy(SEM), respectively. The experimental results showed that the products were mainly of ammonium quartmolybdate by the evaporation method, and the crystal exhibited bulk and cube shape, and uniform in size; the products were mianly of ammoinum heptamolybdate by the acid precipitation method, the crystal exhibited flake and rod-like shape.