Luminescent Properties of Samarium Ion in Calcium Molybdate

Trivalent samarium ion (Sm^(3+)) activated calcium molybdate (CaMoO_4) phosphor was prepared by solid-state reaction in air. The XRD pattern of the powder CaMoO_4∶Sm shows that the CaMoO_4∶Sm single phase is developed fully through our preparation procedure. The excitation spectrum of CaMoO_4∶Sm is composed of a broad absorption of host and some sharp lines of the f-f transition absorption of Sm^(3+). Illustrated in photoluminescence spectrum, CaMoO_4 doped with Sm^(3+) displays orange red emission that is ascribed to the inner 4f^5 electron transitions ~6H_(7/2)(orange)and ~6H_(9/2)(red)of Sm^(3+). Different from the sites of Sm^(3+) in CdWO_4, the Sm^(3+) ions substitute for the Ca^(2+) and form only one type emission center in the CaMoO_4 crystal lattice.

Leaching kinetics of calcium molybdate with hydrochloric acid in presence of phosphoric acid

Calcium molybdate(CaMoO4)is the main component of powellite and is a predominant intermediate in the pyrometallurgical and hydrometallurgical process of molybdenum.The extraction of Mo from CaMoO4 by a combination of phosphoric acid and hydrochloric acid was investigated.For further understanding of the leaching mechanism,the effects of five key factors were studied to describe the leaching kinetics.The results indicated that the dissolution rate of CaMoO4 was independent of the stirring speed.Mo extraction significantly increased with increasing HCl concentration and temperature,but decreased with increasing particle size.A shrinking core model with surface chemical reaction was found to withstand the dissolution of CaMoO4.The apparent activation energy was calculated to be 70.879 kJ/mol,and a semi-empirical equation was derived for the rate of reaction.

Enhancement of CaMoO_(4) calcine decomposition and recovery of calcium resource by HCl cycle leaching

The thermodynamic equilibrium diagrams of CaMoO_(4)-CaSO_(4)-H_(2)SO_(4)-H_(2)O,CaMoO_(4)-HCl-H_(2)O and CaSO_(4)-CaCl_(2)-HCl-H_(2)O systems at 298 K were established.The calculation results demonstrated that HCl displays a much higher solubility of CaSO_(4)than H_(2)SO_(4).The leaching mechanism of Mo from CaMoO_(4)calcine was systematically investigated from the perspective of the micro particle properties variation.HCl exhibits an excellent leaching performance for Mo from CaMoO_(4)calcine due to the elimination of surface coating and the dissolution of a mass of Mo embedded in CaSO_(4)matrix.Excellent Mo leaching efficiency of 99.7%was achieved under the optimal conditions of decomposing CaMoO_(4)calcine by 2.4 mol/L HCl with a liquid/solid ratio of 10:1 at 50°C for 60 min.Based on the experimental results,a highly efficient and green cycle leaching process of molybdenum from molybdenite was proposed,which eliminated surface coating and physical entraining,and converted most of the calcium from CaMoO_(4)calcine into high purity gypsum by-product.

Molybdenum recovery from oxygen pressure water leaching residue of Ni-Mo ore

This article investigated molybdenum recovery from oxygen pressure water leaching residue of Ni-Mo ore using alkaline leaching, followed by chemical treatment of leach liquor. Parameters affecting Mo leaching rate, such as sodium hydroxide concentration, reaction time, a liquid- to-solid ratio, and temperature for the preliminary alkaline leaching were experimentally determined. The results showed that more than 88 % of molybdenum was leached under the optimum conditions （2.5 ml.g-1 NaOH, 80 ℃, a liquid to solid ratio 3 ml.g-1, and reaction time 3 h）. After the purification of leach liquor, a CaMoO4 product of 99.2 % purity could be obtained by CaCla precipitation method. The whole Mo recovery reached about 82.7 %.