Environmental friendly approach for selective extraction and recovery of molybdenum (Mo) from a sulphate mediated spent Ni-Mo/Al2O3 catalyst baked leach liquor.

Solvent extraction separation of molybdenum (Mo) from the sulphate mediated leach solution bearing Aluminium (Al) and Nickel (Ni) was carried out using N-Methyl-N, N, N-tri-octyl-ammonium chloride. Extensive investigation for extraction study molybdenum in the function of time, Eq.pH, extractant concentration, diluents, temperature, strip solution concentration and phase ratio(A:O) for both extraction and stripping was examined to attain a suitable condition on its selective and enriched extraction. As per the equilibrium study and increasing trend of Eq. pH (pHe) at the correspondence initial pH, it was apparent about association of 1 mol of H+ ion during extraction which with was further supported on extraction of Mo as HMO4- at the pHe of 3.48. The association of 1 mol of exrractant during the extraction of Mo was also well evident from the slope analysis study. This indicates about anion exchange phenomenon due to Cl- ion of the N-Methyl-N, N, N-tri-octyl-ammonium chloride (extractant) with HMo4- from aqueous phase during complex formation reaction. The FTIR of the organic sample before and after extraction further confirms in support of the complex formation of the molybdenum with the extractant during extraction. The extraction isotherm was constructed at optmum extraction condition: pHe of 3.48 with 0.08M N-Methyl-N, N, N-tri-octyl-ammonium chloride predicts on need of 2-counter current stages for quantitative extraction of Mo at A:O = 3:1. To investigate the regeneration behaviour of adopted extractant along with enriched stripping of molybdenum, ammoniacal reagents were used in stripping study. The stripping of Mo showed promising and efficient using the mixture of the ammoniacal reagents (NH4OH + NH4Cl) over the either of the solo reagents. The stripping Mc-Cabe Thiele diagram was plotted using 2M NH4OH + NH4Cl ensures on quantitative stripping of Mo at SO: SS = 2:1 at 2 no. of stages. Both extraction and stripping isotherm results are validated at predicted isotherm conditions by 6-cycles counter current simulation (CCS) study leading to obtain 6-fold enrichment of Mo in stripped solution phase. The subsequent enriched content of Mo (∼60 g/L) in stripped solution phase was precipitated out followed by calcinations 400 °C to obtain a high pure MoO3. The recovered calcined product as MoO3 resulted through the proposed processing approach was as ascertained from XRD analysis.

Two step meso-acidophilic bioleaching of chalcopyrite containing ball mill spillage and removal of the surface passivation layer.

Meso-acidophilic bacterial leaching of ball mill spillage (containing chalcopyrite >80%) was carried out in an innovative two-step bioleaching method. The major drawback of meso-acidophilic bioleaching limiting industrial application is the passivation phenomenon over the ore surfaces in iron-sulfur rich environments. In the present study, we present a novel wash solution that efficiently removed the passivation layer. FTIR characterization of the bioleached sample indicated that the residues could be further leached to recover extra copper after wash solution application. XRD study indicated accumulation of sulfates (SO(4)(-)) of Na, K, Fe and oxy hydroxides of iron [FeO(OH)] in the form of jarosite outlining the passivation layer. SEM, FESEM-EDS studies indicated severe corrosion effects of the wash solution on the passivation layer. Two step bioleaching of the ore sample yielded 32.6% copper in 68days in the first interlude and post wash solution application yielded 10.8% additional copper.

Extraction of cadmium from dilute solution using supported liquid membrane.

The extraction efficiencies of three phosphoric acid derivatives (D2EHPA, PC-88A and Cyanex 272) for Cd in supported liquid membrane (SLM) have been reported. The equilibrium study indicated the release of two moles of H(+) ions from the extractant for extraction of one mole of cadmium ion and association of two moles of the extractants in the extracted species in each case. The diffusion constant of Cd-D2EHPA, Cd-PC-88A and Cd-Cyanex 272 complex through the membrane phase was found to be 2.53 x 10(-9), 5.435 x 10(-9) and 11.22 x 10(-9)m(2)/s, respectively. The effects of various parameters such as flow rate, pH of feed solution, concentration of extractants in membrane phase, concentration of H(2)SO(4) in strip solution and concentration of Cd in feed solution on cadmium flux (J(Cd)) have been investigated. At pH 7.5, the percentage of cadmium extraction was found to be maximum with 600 mol/m(3) D2EHPA and PC-88A and 800 mol/m(3) Cyanex 272. The extraction of cadmium using the phosphoric acid derivative follows the order D2EHPA>PC-88A>Cyanex 272.