P.K. Parhi

Supported Liquid Membrane Principle and Its Practices: A Short Review

The present paper on the supported liquid membrane (SLM) deals with the general principles and applications, followed by the uphill transportation characteristic of SLM. The liquid-liquid extraction with supported liquid membrane is one of the best alternate and promising technologies for the extraction of metal ions from solutions over other hydrometallurgical separation processes. The salient features of the supported liquid membrane (SLM) technique such as simultaneous extraction and stripping, low solvent inventory, process economy, high efficiency, less extractant consumption, and operating costs are discussed in detail. The supported liquid membrane of hollow fiber type provides high interfacial surface area for achieving maximum metal flux. Also the use of different organic extractants for SLM has been discussed.

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.

Liquid-liquid extraction and separation of total rare earth (RE) metals from polymetallic manganese nodule leaching solution

Abstract The study on the solvent extraction for quantitative and selective separation of total rare earth metals from the polymetallic nodule leach liquor was investigated. The typical leach liquor bearing 0. 094 g/L total rare earth, 0. 23 g/L Mn, 0.697 g/L Cu, 0.2 g/L Fe, 0.01 g/L Co and 0.735 g/L Ni was subjected to the removal iron content by precipitation method using Ca(OH) 2 at pH 3.95, prior to solvent extraction of rare earth metals. Three different organo-phosphoric acid reagents (D2EHPA, PC88A, Cyanex 272) were used to ascertain their performances and selectivity towards the loading of rare earth metals in presence of other base metals. Based on the results of eq. pH effect, the performances of above three extractants followed the order as: D2EHPA>PC88A>Cyanex 272. To ensure the absence of extraction of base metals (Cu, Co, Ni), the eq. pH of the solution was optimized at the level of 2.21, though higher rare earth metal extraction efficiency was observed at higher eq. pH with either of the extractants. The complete process flow diagram for substantial recovery of total rare earth was developed using D2EHPA. Extraction isotherm plot was constructed at A:O=12:1, 3-stages and pH e =2.21, using 0.8 mol/L D2EHPA and the predicted condition of this study was further confirmed by 6-Cycles Counter Current Simulation (CCS) study. The stripping of total rare earth from loaded organic phase (LO) was conducted using HCl solution. Mc-Cabe Thiele diagram study carried out at A:O=1:5 using 4 mol/L HCl showed that three theoretical stages were needed for quantitative stripping of total rare earth. The subsequent stripped solution resulted thus led to contain total rare earth of 5.6 g/L indicating a very high enrichment of total metals by solvent extraction (SX) process.

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.

Bioreduction of hexavalent chromium by Exiguobacterium indicum strain MW1 isolated from marine water of Paradip Port, Odisha, India

ABSTRACT Hexavalent chromium-tolerant (1500 mg/L) bacterium MW1 was isolated from harbour water of Paradip Port and evaluated for Cr(VI) reduction potential. The isolate was identified as Exiguobacterium indicum by biochemical and 16S rRNA gene sequence methods. Salt tolerance of the bacterium was evaluated in a wide range of NaCl concentrations (0.5–13%, w/v). The Cr(VI) reduction of the strain was evaluated and optimised with varied Cr(VI) concentrations (100–1000 mg/L), pH (5.0–9.0), temperature (30–40°C) and shaking velocity (100–150 rpm) in two different minimal media (M9 and Acetate). Under optimised conditions, after 192 h of incubation nearly 92%, 50% and 46% reduction in the M9 minimal medium and 91%, 47% and 40% reduction in the acetate minimal medium were observed for 100, 500 and 1000 mg/L of Cr(VI), respectively. The exponential rate equation for Cr(VI) reduction yielded higher rate constant value, that is, 1.27 × 10−2 h−1 (M9) and 1.17 × 10−2 h−1 (Acetate) in case of 100 mg/L and became lower for 500 and 1000 mg/L Cr(VI) concentrations. Further, the association of bacterial cells with reduced product was ascertained by Fourier transform infrared spectrometer, UV–Vis–DRS and field-emission scanning electron microscope–energy-dispersive X-ray analyses. The above study suggests that the higher reducing ability of the marine bacterium E. indicum MW1 will be suitable for Cr(VI) reduction from saline effluents.

Separation and recovery of neodymium and praseodymium from permanent magnet scrap through the hydrometallurgical route

ABSTRACT The leaching of neodymium (Nd) and praseodymium from scrap permanent magnet bearing 64.37% Fe, 30.57% Nd and 0.42% Pr and 0.71% B was carried out using HCl solution. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses study ensured the elements of the above metals as Nd-Fe-B in the solid phase . The leaching parameters – HCl concentration, time, temperature, particle size, pulp density (S/L) – were investigated to obtain the suitable leaching condition for the effective dissolution of both Nd and Pr. At the conditions of 0.2 M HCl, temperature 90°C, leaching time 240 min, particle size 76–105 µm, agitation speed 800 rpm and pulp density (PD) 1%, the leaching efficiencies of Nd and Fe were 99.99% and 61.36%, respectively. The optimum leaching condition was established by minimizing iron co-extraction vis-à-vis the quantitative recovery of Nd and Pr. The iron content of the leach liquor was removed by the precipitation method using lime (Ca(OH)2) at pH 4.0. After the removal of iron, the solvent extraction (SX) parameters were optimized and the McCabe–Thiele diagram for extraction and stripping was developed. The McCabe–Thiele plot for extraction with 0.8 M NaD2EHPA (30% neutralized) and stripping with 8% H2SO4 showed two stages at A:O = 2:1 and O: A = 4:1, respectively, for the quantitative recovery of Nd and Pr. The final strip solution bearing 72 g/L Nd and 1.088 g/L Pr was crystallized to produce (Nd) 2(SO4)3 and (Pr) 2(SO4)3, respectively.

Separation and Recovery of Molybdenum from Acidic Solution using LIX 973 N

Leach liquors bearing 10.682 g/L Mo, 2.411 g/L Co, and 3.842 g/L Al obtained by the acid leaching of spent hydrodesulphurization catalysts were treated for the separation and recovery of Mo(VI) leaving Co(II) and Al(III) in the raffinate using solvent extraction by LIX 973 N. Equilibrium conditions for the extraction (loading) and stripping of molybdenum(VI) were determined. Extraction of molybdenum(VI) was increased from 13.9 to 96.7% with an increase in the extractant concentration from 2.5 to 30.0% (v/v) using 30% LIX 973 N in kerosene with feed pH 1.0 and a phase ratio of O: A = 1:1. The McCabe-Thiele plot for extraction of molybdenum(VI) with 30% LIX 973 N illustrated 2-stages at 2:3 (O: A) phase ratio and the loaded organic contained 16.021 g/L molybdenum(VI) indicating complete (99.9%) extraction. Stripping of molybdenum(VI) from the loaded organic was carried out with different (NH 4 ) 2 CO 3 concentration and a maximum of 98.45% stripping efficiency resulted at the unit phase ratio. Strip solution bearing molybdenum at about 48.049 g/L was achieved in 3-counter-current stages at O: A ratio of 3:1 with 1.5 M (NH 4 ) 2 CO 3 . High purity (99.9%) molybdenum trioxide prepared from the strip solution via crystallization was confirmed from the XRD study.

EXPERIMENTAL STUDIES AND PARAMETER OPTIMIZATION OF SEPARATION OF COPPER USING HOLLOW FIBER–SUPPORTED LIQUID MEMBRANE

The separation of copper from a leach liquor bearing 204.59 mol/m3 Cu, 40.83 mol/m3 Zn, 33.94 mol/m3 Co, 255.58 mol/m3 Ni, and 75.72 mol/m3 (NH4)2SO4 has been carried out with a hollow fiber membrane using LIX 84-I as the mobile carrier. Central composite inscribed (CCI) design was used to design the experiments. The factors considered for the CCI design were pH, LIX 84-I concentration in the membrane phase, flow rate, and acid concentration in the strip solution. A reduced quadratic model was found to fit the experimental data. Detailed analysis of the effect of different factors as well as their interaction on the extraction of copper has been done. The optimized condition for maximum copper flux was found to be pH 4.5, 39.88% LIX 84-I, 360 mL/min flow rate, and 7% H2SO4 in strip solution. The highest copper flux of 7.46 × 10−5 mol/m2 · s was obtained experimentally at the above conditions, which is in good agreement with the predicted value of 7.57 × 10−5 mol/m2 · s.

Separation and recovery of Sc(III) from Mg–Sc alloy scrap solution through hollow fiber supported liquid membrane (HFLM) process supported by Bi-functional ionic liquid as carrier

ABSTRACT The Mg–Sc alloy leach solution bearing 2.5 g/L Sc(III), 25.0 g/L Mg(II) and 0.5 M HCl was subjected to investigate for separation of Sc(III) by hollow fibre liquid membrane (HFLM) followed by its recovery through oxalate precipitation route. Ionic liquid (IL) R4ND derived from commercial organo-phosphoric acid (D2EHPA) and aliquot-336 was used as carrier in this study. Equilibrium study ensures on extraction of Sc(III) as ScCl3 with association of 3 mole of R4ND in the extracted phase. The role of chloride and R4ND concentration appears to be critical while enhancing the Sc flux (JSc). The complex formation during extraction of Sc(III) into the carrier phase was confirmed from FTIR analysis. Maximum JSc of 10.41 × 10−5 mol/m2.s was obtained at the optimum condition: pH 4.0, 0.4 M R4ND, flow rate 150 mL/min., 6.0 M NaOH, Feed: Strip = 3:1 and after 90 min. of HFLM continuous run of almost all scandium separation from scrap solution was achieved on yielding threefold enrichment into the strip phase which bears ~7.49 g/L of scandium. The stripped solution resulted was precipitated using oxalic acid and substantially calcined to produce Sc2O3. The pure form of Sc2O3 produced in the present work was ensured from XRD analysis.

Characterization, stabilization, and study of mechanism of coal-water slurry using Sapindous Mukorossi as an additive

ABSTRACT The present study describes the rheological behavior of three types of coal-water slurry in the presence of a dispersant saponin isolated from the fruit of Sapindous Mukorossi. The critical micelle concentrations of the saponin wereas 0.016 and 0.007 g/cc through aqueous extraction and chemical extraction processes, respectively. The rheological characteristics of slurry were measured in the function of coal loadings, pH, saponin concentration, and temperature. The zeta potential of the slurry without additive was found to be 120 mV which exhibited a decreasing trend with the adoption of additives. The static stability of the slurry could be maintained up to a maximum period of 30 days.