K. Sarangi

Extraction studies of cobalt (II) and nickel (II) from chloride solutions using Na-Cyanex 272. Separation of Co(II)/Ni(II) by the sodium salts of D2EHPA, PC88A and Cyanex 272 and their mixtures

Solvent extraction studies of cobalt and nickel have been carried out from 1 M chloride solutions using the sodium salt of Cyanex 272 as extractant diluted with kerosene with tri-n-butyl phosphate (TBP) employed as a phase modifier. Extraction of metal ions increases with increasing aqueous phase pH. The pH0.5 value difference of 1.25 with Na-Cyanex 272 indicates the possible separation of cobalt and nickel. Increasing the concentration of Na-Cyanex 272 increased the percentage extraction of both metal ions. The species extracted into the organic phase appears to be associated with 2 mol of extractant. The observed loading capacity of 99.5% for cobalt and 83.7% for nickel with 0.025 M Na-Cyanex 272 indicates that the extractant is pure in form. Increase of temperature increases the percentage extraction of nickel while for cobalt, the percentage extraction increased up to 303 K, beyond which the extraction decreased. Separation factors obtained with binary mixture of extractants gave a value 5.6 times higher in the case of Na-PC88A as extractant and Na-Cyanex 272 as synergist than that for Na-Cyanex 272 alone.

Separation of cadmium and zinc by supported liquid membrane using TOPS-99 as mobile carrier

Abstract The separation of cadmium and zinc from a dilute aqueous sulfate media using supported liquid membrane (SLM) technique has been studied. The microporous polypropylene film Celgard‐2400 was used as the solid support for the liquid membrane and TOPS‐99 was used as the mobile carrier. The effect of different parameters such as flow rate, pH of feed solution, extractant concentration in membrane phase, acid concentration in strip solution, and Cd(II) and Zn(II) concentration in feed solution on metal ion flux was studied. It was observed that a flow rate of 100 mL/min was sufficient to minimize the resistance due to an aqueous boundary layer at the feed solution membrane interface. The zinc flux increased with an increase of pH from 1.5 to 3.5 and then decreased with a further increase of pH. The cadmium permeation started at a higher pH, i.e., 3.0 and increased with increase of pH up to 3.5 followed by a plateau. Also, with an increase of TOPS‐99 concentration in the membrane phase up to 200 mol/m3, J Zn increased and then decreased. The separation factors for cadmium and zinc were calculated at different experimental conditions and are reported.

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.

EXTRACTION OF CADMIUM(II) BY SUPPORTED LIQUID MEMBRANE USING TOPS-99 AS MOBILE CARRIER

The permeation rate of Cd(II) from a dilute aqueous sulfate media using supported liquid membrane technique has been studied. The microporous polypropylene film celgard 2500 was used as solid support for the liquid membrane and TOPS-99 was used as mobile carrier. Effect of different parameters such as stirring rate, Cd(II) concentration in feed solution, pH of feed solution, extractant concentration in membrane phase, and acid concentration in strip solution on cadmium flux was studied. It was observed that stirring speed of 500 rpm was sufficient to minimize the resistance due to aqueous boundary layer. Cadmium flux, J Cd(II) increases with increase in pH of feed solution from 3.0 to 6.0 as well as with increase of cadmium concentration in feed solution. Also with increase in TOPS-99 concentration in membrane phase up to 100 mol/m3 J Cd(II) increases and then becomes constant.

Extraction of Ruthenium using Both Tertiary and Quaternary Amine from Chloride Media

Ruthenium extraction from a solution bearing 0.1 g/l Ru and 0.0358 M HCl was independently carried out with Alamine 336 and Aliquat 336 in kerosene with tri-n-butyl phosphate as the phase modifier. The effect of various parameters such as concentrations of extractant, hydrochloric acid, sodium chloride and TBP on extraction of ruthenium(III) was investigated. Ruthenium extraction increased with increasing extractant concentration up to 25% beyond which it decreased. With Alamine 336, the percentage extraction increased with increasing HCl concentration up to 6 M and then it decreased, but that with Aliquat 336 increased up to 4 M, and decreased beyond that. Ruthenium extraction from 4.5 M NaCl solution using 25% Aliquat 336 and 20% TBP in kerosene was maximum and that from a 2 M NaCl solution using Alamine 336 was maximum. The extracted species for Alamine 336 and Aliquat 336 were R 3 NH + RuCl . and R 3 NCH RuCl , respectively. The effect of various diluents such as kerosene, benzene, toluene, xylene, hexane, and cyclohexane on extraction of ruthenium was studied. The extraction isotherm with 25% Aliquat 336 indicated quantitative extraction in two stages both at O:A ratio of 1:1 and 2:1. The thermodynamic parameters such as ΔH, ΔG, and ΔS were also determined.

Solvent extraction of zinc, manganese, cobalt and nickel from nickel laterite bacterial leach liquor using sodium salts of TOPS-99 and Cyanex 272

Abstract The extraction and separation of zinc, manganese, cobalt and nickel from nickel laterite bacteria leach liquor were carried out using sodium salts of TOPS-99 and Cyanex 272 in kerosene. The unwanted metal ions were removed by precipitation method and solvent extraction was used to extract/separate Zn, Mn, Co and Ni. The nickel laterite leach liquor which was obtained from bioleaching of chromite overburden samples contained 3.72 g/L Fe, 2.08 g/L Al, 0.44 g/L Ni, 0.02 g/L Co, 0.13 g/L Mn, 0.14 g/L Zn and 0.22 g/L Cr. From this leach liquor, 100% Fe, 96.98% Al and 70.42% Cr were removed by precipitation with CaCO3 at pH 4.4 followed by precipitation of remaining Al and Cr with 50% ammonia at pH 5.4. After precipitation, the extraction of Zn from the Fe, Al and Cr free leach liquor was carried out with 0.1 mol/L TOPS-99 followed by Mn extraction with 0.04 mol/L NaTOPS-99. The yields of Zn and Mn were 97.77% and 95.63%, respectively. After Mn extraction, cobalt was removed from the leach liquor using 0.0125 mol/L NaCyanex 272 and finally nickel extraction was carried out using 0.12 mol/L NaTOPS-99 with 99.84% yield. The stripping of loaded organic (LO) phases were achieved with dilute H2SO4.

Recovery of Copper from a Waste Heat Boiler Dust Leach Liquor using LIX 84I and LIX 622N

The dust collected from the waste heat boiler of a copper plant was leached with sulfuric acid and the leach liquor contained 31.63 kg/m3 Cu, 14.78 kg/m3 Fe, 2.21 kg/m3 Zn, 0.26 kg/m3 Co, 0.09 kg/m3 Ni, and 0.23 kg/m3 Cd. The iron content in the leach liquor was precipitated out using Ca(OH)2 and from the filtrate copper was extracted with the extractants LIX 84I and LIX 622N in kerosene. Extraction of copper with either extractant increased with increasing equilibrium pH and extractant concentration. The McCabe-Thiele plots for quantitative extraction of copper indicated 3-stages at O:A ratio of 3:2 with 30% extractants. The counter-current extraction study showed 0.21 kg/m3 and 6.77 g/m3 copper in the third stage raffinates of LIX 84I and LIX 622N indicating 98.64% and 99.95% extraction, respectively. For extraction of a mole of copper ion, two moles of the extractant was required to release two moles of hydrogen ion to the aqueous phase. The quantitative stripping of copper from the loaded organic phases of LIX 84I and LIX 622N with 180 kg/m3 H2SO4 was possible in 3-stages at O:A ratio of 3:1 and 3:2, respectively. The thermodynamic parameters such as ΔH, ΔG, and ΔS were calculated for both the systems. The enthalpy change (ΔH) values were positive for extraction of Cu with either extractant indicating the processes to be endothermic. The IR spectra indicated the association of phenolic-OH group of oxime molecules in the formation of copper complexes.

Impact of heavy metals on bacterial communities from mangrove soils of the Mahanadi Delta (India)

This study aimed to assess soil nutrient status and heavy metal content and their impact on the predominant soil bacterial communities of mangroves of the Mahanadi Delta. Mangrove soil of the Mahanadi Delta is slightly acidic and the levels of soil nutrients such as carbon, nitrogen, phosphorous and potash vary with season and site. The seasonal average concentrations (μg/g) of various heavy metals were in the range: 14 810–63 370 (Fe), 2.8–32.6 (Cu), 13.4–55.7 (Ni), 1.8–7.9 (Cd), 16.6–54.7 (Pb), 24.4–132.5 (Zn) and 13.3–48.2 (Co). Among the different heavy metals analysed, Co, Cu and Cd were above their permissible limits, as prescribed by Indian Standards (Co=17 μg/g, Cu=30 μ g/g, Cd=3–6 μ g/g), indicating pollution in the mangrove soil. A viable plate count revealed the presence of different groups of bacteria in the mangrove soil, i.e. heterotrophs, free-living N2 fixers, nitrifyers, denitrifyers, phosphate solubilisers, cellulose degraders and sulfur oxidisers. Principal component analysis performed using multivariate statistical methods showed a positive relationship between soil nutrients and microbial load. Whereas metal content such as Cu, Co and Ni showed a negative impact on some of the studied soil bacteria.

Separation of iron and zinc from manganese nodule leach liquor using TBP as extractant

Abstract In this work, the separation of total Fe and Zn leading to the purification of Mn from manganese nodule leach liquor were carried out from hydrochloric acid solution by tributylphosphate with methyl iso-butyl ketone (phase modifier) dissolved in kerosene. The simulated solution comprised of 0·29 mol L−1 Mn, 0·12 mol L−1 Fe, 0·087 mol L−1 Zn and 2·3 mol L−1 HCl was used for the study. Different parameters such as extractant and acid concentrations affecting the optimum extraction condition for the investigated metal ions were examined. The McCabe-Thiele plots for extraction and stripping were constructed and scrubbing studies were carried out. Total Fe was first separated and co-extracted Zn in the loaded organic was removed by scrubbing with ferric chloride solution; and the remaining Zn was then removed by tributylphosphate. Finally, extraction of 100%Fe and 99·7%Zn; and about 99·5% stripping efficiencies in both the cases were achieved.

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.