J. Rajesh Kumar

Liquid-liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions using tri-iso-octylamine.

Liquid-liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions was carried out using tri-iso-octylamine (Alamine 308) as an extractant diluted in kerosene. The percentage extraction of platinum(IV) and rhodium(III) increased with increase in acid concentration up to 8 mol L(-1). However, at 10 mol L(-1) HCl concentration, the extraction behavior was reversed, indicating the solvation type mechanism during extraction. The quantitative extraction of approximately 98% platinum(IV) and 36% rhodium(III) was achieved with 0.01 mol L(-1) Alamine 308. The highest separation factor (S.F.=184.7) of platinum(IV) and rhodium(III) was achieved with 0.01 mol L(-1) Alamine 308 at 1.0 mol L(-1) of hydrochloric acid concentration. Alkaline metal salts like sodium chloride, sodium nitrate, sodium thiocyanate, lithium chloride, lithium nitrate, potassium chloride and potassium thiocyanate used for the salting-out effect. LiCl proved as best salt for the extraction of platinum(IV). Temperature effect demonstrates that the extraction process is exothermic. Hydrochloric acid and thiourea mixture proved to be better stripping reagents when compared with other mineral acids and bases.

Separation of platinum and rhodium from chloride solutions containing aluminum, magnesium and iron using solvent extraction and precipitation methods

The solvent extraction and precipitation methods have been used to develop a process to separate platinum and rhodium from a synthetic chloride solutions containing other associated metals such as (mg/L): Pt-364, Rh-62, Al-13880, Mg-6980, Fe-1308 at <1M HCl acidity. At pH 3.4, the quantitative precipitation of Al and Fe was achieved using 10 wt% Na(3)PO(4)·12H(2)O, with ~4% loss of Pt and Rh due to adsorption phenomenon. The selective separation of platinum was carried out with 0.01 M Aliquat 336 (a quaternary ammonium salt) at an aqueous to organic ratio (A/O) of 3.3 in two stages. Stripping of Pt from loaded organic (LO) at O/A ratio 6 with 0.5 M thiourea (tu) and HCl indicated that ~99.9% stripping efficiency. In stripping studies, needle like crystals of Pt were found and identified as tetrakis (thiourea) platinum (II) chloride ([Pt(tu)(4)]Cl(2)). The selective precipitation of rhodium was performed with (NH(4))(2)S from platinum free raffinate with a recovery of >99%.

Synergistic Solvent Extraction of Neodymium(III) from Chloride Solutions using a Mixture of Triisooctylamine and bis(2,4,4-Trimethylpentyl) Monothiophosphinic Acid

The synergistic solvent extraction of Neodymium(III) with mixture of triisooctylamine (Alamine 308, R3N) and bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302, (HX)2) in kerosene from chloride solutions has been investigated. A significant synergistic effect was found by the addition of Cyanex 302 to Alamine 308. The synergistic enhancement coefficient was calculated to be 44.1 for Nd at a mole fraction of 0.2 of Cyanex 302 in the mixture. Results of the effect of equilibrium pH on the distribution ratio of Nd suggested two moles of H+ released in the extraction of Nd with a mixture of extractants. The effect of variation of one extractant at a fixed concentration of the other extractant has been carried out in order to determine the extracted species as NdClX2.2 R3N. The endothermic nature of extraction with the mixture of extractants was confirmed by the temperature effect and thermodynamic parameters ΔH, ΔG, and ΔS were calculated.

Development of an extractive spectrophotometric method for the determination of copper(II) in leafy vegetable and pharmaceutical samples using pyridoxal-4-phenyl-3-thiosemicarbazone (PPT).

A highly sensitive extractive spectrophotometric method has been developed for the determination of copper(II) using pyridoxal-4-phenyl-3-thiosemicarbazone(PPT) as an analytical reagent. The PPT forms reddish brown species of copper(II) at a pH range of 3.0-5.5, and the complex was extracted into n-butanol. The Cu(II)-PPT complex shows maximum absorbance at 440 nm, with molar absorptivity and Sandells sensitivity being 2.16 x 10(4) L mol(-1) cm(-1) and 2.94 x 10(-3) microg cm(-2), respectively. The system obeys Beers law in the range of 0.2-5.0 mg/L. The regression coefficient of the Beers law straight line is 0.338, and the correlation coefficient is 0.96. The detection limit of the method is 0.0065 microg mL(-1). Most of the common metal ions generally found associated with copper do not interfere. The repeatability of the method was checked by finding the relative standard deviation. The developed method has been successfully employed for the determination of copper(II) in leafy vegetable and pharmaceutical samples. The method is evaluated by analyzing samples from the Bureau of Analyzed Samples (BCS 233, 266, 216/1, 207, and 179) and by intercomparison of experimental values using AAS.

Synergistic Extraction of Zirconium(IV) and Hafnium(IV) with 4‐Acylbis(1‐phenyl‐3‐methyl‐5‐pyrazolones) in the Presence of Neutral Organophosphorus Extractants

Abstract Various 4‐acylbis(1‐phenyl‐3‐methyl‐5‐pyrazolones), namely, 4‐adipoylbis(1‐phenyl‐3‐methyl‐5‐pyrazolone) (H2AdBP), 4‐sebacoylbis(1‐phenyl‐3‐methyl‐5‐pyrazolone) (H2SbBP) and 4‐dodecandioylbis(1‐phenyl‐3‐methyl‐5‐pyrazolone) (H2DdBP) were synthesized and examined with regard to the solvent extraction behavior of zirconium(IV) and hafnium(IV) from hydrochloric acid solutions. The results demonstrate that Zr(IV) and Hf(IV) extracted into chloroform with 4‐acylbis(1‐phenyl‐3‐methyl‐5‐pyrazolones) (H2X), as ZrO(HX)2 and HfO(HX)2, respectively. The equilibrium constants (K ex) of the extracted complexes follow an order H2SbBP>H2AdBP>H2DdBP. The synergistic extraction of Zr(IV) and Hf(IV) was also investigated with mixtures of H2SbBP and tri‐n‐butylphosphate (TBP), tri‐n‐octylphosphine oxide (TOPO), and trialkylphosphine oxide (TRPO), where the complexation strength follows the order TOPO>TRPO>TBP. The equilibrium constants of the synergistically extracted complexes have been correlated with the donor ability of the phosphoryl oxygen of the neutral organophosphorus extractants in terms of their 31P NMR chemical shifts and their basicity values (KH =nitric acid uptake constant).

Studies of zinc(II) in pharmaceutical and biological samples by extractive spectrophotometry: using pyridoxal-4-phenyl-3-thiosemicarbazone as chelating reagent

Piridoxal-4-fenil-3-tiossemicarbazona (PPT) e proposto como um novo reagente sensivel para a determinacao espectrofotometrica de zinco(II). PPT reage com zinco(II) no intervalo de pH entre 5,0 e 6,0, para formar um complexo colorido amarelo, o qual foi adequadamente extraido em n-butanol. A absorbância do complexo Zn(II)-PPT foi medida em diferentes intervalos de tempo, a 430 nm, para averiguar a estabilidade do complexo. Foi observado que o desenvolvimento da cor foi instantâneo e estavel por mais de 48 h. O sistema obedece a lei de Beer ate 6,0 µg mL-1 de zinco(II), com uma excelente linearidade em termos do valor do coeficiente de correlacao, de 0,999. A absortividade molar e sensitividade de Sandell da especie extraida e 1,6 X 104 L mol-1 cm-1 e 4,085 X 10-3 µg cm-2, respectivamente, a 430 nm. O limite de deteccao do metodo e 0,04 µg mL-1. Para avaliar a precisao do metodo, determinacoes foram efetuadas em diferentes concentracoes; o desvio padrao relativo nao excedeu 3,1%. A composicao do complexo de zinco(II) com PPT foi estudada pelos metodos de variacao continua de Job, da razao molar, metodo de Asmus e da razao da inclinacao. PPT tem sido empregado satisfatoriamente para a determinacao de zinco(II) isoladamente, ou na presenca de outros ions, normalmente associados ao zinco(II) em amostras farmaceuticas e biologicas. Varios materiais de referencia (NIST 1573, NBS 1572 e NIST SRM 8435) tem sido testados para a determinacao de zinco, com o proposito de avaliar a exatidao do presente metodo. Os resultados do metodo proposto sao concordantes com os obtidos por espectrometria de absorcao atomica com chama.

Sensitive extractive spectrophotometric determination of Zinc(II) in biological and environmental samples using benzildithiosemicarbazone

ABSTRACT A simple, rapid and highly sensitive extractive spectrophotometric method is developed for the determination of zinc(II) at trace level using benzildithiosemicarbazone(BDTSC). Zinc(II) forms greenish yellow colored complex with benzildithiosemicarbazone(BDTSC) which can be extracted into chloroform under optimum conditions. The maximum absorption of the chloroform extract measured is 405 nm. The Beers law is obeyed over the range 1.0–18.0 µg mL−1 of zinc(II) with a relative standard deviation 1.28. The molar absorptivity of the complex is calculated as 0.4194 × 104 dm3 mol−1 cm−1 and Sandells sensitivity of the complex is 0.01560 µg cm−2. An excellent linearity with correlation coefficient value of 0.999 is obtained for Zn(II)–BDTSC complex. The method has been successfully employed for the determination of zinc(II) in biological and environmental samples. The reliability of the method was assured by analyzing the Certified Reference Materials such as, Tomato Leaves (NIST 1573), Citrus Leaves (NBS 1572) and Whole Milk Powder (NIST SRM 8435) and by the comparison of experimental values using atomic absorption spectroscopy.

Synergistic Enhancement and Separation of Zirconium(IV) and Hafnium(IV) with 3-Phenyl-4-Benzoyl-5-Isoxazolone in the Presence of Crown Ethers

Abstract 3-Phenyl-4-benzoyl-5-isoxazolone (HPBI) was synthesized and examined with regard to the synergistic solvent extraction behavior of zirconium(IV) and hafnium(IV) in the presence of various crown ethers (CEs), namely, 18-crown-6 (18C6), dicylohexano-18-crown-6 (DC18C6) and benzo-15-crown-5 (B15C5) from hydrochloric acid solutions. The results demonstrated that zirconium(IV) and hafnium(IV) were synergistically extracted into chloroform with mixtures of HPBI and CEs as ZrO(PBI)2 · CE and HfO(PBI)2 · CE, respectively. The complexation strength follows the order DC18C6 >18C6 > B15C5. The addition of CEs not only enhances the extraction efficiency of zirconium(IV) and hafnium(IV) but also significantly, especially in the presence of B15C5, improves the selectivity (Zr/Hf = 4.73) between these metal ions as compared to HPBI alone (Zr/Hf = 2.09). On the other hand, selectivity has been moderately decreased by the addition of 18C6 or DC18C6 to the metal-chelate system.

3-phenyl-4-acyl-5-isoxazolones as reagents for liquid-liquid extraction of tetravalent zirconium and hafnium from acidic chloride solutions

Liquid liquid extraction of tetravalent zirconium and hafnium from acidic chloride solutions has been investigated using 3-phenyl-4-acyl-5-isoxazolones in xylene such as 3-phenyl-4-benzoyl-5-isoxazolones (HPBI), 3-phenyl-4-(4-fluorobenzoyl)-5-isoxazolone (HFBPI) and 3-phenyl-4-(4-toluoyl)-5-isoxazolone (HTPI). The extraction of zirconium(IV) / hafnium(IV) shows a ion exchange mechanism: MO2+ (aq) + 2 HA (org) « MOA2 (org) + 2 H+(aq), where M = Zr(IV) / Hf(IV) and HA = HPBI or HFBPI or HTPI. The variation of the D ([MOA2] (org) / [MO2+](aq); ratio of the possible extraction equilibrium species) values with an increase of the acid / extractant concentration showed a linear plot with a slope of 2. The effect of the nature of the diluents like carbon tetrachloride, cyclohexane, n-hexane, benzene, nitrobenzene, xylene, toluene and chloroform on the extraction of zirconium(IV) / hafnium(IV) has been studied. The extraction behavior of zirconium(IV) / hafnium(IV) was also compared with that of other metal ions like titanium(IV), aluminium(III) and iron(III), which can be generally associated with the metal ions studied.

Leaching of Uranium and Vanadium from Korean Domestic Ore

Countries like Korea having very limited uranium resources and founded deposits having low grade metal values. Uranium is the main source to generate the nuclear power as cheap and more quantity of the electricity will generate. For this reasons the upcoming researchers in developed/developing countries are establishing more research and development on extraction and separation technologies for uranium. The present scientific study focused on leaching process of Korean domestic ore. The following experiments are carryout for optimization of the leaching process. Acid influence on leaching process was tested and noted that 2.0 M sulfuric acid concentration is the optimized conditions for present study. The time influence on leaching process was observed and its optimized 2 h for complete leaching process. The temperature influence tested and optimized the 80°C for complete leaching process and pulp density is 50% (wt %).