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A commercial process was developed to treat a Ca-based Mo-V residue generated in Mo processing plant. Vanadium was selectively leached using acetic acid and recovered as iron vanadate by hydro process. Process conditions for selective V leaching and iron vanadate precipitation were investigated. V recovery efficiency of 90.3% was achieved with a V content of 26.5% and an Fe content of 29% in the iron vanadate cake suitable for ferrovanadium industry. The overall Mo recovery in the whole process was 98.6%. The obtained leach residue containing 14.3% Mo with negligible impurities can be used as a feed material for the Mo production process or ferromolybdenum industry. This simple and economical process generates two product streams from a single operation and has the potential to solve a long standing problem of handling such a mixed Mo-V residue.

The Cu–Cr catalyst has been used in many chemical processes and dumped in the landfill after losing the catalytic property. Owing to the toxicity of chromium, the dumping of catalyst is not environmentally acceptable. So metal values should be removed before disposal. One typical Cu–Cr catalyst was leached with H2SO4and from the leach liquor Cu and Cr were extracted using LIX 860N and NaD2EHPA, respectively. The McCabe–Thiele diagram at pH 3.5 with 20% LIX 860N indicated two stages at A:O?=?1:1 for quantitative extraction of copper. The stripping of Cu was achieved by 10% H2SO4. After the extraction of Cu, the extraction of Cr was carried out with NaD2EHPA. The McCabe–Thiele diagram for Cr extraction with 0.5 M NaD2EHPA at pH 3.0 showed two stages at A:O ratio of 1:1. The loaded organic of chromium was stripped with the mixture of Na2CO3, NaOH and H2O2.

ABSTRACTThe Cu–Cr catalyst has been used in many chemical processes and dumped in the landfill after losing the catalytic property. Owing to the toxicity of chromium, the dumping of catalyst is not environmentally acceptable. So metal values should be removed before disposal. One typical Cu–Cr catalyst was leached with H2SO4and from the leach liquor Cu and Cr were extracted using LIX 860N and NaD2EHPA, respectively. The McCabe–Thiele diagram at pH 3.5 with 20% LIX 860N indicated two stages at A:O = 1:1 for quantitative extraction of copper. The stripping of Cu was achieved by 10% H2SO4. After the extraction of Cu, the extraction of Cr was carried out with NaD2EHPA. The McCabe–Thiele diagram for Cr extraction with 0.5 M NaD2EHPA at pH 3.0 showed two stages at A:O ratio of 1:1. The loaded organic of chromium was stripped with the mixture of Na2CO3, NaOH and H2O2.

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 CaCO3at 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.

The selective leaching of copper from the spent Cu-Cr catalyst was carried out with H 2 SO 4 . The effect of different parameters such as acid concentration, pulp density, temperature and particle size on leaching was investigated. The maximum extraction of copper and chromium was 67.25 and 2.3%, respectively at particle size 45–53 μm, pulp density 2.5%, temperature 90 °C, time 180 min. Therefore, baking followed by leaching approach was adopted for dissolution of spent copper-chromium catalyst using H 2 SO 4 to enhance the metal leaching efficiency. At the optimum baking–leaching condition i.e. baking time 2 h, baking temperature 300 °C, baking acid concentration 0.5 M, leaching temperature 35 °C, time 60 min, [H 2 SO 4 ] 4%, P.D. 2.5%, the extraction of copper and chromium was 99.9% and 1.2%, respectively, ensuring the selective dissolution of copper. The XRD and Fe-SEM-Edax characterization analysis of typical samples (original, baked mass and typical residue) were compared and reported. The XRD and Fe-SEM-Edax analysis of the baked mass indicated the complete sulfation of copper and chromium by H 2 SO 4 yielding CuSO 4 (H 2 O) and (Cr) 2 (SO 4 ) 3 , respectively in solid phase. The absence of XRD peaks corresponding to CuSO 4 ·H 2 O in the final typical leach residue (obtained at optimum baking–leaching condition) confirmed the complete dissolution of copper from Cu-Cr catalyst. [ABSTRACT FROM AUTHOR]