Abstract
The input waste was KanthalA4 grade alloy spired in 8-25 mm outer diameter. A sample weighing ≈250 g was leached in HCl or aqua regia at room temperature. The acidic leachate was filtered and the pH value was increased to 4.0 -9.2 with the addition of 3 M ammonia solution. The leachate was freed from iron by H2O2 addition. Chromium ions were separated from nickel ions by pH adjustment and solvent extraction using Lewatite MP 600 ionic exchanger. Ammonium hydroxide gave insoluble hydroxide ppt that was filtered and washed. Different organic salts of acetate Ni(OCOCH3)2, oxalate C2O4, citrate C6H6O5 with ∆E of 74.16 KJ/ mol with Ni and 139.33 KJ/ mol with Cr. Inorganic salts were also prepared like Ni(NO3)2.6H2O, dichloride NiCl2, basic carbonate NiCO3.2Ni(OH)2 as well as free metals of nickel and chromium. The effect of the process parameters was studied. The time of synthesis decreased by stirring at 300 rpm by about 11 %. Ascorbic acid solution reduces the Ni and Cr hydroxide to their respective free metal to give spherical nanoparticles having the molecular size of 15-35 nanometer. SEM showed that Ni particles are spherical in morphology. XRD and XDS showed Ni and Cr are pure.
Highlights
Cyanidation process may be the main technique for precious metals recovery of the mining industry
Nickel was separated from chromium in the nitrate solution by adjusting the pH value using 30% ammonium hydroxide solution
The excellent nickel removal is performed by combining carbonate and hydroxide precipitations probably to benefit a coprecipitation phenomenon., the pH was adjusted by dropwise addition of IN NaOH and an equivalent amount of IN CaCI2 solution to simulate lime addition
Summary
Cyanidation process may be the main technique for precious metals recovery of the mining industry. In which chromium can be conveniently and inexpensively removed from chromium bearing metal scrap containing nickel and/or cobalt It relates to scraps derived from Ni and Co-based superalloys containing Cr., Co and/or Ni and possibly Fe as the principal constituents. [5, 6] studied a hydrometallurgy process to dissolve metal values, followed by chemical purification and/or metals recovery by some methods. Pretreatment before leaching such as calcination can be used to increase leaching rate. [8] reported that oxalic acid was employed to precipitate the Ferron, nickel, cobalt and manganese from the leaching sulfate solution of ferrochrome alloy. A toluene solution of Cyanex 923 is used as an extractant for the separation of Cr(III)
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