Process development for recovery of vanadium and nickel from an industrial solid waste by a leaching-solvent extraction technique

A process for recovering V(V) and Ni(II) from an industrial solid waste using sulfuric acid leaching, solvent extraction, precipitation and crystallization has been developed. The leaching parameters investigated were time, temperature and H2SO4 concentration. To quantify the linear and interaction coefficients a 23 full factorial experimental design was used. Regression equations for the extraction of V(V) and Ni(II) were determined and the adequacy of these equations was tested by Student's t-Test. More than 98% of both V(V) and Ni(II) were extracted in 90 min using 1.35 M H2SO4 at 40 °C. In addition, solvent extraction of V(V) with LIX 84-I in kerosene from the acidic leach liquor bearing 10.922 g/L V(V) and 18.871 g/L of Ni(II) was investigated. V(V) was extracted selectively using 40% LIX 84-I followed by stripping with NH4OH solution. McCabe-Thiele plots at O:A = 2:3 with 40% LIX 84-I and O:A = 3:1 with 15% (v/v) NH4OH showed two and three theoretical stages are needed for quantitative extraction and stripping of V(V), respectively. Ni(II) was selectively recovered from the V(V) free raffinate by adding ammonium oxalate at 60 °C. The purity of different products such as ammonium vanadate, nickel oxalate and nickel oxide obtained during the processes were analyzed and confirmed from the XRD studies.