A study on sulphuric acid leaching of nickel from spent catalysts used for methanation of small quantities of carbon oxide from hydrogen and ammonia synthesis gases (Rang-19), as well as for hydrogenation of benzene to cyklohexane process (KUB-3) are reported. The influence of temperature, sulphuric acid concentration, solid/liquid ratio, particle size and stirring intensity on nickel extraction have been investigated. The leaching rate of nickel from KUB-3 catalyst depends more strongly on temperature than that of Rang-19 catalyst. Increase in temperature from 30 to 80°C causes the rise in nickel extraction from 22 to 98% for KUB-3 catalyst The optimum leaching conditions of nickel extraction from KUB-3 catalyst are 3.0 M H_2SO_4 solution at 70°C and 1 hour of leaching time. Under the above conditions 98% nickel is extracted. Based on the experimental results the process flowsheet incorporating sulphuric acid leaching is proposed. Dissolved aluminium is removed from the solution after leaching by precipitation process, whereas nickel or nickel sulphate is produced from the solution either by electrolysis or crystallization.
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