Abstract
	The dissolution of four types of powdered ZnO samples, which were prepared by sintering of analytical grade ZnO or by air-calcination of zinc hydroxides, was studied  in 0.25, 0.5 and 1M H2SO4 at 20, 40 and 60°C. Zinc hydroxides were precipitated from pure solution of ZnSO4 or from a model contaminated solution of ZnSO4 or from leach liquors originated from leaching waste galvanic sludges in 0.5 M H2SO4 with 50% solution of NaOH. The sintering or calcination was performed at temperatures of 800 or 1000°C within 3 hours. The experimental data expressing the influence of the conditions of preparation of oxide samples, their chemical and phase composition and the different conditions of leaching on the rate of ZnO dissolution were used for the calculation of the additional dissolution characteristics according the grain model. The obtained data will be utilised in processing of zinc waste galvanic sludges.