PREPARATION OF SPHERICAL FINE CUO PARTICULATES FROM CU(II) AMMINE SOLUTION BY HIGH-TEMPERATURE HYDROLYSIS

The applicability of high temperature hydrolysis method to the precipi tation of spherical fine particulates of CuO from aqueous Cu(II) ammin e solution was investigated by examining various conditions. Although Cu(II) ammine complexes are stable at ambient room temperature, they a re decomposed to CuO by aeration at elevated temperatures, loosing amm onia gas outside the solution system. However, it is impossible to pre sipitate spherical fine CuO particulates by high-temperature hydrolysi s of Cu(II) ammine solution. To obtain spherical fine particles of CuO , it is necessary to remove excess ammonia in the solution by aeration at room temperature, followed by the high temperature hydrolysis with out agitation of the solution. The presence of ammonium salts in the s olution system is indispensable to obtain sperical particles. The CO2 gas contained in air is useful to form ammonium salt necessary for sph erical CuO precipitation. The increases in aging time, ammonia concent ration and ammonium salt concentration play an importantrole to increa se the resultant CuO particle size. Also, those factors affect undesir ably the size distribution of CuO and lower precipitates yield. Anions , such as sulfate and carbonate, do not show distinct effect on spheri cal CuO precipitation, however carbonate ions show the increasing effe ct of particle size. On the other hand, chloride ions disturb the form ation of spheritical CuO. This method was found to be applicable to le ach solution of copper metal with Cu(II) ammine solution to produce sp herical fine CuO particulates.