Solvent Extraction Of Zinc From Zn (Ⅱ)-NH₃ Complex System By New Extractant

The extraction of zinc from ammonia leaching solution is hard to carry out because of the low concentration of zinc ion in ammoniacal leaching solution in low grade of zinc oxide ores. A new synthesized organic compound,2-acetyl-3-oxo-dithiobutyric acid-myristyl ester, can extract and enrich zinc from zinc-ammonia solution efficiently. A research subject of "solvent extraction of zinc from Zn(II)-NH3 complex system by new extractant" was proposed. In this paper, extraction mechanism, technological conditions and kinetic parameter were studied, and some academic vale results were obtained. The results indicated that this research subject has a broad prospect in industrial application.Extraction mechanism of zinc extraction by 2-acetyl-3-oxo-dithiobutyric acid-myristyl ester from ammonia solution was studied. The extraction saturation capacity of zinc by this new extractant was 76.4mmol/dm3. Then, the composition of extracted complex and extraction reaction were obtained. The study suggested that the extractant 2-acetyl-3-oxo-dithiobutyric acid-myristyl ester hasβ-diketone structure and is easy tautomeric change to enolform; then ion H+ of hydroxy can exchange with metal ion Men+and they form complexes.The kinetics of zinc extraction by this new extractant in NH4+-NH3-H2O system was carried out by method of invariable interface. All Kinetics studies showed that by using this new extractant to extract zinc, the extraction rate was depended on the mixed-controlled reaction rate, and the solvent extraction reaction rate can be depicted as The apparent activation energy of this extraction reaction is measure as 28206kJ/mol, which consistence that the extraction reaction is controlled by mixed-controlled reaction rate.During the extraction process test, the effects of different ammonia complex systems, composition of organic phase and aqueous phase, temperature and phase ratio of zinc extraction were investigated respectively. The results show that the average extraction ratio of zinc is larger than 97% and the distribution ratio of zinc can reach 112.6 under the following optimum conditions:organic phase composition 50%YORS+45%H (diluent)+5%P (additibe), phase ratio V(A)/V(O)=2:1, temperature 298.15 K, agitation time 5 min, total ammonium concentration 2 mol/L, initial pH value 9-11. TheΔHθof extraction reaction is 6.09 kJ/mol, so extraction process is an endothermic reaction.