Leaching of brass waste and investigation of the use of ionic liquids in solvent extraction

Nowadays, recycling of waste, the efficient use of energy resources and measures against environmental pollution are the most important issues concerning all countries of the world. Infact, these three criteria are not independent from each other, but rather are issues that concern each other in the first degree. Because, recuperation from waste affects directly energy saving and also this topic is one of the most important issue to prevent environmental pollution. In this context, mining and metallurgy are the largest sector in the world. Because of traditional methods could not respond sufficiently to the criteria mentioned above, scientist have directed to develop more efficient and environment-friendly processes and materials. In this direction, one of the most succesful way about recovery sector is hydrometallurgy as an alternative to conventional pyrometallury. Superiority about achievements of the residues and environmentalism against pyrometallurgy have taken hydrometallurgy further up in this sector. Also Hydrometallurgy processes renews itself day by day, and offers more environment-friendly production methods. At the beginning of this innovation new generation chemicals have remarked. Although this new generation chemicals called ionic liquids are described (molten ) as salts that are liguid at below 100°C, recently they have come to the forewith they can be used as liquid at room temperature. They represent a new class of solvents with nonmoleculer and ionic character. This liquids are known as geren solvents because environmental feature are generally composed of organic cations with organic or inorganic anions. Ionic liquids can be used successfully in the two most important steps of hydrometallurgy leaching and solvent extraction. Furthermore these gren solvents have supersaded traditional solvents with unique physical properties. In this study, recovery of sufficient amount of Cu and Zn in brass waste via hydrometallurgical route are examined by applying the leaching in different media and solvent extraction with alternative extractants. For this purpose at first stage we apply the sulfuric acid leaching experiments in presence and absence of oxidizing agent. Leaching time (15-180dk), temperature (25°C-40°C-60°C-80°C), molarity of acid (0,5 - 1-2 and 3M), oxidantaddition (hydrogenperoxide), stirring speed (150 - 300 - 450-600rpm) and solid/liquid rate (10 - 20 - 50-100 g/l) are investigated in this study. After the leaching experiments it is noticed that copper and zinc solubility is directly related to temperature. The recovery rate of copper and zinc increases with increasing temperature. In this research zinc leaching yield is reached to 100% at 80°C. Despite the leaching time affects Zn leaching rate in the positive direction, Cu leaching rate either decreases or remains stabil during leaching time. The amount of sulfuric acid 1M concentration is determined to be sufficient for both metal leaching. Using of oxidant enhanced the Cu recovery more than zinc recovery but in general using of oxidant affected all yield rate positively. Solvent extraction experiments are performed the solution obtained from the leaching. Ionic liquids 1 - Butyl - 3 - methylimidazolium hexafluorophosphate(BmimPF6) and methyltrioctylammonium cholired(MTOACl) which are known to be related to copper and zinc anion are used for solvent extraction experiments and a traditional solvent chloroform is also used for comparison of yield. Firstly these solvent are applied as pure and then BmimPF6, chloroform are used as complex with dithizone and acetonitrile. In solvent extraction experiment, pH (0,25-1,02-1,9 and 5,02), amount of extractant (1, 2 and 4ml) and shaking time (5, 15, 30min) are investigated. After solvent extraction tests, the optimum pH=1,9 is determined. Increasing amount of extractants has no serious effect on the both Cu and Zn extraction. It is realized that for two metals, 1ml of extractant is also sufficient. According to agitation time, the highest values are obtained at the period of 15min agitation. At the and of the experiment it is concluded that a new generation ionic liquids can be applied successfully in the solvent extraction. Keywords: Leaching, solvent extraction, ionic liquid, brass dross, recovery, copper, zinc.