High-Efficiency Zinc Recovery from Industrial Wastes Using Novel Extraction and Optimization Methods
摘要
The slag and soot from the zinc (Zn) casting and cold purification cakes of the zinc production industry are important and strategic wastes in the zinc production industry, which have a very high zinc content of about 70%. But, the high percentage of chlorine (Cl−) in the slag and soot of casting (Cl− = 5%) due to the use of ammonium chloride (NH4Cl) in the furnace and high percentage of nickel (Ni) and cadmium (Cd) impurities in cold refining cakes (Ni = 3.5% and Cd = 10% has made their reusability and retrievability practically impossible. In this research, with new, low-cost, and economical methods, zinc metal from the casting furnace slag and soot wastes, and cold purification cakes were first recovered. The optimum conditions to maximize zinc extraction and dechlorination from the casting slag and soot wastes were determined as solution pH: 1, solution temperature: 65 °C, rotation speed: 300 rpm, reaction time: 120 min, solid to liquid: 300 g/l, and grain size: 1.0 mm. Under optimized conditions, the highest extraction and hydroxide precipitation efficiency of zinc by lime (Ca(OH)2) were obtained above 92.24% with a zinc grade of 24.08%. In addition, the highest zinc recovery efficiency from the cold purification cake was obtained at about 97.5% in the optimal condition of solution pH: 4, reaction temperature: 45 °C, agitation rate: 300 rpm, reaction time: 240 min, solid to liquid: 100 g/l, and grain size: 0.5 mm.