توصيفگر ها :
كاتاليست مستعمل , پلاتين , ليچينگ , استخراج با حلال آلي , حلال يوتكتيك عميق
چكيده انگليسي :
Platinum is a precious metal with high demand in various industries, but its supply is limited. Therefore, the recovery of platinum from spent catalysts has significant economic implications. Additionally, this process can prevent the accumulation of spent catalysts as waste. In this study, deep eutectic solvents (DES) were used for platinum leaching, providing an environmentally friendly alternative to acidic leaching. Due to their high solubility properties, DES have garnered attention from scientists and chemists in recent years. Initially, the potential of several choline chloride-based eutectic solvent compositions as hydrogen bond acceptors, combined with urea, glycerol, ethylene glycol, and oxalic acid as hydrogen bond donors, for platinum leaching was investigated. The analysis of the results indicated that the deep eutectic environment alone was insufficient for platinum leaching, necessitating the use of an external oxidant (nitric acid). The experiments were repeated in the presence of nitric acid, and the highest recovery was achieved with the combination of choline chloride and ethylene glycol, yielding a recovery rate of 83.62%. Subsequent stages of the study utilized this combination. To examine the impact of various parameters on platinum concentration and recovery, the experiments were designed using a fractional factorial method. Five factors, including solid percentage, choline chloride to ethylene glycol ratio, water content, temperature, and nitric acid amount, were analyzed. The results demonstrated that the choline chloride to ethylene glycol ratio was the most influential factor on platinum recovery. This effect was attributed to the increased concentration of chloride species and enhanced solubility of platinum complexes. Ultimately, the optimal leaching conditions for maximizing recovery were determined to be a solid content of 10%wt, a choline chloride to ethylene glycol ratio of 1:1, water content of 25%, a temperature of 90°C, and 10%wt nitric acid. Under these conditions, a platinum recovery of 92.87% and a concentration of 217 mg/L after leaching were achieved. Furthermore, the purification process of the eutectic solution containing platinum through solvent extraction was investigated. In this stage, four factors percentage of TOA extractant in the organic phase, aqueous to organic phase ratio, temperature, and residence time were studied. The results indicated that the platinum extraction reaction was completed in less than 5 minutes. The aqueous to organic phase ratio had the most significant impact on platinum recovery, with a change in the ratio from 3:1 to 1:1 resulting in an approximate 15% increase in recovery. This change was related to the increased capacity of the organic phase and the binding species with platinum ions. The optimal conditions for solvent extraction were determined to be 9.99%wt TOA concentration in the organic phase, an aqueous to organic phase ratio of 1:1, a temperature of 25°C, and a residence time of 5 minutes. Under these conditions, a platinum recovery of 99.93% was achieved. The findings of this research can provide significant benefits to the petrochemical industry, particularly in terms of waste management, resource recovery, and environmental sustainability.
