هیدرومتالورژی

U-500 is a nickel-based superalloy which has significant amounts of some precious elements such as cobalt and chromium. Due to the economic and strategic value of these metals, their recovery from the used superalloys is of great importance. Hydrometallurgy is an economical and effective method for recovering these valuable metals from the superalloy scraps. So in this investigation, the dissolution behavior of nickel, cobalt and chromium elements from the used U-500 superalloy in the electro leaching process as well as the effect of different process parameters (such as: sulfuric acid concentration, applied voltage, process temperature, stirring and cathode-anode distance) on the dissolution of these elements are studied in details. The results show clearly that by increasing the concentration of sulfuric acid in the electrolyte, the applied voltage, and temperature, as well as decreasing the cathode-anode distance, the anodic dissolution of the superalloy U-500 is improved. Electrolyte stirring has no significant effect on increasing the anodic dissolution of the superalloy. The optimum conditions for the anodic dissolution of superalloy U-500 in sulfuric acid electrolyte was determined as acid concentration of 125 g/L, applied voltage of 4 V, stirring speed of 300 rpm, and cathode-anode distance of 3 cm without temperature control (starting with ambient temperature as the initial temperature(. Under these conditions, about 75% nickel, 84% cobalt and 67% chromium were durnig 25 minutes.

The increasing demand for zinc has made it more important to be recovered from secondary sources. Hydrometallurgical processes have been more considered due to numerous pyrometallurgy problems. The most important advantages such as low cost, less pollution, less time and higher purity of product have made the researchers attracted. Accordingly, zinc recovery has been investigated from an induction furnace waste containing more than 30% zinc oxide in this study. Includes crushing and analyzing of waste particles, leaching in citric acid as an organic acid and investigating of the effective parameters were used in the process. Acid concentration, leaching time, temperature and amount of waste particles were the parameters that were studied. According to the results, the optimal conditions were as acid concentration: 1.5M, time: 60min, temperature 60 °C, and waste particles: 1.5g. Under these conditions, a recovery rate of 82% was obtained for zinc metal. The kinetic and thermodynamic zinc acidic leaching were also studied. The results showed that the surface chemical reaction acts as controller.

During recent years recycling of lithium-ion batteries has attracted a lot of attention due to their extensive applications in various electric and electronic vehicles. Recycling of these batteries is of a great importance due to environmental issues and metal sources content, so this paper is to review the current status of these batteries’ recycling technologies. Among different recycling methods, hydrometallurgical based route is an optimized method to separate and recover metals and it has three steps as pre-treatment, leaching and deep recovery. In addition to brief description of these batteries’ structure and components, this paper has summarized the chemical, physical processes utilized in all steps of pre-treatment, leaching and metal recovery. Heat treatment, ultrasonic, dissolving and mechanical treatment are the common methods in the pre-treatment step and crystallization, solvent extraction, electrochemical and precipitation are accounted most used methods in the recovery step. Finally all investigations operated over the recycling issue also have been summarized in this paper. These categorized studies include both research and optimization into each triple step of hydrometallurgical route and new electrodes synthesis.