Study Nickel recycling and leaching of metals from Eco-Friendly Nickel-metal hydride battery by response surface method

Abstract

 In this research, nickel metal hydride batteries were designed in certain sizes and components. In order to evaluate the quality and quantity of the designed batteries, the metal mold was cut lengthwise from the inner layers of the battery. The active materials of the electrode used in this work were black powder and nickel alloy, which were manually separated from the batteries. Battery black powder was investigated by X-ray diffraction analyzes and the presence of nickel as the main constituent of black powder was confirmed. The results of atomic absorption showed that more than 99 % of the alloy were a nickel. In this study, black powder was leached with sulfuric acid. The influence of parameters such as temperature, sulfuric acid concentration and liquid to solid ratio (L/S) on nickel extraction in a discontinuous system at two-phase constant contact time were studied. According to the results, the parameters of sulfuric acid concentration, temperature, liquid to solid ratio and the interaction of acid concentration with itself were important in nickel extraction. Optimal leaching conditions included a temperature of 60 °C, an acid concentration of 1.42 mol/L and a liquid to solid ratio of 10 mL. Under optimal conditions, the leaching efficiency was 81.25%, which was better compared to the batteries with other models and brands. In the next step, the purification of the leaching solution was investigated by sodium carbonate and a combination of sodium carbonate and sodium hydroxide. The results of atomic absorption showed that more than 83% of cobalt, manganese and zinc were removed and more than 98% of nickel ions were recycled, which was better than commercial batteries of various brands. Because the return of cobalt, manganese and zinc to nature by other batteries is higher than the designed battery and the recycling percentage of nickel ions is lower, these results are very important in terms of environmental safety.