Relentless development of technology triggers the smartphone production. The increasing number of smartphone use is followed by escalation of its waste, where its battery is usually left unrecycled. The analysis of the battery content shows that it is consist of a considerable amount of cobalt that can be reutilized based on its relatively high economic value, which valued USD 61/kg. Leaching as a form of hydrometallurgy was used in this research to recover cobalt using HNO3 as leaching agent and H2O2 as reducing agent. Process optimization was done by varying concentration of nitric acid and reaction temperature. The result showed that the optimum leaching condition was earned in 30 minutes of leaching reaction using 3.0 M HNO3 at the reaction temperature of 90°C, resulting 98.01% of cobalt leaching efficiency. Reaction kinetics study was also done in this research and the result demonstrates that recovery of cobalt from spent lithium-ion battery by nitric acid leaching was controlled by diffusion through product layer with activation energy value of 44.67 kJ/mol.

Lithium ion batteries are commonly used as power sources for mobile phone, but by using it continually will degrade their capabilities. Battery replacements will cause a lot of waste in environment. Spent lithium ion batteries cathode contain heavy metals, such as cobalt and nickel. However it is also included as valuable metals thus recovery process is necessary. In this research, hydrometallurgical leaching process has been done for recovery of cobalt and nickel from spent lithium ion batteries using citric acid as a leaching agent by varying citric acid concentration (0.5-1 M), reaction temperature (50-80) and reaction time (5-20 minutes). The spent lithium ion batteries were analyzed by atomic absorption spectroscopy (AAS). The result showed that the leaching of lithium ion batteries using citric acid was depend on citric acid concentration, reaction temperature and reaction time. Based on kinetics study, the leaching reaction of cobalt and nickel from cathode powder using citric acid was chemically controlled process and the activation energy of cobalt and nickel were 67.12 kJ/mole and 58.22 kJ/mole. The reaction order of leaching cobalt and nickel using citric acid was first-order reaction.

Batteries waste is found anywhere in the world because most of the electronic devices use batteries to operate them. Batteries that were used for electronic devices nowadays is lithium ion batteries. Lithium ion batteries is one of the rechargeable batteries where it contained heavy metals which is very dangerous for health and environment. However, in order to minimalize the composition before its being disposed many researchers have found a way to recover heavy metals, because it can be useful to reproduce lithium ion batteries in the future. In this research, hydrometallurgical leaching process has been done for recovery cobalt from used lithium ion using hydrogen peroxide as reducing agent and citric acid as a leaching agent by varying citric acid concentration (0-2 M), reaction temperature (50-80°C), and reaction time (5-60 minutes). The result were analyzed by atomic absorption spectroscopy (AAS) and showed that the best operation condition is at concentration 1 M, temperature 80oC with stirring time 60 minutes can recover more than 90% of Cobalt.

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