Preparation of Zinc Oxide from Used Batteries for the Recycled Oil Transesterification

Currently, in the city of Cuenca in Ecuador, around 35-40 kg of batteries are collected at the collection points each month which does not even represent 10% of the discarded batteries. Therefore, many used batteries are disposed of in landfills or in the trash; due to their composition, health and environmental problems are produced. Etapa EP is the public company in charge of collecting them, and after conducting a stabilization process, they are confined indefinitely. On the other hand, in Ecuador, around of 54 million liters of oil are discarded, 70% of which is vegetable oil. Used cooking oil usually is disposed of in rivers and sewers, polluting water, and soil. In the city of Cuenca, currently, Etapa EP only stored, the little oil collected in the city. In both cases there is no final solution, and it causes storage problems. For these reasons, it is important to generate alternatives within the framework of the circular economy that value these resources, promoting the optimization of their collection and processing. For the above mentioned, this research had as goal the material valorization of the carbon zinc batteries and energy of the vegetable. The material valorization was achieved using the batteries for the preparation of a zinc oxide catalyst supported on a carbon bar of same battery. Briefly, used batteries were dismantled to obtain the zinc case and carbon rods. The zinc case was lixiviated with hydrochloric acid at 100ºC for 60 minutes to obtain zinc chloride; then sulfuric acid was added, and the solution was heated at 100 ºC for one hour. The filtered solution was cool down to obtain zinc sulfate crystals. Next, sodium hydroxide was added obtaining zinc hydroxide. Finally, zinc hydroxide was calcinated at 900 ºC for 6 hours, obtaining zinc oxide. This was dispersed and supported in the coal of the battery. Zinc oxide showed a 98.49 % purity, 56.20 % of yield and a white coloration. Transesterification of the used vegetal oil was performed with the supported catalyst with an ethanol/oil ratio of 6:1. The weights of supported catalysts was 1% W/W (catalyst/solution). Prepared biodiesel had a heating power of 37.553 kJ/g, a density of 0.8916 g/cm3, a viscosity of 4.1887 mm2/s, a water content of 0.001 % and a 70.91 % yield. These parameters were in the ranges given by ASTM normative. In conclusion, two potentially toxic environmental liabilities have been valued through the production of value-added products.