In the laboratory in which professor Jorge Alberto Soares Tenório and his team work, in the Department of Metallurgical and Materials Engineering of the Polytechnic School of the University of São Paulo (Poli-USP), to recycle has become the order of the day. Among diverse projects, the most advanced is the one that foresees the recovery of metals from used batteries. “Our work is opening doors for obtaining two products extracted from batteries, metallic zinc and manganese oxide. They have the same characteristics as the raw materials used originally in common or alkaline batteries that power various electronic equipment such as walkmen, clocks and flashlights and even photographic cameras.”Zinc is also used in the protection of sheets and pipes made of iron, alloyed with copper, pressure foundered alloys (commercially known as zamac), among other products.” says professor Tenório. Nowadays, close to 4% of the zinc produced in Brazil is used by the battery industry, or that is to say, 8,000 tones per year are used and afterwards discarded by consumers as domestic garbage.
Batteries are not yet among those products separated in selective collections or picked up by collectors at dumps. There isn’t any recycling company and the disinterest grew with the publication of Resolution 257/99 of the National Council for the Environment (Conama), which outlined the destiny of batteries in the country. Article 6 of the law determines that, as of the 1st of January of this year, the manufacturing, importation and commercialization of batteries should obey the following limits of active metals in the batteries: 0.010% of its in weight in mercury, 0.015% of cadmium and 0.200% of lead. In Article 13 of the same law, the manufacturers are not obliged to carry out the collection of their used product if specified as in Article 6. This is the case of the batteries sold in Brazil.
According to the resolution, only nickel-cadmium batteries, used in cellular telephones, must be collected by the manufacturer or importer. The law also states that batteries can be placed together with domestic rubbish in landfills, and in Article 8, prohibits the final destination of used batteries in open faced rubbish dumps. The problem is that 76% of urban garbage is thrown onto open faced rubbish dumps, according to the Brazilian Institute of Geography and Statistics (IBGE). Therefore, this is an improper situation forbatteries and cells, which present in their decomposition metals dangerous to human health and the environment, such as mercury, lead, cadmium and manganese.
The correct pathway
Worried with the problem and eager to propose a solution, professor Tenório began the project of the recycling of batteries using hydrometallurgy. This process is based on the concentration of the materials and their dissolving in a bath of sulfuric acid followed by the extraction of the chemical components by organic solvents. In the final phase of this new technique, professor Tenório’s team prepares a solution for the batteries that promises to solve the environmental question and include itself in the Brazilian industry of recycling.
Hydrometallurgical Processing For the Recovery of Metals from Used Batteries (nº 98/10882-9); Modality Regular line of research assistance; Coordinator Professor Jorge Alberto Soares Tenório – Poli-USP; Investment R$ 33,232.50