Utilização de resíduos de pilhas na degradação oxidativa e redutiva de poluentes orgânicos em solução aquosa

Abstract

Water contamination by heavy metals and organic contaminants are two major issues of the global concern. They fall within the problem of water scarcity, one of the greatest concerns of modern society. One of the biggest sources of water pollution by heavy metals is the incorrect disposal of electronic devices, including batteries. In this sense, the present work evaluates the feasibility of using raw materials from discarded zinc-carbon batteries as catalysts for the degradation of contaminants as dyes, indigo carmine (IC) and methyl red (VM), drug diclofenac (DCF), and pesticides imidacloprid (IMD) and thiamethoxam (TMT). A catalyst compound by zero-valent zinc and manganese (ZnMn2O4) from the electrolytic paste of batteries was produced and its efficiency was tested for the degradation of IC in a Fenton-like process. Absorption measurements of the dye solutions indicated degradation rates above 90 % after 2 hours of exposure. The addition of powdered zinc, also obtained from the batteries, promoted IC degradation with even higher rates. Zinc, obtained from the casings of discarded batteries, was also used as an electron donor in acidic medium to cause the reductive degradation of two target pesticides (imidacloprid and thiamethoxam) and one dye (methyl red). The material promoted the complete removal of the contaminants, but with no mineralization. A third material was also produced from the casing of the batteries (compound mainly by zero-valent zinc). Two synthetic methods (calcination and hydrothermal treatment) was evaluated. The materials were employed as photocatalyst in the degradation of IC but none of them showed good efficiency.