Obtenção de compostos lamelares a partir de resíduos industriais

Abstract

Nowadays one of the biggest concerns that affect society worldwide is the disposal of industrial waste. In Brazil, 76% of the industrial waste generated is incorrectly disposed of, without receiving proper treatment. This situation is worsened if the waste contains heavy metals, such as iron, zinc, copper, aluminum, chromium, among others, since they cause irreversible damage to ecosystem. Mostly, the treatments carried out on these types of waste aim at generating a stable material enough to be disposal in landfills, missing the possibility of transform it into something useful. Therefore, this work aims at promoting the recovery of industrial waste containing metals in order to removing/recovering metals and converts them into new products, according to the principles of Green Chemistry and the United Nations' sustainable development objectives. This research proposes an experimental route using waste pickling acid (WPA) in order to produce a lamellar compound, such as a layered double hydroxide (LDH). The LDHs are materials with interesting properties and they have high potential to be used as sorbents, ion exchangers, polymeric stabilizers, catalysts, vehicles for drug release, among others. The synthesis method used was the coprecipitation and LDH was characterized by the analysis of apparent density, X-ray diffraction (XRD), infrared spectroscopy (IR-FTIR), scanning electron microscopy (SEM), adsorption-desorption of nitrogen (BET and BJH), thermogravimetric analysis (TGA), atomic absorption spectrometry (AAS) and ultraviolet–visible spectrophotometry (UV-Vis). Eight LDHs were produced under different synthesis conditions. According to the results, it was possible to produce an LDH formed by zinc, iron and aluminum containing chloride from industrial waste. The characterization techniques used showed the formation of a lamellar material, with low lamellar organization, specific area between 50 and 79m2 g-1, crystallinity dependent on the experimental conditions of the synthesis, especially the temperature. AAS data showed that all industrial waste added to the reaction was consumed, with no significant amount of dissolved metals remaining in the reaction medium. Thus, the applied coprecipitation process may be considered as an alternative to combine industrial waste treatment with the production of advanced materials. Therefore, it is concluded that it is possible to produce an LDH from waste and that the synthesis conditions influence the characteristics of the LDH.