Aplicação da fotocatálise heterogênea com óxidos metálicos semicondutores na redução de cromo VI

Abstract

The intensification of industrial activities has increased the release of heavy metals into the environment, with particular emphasis on chromium in its hexavalent form, Cr(VI), due to its high toxicity, mobility, and carcinogenic potential. The conversion of Cr(VI) to Cr(III), a less toxic and less soluble species, represents a relevant remediation strategy. In this context, the present study evaluated the application of heterogeneous photocatalysis using semiconductor metal oxides for the reduction of Cr(VI) in aqueous solution. The catalysts TiO₂, ZnO, and Nb₂O₅ were investigated without structural modification. Experimental assays were conducted by varying operational parameters, including pH, presence or absence of oxygen, addition of a sacrificial agent (sodium formate), and catalyst concentration. Cr(VI) concentration was monitored by UV–Vis spectrophotometry, allowing the construction of a calibration curve and kinetic monitoring of the reaction. The results demonstrated a strong dependence of the process on solution acidity and reaction system composition. Among the evaluated materials, Nb₂O₅ exhibited superior performance under acidic conditions, in the presence of the additive and absence of oxygen, achieving high reduction rates. After optimizing the operational parameters, a comparison between artificial and solar radiation sources indicated higher reduction efficiency under artificial light; however, solar irradiation also showed significant potential, reinforcing the environmental and economic feasibility of the technique. It is concluded that heterogeneous photocatalysis using metal oxides represents a promising alternative for the treatment of effluents containing Cr(VI), with prospects for further optimization and large-scale application.