Peroxidases can be used in decolorization processes and the treatment of textiles effluents. This study evaluates the potential of the turnip peroxidase enzyme in the decolorization of the phthalocyanine textile dye Reactive Blue 21 (RB21). Some factors such as pH, the amount of H 2 O 2 and the enzyme were evaluated in order to determine the optimum conditions for the enzyme performance. The reaction products formed during the decolorization of the RB21 dye were analyzed by high-performance liquid chromatography-mass spectrometry coupling (LC-ESI/MS). LC-ESI/MS analysis showed that the decolorization of the dye RB21 by turnip peroxidase is due to the breaking up of the chromatogenous system. The tests for toxicity towards lettuce seeds showed an increase of the toxicity after enzymatic treatment of the dye. This study verifies the viability of the use of the turnip peroxidase enzyme in the biodegradation of textile dyes.

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Chitosan beads were prepared, using glutaraldehyde as a crosslinking agent for the immobilization of soybean hull peroxidase (SBP). The activity of free and immobilized SBP was studied. The optimum pH was 6.0 for both the free and immobilized enzyme; however, enzyme activity became more dependent on the temperature after immobilization. This study evaluated the potential use of immobilized and free enzyme in the oxidation of caffeic acid, of synthetic phenolic solution (SPS) and of total phenolic compounds in coffee processing wastewater (CPW). Some factors, such as reaction time, amount of H2O2 and caffeic acid were evaluated, in order to determine the optimum conditions for enzyme performance. Both enzymes showed a potential in the removal of caffeic acid, SPS and CPW, and immobilized SBP had the highest oxidation performance. The immobilized enzyme showed a potential of 50% in the oxidation of caffeic acid after 4 consecutive cycles.

The reformation of CO 2 through photocatalytic processes to obtain products with high energy value and compatibility with the current energy infrastructure is a compelling strategy to minimize the emission of CO 2 into the atmosphere, one of the main greenhouse gases. However, practical application of such a photocatalytic system requires significant efforts for improved CO 2 photoreduction performance and product selectivity. Thus, in the present work, CuO nanoparticles were combined with Nb 2 O 5 in order to improve the photocatalytic properties of these semiconductors in the CO 2 photoreduction process. Nb 2 O 5 / CuO heterojunctions were prepared via a solvothermal treatment method, while the experimental tools, such as FESEM, HRTEM, and DRS, were employed to evaluate the microstructural and electronic properties. We describe how CuO decoration over Nb 2 O 5 adjusts its selectivity for CO 2 reduction to CH 4 , HCOOH, or H 3 CCOOH in different contents. An investigation of CO 2 photoreduction using different electron donors/scavengers (water, sodium oxalate, and potassium bromate) under ultraviolet radiation revealed that its decoration influences local CO production by modifying the selectivity. CO has been confirmed as the main intermediate for HCOOH and CH 3 COOH production, and CO 2 reduction efficiency increases at low CuO content (2.5% wt), leading to the formation of soluble hydrocarbons, and increases for CH 4 in higher amounts (10% wt).