RESUMO
The demand for sustainable and low-cost materials for wastewater treatment is increasing considerably. In this scenario, geopolymers have gained great interest, due to their good mechanical properties, their ability to be produced from industrial waste and their adsorbent or catalytic properties. In this study, novel magnetic mining waste based-geopolymers were produced by incorporating a residue from phosphate waste rocks, which were extensively characterized (XRD, TGA/DTA, SEM, BET, XRF, FTIR, Mössbauer, ss-NMR and XPS). The materials produced showed formation of a dense framework, even with 75% incorporation of the residue. The iron oxides and their magnetic properties remained unchanged, and their application in advanced oxidation reactions were evaluated, in particular, as catalysts in ozonation reactions. All of the geopolymers presented catalytic activity in the ozonation reaction, with catalytic ozone decomposition values of up to 2.98 min-1, which is 99 times greater than non-catalyzed reactions. Moreover, the reuse (performed in three cycles) and hot filtration-like experiments demonstrated, respectively, the regenerability and heterogeneous catalytic properties of the produced materials, showcasing the potential of these waste materials for catalytic geopolymer production. demonstrating the potential of this waste to produce catalytic geopolymers.
RESUMO
A single laccase with molecular weight of 41â¯kDa was produced by the white-rot fungus Oudemansiella canarii cultured on solid state fermentation using a mixture of sugarcane bagasse-wheat bran as substrate. The enzyme (5â¯U) was able to decolourize 80% of 50â¯mg/L Congo red within 24â¯h at 30⯰C and pH 5.5. The relationship between the decolorization rate and dye concentration obeyed Michaelis-Menten kinetics, with KM and Vmax values of 46.180⯱â¯6.245⯵M and 1.840⯱â¯0.101⯵mol/min, respectively. Fourier transform infrared spectroscopy (FTIR) and mass spectrometry allowed to conclude that the laccase acts not only on the dye chromophore group, but also that it cleaves different covalent bonds, causing an effective fragmentation of the molecule. The action of the laccase caused a significant reduction in toxicity, as indicated by the Microtox test. In conclusion, O. canarii laccase could be useful in future biological strategies aiming at degrading azo dyes.