This work proposes the use of plastic residues, more specifically polystyrene packaging, to support TiO, used as a photocatalyst in the degradation of erythrosine and Brilliant Blue food dyes. The scanning electron microscopy and Fourier transform infrared spectroscopy analyses exhibited the surface coating and the presence of TiO in the material, respectively. The UV/HO/TiO process was used in the preliminary study, given the high percentage of degradation, operational advantages and greater reductions in peaks related to the aromatic rings when compared to the other processes studied. For the factorial design, the highest efficiency was reached for 150 mg of TiO, a HO concentration of 11.2 mmol L and pH of 5.0. These conditions were used in the degradation kinetics, which was rapid during the first 30 min, with the concentration of dyes in the solution reaching values close to zero after 180 min. Based on the mechanism proposed, the pseudo-first order kinetic model presented the best adjustment to the experimental data. After treatment, the solution presented greater biodegradability and lower toxicity, verified by the lettuce seed germination test (Lactuca sativa). Thus, the UV/HO/TiO process showed great potential in the treatment of industrial effluents contaminated by these food dyes, as well as in reusing discarded polystyrene packaging to support the photocatalyst.
Agro-industrial waste are seen as potential precursors in the development of adsorbents for the removal of phenolic compounds, which exhibit a harmful effect to human health due to their high toxicity. This work evaluated the use of coal prepared from coconut tree agro-industrial waste, for the adsorption of phenol in aqueous solutions. Three coal samples were prepared as follows: carbonized only (Cb), activated with synthetic air (Cair) and activated with CO2 (CCO2). Based on the results of characterization, it was observed that these adsorbents are mesoporous, with a predominantly amorphous structure. The CCO2 demonstrated the highest thermal stability. Based on pHPZC, it was found that after the activation process, the surface of the material became positively charged at a higher pH range of the solution; therefore, favouring the adsorption of phenol. In the kinetic study the pseudo-nth order model obtained the best adjustment to the experimental data. The intra-particle diffusion model indicated that the adsorption processes are controlled by various steps. The experimental data of the equilibrium adsorption study were also evaluated; with no significant difference being found between the models that were better adjusted (Fritz-Schlunder, Redlich-Peterson, Radke-Prausnitz and Sips) according to the F-test at a 95% confidence level. The maximum adsorptive capacity for Cb, Cair and CCO2 were of 32, 41 and 56 mg g -1 , respectively. In this study, the coconut tree straw, an abundant agro-industrial residue that has not been previously evaluated as a precursor for the preparation of coal was valued being used as an adsorbent in the removal of phenol.
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