Estudo da influência de oxidantes e catalisadores de TIO2 B-N-codopado na degradação de aspartame

Abstract

Artificial sweeteners (AS) are a new class of chemical compounds used in food, beverages, pharmaceuticals and personal care products, they are consumed daily basis in considerable quantities. One of the most used sweeteners in the world is aspartame (ASP), about 180 times sweeter than sugar. The presence of ASP in water has been identified as potentially causing human and animal health problems. Mental and liver problems have been reported. In the face of the controversy surrounding the ASP, its wide use in the world and its possible bioaccumulation, it was decided to use it as a model pollutant. In this study, the degradation and mineralization of ASP by solar / TiO2codoped by B-N in the presence of common oxidants (ie, H2O2, peracetic acid and persulfate) was investigated. The role of oxidant concentration, catalyst dosage, initial concentration of pollutants and the effects of the water matrix using deionize water and secondary influent were investigated. To understand the synergistic effect of the oxidants on the activity of TiO2codoped in B-N and the efficiency in real water, analyzes were performed to quantify the radicals. TiO2codoped by B-N is a homemade catalyst. A hydrothermal method was employed for the synthesis of the catalyst. XRD, XPS, TEM, HR-TEM and BET were used for characterization of the catalyst. The results showed high efficiency of the catalyst in the removal of the pollutant. Achieve 100% removal in 30 and 90 minutes for 2.5 and 50 μM ASP, respectively. The same complete removal of ASP was also obtained by 0.5 g / L of BN-TiO2 / 1.0 mM PS in only 15 min. However, the addition of H2O2 or PAA oxidants to the ASP / BN-TiO2 system under the same conditions decreased ASP degradation, which was corroborated by the mineralization analysis, BN-TiO2 reached about 65% TOC removal and percentage organic nitrogen. The quantification of radicals indicated that the combination of methods that generate the same type of oxidants, can cause inhibition by recombination. The PS / BN-TiO2 system was more effective at removing (100%) the ASP in real sample, since B-N-TiO2 alone did not achieve this.Another interesting result was the monitoring and identification of 8 short - chain carboxylic acids, homogeneous and heterogeneous reactions, simple and combined (oxidates - catalysts), from which these acids were identified, quantified and monitored. Among the compounds studied, oxalic acid was present in all experiments and acetic acid showed to be refractory. An ecologically correct alternative due to the possibility of reducing the dose of catalyst with high catalytic effect was presented.