Photocatalytic degradation of bisphenol-A (BPA) over titanium dioxide, and determination of its by-products by HF-LPME/GC-MS.

In this work, analytical strategies were developed based on the technique of hollow fiber liquid-phase microextraction and chromatographic methods (LC-UV and GC/MS). These methods allowed the identification of the main Bisphenol-A by-products applying heterogeneous photocatalysis in water samples. BPA degradation in this study was in the order of 90%, and the conditions used in the HF-LPME were optimized through 23 factorial design (6 cm fiber length, stirring speed of 750 rpm, and an extraction time of 30 min). Using a HF-LPME/GC-MS analytical strategy, it was possible to identify six by-products of BPA photodegradation, two of which have not been reported in the literature so far. This knowledge was quite important since the degradation can lead to the formation of more toxic and persistent by-products than the BPA. With the Toxtree software, three degradation products were found to be persistent to the environment, in addition to BPA; however, in 360 minutes of reaction, chromatographic peaks of the precursors were not identified, suggesting that there may have been a total degradation of these compounds. The results showed a great application potential of a miniaturized extraction technique to extract and pre-concentrate the degradation products of emerging contaminants.

New insight into monitoring degradation products during the TiO2-photocatalysis process by multivariate molecular spectroscopy.

This study focuses on the feasibility of a spectroscopic multivariate method for monitoring the concentration of phenol and its main degradation products during heterogeneous photocatalysis. Phenolic compounds were chosen as model to evaluate the degradation process due to their toxicity and persistence in the environment and also their well-known degradation pathway. The predictive capability of the multivariate method developed by partial least squares regression (PLSR) over the spectral range of 200-350 nm was satisfactory, allowing mean predicted errors below 5.0 % in the simultaneous determination of the target compounds using six latent variables and smoothing spectra. Suitable results were reported for the simultaneous determination of hydroquinone, resorcinol, pyrocatechol, and p-benzoquinone in accordance to the chromatographic method. Characteristics such as simplicity, low cost, and fast data acquisition are remarkable in this procedure, which makes it appropriate for this type of analytical control.

Microcystin-LR degradation by solar photo-Fenton, UV-A/photo-Fenton and UV-C/H2O2: a comparative study.

This work assessed the effectiveness of several methods on degradation of microcystin-LR (MC-LR) by different Advanced Oxidation Processes, like solar photo-Fenton, UV-A/photo-Fenton and UV-C/H2O2. UV-C/H2O2 and UV-A/photo-Fenton processes were carried out in a bench scale photochemical apparatus and the solar photo-Fenton treatment was performed in a CPC photoreactor. MC-LR degradation was monitored by LC-ESI-MS/MS and kinetic parameters were calculated for all systems evaluated. The results demonstrated that UV-C/H2O2 was the most efficient method, showing a reduction of over 90% of initial MC-LR after 5 min of reaction. Solar and photo-Fenton/UVA had a rate decrease of 88 and 76% after the same time, respectively. The kinetic study indicated that the solar photo-Fenton and artificial radiation (UV-A) processes were very similar in their efficiency. The use of sunlight instead of artificial UV radiation significantly reduced the cost of photocatalytic treatment systems; it is also an environmentally friendly method, since it utilizes renewable energy.

Degradation of aqueous solutions of camphor by heterogeneous photocatalysis.

In this study the photocatalytic degradation of aqueous solutions of camphor was investigated by using TiO2 and ZnO photocatalysts. In the presence of artificial UV-light the highly photosensitive camphor was almost totally degraded after reaction times of 60 min. However, under these conditions the mineralization degree was lower than 25%. In the presence of semiconductors the degradation was complete after a treatment time of about 30 min. Moreover, the mineralization was considerably greater, mainly with the use of TiO2 (> 80% at reaction time of 60 min). Heterogeneous photocatalytic processes applied in the presence of solar radiation show a promising degradation capability. TiO2-based processes afforded mineralization degrees of about 90% after a reaction time of 120 min, when the system was assisted by aeration.

Integração de processos físico-químicos e oxidativos avançados para remediação de percolado de aterro sanitário (chorume) / Integration of physical chemistry and advanced oxidative processes for remediation of landfill leachate

Neste trabalho está sendo proposto um processo integrado para a remediação de chorume, consistente na separação preliminar das substâncias húmicas, por precipitação em meio ácido, e o tratamento subseqüente do sobrenadante por meio de processos oxidativos avançados. Em geral, a precipitação preliminar permite remover uma pequena parcela da DQO (14 por cento) e grande parte da cor, o que permite significativas melhoras no tratamento fotoquímico posterior. Quando aplicado na forma de um sistema de múltiplas adições de peróxido de hidrogênio, o sistema UV/H2O2 permite descolorações da ordem de 95 por cento e reduções de DQO de 75 por cento, em tempos de reação de 120 min. Trata-se de um resultado bastante promissor, principalmente levando-se em consideração a elevada resistência da matriz em estudo.