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The purpose of this study was to investigate the aqueous phase photochemical behavior of enoxacin (ENO), an antibiotic selected as a model pollutant of emerging concern. The second-order reaction rate constants of ENO with hydroxyl radicals (HO) and singlet oxygen (O) were determined at pH 3, 7, and 9. Also, the rate constants of the electron transfer reaction between ENO and triplet states of chromophoric dissolved organic matter (CDOM*) are reported for the first time, based on anthraquinone-2-sulfonate (AQ2S) as CDOM proxy. The sunlight-driven direct and indirect ENO degradation in the presence of dissolved organic matter (DOM) is also discussed. The results show that direct photolysis, which occurs more rapidly at higher pH, along with the reactions with HO and AQ2S*, is the key pathway involved in ENO degradation. The ENO zwitterions, prevailing at pH 7, show k HO, k, and k of (14.0 ± 0.8) × 10, (3.9 ± 0.2) × 10, and (61.5 ± 0.7) × 10 L mol s, respectively, whose differences at pH 3, 7, and 9 are due to ENO pH-dependent speciation and reactivity. These k values, along with the experimental ENO photolysis quantum yield, were used in mathematical simulations for predicting ENO persistence in sunlit natural waters. According to the simulations, dissolved organic matter and water depth are expected to have the highest impacts on ENO half-life, varying from a few hours to days in summertime, depending on the concentrations of relevant waterborne species (organic matter, NO, NO, HCO).

The synthetic hormone sodium levothyroxine (LTX) is one of the most prescribed drugs in the world and the most effective in hypothyroidism treatment. The presence of LTX in the environment has become a matter of major concern due to the widespread use of this hormone and by the fact that it is only partially removed in conventional water and sewage treatment plants. However, information regarding the photochemical fate of this hormone in environmental or engineered systems is scarce in the literature. In this work, the sunlight-driven direct and indirect LTX degradation was investigated by determining the photolysis quantum yield, Φ = 3.80 (± 0.02) × 10, as well as the second-order kinetic constants of the reactions with hydroxyl radicals, k = 1.50 (± 0.01) × 10 L mol s and singlet oxygen, k = 1.47 (± 0.66) × 10 L mol s. Mathematical simulations indicate that LTX photodegradation is favored in shallow, nitrite-rich, and dissolved organic matter (DOM)-poor environments, with LTX half-life times varying from less than 10 days to about 80 days. LTX removals of 85 and 95% were achieved by UVC photolysis and UVC/HO after 120 min, respectively. Three transformation products, triiodothyronine, diiodothyronine, and diiodotyrosine, were identified during LTX degradation by the UVC-based processes studied. The results herein regarding photo-induced kinetics coupled with environmental fate simulations may help evaluate LTX persistence and also the design of water and wastewater treatment processes.

In this work, an alternative utilization of agro-industrial waste coconut endocarp (Cocos nucifera L.) as raw material for the synthesis of magnetic adsorbent aiming the phenol removal is proposed. The synthetized adsorbent, denominated magnetic activated carbon (MAC), was prepared by coprecipitation of cobalt ferrite (CoFe 2 O 4 ) onto activated carbon surface obtained by carbonization of coconut endocarp. Characterization of MAC was carried out by point of zero charge (PZC), Brunauer, Emmett, and Teller (BET) surface area, scanning electron microscopy (SEM), x-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), x-ray diffractometry (XRD) analysis, and magnetization curves. Adsorption experiments were performed in batch system to evaluate kinetics and equilibrium of phenol adsorption. Adsorbent regeneration method was proposed to evaluate the reutilization of MAC in successive cycles of adsorption-desorption. Resultsshowed that obtained magnetic compounds present cubic phase structure covered in activated carbon surface. MAC has microporous structure with functional groups like carbonyl and hydroxyl that can behave as adsorption sites.Kinetic studies indicate that adsorption rate increased rapidly around the initial 60 min, reaching equilibrium at 240 min; following pseudo-first-order and pseudo-second-order kinetic models in characterization concentrations of 50 and 100 mg L À1 , only the second-order model fit the kinetic data at 150 mg L À1 , while both models were outside the chi-square interval at 200 and 230 mg L À1 . The adsorption equilibrium is represented by Langmuir isotherm with high adsorption capacity of 116.0 ± 3.61 mg g À1 . The desorption experiments revealed that adsorption capacities of MAC still viable after three adsorption-desorption cycles. It was observed that chemical affinity of small concentrations of methanol with phenol allowed to exert greater desorption capacity to other solvents with permanence of adsorbed phenol of 17.5 mg g À1 .

O interesse em utilizar a biomassa para produção de energia tem crescido consideravelmente. Além do reaproveitamento de resíduos de indústrias agrícolas e alimentícias a energia da biomassa evita o aumento de dióxido de carbono na atmosfera. A biomassa residual pode ser utilizada de diversas maneiras com o objetivo de gerar energia. Uma delas, e talvez a mais eficiente, é a produção de hidrogênio. O estudo da produção de hidrogênio por fontes alternativas cresceu nos últimos anos em função da necessidade da utilização de fontes renováveis e do desenvolvimento tecnológico de células a combustível. Dentre várias alternativas, a gaseificação em água supercrítica tem a vantagem de não ser específica para determinado resíduo (agrícolas ou de efluentes de processos diversos). Durante a gaseificação em água supercrítica, ou seja, em temperaturas e pressões maiores ou iguais a 374 °C e 22.1 MPa, respectivamente, são produzidos em grande parte hidrogênio (H2) e dióxido de carbono (CO2). No entanto, por atingir temperaturas e pressões elevadas, os materiais para construção e manutenção da planta de produção merecem atenção especial e o alto custo operacional torna-se o maior obstáculo para o desenvolvimento desta tecnologia. Contudo, verifica-se que, além de grande eficiência energética, a utilização de hidrogênio em células a combustível gera apenas água como subproduto, tornando, portanto, a substituição de processos que utilizam combustíveis fósseis por processos que utilizem fontes alternativas, conveniente e oportuna. A tecnologia de geração de hidrogênio em água supercrítica atende a esse anseio e novos estudos vêm sendo realizados para torná-la mais viável.