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Advanced oxidation methods, like ultrasound (US), are a promising technology for the degradation of emerging pollutants in water matrices, such as sulfonamide antibiotics. Nevertheless, few authors report the degradation of sulfonamides by high-frequency US (>100 kHz), and limited information exist concerning the use of ultrasonic-driven processes in the case of sulfadiazine (SDZ). In this study, SDZ degradation was investigated with the aim to evaluate the influence of initial concentration, pH and US frequency, and power. Ultrasonic frequencies of 580, 862, and 1,142 kHz at different power values and SDZ initial concentrations of 25, 50, and 70 mg L(-1) were used. The results show that SDZ degradation followed pseudo first-order reaction kinetics with k values and percent removals decreasing for increasing solute initial concentration. Higher SDZ percent removals and removal rates were observed for the lowest operating frequency (580 kHz), higher dissipated power, and in slightly acidic solution (pH 5.5). Addition of the radical scavenger n-butanol confirmed that hydroxyl radical-mediated reactions at the interface of the cavitation bubbles are the prevailing degradation mechanism, which is directly related to the pKa-dependent speciation of SDZ molecules. Finally, addition of H2O2 had a detrimental effect on SDZ degradation, whereas the addition of the Fenton reagent showed a positive effect, revealing to be a promising alternative for the removal of sulfadiazine.

Mangiferin, a bioactive metabolite having potent antioxidant and pharmacological properties has been obtained in this work by microwave assisted extraction (MAE) technique, from Mangifera indica leaves. A BoxBehnken design was used to evaluate the effect of three parameters: microwave power, the time of extraction, and the ratio of solvent to raw material (mL/g) over the mangiferin yield. Irradiation time was the most important parameter on the recovery of mangiferin. The results indicated that the optimal conditions should be as follows: power of microwave 900 W, extraction time of 5 min and a solvent volume / vegetal material relation of 10. With these parameters the maximum mangiferin yield was 63.22%. The MAE process was compared with the conventional extraction in stirred tank. No significant statistical differences were found (p= 0.5639) between both extraction methods of mangiferin. The presence of the metabolite was confirmed using high performance liquid chromatography. The method was validated with the guidelines set on the International Conference on Harmonization (ICH), for the validation of analytical procedures.

No abstract

Degradation of paracetamol (N-(4-hydroxiphenyl)acetamide) in aqueous solution by gamma radiation, gamma radiation/H2O2 and gamma radiation/Fenton processes was studied. Parameters affecting the radiolysis of paracetamol such as radiation dose, initial concentration of pollutant, pH and initial oxidant concentration were investigated. Gamma radiation was performed using a (60)Co source irradiator. Paracetamol degradation and mineralization increased with increasing absorbed radiation dose, but decreased with increasing initial concentration of the drug in aqueous solution. The addition of H2O2 resulted in an increased effect on irradiation-driven paracetamol degradation in comparison with the performance of the irradiation-driven process alone: paracetamol removal increased from 48.9% in the absence of H2O2 to 95.2% for H2O2 concentration of 41.7 mmol/L. However, the best results were obtained with gamma radiation/Fenton process with 100% of the drug removal at 5 kGy, for optimal H2O2 and Fe(2+) concentrations at 13.9 and 2.3 mmol/L, respectively, with a high mineralization of 63.7%. These results suggest gamma radiation/H2O2 and gamma radiation/Fenton processes as promising methods for paracetamol degradation in polluted wastewaters.