The photo-oxidative destruction of C.I. Basic Yellow 2 using UV/S(2)O(8)(2-) process in an annular photoreactor

The efficiency of UV/S2O8 2- photo-oxidation process in the presence of Al2O3 for the removal of dexamethasone from aqueous solution: kinetic studies

This study aimed to investigate the efficiency of the UV/S₂O₈ ^2- photocatalytic process in the presence of Al₂O₃ nanoparticles for the removal of dexamethasone from aqueous solution. In this experimental study, the variables pH, persulfate concentration, initial concentration of dexamethasone, the catalyst dose were studied in order to investigate the process efficiency. Furthermore, the efficiency of UV/S₂O₈ ^2- in the presence and absence of catalyst was investigated. The Al₂O₃ nanoparticle catalyst was characterized using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses and scanning electron microscopy (SEM) image. The results showed that a decrease in pH and the initial concentration of dexamethasone increased the process efficiency. Given the increased concentrations of the persulfate and Al₂O₃, the removal efficiency was partially increased. In UV/S₂O₈ ^2-/Al₂O₃ under optimum conditions (pH = 3, t = 30 minutes, dexamethasone concentration = 20 mg/L, 0.5 mM of persulfate, and UV radiation = 55 watts), 94% of the dexamethasone was removed. The kinetic response showed that the reaction data corresponded to the pseudo-first-order kinetic model. The results showed that the UV/S₂O₈ ^2- photochemical process can efficiently remove dexamethasone from aqueous solution in the presence of Al₂O₃ catalyst and the mineralization efficiency reached about 98%. Therefore, this process is recommended due to its high efficiency and availability for the removal of pharmaceutical compounds.

Application of activated persulfate for removal of intermediates from antipyrine wastewater degradation refractory towards hydroxyl radical

Complete mineralisation of reaction intermediates refractory towards hydroxyl radical, generated from a previous ineffective degradation of urban wastewater containing antipyrine by HO-mediated sono-photo-Fenton reaction, has been attained using persulfate anions simultaneously activated by heat energy (thermally, ultrasound) and UV-C light. The SO4(-)-based mineralisation process enables another reaction pathway generating more easy degradable derivatives. The influences of the initial concentration of persulfate, ultrasound amplitude, temperature and the reaction time in the previous HO-based previous oxidation on the mineralisation degree were studied by using a Central-Composite Experimental Design. Under optimal conditions ([S2O8(2-)]o=1200mgL(-1), temperature=50°C, amplitude=10%, pH 2.8, HO-based reaction time=25min) practically complete degradation was achieved in approximately 120min. The contribution of HO and SO4(-) radicals in this system was also evaluated. The presence of chloride ion in urban wastewater can benefit the oxidation of acetate by sulfate radical. Results demonstrated that this activated persulfate-based oxidation system is a potential alternative to degrade intermediate compounds, which are refractory against hydroxyl radicals, generated in Advanced Oxidation Processes used to treat wastewater containing emerging contaminants such as antipyrine.

The photooxidative destruction of C.I. Basic Yellow 2 using UV/S2O8(2-) process in a rectangular continuous photoreactor

The photooxidative decolorization of C.I. Basic Yellow 2 (BY2), was investigated using UV radiation in the presence of peroxydisulfate (S(2)O(8)(2-)) in a rectangular photoreactor at experimental condition. S(2)O(8)(2-) and UV-light showed negligible effect when they were used independently. Removal efficiency of BY2 was sensitive to the operational parameters such as initial concentrations of S(2)O(8)(2-), BY2, light intensity, flow rate and pH. The conversion ratios of BY2 at the volumetric flow rates of 330, 500 and 650 ml/min were 84%, 79%, 51% in 30 min, respectively. Our results showed that light intensity was a beneficial parameter for dye removal. The results showed that in the presence of S(2)O(8)(2-), the photooxidation quantum yield obtained was higher than direct photolysis quantum yield, suggesting that photodecay of BY2 was dominated by photooxidation. The electrical energy per order (E(EO)) values for decolorization of BY2 solution was calculated. Results show that applying a desired peroxydisulfate concentration can reduce the E(EO).