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.

Performance, kinetic, and biodegradation pathway evaluation of anaerobic fixed film fixed bed reactor in removing phthalic acid esters from wastewater.

Emerging and hazardous environmental pollutants like phthalic acid esters (PAEs) are one of the recent concerns worldwide. PAEs are considered to have diverse endocrine disrupting effects on human health. Industrial wastewater has been reported as an important environment with high concentrations of PAEs. In the present study, four short-chain PAEs including diallyl phthalate (DAP), diethyl phthalate (DEP), dimethyl phthalate (DMP), and phthalic acid (PA) were selected as a substrate for anaerobic fixed film fixed bed reactor (AnFFFBR). The process performances of AnFFFBR, and also its kinetic behavior, were evaluated to find the best eco-friendly phthalate from the biodegradability point of view. According to the results and kinetic coefficients, removing and mineralizing of DMP occurred at a higher rate than other phthalates. In optimum conditions 92.5, 84.41, and 80.39% of DMP, COD, and TOC were removed. DAP was found as the most bio-refractory phthalate. The second-order (Grau) model was selected as the best model for describing phthalates removal.