RESUMEN
In this study, ozone catalysts (hydrogenation-modified red mud, HM-RM) successfully prepared by hydrogenation-modification of industrial hazardous solid waste red mud (RM) as a raw material in accordance with the viewpoint of treating waste with waste and using waste. Meanwhile, as for the common phenomenon of membrane fouling, uneven distribution of multiphase solid catalysts and ozone in liquids, the addition of ultrasound can not only disperse materials, but also play a role in online cleaning of ceramic membranes and catalysts. The optimum treatment conditions for Rhodamine B (RhB) solution with volume of 2 L and concentration of 40 mg/L were catalyst concentration of 0.4 mg/L, reaction temperature of 45 °C, ultrasonic time of 1 h, ultrasonic intensity of 600 W, removal rate of RhB was up to 90 %. In addition, the computational fluid dynamics (CFD) simulation method was used to investigate the fluid flow between the two gas-liquid phases and the effect of the negative pressure of the membrane pump on the fluid by the analysis of flow, pressure and ozone flux of the ceramic membrane(CM) reaction apparatus. The CFD simulation results showed that at the inlet gas-liquid flow rate of 3 m/s and the negative pressure of 20,000 Pa, the maximum flow rates of CM-1 were 3 m/s, 0.752 m/s for CM-2, and 0.228 m/s for CM-3, respectively. Vortices, which are beneficial to solid-liquid mixing and gas-liquid mass transfer, formed between the suction port CM-1 of CM-1 and the inlets of CM-2 and CM-3. This discovery is consistent with relevant experimental research results. Significantly higher concentrations of both â¢OH and dissolved ozone were observed in the US/HM-RM/O3 system compared to other systems, indicating the significant improvement in ozone utilization rate through the application of ultrasound. The superiority of the US/HM-RM/O3 device was demonstrated. The real dye effluent was tested under optimum operating conditions and the results showed that COD and TOC were reduced by 81.34 % and 60.23 % respectively after 180 min of treatment. The above research can provide technical support for the treatment of dye wastewater using Ultrasound-enhanced ozone oxidation ceramic membranes.
RESUMEN
A low band gap and visible light-responsive heterogeneous Photo-Fenton catalyst of γ-Fe2O3/CQDs micron composite was prepared under the one-pot hydrothermal method. The Photo-Fenton degradation of γ-Fe2O3/CQDs towards dye solution of rhodamine B(RhB), methyl blue (MB), and methyl orange (MO) was studied comparatively with α-Fe2O3. The γ-Fe2O3/CQDs exhibited remarkable catalytic performance for various dyes and with a first-order rate (k) of 14 times higher than that of initial α-Fe2O3 with a low concentration of H2O2 of 0.049 mmol. L-1 and a wider pH range of 3.1-7.1. The microstructure of the compounds was observed by XRD, SEM, TEM, FT-IR, and XPS characterization results suggested that the γ-Fe2O3/CQDs nanocomposite was formed through the stable Fe-O-C bonds, thus, the band gap decreased, and it is more favorable for the distance of holes and electrons. The free radical trapping experiment and EPR analysis indicated that â¢OH and 1O2 were the major active species during the typical photo-Fenton reaction. What's more, the γ-Fe2O3/CQDs also exhibited good stability and magnetic properties. DFT conclusion shows that the mechanism of the potential determination step (PDS) on α-Fe2O3(220) is the cleavage of H2O2 with an energy barrier of only 0.08 eV, which is 0.54 eV lower than that of OH* on γ-Fe2O3(220). Thus it can be deemed that γ-Fe2O3/CQDs perform much higher catalytic activity for the dissociation of H2O2 than α-Fe2O3. This work gives a feasible and economical countermeasure of visible light Photo-Fenton dispose of dye wastewater with a recyclable magnetic γ-Fe2O3/CQDs micron catalyst.