Degradation of Active Brilliant Red X-3B by a microwave discharge electrodeless lamp in the presence of activated carbon

Enhanced degradation of reactive brilliant red X-3B by photocatalysis integrated with micro-electrolysis

The microwave electrodeless lamp UV photocatalysis (MWUV) integrated with iron carbon micro-electrolysis (ME) was applied to degrade reactive brilliant red X-3B. In the present study, the removal rate of X-3B by MWUV/ME was 95%, which was significantly higher than 56% of MWUV and 62% of ME system. The experiment results demonstrated a synergistic effect in MWUV/ME system, wherein the ME system played an important role in color removal and the formation of ·OH in photocatalysis contributed most for the mineralization of X-3B and its intermediates. The removal efficiency of TOC was 32%, 7.5%, and 59.5% under MWUV, ME, and MWUV/ME processes at the end of the reaction, respectively. The Fe³⁺ existed in the system was an enhancer of producing ·OH via self-generation of ·OH by UV irradiation or improving the separation of electron-hole in photocatalysis by capturing the electrons. Therefore, the combined treatment of MWUV and ME system has the potential of synergistic effect compared to the separate process. Lowering the initial solution pH and increasing the iron filing dosage and dissolved oxygen were beneficial for the enhancement of degradation efficiency. The inorganic anions showed a diversity influencing the degradation of X-3B. NO₃^-, CO₃^2-, and SO₄^2- (at higher concentration) promoted the degradation reaction, while Cl^- had non-significant effect.

Advanced Treatment of Pesticide-Containing Wastewater Using Fenton Reagent Enhanced by Microwave Electrodeless Ultraviolet

The photo-Fenton reaction is a promising method to treat organic contaminants in water. In this paper, a Fenton reagent enhanced by microwave electrodeless ultraviolet (MWEUV/Fenton) method was proposed for advanced treatment of nonbiodegradable organic substance in pesticide-containing biotreated wastewater. MWEUV lamp was found to be more effective for chemical oxygen demand (COD) removal than commercial mercury lamps in the Fenton process. The pseudo-first order kinetic model can well describe COD removal from pesticide-containing wastewater by MWEUV/Fenton, and the apparent rate constant (k) was 0.0125 min(-1). The optimal conditions for MWEUV/Fenton process were determined as initial pH of 5, Fe(2+) dosage of 0.8 mmol/L, and H2O2 dosage of 100 mmol/L. Under the optimal conditions, the reaction exhibited high mineralization degrees of organics, where COD and dissolved organic carbon (DOC) concentration decreased from 183.2 mg/L to 36.9 mg/L and 43.5 mg/L to 27.8 mg/L, respectively. Three main pesticides in the wastewater, as Dimethoate, Triazophos, and Malathion, were completely removed by the MWEUV/Fenton process within 120 min. The high degree of pesticides decomposition and mineralization was proved by the detected inorganic anions.

CeO2 mediated photocatalytic degradation studies of C.I. acid orange 7

CeO2 nanoparticles were prepared by a simple precipitation method, followed by calcination treatment. By selecting photocatalytic degradation of acid orange 7 (AO7) as a probe reaction, the influences of calcination temperature of catalyst, the concentration of AO7, initial pH value of AO7 solution and catalyst dosage on the photocatalytic activity of CeO2 were studied. It was found that CeO2 calcined at 550 degrees C shows the highest photocatalytic activity under visible light irradiation. It was revealed that under visible light irradiation the degradation of AO7 over CeO2 nanoparticles follows a dye self-sensitization mechanism. The degradation rate of AO7 increases with decrease in the initial pH value of the reaction solution, and degradation efficiency decreases with increase in the initial dye concentration. The optimal dosage of CeO2 in solution for AO7 degradation is 1 g/L.