Photo-Fenton-Like Treatment of Municipal Wastewater

UV and Zero-Valent Iron (ZVI) Activated Continuous Flow Persulfate Oxidation of Municipal Wastewater

Currently, sulfate-radical-based advanced oxidation processes are promising candidates to become viable post-treatment processes for wastewater purification. In this work, a continuous flow UV light/persulfate (PS)/zero-valent iron (ZVI) system has been applied for wastewater treatment for the first time. The influence of certain photo-Fenton-like process parameters, such as space time, PS concentration, and PS to ZVI molar ratio, on the removal of total organic carbon (TOC), was examined using the Box–Behnken design. First, synthetic municipal wastewater was used for the experiments, and the polynomial regression model was constructed utilizing the real data by using the response surface methodology (RSM). The adequacy of the RSM model was assessed by analysis of variance, which showed that the model was reliable and could be applied to improve the process parameters for TOC removal. Moreover, both synthetic and real municipal wastewater were spiked with carbamazepine (CBZ), which is commonly prescribed as an antiepileptic drug, to investigate its fate in the UV/PS/ZVI system. With a space time of 60 min, PS concentration of 60 mM, and PS to ZVI molar ratio of 15, it was possible to remove 71% of TOC and completely remove CBZ from the synthetic municipal wastewater, whereas a 60% TOC removal and complete removal of CBZ were achieved at a space time of 50 min, PS concentration of 50 mM, and PS/ZVI molar ratio of 15 for the real municipal wastewater. This difference in TOC removal could possibly be linked to the complex matrix of the real wastewater and the presence of radical scavenging agents.

Degradation of 4-Tert-Butylphenol in Water Using Mono-Doped (M1: Mo, W) and Co-Doped (M2-M1: Cu, Co, Zn) Titania Catalysts

Mono-doped (Mo-TiO₂ and W-TiO₂) and co-doped TiO₂ (Co-Mo-TiO₂, Co-W-TiO₂, Cu-Mo-TiO₂, Cu-W-TiO₂, Zn-Mo-TiO₂, and Zn-W-TiO₂) catalysts were synthesized by simple impregnation methods and tested for the photocatalytic degradation of 4-tert-butylphenol in water under UV (365 nm) light irradiation. The catalysts were characterized with various analytical methods. X-ray diffraction (XRD), Raman, Diffuse reflectance (DR) spectroscopies, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Energy dispersive spectroscopy (EDS) were applied to investigate the structure, optical properties, morphology, and elemental composition of the prepared catalysts. The XRD patterns revealed the presence of peaks corresponding to the WO₃ in W-TiO₂, Co-W-TiO₂, Cu-W-TiO₂, and Zn-W-TiO₂. The co-doping of Cu and Mo to the TiO₂ lattice was evidenced by the shift of XRD planes towards higher 2θ values, confirming the lattice distortion. Elemental mapping images confirmed the successful impregnation and uniform distribution of metal particles on the TiO₂ surface. Compared to undoped TiO₂, Mo-TiO₂ and W-TiO₂ exhibited a lower energy gap. Further incorporation of Mo-TiO₂ with Co or Cu introduced slight changes in energy gap and light absorption characteristics, particularly visible light absorption. In addition, photoluminescence (PL) showed that Cu-Mo-TiO₂ has a weaker PL intensity than undoped TiO₂. Thus, Cu-Mo-TiO₂ showed better catalytic activity than pure TiO₂, achieving complete degradation of 4-tert-butylphenol under UV light irradiation after 60 min. The application of Cu-Mo-TiO₂ under solar light conditions was also tested, and 70% of 4-tert-butylphenol degradation was achieved within 150 min.

Decolorization and Oxidation of Acid Blue 80 in Homogeneous and Heterogeneous Phases by Selected AOP Processes

This paper is a kinetic study that compares the rate of decolorization and subsequently the mineralization of Acid Blue 80 in model dyeworks wastewater, both in the homogeneous phase using the Fenton and photo-Fenton reactions, UV-C and UVC/H2O2 processes, and in the heterogeneous phase, where the proven commercial photocatalysts P25, P90, and AV01 based on TiO2 were used. The influence of pH of the environment was studied and in the case of the Fenton reaction, the influence of the concentration of catalyzing Fe2+ ions on the rate of decolorization of the model wastewater was also studied. The optimal molar ratio of H2O2/Fe2+ was 10:1. For describing the reaction kinetics, first-order speed constants were best-suited. In all applied processes, the dye chromophore degraded, which was accompanied by a quantitative decolorization of the model wastewater. Subsequently, the mineralization of colorless intermediate products was studied through a decrease in COD or, more precisely, TOC. The mineralization efficiency in the homogeneous phase ranged between 18.6 and 97.1% after 24 h. In the case of heterogeneous photocatalysis, it ranged between 79.6 and 97.3% after 24 h, with efficiency declining in the order P90 > P25 > AV01.

Assessment of a Novel Photocatalytic TiO2-Zirconia Ultrafiltration Membrane and Combination with Solar Photo-Fenton Tertiary Treatment of Urban Wastewater

The objective of this study was to assess the combination of a photocatalytic TiO2-coated ZrO2 UF membrane with solar photo-Fenton treatment at circumneutral pH for the filtration and treatment of urban wastewater treatment plant (UWWTP) effluents. Photocatalytic self-cleaning properties were tested with a UWWTP effluent under irradiation in a solar simulator. Then, both the permeates and retentates from the membrane process were treated using the solar photo-Fenton treatment. The UWWTP effluent was spiked with caffeine (CAF), imidacloprid (IMI), thiacloprid (THI), carbamazepine (CBZ) and diclofenac (DCF) at an initial concentration of 100 µg/L each. Retention on the membrane of Pseudomonas Aeruginosa (P. Aeruginosa), a Gram-negative bacterial strain, was tested with and without irradiation. It was demonstrated that filtration of a certain volume of UWWTP effluent in the dark is possible, and the original conditions can then be recovered after illumination. The photocatalytic membrane significantly reduces the turbidity of the UWWTP effluent, significantly increasing the degradation efficiency of the subsequent solar photo-Fenton treatment. The results showed that the membrane allowed consistent retention of P. Aeruginosa at an order of magnitude of 1 × 103–1 × 104 CFU/mL.

Prediction of heterogeneous Fenton process in treatment of melanoidin-containing wastewater using data-based models

Predictive capability of response surface methodology (RSM) and ant colony optimization combined with support vector regression (ACO-SVR) models are applied for determining optimal parameters in the process of heterogeneous Fenton oxidation of melanoidin, a high molecular weight polymer widely produced during fermentation processes generating large quantities of wastewater with intense brown color and extremely high chemical oxygen demand (COD). Prediction of the performance of nano zero-valent iron supported on activated carbon cloth-chitosan (ACC-CH-nZVI) catalysts was carried out using Box-Behnken design (BBD) and analysis of variance to evaluate the interaction of independent variables involved in heterogeneous Fenton reaction. The optimized condition with minimal consumption of H₂O₂ (173 mM) resulted in 77.1% decolorization of melanoidin-contaminated water corresponding to 74.4% COD removal at pH 3 (600 mg/l Fe dosage) for 90 min reaction time. The corresponding weight ratio of H₂O₂ to COD was 0.98, much lower than the stoichiometric value 2.125, indicating the effectiveness of ACC-CH-nZVI as a heterogeneous Fenton-like catalyst. In comparison to previously published experimental results, ACO-SVR model shows higher coefficient of determination (R²; 0.9983) but lower root mean squared error (RMSE) and mean absolute error (MAE) than those of RSM model, indicating relative superiority in prediction capability. Besides, ACO algorithm appears to be a promising tool for improving forecasting accuracy of SVR model. This work demonstrates the applicability of ACO-SVR model in predicting the performance of wastewater treatment using Fenton process with limited number of experiment and exhibits satisfactory prediction results.