Fundamentals and applications of the photocatalytic treatment for the removal of industrial organic pollutants and effects of operational parameters: A review (original) (raw)
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Study of COD Removal Efficiency from Synthetic Wastewater by Photocatalytic Process
Environmental Engineering Research
In this research, we compared the COD removal efficiencies of titanium dioxide (TiO2) thin films coated on the surfaces of borosilicate glass that prepared by three different numbers of coating layer; i) 3 layers ii) 4 layers and iii) 5 layers by sol-gel method. All of the prepared TiO2 thin films consisted of pure anatase crystalline structure with grain sizes in the range 20-250 nm. The calculated optical band gaps of the TiO2 thin films were 3.24. The total apparent surface area per total weight of TiO2 thin films were 4.74, 3.86 and 2.79 m 2 g-1 for 3, 4 and 5 layers coating, respectively. The kinetics of the photodegradation reactions of COD under UVA light source were described by the Langmuir-Hinshelwood (L-H) kinetic model. The specific rates of the photodegradation of TiO2 thin films at 3 layers coating was 1.40×10-4 min-1 mW-1 , while for the 4 layers coating and the 5 layers coating were 1.50×10-4 and 4.60×10-4 min-1 mW-1 , respectively. The photocatalytic performance of COD degradation was higher with smaller grain size, higher surface area and narrow optical band gaps. Moreover, the numbers of coating layer on substrate also have great influence for kinetic of COD removal.
Photocatalytic Degradation of a Chemical Industry Wastewater: Search for Higher Efficiency
2017
15 Páginas, 8 Figuras, 3 TablasIn the present research, an annular photocatalytic reactor system was designed and operated to quantify the degradation of a real case chemical company wastewater. The photocatalytic degradation process was analyzed and optimized varying some critical operating variables such as pH, catalyst (TiO2) loading, H2O2 concentration (oxidant agent) and light intensity to find the best criterion warranting a high level of degradation. It was demonstrated that a pH of 7.0 and an amount of 2.0 g/L ofTiO2 resulted in a cleanup allowable level for discharge to river. Furthermore, photo-degradation by H2O2/TiO2/UV process was much more efficient (97%) with respect to the processes carried out individually by H2O2/UV(92%) orTiO2/UV (89%). It is remarkable that the optimum concentration of H2O2 was 11.6mM, and increasing the intensity of light accelerated degradation reaction. Careful selection of industrial wastewater reflected the capability predicting the level of...
Photocatalytic treatment of spent caustic wastewater in petrochemical industries
Advances in Environmental Technology (AET), 2016
In this study, the photocatalytic method was used for treating the spent caustic in the wastewater of Olefin units used in petrochemical industries which contain large amounts of total dissolved solids (TDS). By using the synthetic photocatalyst of suspended titanium dioxide and measuring the chemical oxygen demand (COD) which was reduced in the photocatalyst (lbc) process, the values of COD were modeled and evaluated by means of the Box-Behnken (BBD) and the artificial neural network (ANN) using experimental tests in a double-cylindrical-shell photo reactor. According to the applied calculations, it was found that the artificial neural network was a more suitable method than the experimental design in modeling and forecasting the amount of COD removal. The modeling employed in this research showed that increasing the concentration of the photocatalyst in a state of neutral pH enhanced the COD removal up to the optimal amount of 1.31 g/L without restrictions and 2 g/L with restrictions at the rate of 81% and 79%, respectively. In addition, the study of the parameter effects including oxidizer amount, aeration rate, pH, and the amount of loaded catalyst indicated that all factors except pH had a positive effect on the model; furthermore, if the interactions were neglected, the COD removal efficiency would increase by increasing each of these factors (except pH). In addition, there was no interaction between the aeration and the concentration of the photocatalyst, and the acidic pH was more suitable at low concentrations of the photocatalyst. Besides that, by increasing the pH, the efficiency of removal was reduced when the oxidant was at its low level. The results showed that photolysis and adsorption adoptions had a very small effect on the efficiency of the removal of COD compared to the photocatalyst adoptions, and it was insignificant. In addition, the photocatalytic method had an acceptable capacity for removing the phenol in the wastewater sample, whereas it was inefficient in reducing the sulfide solution in the wastewater.
Applied Sciences
Water resources are depleting, and the availability and supply of clean, potable water are a global concern. Advanced oxidation processes (AOPs) possess immense prospects in water and wastewater treatment settings. This study investigated and optimized the photocatalytic treatment of wastewater using titanium dioxide (TiO2) as the photocatalyst. The one-factor-at-a-time (OFAT) technique was employed to evaluate the effects of reaction time (20–100 min), mixing speed (20–100 rpm), and catalyst load (0.3–1.5 g/L) on pH, colour, turbidity, and chemical oxygen demand (COD) removal from actual municipal wastewater. Reaction time and catalyst load were then identified as the two key factors selected to be modeled and were optimized for turbidity and COD removal using the Central Composite Design (CCD) of response surface methodology (RSM). These statistical models were developed and used to optimize the operating conditions. The results obtained showed a desirability efficiency of 74.7% a...
The aim of this study is to investigate the performance of combined solar photo-catalyst of titanium oxide/zinc oxide (TiO2/ZnO) with aeration processes to treat petroleum wastewater. Central composite design with response surface methodology was used to evaluate the relationships between operating variables for TiO2 dosage, ZnO dosage, air flow, pH, and reaction time to identify the optimum operating conditions. Quadratic models for chemical oxygen demand (COD) and total organic carbon (TOC) removals prove to be significant with low probabilities (<0.0001). The obtained optimum conditions included a reaction time of 170 min, TiO2 dosage (0.5 g/L), ZnO dosage (0.54 g/L), air flow (4.3 L/min), and pH 6.8 COD and TOC removal rates of 99% and 74%, respectively. The TOC and COD removal rates correspond well with the predicted models. The maximum removal rate for TOC and COD was 99.3% and 76%, respectively at optimum operational conditions of TiO2 dosage (0.5 g/L), ZnO dosage (0.54 g/L), air flow (4.3 L/min), reaction time (170 min) and pH (6.8). The new treatment process achieved higher degradation efficiencies for TOC and COD and reduced the treatment time comparing with other related processes.
Water samples from two types of sources: partially treated sewage generated by a medium-sized city, with a high quantity of total coliforms and partially treated industrial wastewater, which contained mostly petroleum products from refineries, were treated using the same concentration of TiO 2 catalyst, for different exposure periods. UV-Vis and fluorescence spectroscopic evaluation of the composition changes of wastewaters under non selective oxidation conditions (achieved by photocatalysis) revealed that the higher removal rate was obtained for the industrial water sample compared to the sewage water sample, with respect to oxidation time. Considering the diverse characteristics and the solution matrix effects of the wastewaters, UV-Vis and fluorescence spectra revealed different patterns by increasing the quantity of TiO 2 catalyst from 0.25 mg mL-1 to 1 mg mL-1 , denoting that the amount of total coliforms in a sample greatly impacts the degree of photocatalytic oxidation.
Photocatalytic degradation of organic compounds in wastewaters
Technologica Acta, 2019
Due to the toxicity effects and endocrine disrupting properties of many organic compounds, their removal from water and wastewater has gained widespread global attention. This review summarizes photocata-lytic degradation of different organic molecules present in wastewaters. This is an overview of photocatalytic degradation with the goal of presenting the technique as an attractive and viable process unit. This process has great potential for replacing other conventional methods for treatment of wastewaters and can be used at the advanced treatment stage. Photocatalytic degradation techniques should be more used in wastewater treatment because with this technique it is possible to decrease contaminants to certain acceptable discharge limits. However, the technique is still not being utilised on an industrial scale. This is mainly due to focus of researchers to study singular contaminants such as alcohols, carboxylic acid, phenol and its derivate, chlorinated aromatic compounds, colours , active pharmaceutical ingredients, and different type of surface active agents. TiO 2 can be used as a photo-catalyst in water purification to degrade organic pollutants.
Journal of Renewable and Sustainable …, 2012
Estimation of radon diffusion coefficients in soil using an updated experimental system Rev. Sci. Instrum. 83, 093503 (2012) Chemical, biological, radiological, and nuclear threats-Decontamination technologies and recent patents: A review J. Renewable Sustainable Energy 4, 012704 Fundamentals and applications of the photocatalytic treatment for the removal of industrial organic pollutants and effects of operational parameters: A review J. Renewable Sustainable Energy 2, 042701 (2010) Static and flowing regions in granular collapses down channels: Insights from a sedimenting shallow water model Phys. Fluids 19, 106601 High-efficiency particulate air filter test stand and aerosol generator for particle loading studies Rev. Sci. Instrum. 78, 085105 Additional information on J. Renewable Sustainable Energy This study has focused on treatment of the metal ions, which have infinite lifetimes and build up their concentrations in food chains to toxic levels. Many researches have been performed about use of photocatalysis processes in treatment of industrial wastewater. The additional advantage is coming from sensitivity of the Cr(VI) photo reduction to the surface catalytic effects or to the presence of an additional electron donor and acceptors; then, a synergistic effect was observed in two-or multicomponent systems. The efficiency of total chromium reduction by photo catalytic treatment under UV-light in different degradation systems, UV, TiO 2 /UV, H 2 O 2 /UV, TiO 2 /citric acid/UV, and TiO 2 /H 2 O 2 /UV, was studied and compared. Even when the TiO 2 /citric acid/H 2 O 2 /UV reaction happened to be the most efficient process, both homogeneous and heterogeneous photocatalysis can be considered as suitable methods to reach the complete mineralization of the solutions. Maximum treatment efficiency of total chromium reduction with increasing citric acid concentration from 20 to 80 mg/l was reduced to 62%, 76.7%, 77.91%, and 100%, and with increasing H 2 O 2 concentration from 20 to 100 ml/l was reduced to 40.57%, 41.84%, 50.77%, 61.03%, and 100%, which is more efficient than the H 2 O 2 /UV process. Finally, the combination of TiO 2 /citric acid/H 2 O 2 /UV result was observed more efficient than the TiO 2 /citric acid and TiO 2 /H 2 O 2 /UV processes in the solutions. V C 2012 American Institute of Physics. [http://dx.
Materials Science in Semiconductor Processing, 2018
In this work, novel triple metal-nonmetal doped TiO 2 (K-B-N-TiO 2) was synthesized by the sol-gel method. The structure and properties of the synthesized nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. Photocatalytic activity of the nanoparticles was assessed by degradation of linear alkyl benzene (LAB) industrial wastewater at different operating conditions. The effects of initial pH, photocatalyst loading, initial COD concentration and reaction time on the photocatalytic performance of the nanoparticles degrading LAB wastewater were determined by response surface methodology (RSM). The region of examination for the process was taken as the area enclosed by initial COD concentration (200-500 mg/l), catalysis loading (1-2 g/l), initial pH (3-11) and reaction time (1-8 h). The doping modes reduced recombination of photogenerated electrons and holes, and extended the absorption of TiO 2 into the visible light. The photocatalyst properties of K-B-N-TiO 2 were more effective than those of pure TiO 2 and other modified single and double doped TiO 2 (B-N, K-N, N, B and K-TiO 2). The COD removal efficiencies by the photocatalysis were increased from pure TiO 2 to multi-doped TiO 2 in the following order; multi-doped TiO 2 > single-doped TiO 2 > pure TiO 2. More than 55% and 81% of COD content of the LAB industrial wastewater was mineralized under visible light and UV irradiation, respectively at optimum condition (COD of 200 mg/l, catalyst loading of 1.5 g/l and pH of 3). The BOD 5 /COD ratio for the remaining COD was obtained to be about 0.4 which indicates higher biodegradability of the treated effluent in comparison with the raw wastewater.