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Study of visible-light photocatalytic degradation of 2,4-dichlorophenoxy acetic acid in batch and circulated-mode photoreactors
摘要： Purpose The consumption of pesticides and chemical fertilizers is one of the major environmental and health problems. In this report, 2,4-dichlorophenoxyacetic acid (2,4-D) was chosen to evaluate the impact of photodegradation using LED (Light-emitting diode) (400 and 365 nm) sources in batch and programmable circulated-mode photoreactors respectively. Methods A β-cyclodextrin (β-CD) grafted titanium dioxide P25 (P25/β-CD) and complexation of 2,4-D and β-CD were synthesized via photoinduced and spray-drying methods, respectively. The structures were characterized. Moreover, we investigated the effects of the amount of catalyst, the β-CD amount on bed catalyst, irradiation time, kind of photoreactor on the photocatalytic degradation efficiency. Results Based on the results of experiments in batch reactor, the optimum amount of TiO2, β-CD grafted by catalyst were 1 and 0.1 g/L, respectively. In batch-mode the photodegradation efficiency of 2,4-D after 5 h with P25, P25/β-CD as a photocatalyst and 2,4-D/β-CD complex with P25 photocatalyst were approximately 81, 85 and 95% respectively. After 8 h of irradiation in circulated-mode reactor, degradation yields with P25, P25/β-CD and 2,4-D/β-CD complex along with P25 were 89, 91 and 96% respectively. On the other hand, the circulated-mode photoreactor with high efficiency was appropriate to degradation of the high concentration of 2,4-D solution (200 mg/L). After 5 successive cycles with 25 h of irradiation, P25 and P25/β-CD maintained as high 2,4-D removal efficiency as 82.6, 84% respectively, with excellent stability and reusability. Conclusion The photodegradation method can be used as an effective and environmental friendly process in the degradation of organic compound.
关键词： 2,4-D/β-CD complex,Batch-mode photoreactor,Light-emitting diode (LED),Circulated-mode photoreactor,2,4-Dichlorophenoxyacetic acid (2,4-D)
更新于2025-11-14 15:18:02
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Immobilization of Fe3O4/TiO2 nanocomposite thin layer on the glass tubes in a component parabolic collector for the treatment of DR23
摘要： Photocatalysis driven by the natural solar light has been proved to be a favorable approach for the degradation of hazardous organic pollutants in water and wastewater. The present work addressed the removal of Direct Red 23 by the solar/Fe3O4/TiO2/S2O8^2- process. The application of the component parabolic collector, which served as a solar light concentrator, could improve the photocatalytic removal efficiency in the presence of immobilized Fe3O4/TiO2 nanoparticles. In this paper, the synthesis of Fe3O4/TiO2 photocatalyst to treat wastewater under solar radiation has been reported. Accordingly, a component parabolic collector solar photoreactor was designed and constructed for wastewater treatment processes. The prepared Fe3O4/TiO2 nanocomposite was precipitated as a thin layer on the glass tubes of the solar photoreactor. The central composite experimental design was also used in order to optimize and model the CI Direct Red 23 decolorization process; then, the influence of operational parameters such as the contaminant concentration, S2O8^2- concentration, and the reaction time was investigated. Due to the solar/Fe3O4/TiO2/S2O8^2- process, 100% of Direct Red 23 could be removed in 90 min at the concentration of 15.16 mg L?1 and S2O8^2- concentration of 0.8 mM. The predicted response for the Direct Red 23 decolorization efficiency in the optimal condition was obtained to be 98.50%, which was in a good agreement with the experimental response (100%).
关键词： Photoreactor,Degradation,Optimization,Photocatalysis
更新于2025-09-23 15:22:29
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Photo-Catalytic Degradation of Trichlorophenol with UV/Sulfite/ZnO Process, Simultaneous Usage of Homogeneous Reductive and Heterogeneous Oxidative Agents generator as a New Approach of Advanced Oxidation/Reduction Processes (AORPs)
摘要： This study develops UV/Sulfite/ZnO (USZ) photoreactor, as a novel method of Advanced Oxidation/Reduction Processes (AORPs), and employs it for degradation, dechlorination and mineralization of 2,4,6-trichlorophenol (TCP) content of wastewaters. Degradation efficiency of the UV-only, UV/ZnO, UV/Sulfite and USZ processes were determined as 23.4%, 37.6%, 44.8% and 87.83% respectively, at 10 min reaction time, 50 mg L-1 TCP concentration and pH of 7. Findings indicated that TCP degrades completely within 15 min treatment of 50 mg L-1 initial TCP concentration. According to Molar ratio evaluations, 1:2:50 is the optimal Molar ratio of sulfite/ZnO/TCP in the USZ process. Analyzing effluents of the USZ reactor by liquid chromatography/mass spectroscopy after 5, 10 and 15 min reaction time revealed that TCP decomposes to ring-shaped compounds in less than 10 min and all TCP and its metabolites convert to linear compounds within 15 min reaction time. Also fourteen little fragments were identified in the degradation of TCP by USZ during 2.5 till 15 min of reaction time. Investigating kinetic of the process through a pseudo first-order model using 10 to 200 mg L-1 TCP over 1 to 15 min reaction time demonstrated that the observed rate constant (kobs) decreases from 0.3811 to 0.0824 min-1 and the observed TCP degradation rate (robs) increases from 3.811 to 16.48 mg L-1 min-1 with increase of TCP concentration. Furthermore, electrical energy consumption (EEO) of the USZ process was calculated with kinetic model 2.21 to 10.25 as 2.19 to 3.55 and with merit-figure model 4.94 to 12.39 kW h m-3 from 10 to 200 mg L-1, respectively. In addition, the effect of co-existing water anions on degradation of 50 mg L-1 TCP was explored during 30 min processing. While 100% degradation was achieved in the absence of any anion, adding nitrate, as the most effective anion, decreased TCP degradation to 78.24%. The highest dechlorination was observed at sulfite/ZnO Molar ratio 1:2 and pH 11.0. Mineralization of TCP by USZ process was achieved 33.2 % after 15 min of reaction.
关键词： Metabolites,Co-existing,Photoreactor,Degradation,Energy consumption,Kinetic
更新于2025-09-23 15:22:29
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Degradation of tetracycline by solar photo-Fenton: Optimization and application in pilot photoreactor
摘要： The objective of this study is to analyze the photodegradation of the antibiotic tetracycline by the solar photo-Fenton process. The optimal conditions were obtained in a 22 (2 × 2) factorial design with the following input variables: reaction time and catalyst concentration (ferrous ion [Fe2+]). After statistical analysis using the Statistica 7.0 software, the optimal conditions determined, time = 120 min and Fe2+ = 166.81 mg/L, were applied in a pilot scale photoreactor, resulting in an 88.7% removal of the drug. In addition, in this stage we studied the reaction kinetics, biodegradability, and phytotoxicity of the products generated by the process. In the kinetic study, a constant of 1.82 × 10?2 min?1 was obtained. For this constant, a reaction time of 38.16 min is required for the initial tetracycline concentration to be reduced by 50%. The biodegradability tests indicated a gradual increase in the five-day biological oxygen demand/chemical oxygen demand ratio over time. The phytotoxicity tests showed an 18.5% decrease in the inhibition rate of the root growth of lettuce seedlings, indicating that the treatment applied reduces the toxicity of the substance.
关键词： photo-Fenton,photoreactor,solar photocatalysis,biodegradability,tetracycline,phytotoxicity
更新于2025-09-23 15:21:21
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Photocatalytic removal of elemental mercury via Ce-doped TiO2 catalyst coupling with a novel optical fiber monolith reactor
摘要： Reduction of mercury emission from coal combustion is a serious task for public health and environmental societies. Herein, Ce-doped TiO2 (Ce/TiO2) catalyst coupling with a novel optical fiber monolith reactor was applied to efficiently remove elemental mercury (Hg0) from coal-fired flue gas. Under the optimal operation condition (i.e., 1.5 mW/cm2 UV light, 90 °C), above 95% of Hg0 removal efficiency was attained over the optical fiber monolith reactor coating with 3.40 g/m2 Ce/TiO2 catalyst. The effects of flue gas compositions on Hg0 removal performance were clarified systematically. Gaseous O2 replenished the surface oxygen, hence maintaining the production of free radicals and promoting the removal of Hg0. SO2, HCl, and NO inhibited Hg0 removal in the absence of O2 due to the competitive adsorption and consumption of free radicals. However, SO2 and HCl significantly enhanced Hg0 removal with the participation of O2, while NO exhibited obviously inhibitory effect even with the assistance of O2. H2O also decreased the Hg0 oxidation capacity owing to the competitive adsorption and reduction of HgO. The optical fiber monolith reactor exhibited much superior Hg0 removal capacity than the powder reactor. Utilization of Ce/TiO2 catalyst coupling with an optical fiber monolith reactor provides a cost-effective method for removing Hg0 from coal-fired flue gas.
关键词： Ce/TiO2,Mercury,Flue gas,Photocatalytic,Photoreactor
更新于2025-09-23 15:21:01
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Scaling-up a heterogeneous H2O2/TiO2/solar-radiation system using the Damk?hler number
摘要： A falling film photocatalytic solar reactor (FFR) and a tubular reactor with compound parabolic collectors (CPCR) were modeled. An empirical reaction mechanism was proposed for the heterogeneous photocatalytic degradation of organic contaminants using TiO2, and H2O2. An analytical kinetic rate was deducted from the mechanism in order to describe the change of H2O2 concentration and the rate of destruction of total organic carbon (TOC). The profiles of the absorption rate of photons in the heterogeneous medium were estimated by using the absorption-scattering radiation six-flux model (SFM). A dimensionless number that we named Damk?hler of a photocatalytic reactor was proposed. Finally, the modeling was validated against experimental data for the TOC destruction obtained from the mineralization of dicloxacillin (DCX) and 4-chlorophenol (4-CP), which we considered as model pollutants.
关键词： Photoreaction scaling-up,Photoreactor design,Emerging pollutants,Titanium dioxide
更新于2025-09-19 17:15:36
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3D-printed, home-made, UV-LED photoreactor as a simple and economic tool to perform photochemical reactions in high school laboratories
摘要： In the paper we present the simple manufacturing of an easy and economical UV-A photoreactor using a desktop 3D printer and its application in chemical transformations. PLA (polylactic acid) was used as inexpensive and not toxic polymer for the 3D printing process, while commercially available decorative ultraviolet LEDs (UV-A) have been employed as a light source. With this device, the photoreduction of benzophenone was performed in high yield and short times, compatible with the duration of a typical laboratory experiment in a high school program.
关键词： UV-LEDs,benzophenone,photoreduction,photoreactor,3D printing
更新于2025-09-16 10:30:52
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Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
摘要： We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes and determine the corresponding photochemical mechanism. Then, we describe a protocol to perform ring-opening metathesis polymerization (ROMP) in solution and in miniemulsion using this NHC-photogenerating system. To photogenerate IMes, a system comprising 2-isopropylthioxanthone (ITX) as the sensitizer and 1,3-dimesitylimidazolium tetraphenylborate (IMesH+BPh4-) as the protected form of NHC is employed. IMesH+BPh4- can be obtained in a single step by anion exchange between 1,3-dimesitylimidazolium chloride and sodium tetraphenylborate. A real-time steady-state photolysis setup is described, which hints that the photochemical reaction proceeds in two consecutive steps: 1) ITX triplet is photo-reduced by the borate anion and 2) subsequent proton transfer takes place from the imidazolium cation to produce the expected NHC IMes. Two separate characterization protocols are implemented. Firstly, CS2 is added to the reaction media to evidence the photogeneration of NHC through formation of the IMes-CS2 adduct. Secondly, the amount of NHC released in situ is quantified using acid-base titration. The use of this NHC photo-generating system for the ROMP of norbornene is also discussed. In solution, a photopolymerization experiment is conducted by mixing ITX, IMesH+BPh4-, [RuCl2(p-cymene)]2 and norbornene in CH2Cl2, then irradiating the solution in a UV reactor. In a dispersed medium, a monomer miniemulsion is first formed then irradiated inside an annular reactor to produce a stable poly(norbornene) latex.
关键词： photoreactivity,ring-opening,miniemulsion,metathesis,Chemistry,photolysis,Polymer,photochemistry,Issue 141,NHC,photoreactor,carbene,ROMP
更新于2025-09-09 09:28:46
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Elemental mercury removal from flue gas over TiO2 catalyst in an internal-illuminated honeycomb photoreactor
摘要： TiO2 catalyst in an internal-illuminated honeycomb photoreactor was prepared for Hg0 removal from flue gas. The Hg0 removal efficiency was above 95% under the optimal operation condition. With the increasing TiO2 coating value, the Hg0 removal efficiency significantly increased. The catalyst calcined at 400 oC presented optimal Hg0 removal performance, while higher calcination temperature weakened the Hg0 photocatalytic removal activity. Similar Hg0 removal performances were obtained under UV irradiation when the reaction temperature was in the range of 25-90 oC, and 1.5 mW/cm2 of UV light irradiation was competent for Hg0 photocatalytic removal. With the same quantity utilization of TiO2 catalyst, the internal-illuminated honeycomb photoreactor presented better Hg0 removal performance than fixed-bed reactor. Finally, the procedure of Hg removal from flue gas over TiO2 catalyst in internal-illuminated honeycomb photoreactor was proposed, and the product in the Hg0 photocatalytic removal process was analyzed as well.
关键词： mercury,coal combustion,TiO2,photocatalytic removal,photoreactor
更新于2025-09-09 09:28:46
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Kinetic spectrophotometric method for real-time monitoring of ultraviolet photoreactions: A mini-photoreactor
摘要： Photoreactors in research laboratories generally consist of UV-C or UV-A mercury lamps and vessels of volume ranging up to about 1.0 L of solutions (suspensions, solvents, reactants and catalysts). This photoreactor’s design implies in large amounts of chemicals - cost problems, considerable amount of co-generated waste - environmental issues, safety problems and the need of large laboratory space. Currently, there is an effort by the scientific community to apply the principles of “green chemistry”, tending to miniaturize reactors and formats [1-8] and use modern sources of radiation such as light-emitting diodes (UV-LEDs), which are much more environmentally friendly than mercury lamps [9-13]. Another disadvantage of classical photochemical reactors is the withdrawal of aliquots at several times intervals. This procedure modifies the total volume of solutions and, consequently, the total number of absorbed photons per chromophore. Besides that, this methodology is time and labor consuming, and sometimes it is unsafe. In this way, a low amount of experimental points can limit the full kinetic description and lead to misinterpretations in kinetic parameters such as reaction order and rate constants. Accurate determinations are also limited by temperature control, which is not commonly effective in classical photoreactors. Here in it is proposed an interesting mini-photoreactor constituted by one UV-LED and a traditional quartz cuvette of 1.00 cm optical length that allows the reaction execution and, simultaneously, continuous monitoring via UV-Vis spectrophotometry (real-time kinetic analysis). In order to validate the use of this new mini-photoreactor we employed the photodegradation of methylene blue (MB) and salicylic acid (SA) in homogeneous and heterogeneous systems. For the proposition, it is necessary a specific spectrophotometer apparatus with a detection system that is not influenced by external light [14] and a Peltier system for controlling temperature with a mini-bar magnetic agitation. Continuous kinetic monitoring was performed in a spectrophotometer with a xenon flash lamp and silicon diode detectors, which emit flashes only during data collection, which prevents extra photodegradation for very photosensitive samples. Another spectrophotometer’s type that can be employed is that one based on diode-array system, whose external light also does not affect the spectrophotometric measurement.
关键词： methylene blue,mini-photoreactor,UV-LED,real-time monitoring,salicylic acid,ZnO,photodegradation
更新于2025-09-04 15:30:14