研究目的
To model the dependence of the degradation kinetics of salicylic acid and methyl orange on TiO2 and TiO2/WO3 composites by varying catalyst load, initial pollutant concentration, and incident light intensity, and to propose a kinetic model for these systems.
研究成果
The degradation kinetics of pollutants are significantly influenced by catalyst load, initial concentration, and light intensity, but not by the hierarchical nature of the materials. A kinetic model was successfully developed and validated, showing that intermediates play a crucial role in the degradation process. The inclusion of WO3 in composites altered parameter impacts but did not change the overall kinetic behavior.
研究不足
The study is limited to specific model compounds (SA and MO) and may not generalize to other pollutants. The kinetic models assume certain reaction orders and intermediates, which might not capture all complexities. The use of UV light limits applicability to visible light conditions. Sample synthesis and characterization methods could have inherent variabilities.
1：Experimental Design and Method Selection:
The study involved synthesizing TiO2 and WO3 nanomaterials via hydrothermal methods, preparing composites by mechanical mixing, and characterizing them using XRD, DRS, and SEM. Photocatalytic degradation tests were conducted under UV irradiation with variations in catalyst load, pollutant concentration, and light intensity. Kinetic modeling was performed using the Langmuir-Hinshelwood approach and implemented in Matlab.
2：Sample Selection and Data Sources:
Samples included commercial TiO2 (Evonik Aeroxide P25), hydrothermally synthesized TiO2 (TiO2-HT), commercial WO3 (WO3-COM), hydrothermally synthesized WO3 (WO3-AMT), and their composites. Model pollutants were salicylic acid (SA) and methyl orange (MO) in aqueous solutions.
3：List of Experimental Equipment and Materials:
Equipment included XRD (Shimadzu 6000), DRS spectrophotometer (JASCO-V650), SEM (FEI Quanta 3D FEG), UV-Vis spectrophotometer (Analytic Jena Specord 250+), HPLC (Agilent 1100 series), photoreactor with UV lamps, and Matlab R2016a for modeling. Materials included TiO2 P25, TiCl4, thiourea, SDS, HCl, AMT, SA, MO, and deionized water.
4：Experimental Procedures and Operational Workflow:
Synthesis involved hydrothermal treatment at 180°C for specified times, washing, drying, and annealing. Photocatalytic tests were done in a reactor with air flow and stirring, with dark equilibration before irradiation. Concentrations were monitored via UV-Vis and HPLC.
5：Data Analysis Methods:
Data were analyzed using kinetic models based on Langmuir-Hinshelwood kinetics, with fitting and simulations in Matlab using ode45 solver.
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X-ray diffractometer
Shimadzu 6000
Shimadzu
Used to determine crystalline phases and particle size of the samples.
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DRS spectrophotometer
JASCO-V650
JASCO
Used to measure diffuse reflectance spectra of the samples to obtain band-gap energy values.
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SEM
FEI Quanta 3D FEG
FEI
Used for microstructural analysis of the samples.
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UV-Vis spectrophotometer
Analytic Jena Specord 250+
Analytic Jena
Used to monitor the concentration of pollutants during degradation experiments.
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HPLC
Agilent 1100 series
Agilent
Used for high-pressure liquid chromatography to detect SA and its intermediates.
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Titanium tetrachloride
TiCl4
Aldrich
Used as a precursor for synthesizing TiO2.
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Thiourea
H2NCSNH2
Aldrich
Used in the synthesis of TiO2.
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Sodium-dodecyl sulfate
SDS
Aldrich
Used as a capping agent in the synthesis of TiO2.
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Hydrochloric acid
HCl
Sigma-Aldrich
Used in synthesis and degradation tests.
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Photoreactor
Used for photocatalytic degradation tests under UV irradiation.
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Software
Matlab R2016a
MathWorks
Used for kinetic modeling and data analysis, including solving ordinary differential equations.
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TiO2
Evonik Aeroxide P25
Evonik
Used as a reference photocatalyst in the experiments.
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Salicylic acid
SA
Sinteza
Used as a model pollutant in degradation tests.
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Ammonium metatungstate hydrate
AMT
Sigma Aldrich
Used for synthesizing WO3 micro-crystallites.
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Tungsten(VI) oxide
WO3
Sigma Aldrich
Used as a reference catalyst.
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Methyl orange
MO
Sigma Aldrich
Used as a model pollutant in degradation tests.
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