Chyow-San Chiou

Preparation, Photocatalytic Activity, and Recovery of Magnetic Photocatalyst for Decomposition of Benzoic Acid

The purpose of this paper is to determine the experimental parameters of TiO2 preparation for optimizing the removal rate of benzoic acid by magnetic photocatalytic oxidation process. Therefore, this paper intended to prepare a magnetic photocatalyst (TiO2/SiO2/Fe3O4) that can be recycled using an external magnetic field. Magnetic photocatalysts are characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), and Fourier transform infrared (FTIR) spectroscopy. The optimal the experimental parameters of TiO2 preparation for the removal rate of photocatalysts were concluded as pH is 3, weight ratio of TiO2/SiO2(Fe3O4) is 1, and calcined temperature of TiO2/SiO2/Fe3O4 is 350∘C. Furthermore, the paramagnetic behaviors of the prepared TiO2/SiO2/Fe3O4 gave rise to the magnetic photocatalyst, which could be separated more easily through the application of a magnetic field for reuse.

Photocatalytic characteristic and photodegradation kinetics of toluene using N-doped TiO2 modified by radio frequency plasma

This study investigates the feasibility of applications of the plasma surface modification of photocatalysts and the removal of toluene from indoor environments. N-doped TiO2 is prepared by precipitation methods and calcined using a muffle furnace (MF) and modified by radio frequency plasma (RF) at different temperatures with light sources from a visible light lamp (VLL), a white light-emitting diode (WLED) and an ultraviolet light-emitting diode (UVLED). The operation parameters and influential factors are addressed and prepared for characteristic analysis and photo-decomposition examination. Furthermore, related kinetic models are established and used to simulate the experimental data. The characteristic analysis results show that the RF plasma-calcination method enhanced the Brunauer Emmett Teller surface area of the modified photocatalysts effectively. For the elemental analysis, the mass percentages of N for the RF-modified photocatalyst are larger than those of MF by six times. The aerodynamic diameters of the RF-modified photocatalyst are all smaller than those of MF. Photocatalytic decompositions of toluene are elucidated according to the Langmuir–Hinshelwood model. Decomposition efficiencies (η) of toluene for RF-calcined methods are all higher than those of commercial TiO2 (P25). Reaction kinetics of photo-decomposition reactions using RF-calcined methods with WLED are proposed. A comparison of the simulation results with experimental data is also made and indicates good agreement. All the results provide useful information and design specifications. Thus, this study shows the feasibility and potential use of plasma modification via LED in photocatalysis.

Study on the indoor volatile organic compound treatment and performance assessment with TiO2/MCM-41 and TiO2/quartz photoreactor under ultraviolet irradiation.

Abstract Volatile organic compounds (VOCs) are the cause of indoor air pollution and are readily emitted from furniture and cleaning agents. In Taiwan, the concentrations of indoor VOCs range roughly from 1 to 10 ppm. It is important to effectively reduce indoor VOC emissions and establish the implementation of long-term, low-cost, controlled techniques such as those found in the ultraviolet/titanium dioxide (UV/TiO2) control systems. This study evaluates the performance of a photoreactor activated by visible irradiation and packed with TiO2/quartz or TiO2/mobile catalytic material number 41 (MCM-41). The photocatalysts tested include commercial TiO2 (Degussa P-25) and synthesized TiO2 with a modified sol-gel process. The UV light had a wavelength of 365 nm and contained an 8-W, low-pressure mercury lamp. Reactants and products were analyzed quantitatively by using gas chromatography with a flame-ionization detector. It is important to understand the influence of such operational parameters, such as concentration of pollutant, temperature, and retention time of processing. The indoor concentrations of VOCs varied from 2 to 10 ppm. Additionally, the temperatures ranged from 15 to 35 °C and the retention time tested from 2 to 8.2 sec. The results show that quartz with TiO2 had a better photoreductive efficiency than quartz with MCM-41. The toluene degradation efficiency of 77.4% with UV/TiO2/quartz was larger than that of 54.4% with the UV/TiO2/MCM-41 system under 10-min reaction time. The degradation efficiency of the UV/TiO2 system decreased with the increasing concentrations of indoor VOCs. The toluene degradation efficiency at 2 ppm was approximately 5 times greater than that at 10 ppm. The photoreduction rate of the VOCs was also evaluated with the Langmuir– Hinshewood model and was shown to be pseudo-first-order kinetics.

Mineralization of Polyethylene Glycol In Aqueous Solution by Hydrogen Peroxide With Basic Oxygen Furnace Slag

This study evaluated the dissolution behavior of basic oxygen furnace slag (BOF slag) and the performance of H2O2 with BOF slag denoted as H2O2 /BOF slag process to degrade polyethylene glycol (PEG) in the aqueous solution. The concentration of total organic carbon (TOC) was chosen as a mineralization index of the degradation of PEG by the H2O2/BOF slag process. A first-order kinetic model with respect to TOC was adopted to represent the mineralization of PEG by H2O2 /BOF slag process. The experimental results in this study suggested that dosages with 3.98 × 10-4 mole min-1 l-1 H2O2 and 15 gl-1 BOF slag loading in the solution at pH 2 provided the optimal operation conditions for the mineralization of PEG yielding a 75.5% treatment efficiency at 100 min reaction time. The H2O2 /Fe2+ ratio was then determined to be 13.5 : 1.

Adsorption Removal of Environmental Hormones of Dimethyl Phthalate Using Novel Magnetic Adsorbent.

Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVAL was prepared after sequential syntheses of magnetic Fe3O4 (M) and polyvinyl acetate (M-PVAC). The saturated magnetizations of M, M-PVAC, and M-PVAL are 57.2, 26.0, and 43.2 emu g−1 with superparamagnetism, respectively. The average size of M-PVAL by number is 0.75 μm in micro size. Adsorption experiments include three cases: (1) adjustment of initial pH (pH0) of solution to 5, (2) no adjustment of pH0 with value in 6.04–6.64, and (3) adjusted pH0 = 7. The corresponding saturated amounts of adsorption of unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22 mg g−1, respectively. Values of heterogeneity factor of Freundlich isotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Values of adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and 7.19 kJ mol−1, indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorption take place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid by applying magnetic field after completion of adsorption.

Optimizing treatment of benzoic acid by ozone process with recyclable catalyst of magnetism

This study is to optimize the multi-quality performance of magnetic catalyst/ozone process by combining a technique for order performance by similarity to ideal solution (TOPSIS) with the Taguchi method, which simultaneously has the best decomposition rate constant of benzoic acid and removal rate constant of total organic carbon (TOC). The optimal experimental parameters were pH of 7, initial concentration of 75 ppm and catalyst loading of 0.05 g/L. More than 93% of the magnetic catalyst was easily separated and redispersed for reuse by the magnetic force due to the paramagnetic behaviours of the prepared SiO2/Fe3O4. It is believed that through the joint efforts improvement, design and manufacturing, new separation and recycling technologies will be available and more easily recyclable magnetic catalysts will be developed in the future.

Photochemical Oxidation of Polyethylene Glycol in Aqueous Solution by UV/H2O2 with Steel Waste

This study evaluated the performance of the photo-Fenton reaction when it was initiated using UV/H2O2 with steel waste and basic oxygen furnace slag (BOF slag), here called the UV/H2O2/BOF slag process, in order to decompose polyethylene glycol (PEG) in aqueous solution. The concentration of total organic carbon (TOC) was chosen as a mineralization index of the decomposition of PEG in the UV/H2O2/BOF slag process. A first-order kinetic model with respect to TOC was appropriately adopted to represent the mineralization of PEG in the UV/H2O2/BOF slag process. The experimental results obtained in this study suggest that dosages with 2.49×10^(-4) mol/min-L H2O2 and 25 g/L BOF slag loading in a solution at pH=2.5 with 120 μW/cm^2 UV provided the optimal operation conditions for the mineralization of PEG, yielding 79.5% mineralization efficiency after 90 min of reaction time.

Adsorption Behavior of Recyclable Magnetites with N-Components for Adsorption of Copper Ion

Recyclable magnetites with thioureido group (poly-allyl-thiourea/oleic acid/magnetite, PAT-adsorbent) and amine functional group (ethylenediamine/methyl methacrylate/oleic acid/magnetite, EDA-adsorbent) were synthesized by modifying magnetite with oleic acid, methyl methacrylate, allyl thiourea and ethylenediamine. PAT-adsorbent and EDA-adsorbent were used and compared for adsorption of copper ions in a batch system due to the existence of amino group (-NH2) both on thioureido group and amine functional group. The kinetics of both PAT-adsorbent and EDA-adsorbent were evaluated utilizing pseudo-first-order and pseudo-second-order kinetic models. The equilibrium data was analyzed and compared using the Langmuir and Freundlich isotherm models. The maximum adsorption capacity (Qm) of PAT-adsorbent (19.126 mg g-1) was higher than that of EDA-adsorbent (7.096 mg g-1). As compared to EDA-adsorbent the magnetic adsorbent (PAT-adsorbent) with good desorption performance (>85% desorption efficiency) and easily reuse (>85% recovery by magnetic force) was the important factors for its potential practical application.