Browsing by Author "Lu, MC"

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Adsorption characteristics of dichlorvos onto hydrous titanium dioxide surface
(1996-07-01)
Lu, MC
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Roam, GD
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Chen, JN
;
Huang, CP
;
環境工程研究所
Adsorption of dichlorvos (2,2-dichlorovinyl-o,o-dimethl phosphate) onto hydrous TiO2 from water was evaluated in the laboratory using a batch reactor. The presence of organic solvents resulted in a decreasing dichlorvos adsorption on TiO, surface. These data were used to assess a cosolvent model. Decreased adsorption of dichlorvos was observed at an initial pH of 4 with increasing ionic strength. The inhibitory adsorption is attributed to the blockade of surface sites by electrolytes. In addition, electrolytes play an important role on the pa-dependent dichlorvos adsorption. It is suggested that at pH < pH(pzc) (point of zero charge), dichlorvos adsorption is inhibited because electrolytes compete with dichlorvos fbr surface sites. At pH > pH(pzc) the adsorption density of dichlorvos decreases with increasing solution pH due to the decrease of surface group, TiOH, on the TiO2 surface. The variation of adsorption density with temperature over the range 10 degrees-40 degrees C has been investigated. Results show that the reaction is controlled by enthalpy. The adsorption of dichlorvos onto the TiO2 surface is primarily brought about by hydrogen bonding. Copyright (C) 1996 Elsevier Science Ltd
An efficient VLSI architecture for full-search block matching algorithms
(1997-03-01)
Lee, CY
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Lu, MC
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper presents a novel memory-based VLSI architecture for full search block matching algorithms. We propose a semi-systolic array to meet the requirements of high computational complexity, where data communications are handled in two styles: (I) global connections for search data and (2) local connections for partial sum. Data flow is handled by a multiple-port memory bank so that all processor elements function on target data items. Thus hardware efficiency achieved can be up to 100%. Both semi-systolic array structure and related memory management strategies for full-search block matching algorithms are highlighted and discussed in detail in the paper.
Catalytic decomposition of hydrogen peroxide and 2-chlorophenol with iron oxides
(2001-06-01)
Huang, HH
;
Lu, MC
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Chen, JN
;
環境工程研究所
;
Institute of Environmental Engineering
The aim of this study was to examine the catalyzed decomposition of hydrogen peroxide and 2-chlorophenol (2-CP) in the presence of iron oxides. C;ranular ferrihydrite, goethite, and hematite were selected as catalysts in this study. 2-CP was used as the model compound because it is a typical toxic compound and has not been investigated in the catalytic decomposition by iron oxides. The catalytic activity for hydrogen peroxide decomposition followed the sequence: granular ferrihydrite > goethite > hematite. However, hematite exhibited the highest activity in catalyzing 2-CP oxidation. The oxidation efficiency of 2-CP corresponded with the inverse sequence of specific area and pH,,, of the iron oxides. The catalytic activity of granular ferrihydrite was affected significantly by the mixing speed and particle size for its large value of Thiele modulus (phi) and Damkohler number (Da). The strong diffusion resistance for granular ferrihydrite was attributed either to its microporous structure or to the formation of oxygen in the pores of the iron oxide leading to the unexpected catalytic activity of granular ferrihydrite to hydrogen peroxide and 2-CP. (C) 2001 Elsevier Science Ltd. All rights reserved.
Catalytic decomposition of hydrogen peroxide and 4-chlorophenol in the presence of modified activated carbons
(2003-06-01)
Huang, HH
;
Lu, MC
;
Chen, JN
;
Lee, CT
;
環境工程研究所
The objective of this research was to examine the heterogeneous catalytic decomposition of H2O2 and 4-chlorophenol (4-CP) in the presence of activated carbons modified with chemical pretreatments. The decomposition of H2O2 was suppressed significantly by-the change of surface properties including the decreased pH(pzc) modified with oxidizing agent and the reduced active sites occupied by the adsorption of 4-CP. The apparent reaction rate of H2O2 decomposition was dominated by the intrinsic reaction rates on the surface of activated carbon rather than the mass transfer rate of H2O2 to the solid surface. By the detection of chloride ion in suspension, the reduction of 4-CP was not only attributed to the advanced adsorption but also the degradation of 4-CP. The catalytic activity toward 4-CP for the activated carbon followed the inverse sequence of the activity toward H2O2, suggesting that acidic surface functional group could retard the H2O2 loss and reduce the effect of surface scavenging resulting in the increase of the 4-CP degradation efficiency. Few effective radicals were expected to react with 4-CP for the strong effect of surface scavenging, which could explain why the degradation rate of 4-CP observed in this study was so slow and the dechlorination efficiency was independent of the 4-CP concentration in aqueous phase. Results show that the combination of H2O2 and granular activated carbon (GAC) did increase the total removal of 4-CP than that by single GAC adsorption. (C) 2003 Elsevier Science Ltd. All rights reserved.
Characteristics of photocatalytic oxidation of gaseous 2-propanol using thin-film TiO2 photocatalyst
(2004-11-01)
Chang, CP
;
Chen, JN
;
Lu, MC
;
環境工程研究所
;
Institute of Environmental Engineering
This work presents a photocatalysis-based method to treat and purify air because of its broad applicability to common, oxidizable, air contaminants. The effect of oxygen content, temperature, water vapor, and 2-propanol concentration on the TiO2 surface was investigated. The rate of 2-propanol decomposition increased with increasing the oxygen content, but was reduced at temperatures higher than 100degreesC. When water vapor concentration was in the range of 10-355 mmol m(-3), the rate of 2-propanol decomposition was proportional to the water content. However, an opposite result was observed at a higher concentration of water vapor. 2-Propanol was photooxidized to acetone, and eventually to carbon dioxide and water. The kinetic model of 2-propanol photooxidation was successfully developed by the competitive Langmuir-Hinshelwood rate form, incorporating the inhibition effect coming from the formation of acetone. (C) 2004 Society of Chemical Industry.
Effect of adsorbents coated with titanium dioxide on the photocatalytic degradation of propoxur
(1999-02-01)
Lu, MC
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Chen, JN
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Chang, KT
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環境工程研究所
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Institute of Environmental Engineering
Photocatalytic oxidation of pesticides in aqueous media irradiated by UV light is a rapidly growing field of research. Therefore, the treatment technology for degradation of propoxur (an insecticide) using titanium dioxide coated on the supports such as activated carbon, zeolite, brick, quartz and glass beads, was performed in this research. Results show that GAC/TiO2 is the best complexing agent for oxidizing propoxur because of its adsorption properities. The others follow the sequence: plain TiO2 > glass beads > zeolite > brick > quartz. The degradation rate of propoxur with plain TiO2 is higher than that with TiO2/GAC complexing agent. But the mineralization rate of propoxur with plain TiO2 is lower than that with TiO2/GAC complexing agent. However, it can be concluded that using GAC as the support can improve the photocatalytic efficiency. (C) 1998 Elsevier Science Ltd. All rights reserved.
Effect of inorganic ions on the oxidation of dichlorvos insecticide with Fenton's reagent
(1997-11-01)
Lu, MC
;
Chen, JN
;
Chang, CP
;
環境工程研究所
;
Institute of Environmental Engineering
This study analyzes the oxidation of dichlorvos with Fenton's reagent in solutions containing various ions. Results show that the larger the added amount of ferrous ions, the higher the elimination rate of dichlorvos and the oxidization rate after the addition of ferric ions is far smaller than that of adding ferrous ions. Anions suppress the decomposition of dichlorvos in the following sequence: H2PO4- > > Cl- > NO3- similar to ClO4-. It can be seen that the Fenton reaction is extremely sensitive to anions, and phosphate ions in particular will seriously suppress the Fenton system's ability to oxidize dichlorvos. The main reason for the suppression of phosphate ions is that phosphate ions will produce a complex reaction together with ferrous ions and ferric ions, which then lowers its ability to catalyze hydrogen peroxide. (C) 1997 Elsevier Science Ltd.
Experimental realization of breaking diffraction limit by planar negative-index metamaterials in free space
(2005-02-01)
Lih, JS
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Wang, YS
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Lu, MC
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Huang, YC
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Chen, KH
The sharpness of the image formed by a conventional lens is always limited by the wavelength of light. Recently, Pendry proposed a superlens, with a negative refractive index. such that the resolution is not limited by wavelength. Herein, we report direct experimental evidence of Pendry's superlens breaking the diffraction limit, in the microwave range of the X band (8-12 GHz), with a periodic array of split ring resonators and continuous wires; i.e. a meta-material with negative index of refraction.
Heterogeneous photocatalytic oxidation of acetone for air purification by near UV-irradiated titanium dioxide
(2003)
Chang, CP
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Chen, JN
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Lu, MC
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環境工程研究所
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Institute of Environmental Engineering
This work presents a photocatalysis-based method to treat and purify air because of its broad applicability to common, oxidizable air contaminants. The effect of oxygen content, temperature, water vapor, and acetone concentration on the photooxidation of acetone on TiO2 surface was investigated. The photocatalytic decomposition reaction of acetone obeyed the first-order equation. The decomposition rate increased with increasing the oxygen content. The rate of acetone oxidation increased when water vapor increased from, 18.7 to 417 muM and decreased at higher than 417 muM. The conversion and mineralization of acetone decreased at higher than 138degreesC. The initial rate of acetone degradation can be well described by the Langmuir-Hinshelwood rate form. The specific reaction rate constant and the equilibrium. adsorption are 15.8 muM/min and 0.0671 L/muM, respectively. The difference between observed and estimated half-lives became larger when the initial concentration of acetone was increased. It is assumed that the intermediates competed with parent compound so that delayed the half-life. The detection of CO2 production can support this assumption.
Influence of surface modification on catalytic activity of activated carbon toward decomposition of hydrogen peroxide and 2-chlorophenol
(2003)
Huang, HH
;
Lu, MC
;
Chen, JN
;
Lee, CT
;
環境工程研究所
The objective of this research was to investigate the influence of the activated carbons modified by chemical treatment on the surface catalyzed loss of H2O2 and 2-CP. The characteristics of the modified activated carbons were examined by several techniques including nitrogen adsorption, SEM, and EDS. The H2O2 decomposition rate would be suppressed significantly either by the change of surface properties modified with chemical treatment or the reduction of active sites occupied with the adsorption of 2-CP. In addition, the H2O2 decomposition rate with activated carbons within a specific time can be described by a second-order kinetic expression with respect to the concentration of GAC and H2O2 in the absence or presence of 2-CP. The catalytic activities of the three activated carbons toward 2-CP reduction followed the inverse sequence of those toward H-2-O-2 loss, implying that acidic surface functional group could retard the H2O2 loss and reduce the effect of surface scavenging resulting in increasing the reduction efficiency of 2-CP. By the detection of chloride ions in reaction mixture, it can be demonstrated that the reduction of 2-CP was not only attributed to the advanced adsorption but also the oxidation of the 2-CP with effective radicals. The real oxidation efficiency of 2-CP for the activated carbon modified with hot nitric acid was observed between 0.04 and 0.01 (mol/mol), offering a comparable efficiency to that of the other oxidation system using metal oxide as catalyst.
Intermediate inhibition in the heterogeneous UV-catalysis using a TiO2 suspension system
(2001-10-01)
Chan, YC
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Chen, JN
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Lu, MC
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環境工程研究所
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Institute of Environmental Engineering
Langmuir-Hinshelwood (L-H) kinetic expression was used to develop a basic mathematical model, which could describe the inhibition of intermediates in the photocatalysis of 2-chlorophenol (2-CP) in a suspended TiO2 system. Results showed that the photocatalytic oxidation of 2-chlorophenol followed the L-H type behavior and the reaction by-products displayed an inhibiting effect on the degradation rate. The inhibition was estimated by comparing to observed and estimated half-lives. The higher the initial concentration of 2-chlorophenol, the higher the inhibition of photocatalytic reaction. The L-H kinetic has been modified slightly in this study to rationalize the contrast of inhibited behavior and to improve in favor of a surface reaction. The concentrations of 2-chlorophenol were investigated ranging from 7.78 x 10(-5) to 7.78 x 10(-4) mol l(-1). The degradation of 2-chlorophenol in this reaction condition approximates a first-order kinetics to near-complete degradation. Calculated kinetic profiles are in an excellent agreement with the experimental observation. The results of the theoretical analysis can be used to estimate reaction rates in different initial concentrations of target compound. (C) 2001 Elsevier Science Ltd. All rights reserved.
MBR/RO/ozone processes for TFT-LCD industrial wastewater treatment and recycling
(2005)
Chen, TK
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Ni, CH
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Chan, YC
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Lu, MC
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環境工程研究所
This research is mainly to explore the treatment capacity for TFT-LCD industrial wastewater recycling by the processes combined with membrane bioreactor (MBR), reverse osmosis (RO) and ozone(03). The organic wastewater from the TFT-LCD industry was selected as the target. MBR, RO and ozone plants were established for evaluation. An MBR plant consisted of a 2-stage anoxic/aerobic bioreactor and an immersed UF membrane unit was employed. The effluent of MBR was conducted into the RO system then into the ozone system. The RO system consisted of a spiral membrane in the vessel. One bubble column, 75 cm high and diameter 5 cm, were used as the ozonation reactor. On the bottom of ozonation reactor is a porous diffuser for releasing gas, with an aperture of 100 mu m (0.1 cm). Over the whole experimental period, the MBR process achieved a satisfactory organic removal. The COD could be removed with an average of over 98.5%. For the TOC item, the average removal efficiency was 97.4%. The stable effluent quality and satisfactory removal performance were ensured by the efficient interception performance of an immersed UF membrane device incorporated with the biological reactor. Moreover, the MBR effluent did not contain any suspended solids and the SDI value was under 3. After the treatment of RO, excellent water quality was found. The water quality of permeate was under 5 mg/l, 2 mg/l and 50 mu s/cm for COD, TOC and conductivity respectively. The treated water can be recycled and reused for the cooling tower make-up water or other purposes. After the treatment of ozone, the treated water quality was under 5 mg/l and 0.852 mg/l for COD and TOC respectively. The test results of MBR, MBR/RO and MBR/RO/ozone processes were compared as possible appropriate treatment technologies applied in TFT-LCD industrial wastewater reuse and recycling.
Oxidation of dichlorvos with hydrogen peroxide using ferrous ion as catalyst
(1999-03-19)
Lu, MC
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Chen, JN
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Chang, CP
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環境工程研究所
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Institute of Environmental Engineering
This study examines how Fenton's reagent (Fe2+ and H2O2) decomposed dichlorvos insecticide. Results showed that dichlorvos decomposed in a two-stage reaction. The first stage is a Fe2+/H2O2 reaction in which dichlorvos swiftly decomposed. In the second stage, dichlorvos decomposed somewhat less rapidly, and it is a Fe3+/H2O2 reaction. The detection of ferrous ions also supports the theory of the two-stage reaction for the dichlorvos oxidation with Fenton's reagent. The dissolved oxygen of the solution decreased rapidly in the first stage reaction, but it slowly increased in the second stage with a zero-order kinetics. The Fenton system decomposed dichlorvos most rapidly when the initial pH in the solution is 3-4. In addition, increasing the concentration of hydrogen peroxide or ferrous ions can enhance the decomposition of dichlorvos. Consequently, the relationship of rate constant (k(obs)), [H2O2] and [Fe2+] at initial pH 3 is determined as k(obs) = 2.67 X 10(4)[H2O2](0.7)[Fe2+](1.2). (C) 1999 Elsevier Science B.V. All rights reserved.
Oxidation of TNT by photo-Fenton process
(2004-12-01)
Liou, MJ
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Lu, MC
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Chen, JN
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環境工程研究所
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Institute of Environmental Engineering
A series of photo-Fenton reactions have been performed for the degradation of 2,4,6-trinitrotoluene (TNT) in a 4.2-1 reactor. The degradation reaction rate of TNT followed a pseudo-first-order behavior; and the rate constants for 2.4 mW cm(-2) UV only, 2.4 mWcm(-2)UV/H2O2, Fenton, photo-Fenton (2.4 mW cm(-2)) and photo-Fenton (4.7 mW cm(-2)) were 0.002 min(-1), 0.007 min(-1), 0.014 min(-1), 0.025 min(-1) and 0.037 min(-1), respectively. Increasing the intensity of UV light, and the concentrations of ferrous ions and hydrogen peroxide promoted the oxidation rate under the experimental conditions in this study. The weighting factor (f), the Fe(II)-promoted efficiency (r) and the promoted-UV light efficiency (p) were calculated to clarify their effects on the TNT oxidation. Moreover, the inhibition effect of hydroxyl radical was also observed in both Fenton and photo-Fenton oxidation when the concentration of Fe(II) were higher than 2.88 mM. Solid phase micro-extraction was first applied to the separation of the organic byproducts from TNT oxidation. GC/MS was employed to identify the byproducts during the Fenton and photo-Fenton oxidation of TNT. These compounds were clarified as 1,3,5-trinitrobenzene, 1-methyl-2,4-dinitrobenzene 2,5-dinitrobenzoic acid and 1,3-dinitrobenzene. By these byproducts, the mechanisms of the methyl group oxidation, decarboxylation, aromatic ring breakage, and hydrolysis can be recognized and demonstrated. The pathway of TNT oxidation by photo-Fenton process was also proposed in this study. (C) 2004 Elsevier Ltd. All rights reserved.
Photocatalytic mineralization of toxic chemicals with illuminated TiO2
(1995)
Lu, MC
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Roam, GD
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Chen, JN
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Huang, CP
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環境工程研究所
Photocatalytic oxidation process can be an effective method for the removal of toxic organic compounds from dilute aqueous solutions. Three toxic compounds, namely, dichlorvos (an insecticide), propoxur (an insecticide), and 2, 4-D (a herbicide), were used as the model compounds for the mineralization experiments. Total organic carbon measurements were used to measure the extent and the rate of the mineralization of these toxic chemicals. Additionally, ions such as chloride, phosphate and ammonia were also measured during the photomineralization reaction. Results show that the photocatalytic system is effective in mineralizing these pesticides. Both pH and the initial concentration of the organic compounds affect the mineralization reaction. The mineralization reaction is favored under an acid condition and increases with increasing initial organic concentration. The initial rate of the photomineralization reaction can be described by a Langmuir-Hinshelwood expression.
Photocatalytic oxidation of chlorophenols in the presence of manganese ions
(1999)
Chen, JN
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Chan, YC
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Lu, MC
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環境工程研究所
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Institute of Environmental Engineering
The decomposition of chlorophenols in aqueous solution with UV-illuminated TiO2 suspensions in the presence of manganese ions was studied. It was found that the removal rare of chlorophenols would be the highest at pH 3 in the presence of 1.18x10(-4) M manganese ion. The effect of ionic strength on the 2-CP decomposition can be ignored in the range from 0.1 to 0.005 M for NaClO4. This study is also to explore the relationship between the adsorption rate and reaction rate. Results showed that the more the adsorption rate the more the decomposition rate for the three chlorophenols. Manganese ions can increase the photocatalytic oxidation of 2-chlorophenol in terms of DOC. The relationship between temperature and reaction rate for 2-CP is k = 0.0043 T - 1.2146. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.
Photocatalytic oxidation of gaseous DMF using thin film TiO2 photocatalyst
(2005-02-01)
Chang, CP
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Chen, JN
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Lu, MC
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Yang, HY
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環境工程研究所
The heterogeneous photocatalytic oxidation of gaseous N,N'-dimethylformamide (DMF) widely used in the manufacture of synthetic leather and synthetic textile was investigated. The experiments were carried out in a plug flow annular photoreactor coated with Degussa P-25 TiO2. The oxidation rate was dependent on DMF concentration, reaction temperature, water vapor, and oxygen content. Photocatalytic deactivation was observed in these reactions. The Levenspiel deactivation kinetic model was used to describe the decay of catalyst activity. Fourier transform infrared (FTIR) was used to characterize the surface and the deactivation mechanism of the photocatalyst. Results revealed that carbonylic acids, aldehydes, amines, carbonate and nitrate were adsorbed on the TiO2 surface during the photocatalytic reaction. The ions, NH4+ and NO3-, causing the deactivation of catalysts were detected on the TiO2 surface. Several treatment processes were applied to find a suitable procedure for the regeneration of catalytic activity. Among these procedures, the best one was found to be the H2O2/UV process. (C) 2004 Elsevier Ltd. All rights reserved.
Photocatalytic oxidation of propoxur in aqueous titanium dioxide suspensions
(1999)
Lu, MC
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Chen, JN
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Tu, MF
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環境工程研究所
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Institute of Environmental Engineering
The photocatalytic oxidation of propoxur, a nitrogen-containing pesticide, has been investigated using aqueous TiO2 suspensions as catalyst in this study. The operating variables considered in the study were initial pH, temperature, [H2O2] and TiO2 loading. Results showed that 1 g/l of TiO2 was the optimum dosage for oxidizing propoxur in this system. Hydrogen peroxide can increase the oxidation rate with increasing its initial concentration. There was no obvious difference in the rate of propoxur oxidation at the initial pH of 4, 6 and 9, and the final pHs of reaction solutions were around 5.5. However, propoxur degraded slower at initial pH 2, and the pH did not vary during the period of photocatalytic reaction. The photocatalytic oxidation of propoxur using TiO2 suspensions as the photocatalyst was reaction-controlled as indicated by the activation energy.
Pretreatment of pesticide wastewater by photocatalytic oxidation
(1997)
Lu, MC
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Chen, JN
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環境工程研究所
;
Institute of Environmental Engineering
The toxic chemicals, 2,4-D (a herbicide) and propoxur (an insecticide), were used as the model compounds in these experiments. Total organic carbon analyzer was used to assess the efficiency:of photocatalytic mineralization. Microtox bioassay was employed in evaluating the toxicity of solutions treated by photocatalysis. Ultraviolet absorption spectra were also used for showing the different characteristics of the compounds undergoing photocatalytic oxidation. Results show that propoxur is less degradable than 2,4-D, and the photomineralization of these pesticides follows a behavior of first-order reaction. Products of 2,4-D and propoxur are more toxic than the parent compound after partial photodegradation. This shows that complete mineralization is necessary for total detoxification of these pesticides. In other words, toxicity is an important criteria in assessing the pretreatment process. (C) 1997 IAWQ. Published by Elsevier Science Ltd.
The influence of metal ions on the photocatalytic oxidation of 2-chlorophenol in aqueous titanium dioxide suspensions
(1999)
Lu, MC
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Chen, JN
;
Lin, HD
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環境工程研究所
;
Institute of Environmental Engineering
This study investigated the effect of metal ions,such as Fe3+, Cu2+, Ni2+, Cr3+ and Zn2+, on the photocatalytic oxidation of 2-chlorophenol with illumination of 254 nm and 365 nm UV lights. Different metal ions have individual reduction potentials, and hence, their abilities to capture electrons also differ; the rates of 2-chlorophenol decomposition vary as well. This study was made to explore the relationships between the reduction potentials of different metal ions and their photocatalytic rates of 2-chlorophenol. Results show that when the reduction potential is greater than zero, regardless of illumination wavelength, the reaction rate increases with increasing reduction potentials of the metal ions. When the reduction potential is less than zero, the reaction rates are about the same for illumination of 365 nm or 254 nm UV lights.