Huan-Jung Fan

Degradation pathways of crystal violet by Fenton and Fenton-like systems: Condition optimization and intermediate separation and identification

The main advantage of Fentons reagent (FR) over other OH systems is its simplicity. FR has the potential for widespread use in treating wastewater, but compared to other OH systems, little information on the dye degradation pathways of FR exists. The degradation of crystal violet (CV), a triphenylmethane dye, by FR was determined as a function of reagent concentration and ratio and pH in the batch treatment. The experimental results showed the optimum Fe(2+)/H(2)O(2) ratio to be 0.5mM:50mM and the optimum Fe(3+)/H(2)O(2) ratio to be 1mM:50mM. Optimal pH was about 3. To obtain a better understanding of the mechanistic details of Fenton reagents degradation of CV dye, the intermediates of the process were separated, identified, and characterized by HPLC-PDA-ESI-MS and GC-MS techniques in this study. Indications were that the probable degradation pathways were N-de-methylation and cleavage of the conjugated chromophore structure. The intermediates were generated in the order of the reaction time and relative concentration, indicating that the N-de-methylation degradation of CV dye is a major reaction pathway. The reaction mechanisms proposed in this research should prove useful for future application of the technology to the decolorization of dyes.

Mechanistic pathways differences between P25-TiO2 and Pt-TiO2 mediated CV photodegradation

The Crystal Violet (CV) dye represented one of the major triphenylmethane dyes used in textile-processing and some other industrial processes. Various metals doped titanium dioxide (TiO(2)) photocatalysts have been studied intensively for the photodegradation of dye in wastewater treatment. In order to understand the mechanistic detail of the metal dosage on the activities enhancement of the TiO(2) based photocatalyst, this study investigated the CV photodegradation reactions under UV light irradiation using a Pt modified TiO(2) photocatalyst. The results showed that Pt-TiO(2) with 5.8% (W/W) Pt dosage yielded optimum photocatalytic activity. Also the effect of pH value on the CV degradation was well assessed for their product distributions. The degradation products and intermediates were separated and characterized by HPLC-ESI-MS and GC-MS techniques. The results indicated that both the N-de-methylation reaction and the oxidative cleavage reaction of conjugated chromophore structure occurred, but with significantly different intermediates distribution implying that Pt doped TiO(2) facilitate different degradation pathways compared to the P25-TiO(2) system.

Prediction for Energy Content of Taiwan Municipal Solid Waste Using Multilayer Perceptron Neural Networks

Abstract In the past decade, the treatment amount of municipal solid waste (MSW) by incineration has increased significantly in Taiwan. By year 2008, ~70% of the total MSW generated will be incinerated. The energy content (usually expressed by lower heating value [LHV]) of MSW is an important parameter for the selection of incinerator capacity. In this work, wastes from 55 sampling sites, including villages, towns, cities, and remote islands in the Taiwan area, were sampled and analyzed once a season from April 2002 to March 2003 to determine the waste characteristics. The LHV of MSW in Taiwan was predicted by the multilayer perceptron (MLP) neural networks model using the input parameters of elemental analysis and dry– or wet–base physical compositions. Although all three of the models predicted LHV values rather accurately, the elemental analysis model provided the most accurate prediction of LHV values. Additionally, the wet–base physical composition model was the easiest and most economical. Therefore, the waste treatment operators can choose the more appropriate analysis method considering situations themselves, such as time, equipment, technology, and cost.

Degradation of crystal violet by an FeGAC/H2O2 process.

Because of the growing concern over highly contaminated crystal violet (CV) wastewater, an FeGAC/H(2)O(2) process was employed in this research to treat CV-contaminated wastewater. The experimental results indicated that the presence of iron oxide-coated granular activated carbon (FeGAC) greatly improved the oxidative ability of H(2)O(2) for the removal of CV. For instance, the removal efficiencies of H(2)O(2), GAC, FeGAC, GAC/H(2)O(2) and FeGAC/H(2)O(2) processes were 10%, 44%, 40%, 43% and 71%, respectively, at test conditions of pH 3 and 7.4mM H(2)O(2). FeGAC/H(2)O(2) combined both the advantages of FeGAC and H(2)O(2). FeGAC had a good CV adsorption ability and could effectively catalyze the hydrogen peroxide oxidation reaction. Factors (including pH, FeGAC dosage and H(2)O(2) dosage) affecting the removal of CV by FeGAC/H(2)O(2) were investigated in this research as well. In addition, the reaction intermediates were separated and identified using HPLC-ESI-MS. The N-demethylation step might be the main reaction pathway for the removal of CV. The reaction mechanisms for the process proposed in this research might be useful for future application of this technology to the removal of triphenylmethane (TPM) dyes.

Simultaneous determination of intraparticle diffusivity and liquid film mass transfer coefficient from a single-component adsorption uptake curve.

In general, the rate of adsorption involves both rates of liquid film mass transfer and intraparticle diffusion. Many researchers tried to minimize the effect of liquid film resistance when determining the effective intraparticle diffusivity. However, in some cases (for example, small adsorbent particle size), the liquid film resistance may not be easily eliminated in a fixed bed process. Therefore, this research proposed using the shallow bed technique to determine both intraparticle diffusivity (D(S)) and liquid film mass transfer coefficient (k(F)) simultaneously from a single-component adsorption uptake curve (AUC). The task was accomplished by the determination of the Biot number (Bi) from experimental adsorption uptake curve (EAUC). The Bi represents the ratio of the rate of transport across the liquid film to the rate of intraparticle mass transfer. The detailed calculation method is addressed in this paper. The method proposed in this research can be applied in the range of Bi between 0.5 and 200 where both liquid film resistance and intraparticle diffusion are significant.

Characterization of adsorption uptake curves for both intraparticle diffusion and liquid film mass transfer controlling systems

In general, the adsorption uptake curve (AUC) can be easily determined in either intraparticle diffusion or liquid film mass transfer dominating systems. However, for both intraparticle diffusion and liquid film mass transfer controlling systems, the characterization of AUC is much more complicated, for example, when relatively small adsorbent particles are employed. In addition, there is no analytical solution available for both intraparticle diffusion and liquid film mass transfer controlling systems. Therefore, this paper is trying to characterize AUC for both intraparticle diffusion and liquid film mass transfer controlling adsorption systems using the shallow bed reactor technique. Typical parameters influencing AUC include liquid film mass transfer coefficient (k(F)), effective intraparticle diffusivity (D(S)), influent concentration (c(0)) and equilibrium parameters (such as Freundlich isotherm constants k and 1/n). These parameters were investigated in this research and the simulated results indicated that the ratio of k(F)/D(S) and Freundlich constant 1/n had impact on AUC. Biot number (Bi) was used to replace the ratio of k(F)/D(S) in this study. Bi represents the ratio of the rate of transport across the liquid layer to the rate of intraparticle diffusion. Furthermore, Bi is much more significant than that of 1/n for AUC. Therefore, AUC can be characterized by Bi. In addition, the obtained Bi could be used to determine D(S) and k(F) simultaneously. Both parameters (D(S) and k(F)) are important for designing and operating fixed bed reactors.

Simultaneous determination of intraparticle diffusivities from ternary component uptake curves using the shallow bed technique

In order to design and operate a fixed-bed reactor, accurate modeling is important. For a single component system, the determination of intraparticle diffusivity is rather easy. However, the calculations of multi-component systems are normally complicated and very time-consuming. Therefore, an alternative simple determination procedure using the shallow bed technique is proposed in this research to determine the intraparticle diffusivities for multi-component systems. Ternary component systems of phenol (PH), benzoic acid (BA), and p-nitro-phenol (PNP) were investigated as model components. This study illustrated that adsorption uptake curves of different components in ternary systems can be converted into one typical characteristic curve (theoretical uptake curve, TUC) by using a set of dimensionless groups. By matching the dimensionless experimental uptake curve (DEUC) with TUC, diffusivities of PH, BA and PNP were determined as 8.00 x 10(-8), 5.92 x 10(-8) and 5.05 x 10(-8)cm2 s(-1), respectively. These values are in good agreement with simulated experimental values. This study demonstrated that the shallow bed technique can be used to simultaneous determination of intraparticle diffusivities from multi-component systems.

Prediction of individual Freundlich isotherms from binary and ternary phenolic compounds mixtures.

Method for simultaneous determination of individual components adsorption equilibrium parameters for binary and ternary phenolic compounds mixtures was investigated in this research. The Freundlich equilibrium parameters of binary and ternary component of phenolic compounds were determined from one fixed composition of phenolic wastewater. The simulation results obtained from both binary and ternary systems on the basis of ideal adsorbed solution theory were consistent with single component equilibrium data.

Optimization of a modification technique for reducing irreversible adsorption within synthetic resins

Synthetic resin adsorbents comprise agglomerated gel-type microparticles. Although the excellent adsorption capacities of resins are useful in adsorbing various organic substances, the adsorbed molecules cannot be completely desorbed. A majority of the irreversible adsorbed molecules can be attributed to slow mass transfer within microparticles of resins and it may lower the recovery efficiency of resins. This study focuses on reducing the irreversible adsorption that occurs within a resin (FPX-66) to improve the overall recovery efficiency of the adsorbate. In order to reduce the irreversible adsorption capacity of the resin, styrene monomer was polymerized in microparticles of the resin. Effects of polymerized styrene concentrations and multi-cycle polymerization on irreversible adsorption capacity of the resin were investigated. The experimental results indicated that using one cycle of polymerization with 30–40 vol% of styrene solution is the most effective modification process. The irreversible adsorption capacity could be lowered by half with the above process.

A simple method for the determination of adsorption kinetic parameters using circulating-type shallow bed reactor (CSBR)

aZenkosha Co. Ltd., Tokyo, Japan, email: takashi@zenko.co.jp bDepartment of Safety, Health and Environmental Engineering, Hungkuang University, Taichung 433, Taiwan, Tel. +886 4 26318652; Fax: +886 4 26525245; email: fan@sunrise.hk.edu.tw cNatural Science Laboratory, Toyo University, Tokyo, Japan, email: seida@toyo.jp dDepartment of Applied Chemistry, Meiji University, Kawasaki, Japan, emails: tkino@meiji.ac.jp (T. Kinoshita); egfuruya@meiji.ac.jp (E. Furuya)