Neng-Chou Shang

Photocatalytic degradation of dimethyl phthalate in an aqueous solution with Pt-doped TiO2-coated magnetic PMMA microspheres

This study investigates the photocatalytic degradation of dimethyl phthalate (DMP) with both the titanium dioxide-coated magnetic poly(methyl methacrylate) (TiO2/mPMMA) and platinum-doped TiO2/mPMMA (Pt-TiO2/mPMMA) microspheres. The TiO2/mPMMA and Pt-TiO2/mPMMA microspheres are employed as novel photocatalysts that offer high photocatalytic activity, magnetic separability and good durability. The photocatalytic experiments of DMP under various conditions are conducted to examine the effects of the initial DMP concentration, photocatalyst dosage, UV radiation intensity and Pt doping content on the degradation of DMP. In addition, the correlations of the photocatalytic kinetics and quantum yield for DMP removal are proposed associated with the system parameters. According to the experimental results, there exists a distinct relationship between the reduction percentages of total organic carbons and DMP. Furthermore, the photodegradation mechanism of DMP in the photocatalytic process is established based on the identification of the intermediates. Moreover, the good repeatability of the photocatalytic performance with the use of the Pt-TiO2/mPMMA microspheres has also been demonstrated in the multi-run experiments. Therefore the Pt-TiO2/mPMMA microspheres are considered as a practical and promising photocatalyst in a suspension reaction system and they can be effectively recovered after use. This study provides useful information about the applications of the TiO2/mPMMA and Pt-TiO2/mPMMA microspheres for the photodegradation of DMP.

Decomposition of 2-naphthalenesulfonate in aqueous solution by ozonation with UV radiation

This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined with ultraviolet (UV) radiation. Naphthalenesulfonic acids are of importance as dye intermediates for the dye and textile auxiliary industries. Its derivatives, such as 2-NS, have been found in rivers and tannery effluents causing pollution problems. Thus, the 2-NS is of concern for the aquatic pollution control especially in the surface and waste waters. Ozonation combined with UV radiation is employed for the removal of 2-NS in the aqueous solution. Semibatch ozonation experiments were proceeded under different reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS and sulfate are analyzed at specified time intervals to elucidate the decomposition of 2-NS. In addition, values of pH and oxidation reduction potential are continuously measured in the course of experiments. Total organic carbon is chosen as a mineralization index of the ozonation of 2-NS. The mineralization of 2-NS via the ozonation is remarkably enhanced by the UV radiation. These results can provide useful information for the proper removal of 2-NS in the aqueous solution by the ozonation with UV radiation.

VARIATION OF TOXICITY DURING THE OZONATION OF MONOCHLOROPHENOLIC SOLUTIONS

ABSTRACT This study investigates the variation of toxicity during ozonation of 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 4-chlorophenol (4-CP) in neutral condition. Acute toxicity of pure chlorophenols (CPs) and their ozonated intermediates was evaluated by Microtox assay. The results revealed that the intermediates of oxidized CPs induced new toxicity during the early stage of ozonation, and the ozonated 2-CP showed higher degree of toxicity increase than 3-CP and 4-CP. The maximum toxicity normally occurred before the maximum color intensity was monitored, while ozone dosage applied was within 1 mg of ozone per mg of initial CPs. This increasing toxicity was mainly contributed from ozonated intermediates. Formation of chlorocatechols, chloromuconic acids and hydroxylated/chlorinated dimeric compounds were detected in ozonation of CPs. These chlorinated by-products may cause greater toxicity than the parent chlorophenols. The required ozone dosage to detoxify the CPs solution into a complete non-toxic condition follows the order: 4-CP> 3-CP>2-CP.

Ozonation of dyes and textile wastewater in a rotating packed bed.

This study investigates the ozonation of Reactive Red 120 and Acid Red 299 dyes in the synthesized solution and textile wastewater by using a rotating packed bed. The decomposition rate of Reactive Red 120 and Acid Red 299 dyes via ozonation can be described by the pseudo-first-order kinetics. Ozonation of Reactive Red 120 exhibited the higher mineralization rate compared with that of Acid Red 299. The biodegradability of the two dyes could be significantly promoted during the ozonation. The BOD5/TOC (5-day biological oxygen demand/total organic carbons) ratios of the ozonated Reactive Red 120 and Acid Red 299 solutions would increase and have the maximum values. Moreover, the oxidized textile wastewater revealed the fast decolorization and moderate COD (chemical oxidation demand) removal rates. The optimal ADMI (American Dye Manufactures Institute) and COD removal of the textile wastewater were 93% and 37% in 30 minutes ozonation time, respectively. The performance evaluation of ozonation in the rotating packed bed indicated that the higher water flow rate, gas ozone concentration and rotational rotating speed would increase the efficiency of mineralization.

THE BIOTOXICITY AND COLOR FORMATION RESULTS FROM OZONATION OF WASTEWATERS CONTAINING PHENOL AND ANILINE

This study was undertaken to investigate the color forming phenomena and biotoxicity related problems during the initial stage of ozonation in the wastewater containing phenol or aniline. Experimental results indicate that the phenol under alkaline condition and aniline in all pH conditions cause a serious color problem during the period of early initial ozonation. In addition, the ozonated aniline exhibited more severe color formation than the ozonated phenol did. Both of these compounds revealed that either a high compound concentration or low ozone dosage applied incurred a strong color forming phenomena. Moreover, according to the Microtox test, both ozonated byproducts increased the toxicity during early ozonation when the color formation occurred. The EC50-value as COD decreased from 0.72 (for phenol, pH = 7) to 1.38 (for aniline, pH = 4) orders-of-magnitude. This observation implies that the ozonated color formation would generate new toxicity problems if these colored matters were not further oxidized.

Material flow analysis of cadmium applied to review msw treatment in taiwan

Abstract This study applies the material flow analysis (MFA) of Cadmium to evaluate municipal solid waste (MSW) management policy in Taiwan. In 2002, the Cd flow in Taiwan was approximately 441.2 tons, mainly contributed by the Cd in nickel‐cadmium batteries (60.15%) and plastics (33.45%). 415.6 tons of Cd entered the MSW treatment system from consumers. However, aside from the Cd emitted into the atmosphere (0.4 tons) and the Cd in incinerator ash (15.1 tons), the recycled Cd was 5.2 tons, representing a recycling rate of 1.2%. Moreover, instead of being effectively used, the recycled Cd is often casually deposited in the environment. Currently, Taiwans Cd MFA data indicates that the MSW treatment is mainly performed by incineration, which does not conform to the main principles of sustainable development. To achieve a more sustainable policy, recycling and/or restriction of nickel‐cadmium batteries and plastics turn out to be important issues.