Browsing by Author "CHEN, JN"

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APPLICATION OF A FLUORINATED SOLVENT TO THE CONVENTIONAL OZONATION PROCESS FOR THE DESTRUCTION OF 2,4-DICHLOROPHENOL
(1995)
CHANG, CY
;
CHEN, JN
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
The removal of 2,4-dichlorophenol from aqueous solution with fluorinated solvent, with ozone, and with fluorinated solvent/ozone combined was investigated. The fluorinated solvent/ozone combined system consists of a chemical extraction from the aqueous phase accompanied by oxidation with ozone in both the solvent and aqueous phase. The results of extraction tests showed that the distribution coefficient decreased with increasing initial pH value of the aqueous phase. The apparent oxidation rate constant of the aqueous ozonation for the initial pH 5.8 was close to that measured of organic phase ozonation. The initial pH value of aqueous phase plays an important role in the fluorinated solvent/ozone combined system for affecting the removal efficiency. The experiment results indicated that 2,4-dichlorophenol was removed at a faster rate at low initial pH value. Although the accumulation of 2,4-dichlorophenol in the organic phase in the fluorinated solvent/ozone combined system was observed under the condition of initial pH 10.0, the overall removal of 2,4-dichlorophenol under the condition of initial pH of 10.0 was close to the condition of initial pH 7.0. Moreover, a comparison test showed that the removal efficiency of 2,4-dichlorophenol by fluorinated solvent/ozone combined system is higher than that by homogeneous phase ozonation or extraction.
FACTORS AFFECTING THE PHOTOCATALYTIC DEGRADATION OF DICHLORVOS OVER TITANIUM-DIOXIDE SUPPORTED ON GLASS
(1993-12-01)
LU, MC
;
ROAM, GD
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CHEN, JN
;
HUANG, CP
;
環境工程研究所
The photocatalytic degradation of organophosphorus insecticide, dichlorvos, on glass-supported titanium dioxide was investigated. The photoreactor coated with titanium dioxide was illuminated with a 20 W black-light W fluorescent tube. The aqueous solution containing dichlorvos was continuously pumped through the photoreactor. Several factors, such as the initial dichlorvos concentration, dissolved oxygen, electrolytes, flow rate and temperature, affecting the oxidation rate of dichlorvos were studied. The results indicate that photocatalysis can be an effective process for the degradation of dichlorvos. The activated energy for the photocatalytic degradation of dichlorvos is 28.4 kJ mol(-1). The initial quantum yield for the destruction of dichlorvos is 2.67%. Increasing the flow rate and initial dichlorvos concentration increases the dichlorvos degradation rate. Total mineralization requires a much longer illumination time than the disappearance of dichlorvos. Phosphate-containing intermediates are more stable than chloride-containing intermediates. It is shown that the photocatalytic oxidation of dichlorvos follows the Langmuir-Hinshelwood-type behavior, and reaction byproducts display an inhibiting effect on degradation rate.
MICROTOX BIOASSAY OF PHOTODEGRADATION PRODUCTS FROM PHOTOCATALYTIC OXIDATION OF PESTICIDES
(1993-11-01)
LU, MC
;
ROAM, GD
;
CHEN, JN
;
HUANG, CP
;
環境工程研究所
The mineralization of toxicants and the reduction of toxicity were investigated via the photocatalytic reaction. Dichlorvos (an insecticide), 2,4-D (a herbicide) and propoxur (an insecticide) were used as the model compounds in these experiments. Total organic carbon analyzer was used as a measure of mineralization of toxic compounds to assess the efficiency of photocatalytic mineralization. Microtox bioassay was employed in evaluating the toxicity of solutions treated by photocatalysis. The rate of photocatalytic mineralization is more efficient in acidic than in alkaline solution. The degradation pathway and toxicity of pesticides treated in photocatalytic process are pH dependent. Ultraviolet absorption spectra were also used for showing the different characteristics of the compounds undergoing photocatalytic mineralization.
OZONOLYSIS OF 2,4-DICHLOROPHENOL IN A 2-PHASE SOLVENT WATER-SYSTEM
(1994)
CHANG, CY
;
CHEN, JN
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
The ozonolysis of 2,4-dichlorophenol was investigated in a two-phase system. A new contact flow system was proposed in this study. The experimental results show that the mechanisms of organic removal can be divided into two stages. The first stage is a solvent extraction and the second stage is ozonolysis. The disappearance of organic is very quick in the first stage and slows down in the second stage. The kinetic of ozonolysis in this system approximately obeys second order behavior.
PHOTOCATALYTIC OXIDATION OF DICHLORVOS IN THE PRESENCE OF HYDROGEN-PEROXIDE AND FERROUS ION
(1994)
LU, MC
;
ROAM, GD
;
CHEN, JN
;
HUANG, CP
;
環境工程研究所
The photocatalytic oxidation of dichlorvos has been investigated with two different reactors. The reactor using 254 nm light is a system with TiO2 suspensions. The 360 nm light is used as the light source of the fixed system which was TiO2 coated on the inner surface of the reactor. In terms of quantum yield, the 254 nm radiation is more effective for dichlorvos oxidation than the 360 nm light. The effect of H2O2 on dichlorvos oxidation shows a negative performance. The influence of H2O2 on the photocatalytic oxidation of dichlorvos is greater in the fixed system than that in the suspension system. The ferrous ions can induce the photo-Fenton-type reaction. However, the photocatalytic oxidation of dichlorvos will be inhibited slightly at the concentration of 1.0 x 10(-5) M Fe+2. This result is explained in terms of the net production of hydroxyl radical.