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1996 Fiscal Year Final Research Report Summary

Photocatalyzed Degradation of Agrochemicals in Water

Research Project

Project/Area Number 07680599
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 環境保全
Research InstitutionToyama University

Principal Investigator

HASEGAWA Kiyoshi  Toyama University, Chemistry, Professor, 工学部, 教授 (20019186)

Co-Investigator(Kenkyū-buntansha) SHINODA Misao  Toyama University, Chemistry Assistant, 工学部, 教務職員 (90196395)
KAGAYA Shigehiro  Toyama University, Chemistry, Assistant, 工学部, 助手 (50272894)
KANBARA Takaki  Toyama University, Chemistry, Assistant Professor, 工学部, 助教授 (90204809)
Project Period (FY) 1995 – 1996
KeywordsAgrochemical / Photocatalyst / Titanium dioxide / Water treatment / Photocatalysis
Research Abstract

1. The phtocatalyzed degradation of agrochemicals (simazine, benthiocarb, thiram, diazinon, fenitrothion, isoprothiolane, propyzamide, dichlorvos, fenobucarb, and iprobenfos) has been investigated in an aqueous suspension of TiO_2 using a ultra high-pressure mercury lamp (lambda>290nm and 365nm) at 35゚C.2. The degradation is much faster than direct photolysis without TiO_2 and depends on the first order kinetics to the concentrations of the agrochemicals. 3. The degradation depends on the structures of the agrochemicals. The half-lives of the agrochemicals ranged from 4.11-11.9min (lambda>290nm) and 5.0-24.3min (lambda=365nm). Quantum yields were estimated to be 0.0086-0.032min (lambda=365nm). The agrpchemicals were ultimately mineralized to form Cl^-, SO_4^<2->, NO_3^-.4.Several factors affecting the degradation were examined in details with iprobenfos. 5. Optimum concentration of TiO_2 was found to be 0.5-1.0mg/ml. The initial reaction rate (r_0) is proportional to the photons absobed by TiO_2 (I_a) and quantum yield (PHI). r_0 follows the langmuir-llinshelwood relationship with the initial concentration (C_0) of iprobenfos and the partial pressure of O_2 in the bubbling gas (pO_2). The action of adsorbed O_2 (O_2(ads)) is discussed. We propose the empirical rate of the photocatayzed degradation of iprobenfos as follows : r_0=I_aPHIpO_2, _<ads>(iprobenfos)_<ads>. Fair agreement of r_0 was found between experiment and calculation. 6. Based on the GC/MS analysis of the degradation products, degradation pathways were examined. One pathway is OH attack on alpha, beta, and gamma bond of iprobenfos, another pathways is OH attack on the benzene ring of iprobenfos followed by the alpha cleavage. It was found that the photocatalyzed degradation could be applicable to the degradation of water contaminants.

  • Research Products

    (2 results)

All Other

All Publications (2 results)

  • [Publications] Kiyoshi, Hasegawa: "Photocatalyzed Degradation of Agrochemicals in TiO_2 Aqueous Suspensions" Denki Kagaku,. Vol66,No6(in press). (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Kiyoshi Hasegawa, Takaki Kanbara, and Shigehiro Kagaya: "Photocatalyzed Degradation of Agrochemicals in TiO_2 Aqueous Suspensions" Denki Kagaku. Vol.66, No.6(in press).

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-03-16  

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