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Degradation Research of Pesticides on Cotton Fiber

Author: ZhangZhongQing
Tutor: ZhouWenLong
School: Zhejiang University of Technology
Course: Materials Physics and Chemistry
Keywords: Cotton fiber Diuron Profenofos Prometryn HPLC
CLC: S481.8
Type: Master's thesis
Year: 2014
Downloads: 1
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Abstract

As an important strategic resource, cotton plays an important role in national economy. Atpresent, China has become the world’s largest cotton consume and import country. Respectively,and has an annual consumption of about28million tons in2011. With the development ofeconomy, more and more people care about the clothing quality and safety. Green andenvironment friendly concept has been deeply rooted into people’s mind. As we know, a largenumber of pesticides are needed during the cotton production process and it could be carried bycotton fiber by directivity spraying on, in vivo metabolism and other routes. The pesticides oncotton fiber, although no report about their toxicity has been published, would be a potentialhazard to the environment and the people who are exposed to. However, there are no clearunderstanding about the destiny of pesticides on fiber during the production, processing andusage. The investigation of the rules of their dissipation in the field and during the processingwould be helpful to the risk evaluation of cotton-pesticides applications.In this work, we researched the residues of three kinds of common pesticides (diuron,profenofos and prometryn) on cotton fiber for the first time, using high performance liquidchromatography (HPLC).Diuron’s degraded significantly in the alkali solution at96.5℃for2h, reduced about76.8%. The rule of degradation follows the first-order kinetic reaction equation, and theactivation energy of hydrolysis for diuron is98.9kJ/mol at20g/L NaOH. Its degradationproducts identified to be3,4-dichloroaniline.Due to high temperature and alkali, profenofos degradation rapidly at96.5℃for20min,profenofos characteristic absorption peak did not find at tR=7.65min in the chromatogram. Therule of degradation follows the first-order kinetic reaction equation and the activation energy ofhydrolysis for profenofos is12.56kJ/mol at20g/L NaOH. Its degradation products identified tobe2-chloro-4-bromophenol.Prometryn’s hydrolysis rate is slow in the alkali solution. Detecting the extract of on cottonfiber prometryn, it was found that the prometryn still remained about0.97%scouring for120min at96.5℃. So, prometryn cannot be completely removed from cotton fiber. Its hydrolysis process follow the first-order kinetic reaction equation, the activation energy ofhydrolysis for prometryn is105.20kJ/mol at20g/L NaOH. Its degradation product is1,2-hydroxy-4,6-isopropyl amino-1,3,5-triazine.In this research, we established a method to detect the pesticides on the cotton fiber basedon the HPLC. The method has good sensitivity and reproducibility, good practicality. From theresults, although pesticides will be significantly attenuated or even completely degraded withthe role of the natural environment during the cotton growing, there are still some pesticidesresidues on cotton fiber, which are harmful to the workers. Pesticides can be substantiallyremoved by scouring, so, scouring or dyed cotton products is scarcely harm to people. For theraw cotton fabric, because of the residue of pesticides, you should wash it before you use it. Indomestic washing conditions, pesticides removed extremely fast, most of the pesticides can beremoved by once, with twice or more can be substantially removed. Pesticides, especially thosebecome more noxious after hydrolyzation, may have a greater potential threat to people whouse those cotton products such as the cotton wools, without scouring or washing. Relevantinspection and quarantine departments should pay more attention to it.

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