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Study on Adsorption and Photocatalytic Degradation of Diuron in Modified Montmorillonite

Author: YeXiaoBei
Tutor: YuanShouJun
School: Hefei University of Technology
Course: Municipal Engineering
Keywords: diuron modified montmorillonite adsorption photocatalyticdegradation repai
CLC: S482.4
Type: Master's thesis
Year: 2012
Downloads: 46
Quote: 0
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Abstract


A variety of pesticides including insecticides and herbicides are widely used toimprove crop yields in the agricultural production industry. Only a small fraction ofthis pesticides can play a direct role in killing insect and weeding on crop.Themajority of pesticides is sprayed into the ecological environment with rainoff andatmospheric,and become organic pollutants which threat to humans andanimals,resulting in eclolgical risks.In this paper,the herbicide diuron were selectedto investigate its behavior of adsorption and photocatalytic degradation on modifiedmontmorillonite in environment.The main comclusions were obtained as follows:Firstly,the adsorption mechanism and influencing factors of diuron on organicmodified montmorillonite(CTAB-MMT) was investigated. The results indicate thatthe adsorption reaction is spontaneous endothermic reaction which fits well forFreundlich isotherm model and can be described by pseudo-second order kineticsmodel. Ionic strength inhibit the adsorption of diuron within a certain range. Humicacid could promote the adsorpton of diuron on montmorillonite to a certain extent.The solution of pH have slightly affected on the adsorption process,and it isconducive to adsorption when pH=6to8. Herbicide prometryn has a similaradsorption mechanism of diuron,and adsorption of prometryn have synergy withdiuron on modified montmorillonite.Secondly,the photocatalytic degradation mechanism of diuron on titaniumpillared montmorillonite(TiO2-MMT) was investigated.The results show that thephotocatalytic degradation efficiency are highest when the amount of TiO2pillaredmontmorillonite is1.5g/mg diuron. Degradation efficiency increases withincreasing pH in the range of pH=2to8and the efficiency changes slowly with therise pH when pH>8. Four clay materials, the degradation effect of TiO2-MMT andCTAB-TiO2-MMT was better than that of MMT and CTAB-MMT, the adsorptioneffect of CTAB-MMT and CTAB-TiO2-MMT was better than that of MMT andTiO2-MMT. So, CTAB-TiO2-MMT have the best adsorption and degradationperformance,and the photocatalytic degradation reaction for diuron and prometryncould be described by first kinetic model. The half-life of diuron was47.47min andprometryn was54.96min. TiO2-MMT and CTAB-TiO2-MMT have a goodreuseability performance. The repair behavior of diuron in the environment soil was investigated. Theresults indicate that pesticide diuron was firstly adsorbed by the soil after spraying,then the photocatalytic degradation will be happened when irradiated by sunlight,and the more from the surface of soil, the more obvious photocatalytic degradation.

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CLC: > Agricultural Sciences > Plant Protection > Pesticide ( chemical control ) > Various pesticides > Herbicides ( herbicide )
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