The Adsorption And Its Mechanisms Of Mefenacet On Six Kinds Of Minerals

Adsorption was an important process in govering the fate of pesticides in soil system.Adsorption on minerals was shown to control the transport,transformation and biological processes of pesticides.It was also of great significance in evaluationg the potential effects on soil and groundwater and developing the soil chemical remediation.In this study,six kinds of natural minerals were selected as absorbent.The adsorption characteristics,kenetics and thermodyanamics of mefenacet on six types of minerals were systematically probed on the laboratory simulation by bathch equilibrium technique.Its mechanisms on minerals were analyzed by Fourier thansform infrared spectra(FTIR) and X-ray diffraction(XRD) methods.At the same time,the effects of pH value and temperature on the adsorption of mefenacet was also explored.The effect of heavy metals,pesticides and fertiliaers on adsorption of mefenacet on minerals were researched to predict the adsorption behavior of mefenacet on combined pollution. The effect of low nolecular weight organic acids(LMWOA) on adsorption of mefenacet on minerals was researched to predict the adsorption behavior of mefenacet on plant rhizosphere enviroment,and the effect reasons of heavy metals,pesticide,fertilizers and LMWOA to the adsorption of mefenacet were analyzed by FTIR method.The main conclusions were as follows:1.The adsorption properties of mefenacet on minertals:The adsorption of mefenacet on six kinds of mineral concluded both rapid adsorption stage and slow adsorption eauilibrium stage.Its adsorption kinetics could be described by Pseudo-second-order. The adsorption isotherm of mefenacet on six kinds of minerals were well described by Liner equation and Freundlich equation.When the initial concentration of mefenacet ranged form lmg/L to 20mg/L and pH value was 6.0,the adsorption auantity of mefenacet on six kinds of mineral decreased with the temperature increasing and the absorption free energy(ΔG) being negative and less than 40KJ/mol on six kinds of minerals.This indicated that the absorption has spontaneous and belonged to physical adsorption.The effect of pH value on the adsorption on minerals was related to t the zero point charge(ZPC) of minerals.2.Effect of heavy metal on the adsorption of mefenacet on six kinds of mineralsThe adsorption quantity of mefenacet on six kinds of minerals with heavy metal(Cu2+, Zn2+、Cr6+) were larger than without heavy metal.The effect of heavy metal on adsorption isotherm of mefenacet on six kinds of minerals could be well described by the Linear equation and Freundlich equation.When the initial concentration of heavy metals was between Omg/L and 100mg/L,the overall trend became more balanced,with the increase of the adsorption capacity going up at first phenomenon.3. Effect of pyrazosulfuron-eyhyl/bensulfuron-methl on the adsorption of mefenacet on mineralsWhen pyrazosulfuron-eyhyl existed.the adsorption amount of mefenacet on kaolinite, montmorillonite, sepillite, attapulgite and zeolites was increased,while the adsorption amount of mefenacet on diatomite was decreased. When bensulfuron-methl existed,the adsorption amount of mefenacet on sepillite, zeolites and montmorillonite was increased,while the adsorption amount of mefenacet on attapulgite,diatomite and kaolinite was decreased. The effect of pyrazosulfuron-eyhyl on adsorption isotherm of mefenacet on minerals could be well described by the Linear equation and Freundlich equation. The effect of pyrazosulfuron-eyhyl on adsorption isotherm of mefenacet on sepillite could be also described by the Langmuir equation.The effect of bensulfuron-methl on adsorption isotherm of mefenacet on minerals could be well described by the Freundlich equation. The effect of bensulfuron-methl on adsorption isotherm of mefenacet on zeolites, diatomite and sepillite could be also described by the Linear equation.The effect of pyrazosulfuron-eyhyl and bensulfuron-methl on the adsorption of mefenacet on kaolinite,montmorillonite,sepillite and zeolites showed activation.The effect of pyrazosulfuron-eyhyl on the adsorption of mefenacet on attapulgite showed activation,while inhibition in bensulfuron-methl.The effect of pyrazosulfuron-eyhyl and bensulfuron-methl on the adsorption of mefenacet on diatomite showed inhibition.4. Effect of potassium chloride and urea on the adsorption of mefenacet on mineralsBecause of the presence of potassium chloride and urea,the adsorption of mefenacet on six kinds of minerals was increased.The effect of fertilizer on adsorption isotherm of mefenacet on minerals could be well described by the Linear equation and Freundlich equation. The adsorption of mefenacet with potassium chloride was stronger than urea on montmorillonite and attapulgite,while urea was stronger than potassium chloride on kaolinite, sepillite, diatomite and zeolites. The effect of potassium chloride and urea on the adsorption of mefenacet on kaolinite, montmorillonite, sepillite, zeolites and attapulgite showed activation. When the concentration of potassium chloride or urea was less than 10mmol/L,the adsorption of mefenacet on diatomite showed inhibition.This inhibition gradually changed into activation with the concenstration inceasing.5. Effect of LMWOA on the adsorption of mefenacet on six kinds of mineralsThe effect of LMWOA on adsorption isotherm of mefenacet on six kinds of minerals could be well described by Freundlich equation. The concentration has a greater impact on the adsorption of mefenacet on clay minerals. The trends of the affection are depending on the type of the organic acids and the minerals.6.The mechanisms of mefenacet on six kinds of mineralsThe interaction mechanism between mefenacet,mefenacet-heavy metal, mefenacer-pyrazosulfuron-eyhyl or bensulfuron-methl,mefenacet-potassium chloride or urea,mefenacet-LMWOA) and minerals was discussed by means of Fouries transform infrared spectra in this experiment.The results of FTIR showed that the formation of hydrogen bonds, charge Transfer, charge-dipole and complexation was the main interaction mechanism.The interaction mechanism between mefenacet and mineral were discussed by means of X-ray diffraction in this experiment.The results of XRD showed that the adsorption of mefenacet on six kinds of minerals not only occurred on the surface but also reached their interlayer.