The Preparation And Characterization Of Nanoscale Zero-valent Iron Supported On Organomontmorillonite For Removal Of4-Chlorophenol

Chlorophenols(CPs) is a kind of Teratogenic、carcinogenic and mutagenic persistentorganic pollutants with a strong toxicity. U.S. EPA and the China Environmental MonitoringCenter are listed most of the CPs as priority pollutants. With broad spectrum bactericidalproperties chlorophenols are widely used in the preservative treatment of wood, vegetablesand paint; As an intermediate CPs applications in the process of production of herbicides,pesticides and dyes in a large number. A large quantity of applications in industrial andagricultural, inevitably lead CPs or by accident or direct emissions into the natural water body,which cause extremely bad effect on the natural environment.Nanoscale zero valent iron (NZVI)materials is the superfine iron powder material withparticle size of1~100nm. With the small particle size and high reactivity as well asenvironment-friendly features, NZVI materials showed an obvious advantage in thedegradation of pollutants.But the degradation of chlorinated organic pollutants by nanoscalezero valent iron mainly by the surface reaction pathway, its removal efficiency is limited bythe mass transfer ability of zero-valent iron.The different polarity of zero-valent iron andhydrophobic organic compounds in the liquid phase will lead to low efficiency of electrontransfer between the zero-valent iron and pollutants which cause iron is difficult to fully playits role,and the characteristics of agglomerated and oxidized easily affect effect of its practicalapplication. supported nanoscale zero valent iron on the porous adsorbing medium isconsidered to be a good way to acquire efficient, stable nano-iron.By virtue of the large surface area, good ion exchange and excellent adsorption,montmorillonite has been widely applied to the adsorption treatment of pollutants in recentyears.Organomontmorillonite(CMt) prepared by ion exchange method can increase theprocessing capacity on the adsorption of hydrophobic organic compounds and also serve asnanoscale iron excellent load media because montmorillonite transition from hydrophilic tohydrophobic.Based on the ability of montmorillonite and NZVI to remove pollutants, preparation ofsynthetic materials which supported NZVI on organomontmorillonite(NZVI-CMt) by a seriesof tests of synthesis, characterization and degradation,intended to give full play of the twomaterials to remove pollutants and overcome the adverse features of montmorillonitehydrophilic and nanoscale zero valent iron is easily oxidized and agglomerated at the sametime. The topics include three parts, the first part of is the research on preparation ofOrganomontmorillonite and its influencing factors,intends to determine the optimal reaction conditions for organic modification process and find the optimal CTMAB join ratio. The experimental results showed:the addition amount of CTMAB and reaction timehave obvious influence on the modification effect,the best reaction time is2h,1CECis the optimum amount of modifier.The second part is study on preparation of NZVI-CMt and its influencing factors,intends to explore the way of supporting NZVI on CMt and discuss the affect of the addition amount of iron on supporting effect in orderto determine the optimal reaction conditions, preparation of a good dispersion and small particle size of supported nanoscale iron. The experimental show:the introduction ofCMt can good solve the agglomeration of nanoscale iron, particle size of supportednano-iron increasing with the increase of addition iron amount, when iron/soil massratio is1:4the particle size of nano-iron is less than100nm and forming complete.The third part is the experiment of removing4-chlorophenol by NZVI-CMt.The results have shown that: When the initial concentration of4-chlorophenol was10mg/L, the removal rate by NZVI-CMt reached90%after30mins under25℃. What’s more，theNZVI-CMt performed good removal efficiency as the4-CPs concentration varied. In this process4-CPs were removed by two paths，one was adsorption and the other wasdegradation. Temperature is an important factor influencing the removal pathway. Withexcellent absorbability, NZVI-CMt enhanced the effect of4-CPs degradation by raising the efficiency of mass transmission of Fe~0.