Study On The Preparation Of Stabilized Nanometer Zero-valent Iron And Application Of Hexavalent Chromium Pollution In Environmental Treatment

In this thesis,we use liquid phase reduction method,select different dispersant types(Starch,Chitosan,Polyvinylpyrrolidone)and dosage to prepare stabilized nanometer zero valent iron.And XRD,SEM,thermogravimetric and other instruments were used to analyze the nanometer zero valence iron,exploring the Characteristics and Stability of Nanometer Zero-valent Iron,and seleciting the appropriate dispersant and preparation method.The prepared stabilized nanometer zero-valent iron was applied to the removal of hexavalent chromium in polluted environment,and we explore the feasibility of its application,to provide a strong theoretical and technical support for the application of nanometer zero-valent iron in polluting environmental management.The main results of this paper are as follows:(1)In the nano-zero-valent iron particles which use starch,chitosan,polyvinyl pyrrolidone and other dispersants prepared by the stability,stabilized nano-zero-valent iron surfaces prepared with starch as a dispersant have no oxide film,which does not contain impurities in the oxide,the particle size is 60 to 100 nm,which are presented spheres and scattered evenly,the nanometer zero-valent iron is chained.The preparation process does not require nitrogen protection,it requires low equipment requirements,the process is simple.(2)The stabilized nano-zero-valent iron can effectively remove hexavalent chromium from simulated wastewater,In the simulated waste water with hexavalent chromium concentration of50 mg / L.The amount of dosage,pH,reaction time,the reaction temperature will affect the removal of hexavalent chromium.Experimental results show,when the iron-iron ratio is 0.025,the pH is 7,the reaction temperature is 35 ?,the reaction time is 2h,the removal rate of hexavalent chromium is the highest,it can almost reach 100%.After drying the nano zero-valent iron placed in the air atmosphere for 30 days,Composition and chemical structure did not change,The removal of hexavalent chromium in water still has a strong effect.The reduction process of stabilizednano-zero-valent iron to hexavalent chromium is in accordance with the pseudo-first-order reaction kinetics,and the apparent rate constant kobs = 0.0121 min-1.(3)Starch stabilized nano-zero-valent iron has a good effect on soil leaching wastewater and Cr(VI)in contaminated soil.The best dosage of nano zero price iron the best dosage is 3%.the optimum ratio of soil to water is 1: 5.the best reaction time is 24 h.the best Cr(VI)removal effect is achieved when pH is acidic.The reaction rate between Cr(VI)and nano zero-valent iron in soil leaching wastewater is faster,5min or so will be able to reach the best removal effect,compared to the removal of Cr(VI)in the soil,the rate of removal in soil leaching wastewater is faster,and the choice of the minimum dosage effect is very good.Therefore,starch stabilized nanometer zero-valent iron has a good prospect in the treatment of polluted environment.