Environmental Application Of Nano Magnetic Composites Based On Fe₃O₄@SiO₂

With the development of the industry and agriculture,toxic and harmful substances are continuously discharged into the ecosystem.The most typical and serious pollutants are toxic heavy metal ions and harmful organic matters.Due to their widespread concerns,treatment technologies have been developed and innovated.However,due to the high cost,a lot of effective treatment technologies are constrained in the stage of laboratory research.Reducing costs is the only way to realize the practical application of these technologies.Hydrous manganese dioxide（HMO）is an environmental friendly adsorbent,which has good adsorption efficiency on heavy metal ions;palladium nanoparticles as a noble metal catalyst is efficient in catalyzing the hydro dechlorinated of halogenated organic compounds.These two materials have played important roles in Controlling of environmental pollutants.However,the two materials are hard to recycle with small particle size,which making it difficult to break through the technical bottleneck to be applied for actual wastewater.This study utilizes Fe₃O₄@SiO₂ as a magnetic support to immobilize HMO and Pd nanoparticles and therefore promote the dispersion of these two materials and realize the recycling of the materials after use.In this way,the treatment cost is reduced,which make practical application possible.The adsorption of Fe₃O₄@SiO₂-MnO₂ to cadmium and copper was evaluated as a function of solution p H,competing ions and reaction time.The experimental results indicated that the Fe₃O₄@SiO₂-MnO₂ exhibited strongly preferable sorption towards Cu（II）and Cd（II）with a fast kinetics,which can reach equilibrium at 15 min.Adsorption rate is affected by the p H and the optimum p H is over 6.Compared to Fe₃O₄NPs-MnO₂,Fe₃O₄@SiO₂-MnO₂ has better chemical stability in strong acidic environment,which is beneficial for the regeneration of the adsorbent under acidic environment.In the experiments of treating synthetic wastewater,it showed good recycling efficiency for the removal of Cu（II）,but the recycling efficiency for the removal of Cd（II）was not ideal.The effects of solution p H,chloride ion and dissolved organic matter（DOM）were studied in the dechlorination of trichloroethylene（TCE）by Fe₃O₄@Si O₂-Pd.The experimental results indicated that dechlorination was not affected by p H between 4-10.However,high concentration of chloride ion and DOM affected the dechlorination rate.The adsorption of chloride ions has a negative effect on catalyst with the temporary deactivation.