Preparation Of Functionalized Nanocomposites For Controlling The Migration Of Heavy Metal And Nitrogen

The discharge of toxic pollutants into the environment by human activities has been caused the increasingly environmental pollution,which is seriously harmful to human health and the ecological environment.Particularly,heavy metal pollution caused by industrial activities and nitrogen pollution caused by the abuse of chemical fertilizers have become more and more,which are suffering the attention of the public opinion.Therefore,remediate heavy metal contaminated enviromental,control the loss of nitrogen fertilizers and thus reduce the nitrogen pollution have become an urgent issue in agriculture and environment of all the world.Nanomaterials are widely used in the removal of heavy metals and nitrogen pollutants from the environment because of their large specific surface area,many active sites,and so on.Nowadays,there have many researches on water pollution treatment,however,very little research foucs on remadiate soil pollutants because of the challenge of separation after removal.Compared with single nano-material,functionlized nanocomposites generally dispalyed more excellent properties,which could not only effectively remove pollutants from water environment,but also could be used for the treatment of soil pollutants.This dissertation mainly studies on properation of functionlized nanomaterials.Because of the poperities of large specific surface area,high porosity,and many active sites,these functionlized nanomaterials exhibit high performance on heavy metal contaminants treatment in water and soil,or could efficiency control the loss of nitrogen fertilizer,and thus reduce the nitrogen pollution.In summary,the results are included in four chapters as follows:1.Magnetic core-shell carbon nanomaterials have been fabricated and used in removing Cr(?)from the environment.However,in previous research,thin carbon layer and lack of functional groups resulted in low amount of active adsorption sites and thus weak adsorption capacity,which was unfavorable for the application in heavy metal ions treatment.In the second chapter,core-shell magnetic Fe3O4@C nanospheres functionalized with active chemical groups were synthesized via a one-step template-free solvothermal process and employed to remove hexavalent chromium(Cr(?))in aqueous media.The structure of Fe3O4@C nanoparticles could be effectively adjusted by the concentration of precursor.The Fe3O4 core possessed a high magnetism for the convenient separation of Fe3O4@C from aqueous solution,high porosity and abundant functional groups(-OH,-COOH and C=C)of carbon layer contributed to a superior performance on Cr(?)removal.Therein,Cr(?)ions could be efficiently adsorbed into the carbon layer,and reduced to trivalent chromium(Cr(?))mainly by C=C,and the resulting Cr(?)were chelated by the-COOH group.Noteworthily,the carbon layer thickness,pore size,and amount of chemical groups significantly increased with the increase of Fe3O4@C particle size resulting in a rising removal efficiency on Cr(?).This study provides a promising approach for removing Cr(?)and may have a huge application potential.2.In recent years,magnetic ceramsite has been reported to be used in wastewater treatment due to its advantages of convenient separation from water and high mechanical strength.However,it is difficult for magnetic ceramsite to remove pollutants such as heavy metals from soil due to its low porosity,insufficient active sites,and more importantly,lack of continuous separation method.In the third chapter,a magnetic ceramsite coated by nano carbon spheres(MCCS)was fabricated,and then the MCCS was stabilized and functionalized by polyethylenimine to obtain a nanocomposite named as MCCSP.The nano carbon spheres possessed plenty of amino and oxygen-containing groups(-OH,-COOH)and distributed homogeneously on the surface of MC,meanwhile the size and dispersion of these NCS could be conveniently adjusted.MCCSP demonstrated a high adsorption capacity for Cr(?)which could be then reduced to low toxic trivalent chromium(Cr(?)),and the obtained Cr(?)could be chelated on the surface of MCCSP by protonated amine groups.Importantly,the resulting MCCSP-Cr could be conveniently collected from water and soil by a magnetic separation system.Therefore,this work provides a promising approach to remediate Cr(?)-contaminated water and soil and may have a high application value.3.With the development of industry,more and more waste RW was generated and most of it was dumped or buried,which not only led to a great consumption of manpower and material resources,but also caused serious environmental pollution because of its hard biodegradation.In recent years,several approaches have been developed for the application of waste RW as packing material or filter bed for NH3,H2S,and toluene.However,it was rather difficult for these approaches to be industrialized because of the low efficiency resulting from lack of effective modification method for waste RW.In the fourth chapter,a novel nanocomposite,named as ARWZ,was fabricated using zero-valent iron(ZVI)nanoparticles supported by acid-modified waste rock wool(ARW).ARW displayed a porous rod-like structure and could load plenty of ZVI nanoparticles.Meanwhile,ARW could effectively inhibit the aggregation and oxidation of ZVI nanoparticles because of steric-hindrance effect.ARWZ exhibited a large specific surface area and high removal capacity(197.69 mg/g)in 30 min for hexavalent chromium(Cr(?))from water and soil through adsorption and reduction,and the resulting ARWZ-Cr could be easily collected under a magnetic field because of the superior magnetic property.Importantly,when ARWZ was loaded in filter cotton with a micro/nano networks structure,the resulting system could be conveniently used as an excellent filter layer to control the migration of Cr(?).This work provides a low cost and promising approach to remove Cr(?),which also promotes the reuse of waste rock wool.4.Urea tends to be hydrolyzed by urease and then migrate to the environment,resulting in low utilization efficiency and severe environmental contamination.To solve this problem,a fertilizer synergist(FS)was developed using sodium humate transported by a nanonetwork through hydrogen bonds in the fifth chapter.FS could effectively inhibit the hydrolysis,reduce the loss amount,and enhance the UE of nitrogen.Furthermore,FS exerted significant positive effects on the expression of several nitrogen uptake-related genes,ion flux in maize roots,the growth of crops and the organic matter in soil.FS could modify the microbial community in soil and increase the number of bacteria involved in nitrogen metabolism,organic matter degradation,the iron cycle and photosynthesis.Importantly,this technology showed high biosafety and great potential in reducing non-point agricultural pollution.