| The rapid development of modern industry has caused serious environmental pollution.Heavy metal ion wastewater pollution has become a worldwide environmental problem.The methods used to remove heavy metals in water include ion exchange,ultrafiltration,reverse osmosis,electrodialysis,adsorption,chemical precipitation and so on.Adsorption method was widely used because of its simplicity,easy operation and repeatability.The key of adsorption method was to select suitable adsorbent.Cassava residue is the waste after cassava production of starch or alcohol,rich in starch and cellulose and other effective ingredients,rough surface,porous interior,can be modified by chemical,to increase its ability to capture heavy metal ions.The preparation of magnetic polymer microspheres with inorganic magnetic ions not only has the advantages of low cost and reproducibility,but also can be separated rapidly under magnetic conditions,thus becoming a promising adsorbent.In this study,cassava residues were used as raw materials to prepare heavy metal ion adsorbents of high molecular magnetic microspheres.The research includes three parts:(1)The magnetic microspheres of cassava residues were prepared by inverse emulsion method using cassava residues as raw materials,methyl methacrylate(MMA),acrylic acid(AA)and acrylamide(AM)as monomers.Cassava residues and magnetic microspheres were characterized by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR).The effects of different monomers on the adsorption properties of Pb2+ and Zn2+ by magnetic microspheres were investigated.(2)The magnetic microspheres were prepared from the cassava residues which was chemically modified by ethylenediamine and carbon disulfide.The structure and morphology of the product were characterized by scanning electron microscope(SEM),Fourier infrared spectrometer(FTIR)and X-ray diffractometer(XRD).The effects of grafting process parameters and adsorption conditions on the adsorption properties of Pb2+ and Zn2+ by magnetic microspheres were investigated,and the adsorption process was fitted by kinetics and isotherm model.(3)New aminated cassava residues magnetic microspheres were prepared by adding porogen on the basis of the above research.The ACRPM were characterized and analyzed by SEM,TEM,TGA,VSM,etc.The effects of adsorption conditions on the adsorption properties of Pb2+ and Zn2+ by ACRPM were investigated and the adsorption process was fitted by kinetics and isotherm model.The main findings are as follows:(1)When the volume of acrylic acid and methacrylate are 3.75 mL and 3 mL,respectively,the acrylamide is 1 g,the magnetic microsphere size is uniform,surface is smooth,shape is regular,and sphericity is good.The adsorption capacities of Pb2+ and Zn2+ on magnetic microspheres are 181 and 127 mg/g,respectively.(2)Cassava residue is successfully modified by ethylenediamine and carbon disulfide.When reaction temperature is 80 ?,time is 360 min,ethylenediamine is 120 mL,cassava residues amination effect is the best,and carbon disulfide is 10 mL,it is the best amount of yellowing reaction of cassava residues.The ACRM and SCRM have good dispersity and sphericity and the adsorption effect of Pb2+ and Zn2+ are improved obviously.The adsorption effect of SCRM on Pb2+ and Zn2+ is the best.When 35?,pH=5.5,the adsorption capacity of Pb2+ and Zn2+ on SCRM is 301 and 222 mg/g after 30min,respectively.The adsorption process was in accordance with the Langmuir isothermal adsorption model and the pseudo-second-order kinetic model.(3)The ACRPM have wrapped magnetic nanoparticles,which possess superparamagnetic properties.Added in porogen after,the microspheres size decreased from 18.5?m to 150 nm,and microsphere particle size reduction,the specific surface area increased,which provided more adsorption area for the adsorption adsorbents,and the adsorption capacity of Pb2+ and Zn2+ increased to 390 and 307 mg/g.The adsorption kinetics and isothermal adsorption model were fitted,and the results showing that the intraparticle diffusion is not the only control factor for the adsorption of Pb2+ and Zn2+.The adsorption and desorption results show that the adsorbent has good stability to remove Pb2+ and Zn2+ by 48%and 50%respectively after sixth reuse. |
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