Preparation And Heavy Metal Ions Adsorption Properties Of Porous Organic Frameworks Materials

Pollution of heavy metal ions is a seriously environmental problem all over the world.Heavy metals ions may cause serious health risks toward human beings such as emphysema,neurological effects,kidney damage,hypertension and even cancer.Various methods,including adsorption,membrane filtration,chemical precipitation,ion exchange,etc.,have been applied for removal of heavy metal ions from wastewater.Adsorption is one of the most promising methods due to its relatively low-cost,highly effective,simple in operation and flexible in design.Porous organic frameworks(POFs)are widely used as adsorbent materials due to their high surface areas,excellent porosity and good physicochemical stability.Nitrogen atoms in at POFs have lone pair electrons which may coordinate with heavy metal ions,therefore,the porous materials containing nitrogen atom would exhibit a large number of adsorption sites and high adsorption capacities for metal ion removal.Cyanuric chloride has a triazine ring,therefore it is a good raw materials for preparation of nitrogen rich organic porous materials.In this paper,a series of new porous organic materials were synthesized using cyanuric chloride as raw materials.Then,their structures were characterized and adsorption properties were investigated.This thesis includes main research contents as followings.(1)Preparation and characterization of porous organic frameworks.Five novel porous organic frameworks(POF-1,POF-2,POF-3,POF-4 and POF-5)were synthesized by reactions of cyanuric chloride with compounds Bisphenol A,Bisphenol AF,Hydroquinone,1,5-Dihydroxynaphthalene or 4,4’-Sulfonyldiphenol,respectively.Their structures were characterized by FT-IR,elemental analysis,thermal stability analysis,scanning electron microscopy,X-ray diffraction and BET etc.(2)Adsorption properties of porous organic frameworks for heavy metal ions.Effects of pH values,initial metal ion concentration and adsorption time on adsorption of POF-1,POF-2,POF-3,POF-4 and POF-5 for heavy metal ions Pb(Ⅱ),Cu(Ⅱ),Cd(Ⅱ),Ni(Ⅱ)and Cr(Ⅲ)were investigated.Adsorption capacities of all five adsorbents for Pb(Ⅱ)and Cd(Ⅱ)were higher than that of Cu(Ⅱ),Ni(Ⅱ)and Cr(Ⅲ).Equilibrium time of these adsorbents for heavy metal ions are 60 minutes or so.(3)Adsorption properties of porous organic frameworks for heavy metal ions based on theoretical calculations.Porous organic frameworks(POFs)were designed based on DFT using the software Guassian09.The molecular structures and the adsorption model were optimized.Electron transfer and adsorption energy of POFs on Pb(Ⅱ),Cu(Ⅱ),Cd(Ⅱ),Ni(Ⅱ)and Cr(Ⅲ)were calculated.The results show that the nitrogen atom at POFs plays an important role in the adsorption of POFs for heavy metal ions,moreover,the adsorption of heavy metal ions is a spontaneous process.(4)Resourcizing technology of ammonium thiocyanate from phenol cyanogen wastewater.Mechanism of isomerization from NH4SCN to thiourea was supposed based on quantum chemistry calculations.Ammonia was employed as a catalyst to lower isomerization temperature and improved the yield of thiourea in the isomerization reaction.The yield of thiourea in the isomerization catalyzed by NH3 was improved up to 45.30%at the temperature of 80℃ and activation energy in the process of isomerization was reduced 54.71 kJ/mol.