Preparation Of Amino-based Organic Composite Modified Bentonite And The Adsorption Properties For Uranium(?)

The ever-increasing demands of energy has accelerated the development of nuclear energy.The demands of uranium decreased as the application of nuclear power decreased.During the process of uranium mining and reactor,ammonds of high level waste water contained uranium was product.Which has potential harm to human body and environment.Therefore,it is essential to find an adsorbent to adsorb waste water in an economic and efficient way.Due to the adventures of large specific surface area and strong cation exchange capacity,bentonite has great value for adsorbing waste water.Based on Ca-Bentonite produced by Gaomiaozi,the surface modification of NaBentonite was carried out by polydopamine(PDA)on the basis of artificial sodium pretreatment.Dopamine modified bentonite(PDA-Bentonite);4-aminopyridine modified bentonite(4-AP-Bentonite)was prepared with 4-aminopyridine(4-AP)as organic modifier;Synthesis of organic composite adsorbent based on Na-Bentonite by chemical properties of chitosan quaternary ammonium salt(HACC),dodecyltrimethylammonium bromide(DTAB)and bentonite(DTAB-HACC/Bentonite).The effects of pH,temperature,contact time,initial concentration of U(?)and dosage on the adsorption of U(?)on the above three materials were investigated.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)were used.Fourier bentonites before and after modification were characterized by Fourier transform infrared spectroscopy(FT-IR)and energy dispersive spectroscopy(EDS).The morphology and structure of the modified bentonite were observed and analyzed.The mechanism.The research results show that:1.The PDA-Bentonite static adsorption experiment on U(?)shows that the optimum pH value of adsorption is 6,the removal rate of U(?)by PDA-Bentonite is up to 93.56%,and the reaction reaches equilibrium in about 120 min.The Langmuir isothermal model showed that PDA-Bentonite adsorption U(?)was a single-layer adsorption,and the saturated adsorption capacity was calculated to be 161.29 mg/g.The adsorption of U(?)by PDA-Bentonite was found to be a spontaneous endothermic reaction by thermodynamic parameters.The kinetic fitting results show that the adsorption reaction conforms to the quasi-second-order kinetic equation and is mainly affected by chemical adsorption.According to the characterization results of SEM,XRD and FT-IR,PDA was successfully coated on the surface of Na-Bentonite,and the-NH group on the surface of Na-Bentonite enhanced the adsorption capacity of U(?).2.The optimal pH of 4-AP-Bentonite adsorption U(?)is 6,the amount of adsorbent is inversely proportional to the adsorption amount,and the increase of temperature and initial concentration of U(?)is beneficial to the adsorption reaction.The reaction is at 120.The equilibrium is reached around min,and the maximum adsorption capacity can reach 136.43 mg/g.According to the Langmuir isotherm model,the saturated adsorption capacity was calculated to be 149.47 mg/g.The kinetic fitting results showed that the adsorption of U(?)by 4-AP-Bentonite accorded with the quasi-second-order kinetic equation,which was mainly affected by chemical adsorption.The thermodynamic parameters were used to infer that 4-AP-Bentonite adsorbed U(?)as a spontaneous endothermic reaction.According to the characterization results of XRD and FT-IR,the organic modifier 4-AP enters the layer of bentonite,and the interlayer spacing increases from 1.512 nm to 1.891 nm.The organic functional groups successfully combined with U(?)occur in Na-Bentonite.The complexation reaction increases the ability to adsorb U(?).3.The results of XRD and FT-IR analysis showed that the organic macromolecule DTAB-HACC entered the bentonite layer and the interlayer spacing increased to 2.207 nm.The adsorption of U(?)by DTAB-HACC/Bentonite mainly showed organic functional groups and U.(?)Coordination occurs.The optimum pH value of DTAB-HACC/Bentonite for U(?)adsorption was determined at pH=5 by static adsorption method,and the reaction reached equilibrium at about 90 min.According to the Langmuir isotherm model,the saturated adsorption capacity was calculated to be 74.46 mg/g.It was found by thermodynamic parameters that DTAB-HACC/Bentonite adsorption U(?)was an endothermic process and spontaneously proceeded.The adsorption was mainly by chemical adsorption.4.The maximum adsorption capacities of the three modified bentonites,Na-Bentonite and Ca-Bentonite were 146.05 mg/g,136.43 mg/g,69.93 mg/g,52.31 mg/g,22.67 mg/g,respectively.The order of adsorption effect is: PDA-Bentonite?4-AP-Bentonite?DTABHACC/Bentonite? Na-Bentonite?Ca-Bentonite,the adsorption capacity of U(?)is obviously improved after modification of Na-bentonite.