| The styrene-divinylbenzene copolymer?SDB?hydrophobic catalyst carrier is commonly used as a carrier for hydrogen-water liquid-phase catalytic exchange?LPCE?,and plays a crucial role in the treatment of thorium-containing wastewater and recovery of thorium.However,the currently used SDBs still have disadvantages such as low strength,poor dispersion and uniformity of load Pt,insufficient joint firmness,and poor mass transfer performance of Pt/SDB.In view of this,this paper carried out the study of copolymerization modification and synthesis of SDB,nanoparticle doping modification and synthesis,and the influence of SDB carrier loading on the mass transfer performance.Study on chemical doping modification of SDB:tyrene?St?,divinylbenzene?DVB?,methyl methacrylate?MM A?and tert-butyl styrene?tB S?synthesized?MMA-tBS?@SDB through quaternary copolymerization,which MMA and tBS used as modified monomers.Taking the volume ratio of MMA,tBS,DVB and the volume ratio of toluene and n-heptane as variable factors,the adsorption capacity of nickel ions was used as the evaluation standard,and the?MMA-tBS?@SDB optimization was obtained by using L9?34?orthogonal experimental design.The preparation conditions were as follows:n-heptane was used as a porogen,and the ratio of reactive monomers was St:DVB:MMA:tBS=1:0.85:0.3:0.3.On this basis,the MMA was replaced by acrylonitrile?AN?,methacrylic acid?MAA?and hydroxyethyl acrylate?HEA?,?MAA-tBS?@SDB,?HEA-tBS?@SDB and?AN-tBS?@SDB was synthesized by tetramer copolymerization with tBS,St,and DVB.FT-IR shows that the above monomers were successfully introduced into the quaternary copolymerization.TGA test analysis shows that the thermal stability of modified SDB carriers were better than that of SDB.The Ni2+ adsorption performance of the?MAA-tBS?@SDB is the best,close to SDB.The static water contact angle of?MMA-tBS?@SDB reached 154.08°,showing superhydrophobic properties,and the rest of the modified carriers were also superior to SDB?130.19°?.The compressive strength of?MMA-tBS?@SDB?AN-tBS?@SDB??HEA-tBS?@SDB were 68.38N,42.70N,and 43.61N,respectively,superior to SDB?31.10N?.Study on physical doping modification of SDB:Co-precipitation method was used to successfully prepare nano-Fe3O4 with the diameter of 6.05 nm.It was treated with silane coupling agent KH570 to increase the hydrophobicity,and further nano-Fe3O4@SDB was synthesized by suspension polymerization.The FT-IR results show that the modified nano-Fe3O4@SDB hydrophobic catalyst supports have been successfully synthesized.XRD results show that before and after hydrophobic modification of nano-Fe3O4 and before and after incorporation of SDB,the crystal form remains unchanged.The static water contact angle of nano-Fe3O4@SDB reaches 148.05°.The specific surface area,pore volume and pore size of nano-Fe3O4@SDB decrease with the increase of doping amount.With the increase of doping content,the adsorption rate of Ni2+ decreases,the compressive strength increases.As the doping amount increased,the compressive strength could reach 109.43 N,3.52 times that of SDB.Study on adsorption properties before and after SDB doping modification using Ni2+ simulated Pt2+:Testing the adsorption performance of SDB,?MAA-tBS?@SDB,and nano-Fe3O4@SDB for Ni2+.It was found that the adsorption process of Ni2+ by SDB and?MAA-tBS?@SDB accords with the Lagrangain pseudo first-order kinetics and belongs to physical adsorption.The adsorption process of nickel ion by nano-Fe3O4@SDB composite carrier conforms to the Lagrangain pseudo second-order kinetics.The adsorption enthalpies of Ni2+ on the three kinds of carriers are ?Ho<0,and all of them are exothermic reactions.In the experimental temperature range,The ?Go of?MAA-tBS?@SDB,nano-Fe3O4@SDB were more than 0.The ?Go of SDB with the temperature rises goes from negative to positive,indicating that lowering temperature favors adsorption reaction;the adsorption entropy of?MAA-tBS?@SDB,nano-Fe3O4@SDB were less than 0,indicating that the adsorption reaction is an entropy decreasing process,and SDB adsorption entropy ?So>0,expressed as the entropy increasing process.Langmuir and Freundlich adsorption isotherm fitting results show that the Langmuir adsorption isotherm is suitable for describing the adsorption kinetics of SDB and?MAA-tBS?@SDB,and the Freundlich adsorption isotherm is suitable for describing the adsorption kinetics of nano-Fe3O4@SDB.The theoretical parameters of KF adsorption isotherm are:10.422,74.022,and 79.458.The order of binding force to nickel ions from large to small is:nano-Fe304@SDB,?MAA-tBS?@SDB,SDB,indicating that nano-Fe304@SDB is stronger and more stable to nickel ions;the 1/n of SDB is greater than 1,and the 1/n of nano-Fe3O4@SDB and?MAA-tBS?@SDB are all less than 1,indicating that the adsorption performance was successfully obtained by modifying SDB.A 30mm x 400mm glass column was used to simulate the catalytic reaction bed in LPCE,and the conditions affecting the mass transfer performance were investigated within the glass column.In view of the relatively small mass of Pt nanoparticles and their negligible influence on the mass transfer performance,the SDB carrier on the size of 2.4 mm was directly used in this paper,which mixed with stainless steel ? filler on the size of 5 mm.Some processing conditions such as loading on mass transfer performance were also studied.The test results show that when SDB and filler are mixed in a glass column,the pressure drop is smaller and the mass transfer performance is better;and the pressure drop is reduced with the decrease of the gas flow rate,liquid flow velocity and temperature.Before the volume ratio reaches 4:1,the pressure drop decreases with the increase of the filling volume ratio.When the layered loading mode is two layers which the layer height is 6 mm,the pressure drop is the minimum.The liquid holding capacity is mainly affected by the liquid flow rate,and increases with the increase of the liquid flow rate and decreases with the flow rate of the gas. |
PDF Full Text Request