The Synthesis Of Magnetic Dual-mesoporous Carbon Spheres And Their Adsorption Properties

Mesoporous carbon materials with concentrated pore-size distribution, high surfacearea, large pore volume, and excellent biocompatibility have attracted technological interestfor their potential applications in adsorption, catalysis, gas separation, drug delivery,electrochemical energy storage and other fields, and energy storage systems on account oftheir mesoporous structure. However, carbon powders are difficult to separate fromsolutions. The conventional approach normally involved a filtration or centrifugationprocedure, which was rather complex. On the other hand, mesoporous carbon materialsoften feature low micropore sizes, which limit their application in many fields.Herein, we present a simple one-step method to synthesize magnetic Fedual-mesoporous carbon spheres, magnetic Ni dual-mesoporous carbon spheres andmagnetic FeNi dual-mesoporous carbon spheres. In this method, furfuryl alcohol was usedas a carbon precursor, silica nanoparticles were used as a template precursor, hydrated ironnitrite, hydrated nickel nitrite, hydrated iron nitrite and hydrated nickel nitrite were used asa magnetic precursor. The morphologies, structural parameters, and magnetic properties ofthe materials were evaluated via X-ray diffraction, N2sorption analysis, scanning electronmicroscopy, transmission electron microscopy, Raman spectroscopy and physical propertymeasurements. Bovine serum albumin (BSA), methylene blue (MB), acid red114(AR114),tretinoin was selected as the adsorption model, the adsorption behavior of macromoleculesand small molecules on magnetic dual-mesoporous carbon microspheres was investigated. (1) The synthesis of magnetic Fe dual-mesoporous carbon spheres and modification.Magnetic Fe dual-mesoporous carbon spheres with large pore sizes were synthesized by asimple one-pot method, in which furfuryl alcohol was used as a carbon precursor, silicananoparticles were used as a template precursor, and hydrated iron nitrite were used asnickel sources. The effects of Fe(NO3)3·9H2O loading amount on the morphologies,structural parameters, and magnetic properties of the materials, were evaluated via someway. The materials show two systems of pores centered at8and27nm. The specificsurface area and the total pore volumes decreased with increasing amount ofFe(NO3)3·9H2O by N2sorption analysis. The increase in saturation magnetization strengthswith increasing Fe(NO3)3·9H2O loading amount. The SEM images show a sphericalmorphology and a particle diameter of15μm to20μm. Fourier transform infrared (FTIR)spectroscopy showed that the amino group was grafted onto the surface of the materials.The materials of amino-functionalized grafting still show a spherical morphology and twosystems of pores.(2) The synthesis of magnetic Ni dual-mesoporous carbon spheres. Magneticdual-mesoporous carbon spheres containing nickel nanoparticle were synthesized throughin-situ in one pot, wherein furfuryl alcohol was used as a carbon precursor, silicananoparticles as a silica template precursor and hydrated nickel nitrite as a nickel source.The effects of hydrated nickel nitrite loading amount on the structural parameters,morphologies, and magnetic properties of the samples were evaluated by some way. SEMexhibited a spherical morphology and had a particle diameter about16μm. The materialsshowed two systems of pores centered at9and27nm. The specific surface area and thetotal pore volumes decreased with the increase of hydrated nickel nitrite loading. Thesaturation magnetization strengths increased with increasing Ni(NO3)2loading.(3) The synthesis of magnetic FeNi alloy dual-mesoporous carbon spheres. We present asimple one-pot method to synthesize magnetic FeNi alloy dual-mesoporous carbon sphereswith large pore sizes. Furfuryl alcohol was used as a carbon precursor, silica nanoparticleswere used as a template precursor, and hydrated iron nitrite and hydrated nickel nitrite wereused as FeNi alloy sources. The effects of Fe(NO3)3and Ni(NO3)2loading amount on the structural parameters, morphologies, and magnetic properties of the samples were evaluatedby some way. Experimental results showed that two systems of pores centered at8and27nm, the specific surface areas and total pore volumes of the carbon microspheres decreasewith increasing loading amount of metal nitrates. The SEM images show a sphericalmorphology and a particle diameter of10μm to30μm. These saturation magnetizationstrengths increased with increasing metal nitrate loading. The saturation magnetizationstrength of the products could easily be adjusted by varying the amount of metal nitratesused during synthesis.(4) The adsorption of BSA on magnetic Fe dual-mesoporous carbon spheres. BSA wasselected as the adsorption protein model, the adsorption behavior of BSA on magnetic Fedual-mesoporous carbon microspheres was investigated. The adsorption capacity of BSAon magnetic Fe mesoporous carbons was mainly affected by the specific surface area, porevolume of the material, pH value of solution, and ionic strength. The adsorption capacitydecreased with increasing Fe(NO3)2loading. For M-1, M-2and M-3, qmwas591,538,465mg/g, respectively. At pH4.7(isoelectric point of BSA), the maximum BSA adsorptionwas achieved. The reason was that the carbon surface-BSA electrostatic attractiondisappears. The concentration of NaCl is1M, the maximum BSA adsorption was achieved.When the concentration of NaCl exceeded1M, BSA might form larger agglomeration,which is difficult to diffuse into the pore channel with a pore size of8nm, thereby blockingmthe pore entrance. The Sips adsorption isotherm equationq q(Kc)m1(Kc)mwas used to fitthe adsorption data, qmis the adsorption capacity, K is the equilibrium constant and m is theheterogeneity coefficient.(5) The adsorption of methylene blue (MB) and acid red114(AR114) on magnetic Nidual-mesoporous carbon spheres. MB and AR114as model dye pollutants, the adsorptionbehavior of MB and AR114on magnetic Ni dual-mesoporous carbon microspheres wasreported. The results showed that the samples had fast adsorption ability for dye andexcellent magnetic responsiveness. The adsorption capacity decreased with increasingNi(NO3)2loading. The adsorption capacity of MB is higher than that of AR114for the same carbon materials, which was explained by solubility, electrostatic interactions, molecularweight, and molecular size. The adsorption amount could be described bypseudo-second-order equation with the coefficients (R2)>0.99: tq11kq2t, qmwasmqmadsorption capacity, k was adsorption rate constant. The adsorption capacity and adsorptionrate constant increased with the increase of the specific surface area and pore volume of thematerials.(6)The adsorption of tretinoin on magnetic FeNi dual-mesoporous carbon spheres.Tretinoin as model teratogens, the adsorption behavior of tretinoin on magnetic FeNidual-mesoporous carbon microspheres was investigated. The results shows that theadsorption capacity decreased with increasing Fe(NO3)2and Ni(NO3)2loading. Rapidadsorption was observed followed by a slower adsorption process until equilibrium wasachieved. This phenomenon could be explained to involve two steps: adsorption of tretinoinmolecules from the bulk solution to the carbon microsphere surface and diffusion of themolecules into the interior pores of the carbons. A simple equationq qmkt/(1kt)couldbe used to fit the data with a correlation coefficient of0.999, k is the initial adsorption rateand qmis the maximum adsorption amount. Increases in k and qmwere in accordance withthe increases in specific surface area and pore volume of the nanoparticles.In the present paper, we present a simple one-pot method to synthesize magnetic Fedual-mesoporous carbon spheres, magnetic Ni dual-mesoporous carbon spheres andmagnetic FeNi dual-mesoporous carbon spheres. Synthesis of the silica template andimpregnation are completed in situ in one pot such that presynthesis of the silica templateand additional impregnation steps are no longer necessary. The synthesized materials withbimodal pore structures can enhance their surface areas and pore size.Part of this research has passed the production appraisal hosted by Guangdongdepartment of science and technology and has won the third level prize of scientific andtechnological achievements of Guangdong Province (2013).