Preparation And Performance Study Of Functional Sodium Alginate-based Aerogel

Aerogel materials have ultra-low density,high porosity,and high specific surface area,which exhibite superior performance in applications such as high-efficiency adsorbents,chemical sensing,electrocatalysis,and electrode materials.In recent years,with the deep development and utilization of marine resources,the high value application of sodium alginate-based aerogel materials has attracted much attention.In this paper,sodium alginate-based aerogel(ESA)was prepared by freeze-drying sodium alginate extracted from seaweed and its function was regulated.Surface chemical modification of sodium alginate-based aerogel by octadecyltrichlorosilane(OTS);regulation of its fluorescence performance by blending sodium alginate solution with nano-carbon quantum dots and the construction of magnetic alginate carbon aerogel(CA-900/Ni-P-13)by high-temperature carbonization and electroless plating.The functionalized sodium alginate-based aerogel materials were characterized by field emission scanning electron microscopy(FESEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and specific surface area test(BET).The research conclusions are as follows:(1)ESA and OTS were esterified,the surface free energy was reduced from 58.9 J to 9.6 J,and the static contact angle was increased from 44° to 134°,indicating that ESA has changed from hydrophilic to hydrophobic.As shown in the SEM images,streaky micro-nanostructures appeared on the surface of sodium alginate-based hydrophobic aerogel(S-ESA).X-ray energy spectrometer(EDS)analysis showed that Si element appeared in S-ESA and the distribution was relatively uniform.Further analysis by XPS showed that the Si element mainly existed in the form of Si-O-Si and Si-O-C.The adsorption properties of two aerogel materials on peanut oil,dimethyl silicone oil,vacuum pump oil were tested before and after modification.Compared with pure sodium alginate-based aerogel,OTS-modified S-ESA has a selective adsorption for the above three Oils.(2)With L(+)-ascorbic acid as the carbon source,the nano-carbon quantum dot solution prepared under the conditions of methanol-water ratio of 1:1,90 min and 160 °C has the highest fluorescence intensity and no dependence on the excitation wavelength.From the transmission electron microscope(TEM),it was observed that the nano-carbon quantum dots were uniformly distributed in the solution,and the average particle diameter was 3.7 nm.The nanocarbon quantum dots are blended into the ESA in different ratios.It was observed from the SEM that the nano-carbon quantum dot-regulated alginate-based fluorescent aerogel(FCSA)maintained the original sheet-like hierarchical structure,but the layer thickness increased slightly and the layer was looser between layers.Fluorescence emission spectroscopy(PL)analysis showed that the fluorescence intensity of FCSA was proportional to the content of nano-carbon quantum dots,and reached the maximum when the nano-carbon quantum dots increased to 10%,but the fluorescence intensity was sharp declined when the proportion of nano-carbon quantum dots continued to increase to 15%.(3)Alginate carbon aerogel(CA)is formed by a high temperature carbonization.At the carbonization temperature of 900 °C,the surface of the prepared sample was rich in nano-scale porous structure,and BET analysis showed that the specific surface area of CA was as high as 1234 m2/g after high-temperature carbonization and the pore diameter was about 4.2 nm.The surface of CA was doped with heterogeneous micro-nanoparticles by electroless plating technique,and alginate carbon aerogel with magnetic properties was obtained.SEM observation indicated that the nickel(Ni)and phosphorus(P)elements were uniformly doped to the surface and inside of CA;XRD analysis showed that there was a distinct diffraction peak at 2?=45.6°,corresponding to Ni with face-centered cubic structure(111)crystal plane;EDS analysis indicates that the formed magnetic carbon aerogel material is mainly composed of four elements: C,O,Ni and P,and further analysis by XPS showed that Ni and P elements exist mainly in the form of Ni,P element and their compounds.