Vertical Porous Nitrogen/boron Doped Carbon@clay Aerogels For Water Treatment

The shortage of fresh water resources is one of the important factors restricting human development.On one hand,polluted water need to be treated;on the other hand,advanced fresh water extraction technologies also need to be continuously developed.In this paper,green cellulose nanofibers(CNF)and montmorillonite(MMT)were blended to make aerogels that were carbonized to obtain carbon@clay aerogels for dye removal in water and photothermal seawater desalination.A vertical porous structure was realized in aerogels by directional freezing.Melamine formaldehyde(MF)and boric acid(BA)were used as dopant agent and also crosslink aerogel.The prrsent work analyzed the microstructures of aerogels.The adsorption and photothermal performance of composite aerogels were studied.The mechanism of dye adsorption and photothermal conversion were demonstrated.Nitrogen doped carbon@clay aerogels were prepared by adding different amounts of melamine formaldehyde.Their microstructure and dye adsorption properties were studied.The SEM image showed the nitrogen-doped carbon@clay aerogels still maintained horizontal microcellular structure with microchannels.The adsorption equilibrium concentration of nitrogen-doped carbon@clay aerogel on methylene blue and malachite green dyes were 192 mg/g and 900.5 mg/g,respectively.The adsorption fit well with the pseudo-second-order kinetic model and the Langmuir isotherm model.Methylene blue belong to a single atom layer adsorption on nitrogen-doped carbon@clay aerogel.When the mass percentages of MF accounted for 60% in organic precursor,carbon@clay aerogel had higher specific surface area,more mesopores and better adsorption performance.On this basis,nitrogen/boron co-doped carbon@clay aerogel were prepared by adding boric acid.We studied the microstructure,mechanical strength and adsorption properties of the nitrogen/boron co-doped carbon@clay aerogel.Comparing to nitrogen-doped carbon@clay aerogel,the specific surface area and pore volume of nitrogen/boron-doped carbon@clay aerogel increased by 3.20 and 2.75 times,respectively.The equilibrium adsorption capacity of methylene blue and malachite green increased to 223.2 mg/g and 1021.4mg/g,respectively.When the mass percentages of MF and BA were 66% and 8%,respectively,carbon@clay aerogel had a larger specific surface area,a more common mesopores and the best dye adsorption properties.Moreover,the nitrogen/boron co-doped carbon@clay aerogels displayed a higher mechanical robustness in liquid.The doped carbon@clay aerogel show higher light absorption.High framework stability enabled the application of carbon@clay aerogel as photothermal materials.The vertical porous structure of carbon@clay aerogel utilized Laplace force to have high water transport efficiency.The mesoporous structure and the rough inner surface contributed to the long distance of water and high efficiency transmission capacity.When the MF and BA in carbon@clay aerogel accounted for 66% and 8%,respectively,it had better photothermal conversion performance.