Study On The Performance Of Chitosan Derived Carbon Aerogel On The Adsorption And Removal Of Sulfamethoxazole In Water

In recent years,antibiotic pollution and the accumulation of resistance genes caused by it have become increasingly prominent in the environment,posing a serious threat to the environment and human health.The adsorption method utilizes adsorption materials to enrich pollutants in water on the surface,and then uses solvent extraction,heating,and other methods to desorb pollutants,ultimately achieving the goal of removing pollutants.It has the characteristics of simple operation,low cost,and no secondary pollution.The carbon aerogel synthesized with natural polymer as precursor is a porous carbon material with three-dimensional network structure.It has rich surface functional groups,high specific surface area,good conductivity,and is environmentally friendly.It is an ideal adsorption material.In this paper,a series of porous carbon aerogel were prepared with chitosan and ZnCl₂ as precursors,and their adsorption and removal effects on sulfamethoxazole（SMX）,a target pollutant in water,were investigated.The main research content and conclusions are as follows:（1）Carbon aerogel with microporous structure were prepared using chitosan and ZnCl₂ as precursors.It was found that the specific surface area and total pore volume of carbon aerogel increased with the addition of ZnCl₂ and the increase of pyrolysis temperature.Among them,the carbon aerogel(Zn₁-CCA₁₀₀₀)prepared at a mass ratio of ZnCl₂ and chitosan of 1 and a pyrolysis temperature of 1000 ℃ showed the highest specific surface area（2899.9 m²/g）and total pore volume（1.2007 m³/g）.Scanning electron microscopy（SEM）observation revealed that the interior of Zn₁-CCA₁₀₀₀ is composed of large"shuttle"shaped pores,with rough pore walls and a structure filled with micropores（<2 nm）.Through X-ray photoelectron spectroscopy（XPS）and Fourier transform infrared spectroscopy（FTIR）characterization,it was found that the surface of Zn₁-CCA₁₀₀₀ contains functional groups such as C-N,C-O,C=O,pyridine-N,pyrrole-N,and graphite-N,which can provide sufficient sites for the adsorption of SMX.（2）The adsorption performance of carbon aerogel for SMX was investigated.The adsorption of SMX by Zn₁-CCA₁₀₀₀ includes a rapid adsorption stage before 24 hours and a slow adsorption stage after 24 hours.The adsorption conforms to the quasi second-order kinetic model and Langmuir isotherm model,and the equilibrium adsorption amount（q_e）and maximum adsorption amount obtained by fitting are 53.9 mg/g and 128.510 mg/g,respectively.Thermodynamic analysis shows that the adsorption of SMX on Zn₁-CCA₁₀₀₀ is a spontaneous,entropy increasing endothermic process.The adsorption of SMX by Zn₁-CCA₁₀₀₀ showed little change in the pH range of 3.0～9.0,and the presence of 2 m M Cl^-,NO₃^-,HCO₃^-,SO₄^2-,and NH₄⁺did not have a significant impact on the adsorption process.In addition,Zn₁-CCA₁₀₀₀ also has good adsorption effects on bisphenol A（BPA）,dimethyl phthalate（DMP）,and atrazine（ATZ）,indicating its universality in the adsorption and removal of pollutants.By comparing the FTIR and XPS spectra of carbon aerogel surface before and after adsorption,it can be inferred that the adsorption mechanism of carbon aerogel for SMX mainly includes pore filling,π–πEDA interaction,hydrogen bond interaction,electrostatic interaction and hydrophobic interaction.（3）The desorption removal of SMX and the regeneration performance of Zn₁-CCA₁₀₀₀under the assistance of Joule heat were investigated.Based on the experiments,compared to H₂O,dilute HCl（0.1 M）,Me OH,and Me OH/HCl（0.1 M）mixture with a volume ratio of 1:1had the best desorption effect on SMX.After regeneration,the q_e value returned to 42.6 mg/g,and the recovery percentage reached at 78.5%.The temperature has a significant impact on the desorption of SMX.As the desorption temperature increases from 20℃ to 60℃,the q_e value and removal rate of regenerated Zn₁-CCA₁₀₀₀ on SMX increase from 42.1 mg/g vs 63.1%to54.2 mg/g vs 81.0%.Zn₁-CCA₁₀₀₀ has high conductivity and exhibits good Joule heating effect under a certain applied voltage.When the input voltage is 3 V,using the Joule heat generated by the Zn₁-CCA₁₀₀₀ pore wall in a filtration mode with a flow rate of 2.5 m L/min,the desorption solvent temperature can be maintained at around 60℃,and the desorption rate of SMX can reach 98.4%.After three adsorption desorption cycles,the desorption rate of SMX can still reach 84.8%,which is higher than the room temperature desorption system（69.5%）.