Preparation Of β-cyclodextrin-reduced Graphene Oxide Aerogel And Its Removal Of Two Herbicides

Herbicides are the main pesticides that easily pollute water enviroment.How to effectively remove herbicides from the water environment has attracted extensive attention.Graphene aerogel has extremely low density,high porosity and large specific surface area,making it an ideal adsorbent with superior adsorbability and recyclability.In addition,graphene aerogel can also be used as an ideal platform for improving photocatalytic efficiency due to its unique and excellent properties.In this study,β-cyclodextrin-reduced graphene oxide（β-CD-rGO）aerogel andβ-CD-rGO aerogel loaded with Ti O₂（β-CD-rGO/Ti O₂）were prepared by self-assembly hydrothermal method.Then,the adsorption of the aerogel and the effects of p H and ion concentration on the weakly acidic herbicide quinclorac and sulfentrazone were studied.The photocatalytic capacity ofβ-CD-rGO/Ti O₂ aerogel and the reusability of the two aerogels were also investigated.The main results were as follows:（1）β-CD-rGO aerogel was characterized by scanning electron microscope（SEM）,fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）,Raman spectra,thermal gravity analysis（TG）.Compared with rGO aerogel,β-CD-rGO had a more stable lamellar structure,was not easy to be deformed,had a larger specific surface area,more abundant porosity,and more abundant oxygen-containing functional groups.β-CD-rGO aerogel had stronger adsorption performance,and its adsorption capacity（Q=46.8 mg/g）for quinclorac was nearly doubled compared with rGO aerogel（Q=26.5 mg/g）.（2）The adsorption of weakly acidic herbicides sulfentrazone and quinclorac byβ-CD-rGO aerogel,as well as the effects of p H and ion concentration on the adsorption was investigated.It was found that the aerogel adsorbed the two herbicides spontaneously and exothermally,and the adsorption forces were mainlyπ-πinteraction and electrostatic interaction.The adsorption kinetics of sulfentrazone on aerogel conformed to pseudo-first-order kinetics（R²=0.9965）,and the adsorption isotherm was more in line with the Langmuir equation with all R² greater than 0.911.Therefore,the adsorption process was monolayer adsorption.And the adsorption process was divided into two stages.Intraparticle diffusion was the main control process of the adsorption rate.The p H had little influence on sulfentrazone adsorption.However,the increase of ion concentration inhibited the adsorption of sulfentrazone.The adsorption of quinclorac on the aerogel was more conform to pseudo-second-order kinetics（R²=1.0000）,adsorption isotherm conforms to be the Freundlich equation with all R²greater than 0.972,so the adsorption process was multi-layer adsorption.The adsorption process was also divided into two stages.Intraparticle diffusion was not the primary rate-controlling process for adsorption.The p H had a great influence on the adsorption of quinclorac,with an increase of p H,aerogel adsorption was weakened,and the increase of ion concentration slightly promoted on the adsorption of quinclorac.（3）β-CD-rGO/TiO₂ aerogel was prepared by hydrothermal self-assembly method,and characterized by SEM,FT-IR,XPS,XRD,Raman spectra,TG.Through the photocatalytic experiments,it was found that in the range ofβ-CD concentration of 0.5g/L-2 g/L,increase ofβ-CD concentration enhanced the photocatalytic ability.It was proved thatβ-CD-rGO/Ti O₂ could catalyze the degradation of quinclorac faster than Ti O₂,and the quinclorac could be completely degraded within three hours in UV lamp.Moreover,the photocatalytic capacity of the aerogel increased with the increase of Ti O₂content in the range of GO:Ti O₂=1:1-1:5.Theβ-CD-rGO aerogel prepared in this study had good reproducibility and was an environmentally friendly and economical adsorbent.β-CD-rGO/Ti O₂ aerogel had stronger photocatalytic ability compared with Ti O₂.β-CD-rGO andβ-CD-rGO/Ti O₂aerogel had good application prospects in the remediation of pesticide pollution.