Adsorption Of Quinolons By Covalent Organic Gel Materials H_cOGS

As antibiotics are widely used,some antibiotics inevitably flow into the environment,and the resulting environmental pollution problems pose a serious threat to human health and ecological safety.The adsorption method is favored because of its several advantages such as simple process,low cost,low energy consumption,high removal efficiency,and no toxic intermediates.Therefore,the search for green,efficient,and cheap adsorbents has become the focus of scholars'research.In recent years,it has discovered the excellent potential of covalent organic polymers in the environmental field.As a class of covalent organic polymers,covalent organic gels have the characteristics of simple synthesis and high yield.In this paper,a set of covalent organic gel materials H_COGs were designed and prepared as adsorbents,and their research was carried out on their adsorption properties and mechanisms for two typical quinolone antibiotics,ciprofloxacin and norfloxacin.Based on the properties and structural characteristics of ciprofloxacin and norfloxacin,this paper designs a group of porous covalent organic gel materials HCOGs,which have anionic skeleton,conjugated?bonds,hydrophobic characteristic and hydrogen bonding sites.Benzene-1,3,5-tricarbohydrazide,terephthalaldehyde,4,4'-biphenyldicarboxaldehyde,and 4,4''-p-Terphenyldicarboxaldehyde were used as raw materials,and the three covalent organic gel materials H_COG-1,H_COG-2,and H_COG-3 were synthesized through Schiff base condensation reaction.X-ray diffraction?XRD?,solid-state ¹³C cross-polarization/magic-angle spinning nuclear magnetic resonance(¹³C CP/MAS NMR),Field-scanning electron microscope?SEM?,BET surface area?BET?,Fourier transform infrared spectra?FT-IR?,thermogravimetric analysis?TGA?,Zeta potential,rheology test and other analytical methods were used to characterize the physical structure and chemical properties of HCOGs.The results of characterization show that H_COGs materials were successfully synthesized and all have good thermal stability;the three materials are all amorphous structure;the BET surface area of H_COG-1,H_COG-2,H_COG-3 are measured to be 150,50,4 m²/g,respectively,and all the three materials have a wide pore size distribution from micropores to macropores.The adsorption properties and influencing factors of ciprofloxacin and norfloxacin by H_COG-1,H_COG-2,and H_COG-3 were studied respectively.The results show that all three materials can achieve quick adsorption,equilibrium can be reached in 30 minnutes.The adsorption amount of H_COGs to antibiotics gradually increased with the increase of the initial pH value of the solution.When the pH value exceeded 8.0,the adsorption amount hardly increased.The metal cations in solution will compete with antibiotics for adsorption,which will reduce the amount of adsorption,but as the concentration of metal cations increases,the rate of reduction of the amount of adsorption tends to be gentle.The adsorption process conforms to pseudo-second-order kinetic model,and the adsorption rate is linearly related to the amount of HCOGs as well as the concentration of antibiotics.According to the Weber-Morris intraparticle diffusion model,the adsorption process is divided into two steps involving external film diffusion and intraparticle diffusion,and the rate of external film diffusion is greater than intraparticle diffusion.The adsorption process of all the three H_COGs abide by the Langmuir isotherm model,which means the antibiotics are uniformly adsorbed on the surface of H_COGs,and furthermore,the adsorption is a chemical process.At a temperature of298K,the saturated adsorption capacity of H_COG-1,H_COG-2,H_COG-3 to ciprofloxacin was 46.55,19.25,10.18 mg/g,and to norfloxacin was 71.02,20.13,11.20 mg/g,respectively.The adsorption mechanism of quinolones on HCOGs includes electrostatic interactivity,hydrophobic interaction,?-?stacking/interactions,hydrogen bonding,and the pore filling effect of H_COGs due to their BET surface area and proper porosity.All the five action mechanisms above coexist and play a role in the adsorption process.The H_COGs materials designed and prepared in this paper show fast and stable adsorption of quinolones,and they have good reproducibility.The structure of the regenerated material has no significant change compared with the structure of the original material.This work has certain guiding significance for the application of covalent organic polymer materials to the adsorption of antibiotics in wastewater.