Preparation And Characterization Of Magnetic Carbon Materials And Their Adsorption Properties For Tetracycline Hydrochloride In Aqueous Solution

Tetracycline antibiotics are a class of antibiotics produced by actinomycetes,including chlortetracycline,oxytetracycline,tetracycline and some semi-synthetic derivatives.Among them,tetracycline is widely used in the prevention and treatment of various pathogens in humans,livestock and aquaculture due to its broad spectrum and one of the most widely used and widely used antibiotics.With the dramatic increase in the use of tetracycline antibiotics,direct or indirect access to the environment poses a threat to ecosystems and human health.At present,the commonly used treatment methods for wastewater containing tetracycline antibiotics include chemical oxidation,biodegradation,and physical adsorption.Among them,the adsorption method is widely used for the removal of tetracycline in water due to its high efficiency and no by-product generation.In recent years,magnetic carbon materials with a core-shell structure have been widely used for adsorption and removal of heavy metals in water,but it is still rare to adsorb and remove tetracycline antibiotics in water.In view of this,in this study,magnetic carbon microspheres were prepared by one-step hydrothermal carbonization using chitosan and ferric chloride as raw materials,using scanning electron microscopy（SEM）,hysteresis loop（VSM）,and Raman spectroscopy（Raman）.Spectrum,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,thermogravimetric analysis（TGA）and other characterization methods were used to analyze the structural properties of magnetic carbon materials,and the initial concentration,pH,and coexistence were investigated.The effects of salt ion(k+,Ca²⁺,Na+),salt ion and pH compounding and temperature on adsorption removal were studied.The adsorption kinetics of tetracycline hydrochloride（TC）by magnetic carbon materials was studied,and the adsorption mechanism was discussed.The main research conclusions are as follows:（1）The magnetic carbon material is micron-sized spherical and the surface is rugged;the saturation ratio of the magnetic carbon material is between 57.7 and 12.7emu/g;the carbonized layer on the surface of the magnetic carbon material is amorphous carbon;the surface of the magnetic carbon material is rich.Containing active groups such as-C=O,-COOH,-NH₂;XPS wide scan results show that the magnetic carbon material adsorbent contains four elements of C,N,O and Fe.X-ray diffraction analysis showed that the magnetic carbon material contained five diffraction peaks,which was consistent with the triiron tetroxide standard card.（2）The adsorption amount of tetracycline hydrochloride increased with the increase of initial concentration of magnetic carbon material;when the concentration was less than 250 mg/L,the adsorption amount increased gradually;when the concentration was≥250 mg/L,the adsorption basically maintained equilibrium,and the adsorption amount was 19.31 mg/g.The adsorption amount of TC on the magnetic carbon material increases first and then decreases with the increase of pH.When pH=6,the TC removal rate was the largest,51.8%,and the adsorption amount was 46.5 mg/g.The amount of TC adsorbed by magnetic carbon material increases with the increase of NaCl,Na₂SO₄ and KCl concentration,but increases first and then decreases with the increase of CaCl₂ concentration.Under the condition of fixed NaCl concentration of0.5 mol/L,the adsorption amount increases first and then decreases with the increase of pH.Compared with the absence of NaCl,the adsorption amount increased to different degrees under the same pH condition after adding NaCl.In addition,after the addition of NaCl,the optimum pH of the adsorption is acid shifted.The change trend of adding KCl and NaCl is basically the same,but the adsorption trend is opposite when CaCl₂ is added.（3）At a temperature of 30℃,the adsorption of TC by magnetic carbon material accords with the Freundlich model.The adsorption of TC on the magnetic carbon material belongs to the physical attraction of the monolayer to attract each other under the action of hydrogen bonding;the electron acceptor interaction or the cation-πbond on the surface of the material can form a conjugate in the ring of the TC molecule.