Preparation Of Magnetic Bioch Ar And Investigation Into Adsorption Behavior Of Antibiotics In Aqueous Solution

Since its introduction in 1940,the antibiotics is widely used in every field of human life.However,in the global scope,the abuse of antibiotics results in an issue that antibiotics were released into the ecological environment,which poses a serious threat to human and the ecological environment.Because of unique advantages,the magnetic biochar is widely used as adsorbent for wastewater treatment.The magnetic biochar(MBC)was prepared using salix mongolica and has been adopted as a potential adsorbent for the removal of two sulfonamide antibiotics(sulfadiazine sodium and sulfadimidine sodium,SAS and SMS)and quinolone antibiotics(norfloxacin,NOR)from aqueous solution.The adsorption behavior and mechanism were analyzed.In this paper,salix mongolica was applied as a precursor to prepare the magnetic biochar(MBC)with the method of one-step pyrolysis,using zinc chloride as activator and ferric chloride as magnetizer.After complete randomalized design,the optimal preparation conditions of MBC was found.The mass ratio of salix mongolica,zinc chloride and ferric chlorider was 4:4:1,with activation temperature of 700°C and activation time of 1 h.Then the MBC was characterized by Scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),Fourier transform infrared spectrum(FT-IR),Specific surface area analysis(BET),Vibrating sample magnetometer(VSM),and The point of zero charge(pHPZC).The results showed the features of biochar and the magnetic properties of iron oxides were combined in a composite of MBC with a large specific surface area(1348 m~2/g)and fine magnetic properties(3.57 emu/g).Condition effects such as adsorption time,the pH of solution,salt concentration,temperature and initial solution concentration on the adsorption capacity of SAS,SMS and NOR onto MBC were studied by a series of static adsorption experiments.It showed the adsorption capacity of SAS and SMS onto MBC had no obvious relationship with the pH of solution and salt concentration.But it's opposite for NOR.The obtained experimental data were fitted by adsorption kinetic models and adsorption isotherm models respectively,and the models of fitting degree was analyzed according to the correlation coefficient and error.The results of kinetic research showed the adsorption kinetics of three kinds antibiotics was all best described by Elovich model and the pore diffusion was not the unique rate-limiting step for the process of adsorption.The isotherm research showed the Freundlich and Koble-Corrigan models were more validity to fit the process of adsorption for three kinds antibiotics.According to Langmuir model,the maximum monolayer adsorption capacity of MBC for NOR,SAS and SMS was 0.653,0.93 and 0.729 mmol/g at 298K,respectively.Thermodynamic parameters(such as gibbs free energy,enthalpy and entropy)were calculated,and the results indicated that the adsorption process of SAS,SMS and NOR onto MBC were spontaneous and endothermic.Based on the above research including the effect of pH,ionic strength and the infrared spectrum of MBC,The adsorption mechanism of SAS and SMS onto MBC was mainly including hydrophobic,hydrogen bond and?-?dispersion.For the adsorption process of NOR,the interaction of the?-?dispersion,the hydrophobic interaction,hydrogen bonding and the electrostatic interaction were critical factors.Moreover,the different adsorption behaviors of three substances adsorbed by MBC were different.Through analysises and comparison of results,the difference between the size of molecular and the adsorption interactions resulted in different adsorption behaviors in the microporous system.