Adsorption Characteristics Of Tetracycline In An Aqueous Solution Using Magnetic Modification Biochar

With the rapid development of animal husbandry and pharmaceutical industries,the excessive use of tetracycline leads to its residue in the environment,posing a threat to the ecological environment and biological health.How to effectively reduce the residue of tetracycline in the environment has attracted much attention.Previous studies have shown that biochar has good adsorption capacity for antibiotics.Therefore,the adsorption method is an effective way to remove tetracycline from aqueous solution.The key is to choose an adsorbent with better adsorption effect and highly cost-effective performance.This research uses Lentinus edodes,an agricultural waste,as raw material.The pristine biochar(PBC)was prepared by the muffle furnace oxygen-limited burning method at different pyrolysis temperatures.In order to solve the problem that PBC is difficult to separate from the aqueous solution after adsorption,the PBC was magnetized by the co-precipitation method and the pyrolysis impregnation method.Through the characterization of biochar and batch adsorption experiments,the adsorption behavior of tetracycline was systematically analyzed.Furthermore,the adsorption effect of tetracycline on the magnetic biochar(MBC)prepared by different magnetization methods was compared.Finally based on machine learning theory,a random forest,gradient boosting tree,and artificial neural network model are constructed to fit the adsorption effect of biochar on tetracycline in aqueous solution,combining this research and related reference and taking the physical and chemical properties and adsorption conditions of biochar as input variables.The main results of this study are as follows:(1)Three kinds of PBC(PBC300,PBC500,PBC700)were prepared using Lentinus edodes as raw material at different pyrolysis temperatures.With the increase of pyrolysis temperature,the content of C element in biochar increased from 43.58%to 50.57%,the content of O element decreased from 30.44%to 11.63%,and then H/C,O/C and(O+N)/C decreased accordingly.The number of surface functional groups of biochar gradually decreases with increased aromaticity and decreased polarity and the specific surface area of biochar increased.These changes in physical and chemical properties increase the adsorption capacity of biochar.The results of adsorption experiments show that PBC300 and PBC500conform to the Langmuir isotherm adsorption model,and PBC700 conforms more to Freundlich.The quasi-secondary kinetic model can better fit the adsorption process of tetracycline on the three PBC.(2)Two MBC(MBC-1 and MBC-2)were prepared by co-precipitation method and pyrolysis impregnation method,respectively.Compared with the PBC,MBC-1 and MBC-2had a larger specific surface area and more abundant surface functional groups.The adsorption process of tetracycline by MBC-1 and MBC-2 conforms to the quasi-second-order kinetic model,and the isotherms of MBC-1 and MBC-2 conform to the Langmuir model best.The maximum adsorption capacity of MBC-1(51.10mg/g)and MBC-2(39.15mg/g)were both greater than that of PBC(PBC700,16.95mg/g),indicating that magnetization effectively promotes the effect of biochar on tetracycline adsorption.The Fe content of MBC-1 was 2.3times that of MBC-2.The iron oxide in MBC-1 provides more-OH groups,which act as hydrogen bond donors and recipients,thereby enhancing the hydrogen bond between MBC and tetracycline.In addition,the p Hpzc of MBC-1 and MBC-2 were 4.2 and 6.1,respectively.Compared with MBC-2,the p Hpzc of MBC-1 is closer to the p Ka(3.3)of tetracycline,which indicates the charge auxiliary hydrogen bond formed between MBC-1 and tetracycline was stronger,so MBC-1 has better tetracycline adsorption performance than MBC-2.(3)The prediction results of the machine learning model about biochar adsorption on tetracycline showed that the random forest prediction effect(RMSE=0.0288,R~2=0.9816)was better than the gradient-enhanced tree and artificial neural network.The results of the relative importance analysis showed that the initial concentration ratio,solution p H,specific surface area,and ash had a greater influence on the predicted results of adsorption efficiency.MBC-1 has good magnetic recyclability and reusability,which provides new ideas for adsorption tetracycline in aqueous solution by using biochar and resource utilization of Lentinus edodes.The relative importance and partial dependence graph analysis can guide the rational application of biochar treating tetracycline in the wastewater.