Preparation Of Iron-based Biochar And Experimental Study On Removal Of Tetracycline And Ciprofloxacin

In recent years,drugs as emerging trace organic pollutants have received extensive attention.Among various medicines,the use of antibiotics is rapidly increasing worldwide and thus has received widespread attention.Adsorption is regarded as a promising method to remove antibiotic wastewater due to its advantages of low cost,simplicity and high efficiency,and no by-products.Among them,biochar is a new type of low-cost and high-efficiency adsorbent,and it is the most commonly used and effective adsorbent in the world to remove various pollutants in water.As a renewable resource,biochar is an ideal resource for water pollutant treatment environmental technology due to its economic and environmental benefits.Iron-based biochar material（MBC）can not only maintain the good pore structure of biochar material but also introduce oxygen-containing functional groups.At the same time,after adsorbing pollutants,rapid solid-liquid separation can be achieved through an external magnetic field,which improves the circulation of the material.Take advantage of performance and save costs.Therefore,MBC materials have great potential and application prospects in the treatment of antibiotic wastewater.In this study,starting from the preparation of iron-based biochar and activated with different activators,a series of excellent adsorbents were developed to remove antibiotic wastewater.Tetracycline（TC）and ciprofloxacin（CIP）were selected as target pollutants,and a series of MBCs prepared were characterized and analyzed by SEM,FTIR,BET,XRD,XPS,VSM,Raman,zeta potential and other analytical methods.The effects of different preparation methods and different activators on the structure and properties of MBC and the adsorption performance of TC and CIP were investigated.By exploring the influence of influencing factors（time,solute concentration,initial p H of solution,temperature,coexisting ions）on the adsorption performance of MBC,combined with adsorption kinetics,adsorption isotherm,and adsorption thermodynamic model fitting,we tried to explain the effect of MBC on TC and TC in aqueous solution.adsorption behavior of CIP,and further elucidated the adsorption mechanism.In addition,the reuse performance of MBC was also investigated by regeneration experiments.The main research contents of this paper are as follows:（1）The biochar base material BC（without using activator）was prepared by high temperature pyrolysis by using sugarcane bagasse as the biomass substrate,,and the adsorption characteristics and adsorption characteristics of BC on TC and CIP were investigated to provide a blank control for the subsequent MBC.The results showed that without the use of activator,the specific surface area of BC was only 241.24 m²/g,the surface morphology was blocked by large pores,and its maximum adsorption capacity for TC and CIP was 145 mg/g and 102 mg/g,and showed a high dependence on p H.（2）KFBC was prepared by a two-step method by using KOH as the activator and Fe Cl₃·6H₂O as the immersion solution.KFBC was prepared by a two-step method using KOH as the activator and Fe Cl₃·6H₂O as the impregnation solution.The characterization results show that the specific surface area of KFBC is increased to 241.24 m²/g,and the pore structure is also better.The maximum adsorption capacities of TC and CIP by KFBC were 563.07 mg/g and587.96 mg/g,respectively.The model fitting results indicated that the pseudo-second-order kinetic model was more suitable to describe the adsorption of TC and CIP on KFBC.The Freundlich isotherm model is more suitable to describe the adsorption of TC and CIP on KFBC.The main mechanisms for the adsorption of TC and CIP by KFBC include surface complexation of oxygen-containing functional groups,pore filling,π-πconjugation,and electrostatic attraction.（3）ZFBC was prepared by one-step co-pyrolysis of bagasse with Zn Cl₂ and Fe Cl₃ 6H₂O.ZFBC has good adsorption capacity and fast adsorption speed for TC and CIP,and the maximum adsorption capacity were 446.75,774.95 mg/g,respectively.The characterization results show that ZFBC has a good pore structure(S_BET=654.3 m²/g),strong magnetic properties（25 emu/g）and a high degree of graphitization.The pseudo-second-order model and the Freundlich model can describe the experimental data well,indicating that chemisorption is involved in the adsorption of TC and CIP on ZFBC,and the adsorption process is mainly a heterogeneous multi-layer physical adsorption.The possible adsorption mechanisms are mainlyπ-πconjugation,hydrogen bonding,pore filling,and electrostatic attraction.（4）In order to prepare an economical,efficient and easy-to-prepare green iron-based biochar,K₂Fe O₄ was innovatively used as an activator to modify the biochar.A new type of magnetic graphite biochar HFBC was prepared by one-step method using potassium ferrate as activator.The characterization results show that the material has the characteristics of high graphitization,strong magnetism,and porosity.HFBC-800 exhibits excellent adsorption capacity for TC and CIP,and its adsorption capacity is 2.7 and 4 times that of BC,respectively.The kinetic studies showed that the kinetic data fit the pseudo-second-order kinetic model.The experimental data of the isotherm fit the Freundlich model better.HFBC-800 can maintain stable and efficient adsorption capacity for TC and CIP in a wide p H range and under the interference of coexisting ions.In addition,HFBC-800 exhibits excellent regeneration performance and good superparamagnetic properties.The main adsorption mechanisms of TC and CIP by HFBC-800 may beπ-πconjugation,hydrogen bonding and pore filling.In conclusion,HFBC-800 has stable and high-efficiency adsorption capacity,good regeneration and excellent magnetic separation capacity,and is a very potential green adsorbent.