Preparation Of Modified Sycamore Flocs-based Biochar And Its Adsorption Of Antibiotics In Water

In recent years,the environmental problems caused by antibiotic pollution are very serious,and the antibiotics entering the water body pose a serious threat to human health and environmental safety.Biochar prepared by using waste biomass as raw material can well adsorb antibiotic drugs in water.In this study,Sycamore Flock(SF),which has an impact on human health and environmental safety,was used as raw material to prepare sycamore flock-based biochar(SFB2-900)by K2CO3 modification.Oxytetracycline hydrochloride(OTC-HCl)and Ciprofloxacin(CIP)were selected as typical antibiotics,and single antibiotics and compound antibiotics were removed from water by adsorption method.The specific research results are as follows:(1)The preparation conditions of SFB2-900 are K2CO3:BC(g/g)is 2:1,activation temperature is 900℃ and activator is K2CO3.The material prepared under the above conditions is a mesoporous material with high specific surface area(1651.27 m2/g),aromaticity and hydrophobicity.The adsorption capacity of SFB2-900 for OTC-HCl reached 730.24 mg/g at room temperature,and the adsorption process was significantly inhibited at high pH(pH>9).Na+ in the solution promotes the adsorption through the salting-out effect and shielding effect,while Mg2+ and Al3+ inhibit the adsorption,and HCO3-and CO32-reduce the pH of the solution by hydrolysis,thereby inhibiting the adsorption of SFB2-900 on OTC-HCl.Kinetic analysis showed that the adsorption process conformed to pseudo-second-order kinetics,and chemical adsorption was involved in the adsorption process.The isotherm data at 15℃,25℃ and 35℃ fit well with the Langmuir model,indicating that SFB2-900 adsorbs OTC-HCl in a single layer.SFB2-900 shows excellent OTC-HCl adsorption capacity in different water bodies and has a good regeneration effect.The adsorption experiments,the characterization of the materials before and after the adsorption,and density functional theory(DFT)calculations show that the adsorption of OTC HCl by SFB2-900 involves pore filling,ππ electron donor-acceptor interaction(π-π EDA),electrostatic interaction and H-bond interaction(2)The adsorption capacity of SFB2-900 for CIP reached 430.25 mg/g.The adsorption capacity at different pH values is still above 400 mg/g.Both Na+ and Mg2+promoted the adsorption of CIP by SFB2-900,while Al3+ inhibited the adsorption of CIP.HCO3-and CO32-decrease the pH of the solution by hydrolysis slightly inhibiting the adsorption.The kinetic data fit best with the pseudo-second-order kinetic model,and the larger the dosage,the faster the initial adsorption rate.The isotherms at different temperatures(25℃,35℃ and 45℃)fit the Langmuir model well,and thermodynamic studies show that the increase in temperature is not conducive to the adsorption of CIP by SFB2-900.DFT calculation shows that the absolute value of Eabs of neutral CIP molecules is the largest,indicating that the adsorption effect is the best under neutral conditions.Response surface optimization experiments show that SFB2-900 has the largest CIP adsorption capacity(460.323 mg/g)under the optimal adsorption conditions(Dosage:0.06 g/L,C0:52.93 mg/L,pH:7.01).After 16 adsorption-desorption cycles,SFB2-900 completely lost its adsorption capacity for CIP.The characterization results show that pore filling,π-π EDA and electrostatic attraction are all involved in the adsorption of CIP.(3)Due to the antagonism between antibiotics in the composite system,the adsorption performance of SFB2-900 to antibiotics is much lower than that of the single system.Dosing research shows that SFB2-900 is more likely to adsorb OTC-HCl in water.The adsorption capacity of SFB2-900 for OTC-HCl and CIP decreased with the increase of pH,and the adsorption of CIP by SFB2-900 was less affected at high pH.Al3+ and CO32-in the solution inhibited the removal of antibiotics in the composite system.The kinetic data show that the adsorption of antibiotics in the composite system fits the pseudo-second kinetic order model well(R2>0.999).The adsorption isotherm data at different temperatures are in line with the Freundlich model,indicating that the adsorption of antibiotics in the composite system is double-layer adsorption,and heating is beneficial to the removal of antibiotics.The characterization analysis of the materials before and after adsorption shows that the adsorption of antibiotics is mainly caused by pore filling,π-π EDA interaction and electrostatic interaction.