Study On Adsorption And Photocatalytic Degradation Of Ciprofloxacin On Biochar And C/BiOBr Composite

Ciprofloxacin（CIP）is a representative fluoroquinolone antibiotic with good antibacterial and antibacterial effects.Due to the abuse of antibiotics and the problem of difficulty in self-degradation in the environment,it was becoming more harmful to humans.Therefore,it was an urgent need to find a treatment method for efficiently removing CIP.In this study,CIP was used as the target pollutant,and biochar prepared under different conditions（pyrolysis temperature 300℃,400℃,500℃,pyrolysis time 2h,3h,4h）through adsorption test,and carried out structure morphology and CIP adsorption Characteristic analysis,and screened out the best adsorption effect of biochar.The biochar with the best adsorption effect was combined with BiOBr,the composite material was characterized and analyzed,and the optimal synthesis ratio of the composite material was discussed and its adsorption and degradation characteristics of CIP were analyzed.In order to further enhance the removal ability of CIP,the biochar with the best adsorption effect was modified with HNO₃,CaCl₂,H₂O₂ and Na OH,respectively,and the modified biochar was compounded with BiOBr to explore its CIP adsorption and degradation characteristics.The main research results are as follows:（1）The corn stalk was used as the raw material,the adsorption kinetics of biochar prepared under different conditions（pyrolysis temperature 300℃,400℃,500℃;pyrolysis time 2h,3h,4h）for CIP adsorption were consistent with Pseudo-second-order kinetics,the adsorption isotherm conforms to the Langmuir adsorption isotherm model,and the adsorption of biochar on the CIP was spontaneous,endothermic,and random.Among them,the biochar with a pyrolysis temperature of 500℃and a pyrolysis time of 3h had the largest adsorption capacity of 5.20 mg·g^-1.（2）As the pyrolysis temperature increased,the yield of biochar is less affected by the pyrolysis time.An increase in the pyrolysis temperature would make the walls of the pores of the biochar thinner and reduce the surface functional groups.Inorganic substances would be formed at the pyrolysis temperature of 400～500℃.（3）In the test pH range（3～11）,the adsorption capacity of biochar to CIP first increased and then decreased with the increase of pH,reached the maximum value of 5.20 mg·g^-1 at pH=5.In the influence of background electrolyte type on biochar adsorption CIP:Al³⁺>Ca²⁺>K⁺,except for Al³⁺,the adsorption of biochar to CIP would decrease with the increase of background electrolyte concentration.Cationic surfactants could inhibit the adsorption of biochar to CIP;as the concentration of anionic surfactants increased,it would first promote the adsorption of biochar to CIP and then decrease;non-ionic surfactants would keep the adsorption of biochar to CIP to a certain extent.（4）The biochar with the best adsorption effect and BiOBr prepared C/BiOBr composites according to different C/Bi mass ratios（1%C,2%C,4%C and 6%C）.Among them,the analysis of SEM,XRD and XPS proved that biochar and BiOBr had been compounded.In the PL analysis,it was proved that the introduction of biochar can inhibit the recombination of the photogenerated electron holes of BiOBr.The adsorption behavior of C/BiOBr on CIP conforms to the Pseudo-second-order kinetic equation and Langmuir adsorption isotherm model.In the photocatalytic degradation process,2%C/BiOBr had the highest photocatalytic efficiency of 92%.（5）When the initial CIP concentration was 10 mg·L^-1,pH=5,and the catalyst dosage was 1.0g·L^-1,2%C/BiOBr has the highest catalytic efficiency of 96.8%.After 4 times of degradation,2%C/BiOBr still had a degradation efficiency of 85%.The order of action of the three active species in the degradation process was·O₂^->h⁺>·OH.（6）The biochar with the best adsorption effect was modified in a solution of HNO₃,Na OH,CaCl₂ and H₂O₂ with an impregnation ratio of 1:10 and a concentration of 0.1 mol·L^-1.Modified C/BiOBr composites were prepared by compounding with BiOBr at a ratio of 2%C with the above-mentioned optimum C/Bi.It was analyzed by SEM,XRD,FT-IR,XPS and PL.The surface of the modified biochar became smooth,and the oxygen-containing functional groups became less.Among the modified C/BiOBr composite materials,the C/BiOBr composite material modified by HNO₃ has the lowest electron-hole recombination efficiency.（7）Under dark adsorption conditions,the adsorption capacity of the C/BiOBr composite modified by CaCl₂,HNO₃,H₂O₂ and Na OH was 9.28 mg·g^-1,9.89 mg·g^-1,8.01 mg·g^-1 and 8.85mg·g^-1.The adsorption behavior of the modified C/BiOBr composite on the CIP is consistent with that of the C/BiOBr composite.（8）The C/BiOBr composite material modified by HNO₃ has the highest photocatalytic efficiency of 96%.After 5 cycles,the degradation rate reached 91%,and its stability was higher than that of C/BiOBr composites.The photocatalytic mechanism of modified C/BiOBr on CIP was consistent with that of C/BiOBr composite.