Experimental Study On The Removal Of Sulfadiazine From Water By Modified Biochar

Sulfonamide antibiotics（SAs）are new pollutants that are closely related to people’s production and life.Although their concentration in the environment is low,their input pathways are diverse and continuously input into the environment,and they have structural stability and stability.The persistence of the environment,the conventional treatment of drinking water,and the biochemical treatment of sewage treatment plants are not ideal for the treatment of antibiotics,and are likely to cause environmental hazards.In this paper,reed biochar was prepared by high temperature pyrolysis method and modified by phosphoric acid impregnation to obtain phosphoric acid modified biochar（GBC）.TiO₂ sol was prepared by sol-gel method and loaded onto modified biochar.The TiO₂/GBC composites were used.The sulfadiazine was used as the target contaminant to investigate the adsorption properties of biochar（BC）and phosphoric acid modified biochar（GBC）and the photocatalytic degradation of TiO₂/GBC.The main results are as follows:（1）Preparation and Characterization of Biochar MaterialsIn the condition of 500°C,the reed rod was pyrolyzed to obtain BC;then it was impregnated and modified with phosphoric acid to obtain GBC;TiO₂ sol was prepared by sol-gel method and loaded on GBC to obtain TiO2/GBC.The physicochemical properties of GBC and TiO₂/GBC were characterized by means of SEM,EDS,FTIR and XRD.The SEM results show that GBC has more pores than BC,and the pore volume becomes smaller,which significantly increases the specific surface area of the adsorbent.The TiO₂ powder is granular and has a large particle size and is the result of large-area agglomeration;the GBC surface is covered with white TiO₂.Powder.The XRD results show that Ti O₂ is a powdery mesoporous material and mesoporous ordered.The period of the alignment is about 3-4 nm.EDS and FT-IR results showed that the surface element composition and content of biochar changed significantly before and after modification.（2）Study on Adsorption Characteristics of Sulfadiazine on Biochar Modified by Phosphoric AcidTaking sulfadiazine as the target pollutant,the adsorption performance of phosphoric acid-modified reed biochar was studied.It was found that the removal rate of sulfadiazine from GBC could be increased from 60.47%before modification to93.14%.When the strong alkaline condition was used（pH>9）The removal rate of sulfadiazine was significantly reduced.Using Langmuir and Freundlich model fitting,the maximum adsorption capacity of GBC for sulfadiazine was 5.5035mg·g-1,and the adsorption of sulfadiazine by GBC was preferential adsorption.The adsorption process is more suitable for fitting with pseudo-second-order kinetic equations,indicating that the adsorption rate of sulfadiazine biochar has a linear relationship with the square of the adsorption site of biochar.The thermodynamic calculation data show that the adsorption process is a spontaneous endothermic reaction,and the physical adsorption between GBC and SDZ is mainly.The main adsorption mechanisms in the adsorption process includeπ-πEDA,hydrogen bonding,hydrophobic interactions,and electrostatic interactions.（3）Photocatalytic Degradation of Sulfadiazine by TiO₂/GBC CompositesUsing sulfadiazine as the target pollutant,the photocatalytic properties of TiO₂/GBC composites were investigated.The photocatalytic degradation of sulfadiazine showed that the optimal mass ratio of TiO₂ and GBC in TiO₂/GBC composites was 3:1,and the removal rate of sulfadiazine was 57%under 25 W ultraviolet lamp irradiation alone.The rate rose to 94%.Under the optimal mass ratio of TiO₂/GBC composites,the best removal rate of sulfadiazine（94.6%）was achieved when the optimal dosage was 2 g/L,and the removal rate of SDZ was significantly lower under strong acid conditions（pH<3）.difference.After 5 repeated experiments,TiO₂/GBC composites still have high photocatalytic activity.