Adsorption Characteristics And Mechanisms Of Thiamphenicol In Aquatic Solutions By Biochars Derived From Different Biomass Materials

Since Fleming’s discovery of penicillin in 1928,antibiotics have been widely used in every field of human life.Because of its huge usage and stable nature,it is abundant in the environment and poses a great threat to the ecological environment and human health.Biochar is a functional material with wide source,low cost,friendly environment,large specific surface area and rich pore structure which is prepared from waste raw materials.It can be used as a highly effective adsorbent for the adsorption treatment of antibiotics in aquatic solutions.In this study,thiamphenicol（TAP）was used as the target pollutant pigeon feces and composting waste were used as raw materials.The original biochar P600,P700,P800,C600,C700,C700 and C800 were prepared by oxygen limit pyrolysis of muff furnace at 600,700 and800℃.Analyzed the differences of element composition,surface morphology,functional groups,physical and chemical properties of biochar.Explored the influence of different factors on TAP adsorption effect in water.In addition,C800 with the best adsorption effect was modified with iron oxide by chemical co-precipitation method to obtain the magnetic biochar Fe-C800.Analyzed its adsorption characteristics,investigated the magnetic stability and recycling performance.（1）The results of SEM and elemental composition of biochar showed that the surface structure and elemental composition of biochar prepared under different conditions were very different.With the increase of pyrolysis temperature,the large particles decreased and the dense pore structure increased;the carbon content of the biochar of composting waste was higher than that of the pigeon feces biochar,which had higher oxygen and nitrogen content.The C800 has the largest specific surface area（285.92 m²/g）,followed by P800（174.27 m²/g）.The effects of pH,ionic strength and initial TAP concentration on the adsorption process of TAP for biochar were investigated by static adsorption test.Results showed that PH value had little influence on adsorption process,ionic strength significantly influenced the adsorption process.Under the condition of biochar addition=0.5 g/L,TAP initial concentration=20 mg/L,the equilibrium adsorption of P800,C800 on TAP were 31.3 mg/g and 41.7 mg/g,significantly greater than the P700（15.9 mg/g）,P600（4.7 mg/g）,C700（17.1 mg/g）,C600（6.4 mg/g）.（2）Elovich kinetic model and Freundlich isothermal model were used to describe the adsorption process of TAP on the prepared biochar.According to the analysis of the particle internal diffusion model,it is not the only speed control step in the process of biochar adsorption TAP.Thermodynamic calculation results show the adsorption process of TAP in water by P700,P800,C700 and C800 are all spontaneous heat absorption.Adsorption is a chemical adsorption that occurs on multilayer and multiphase surfaces.Hydrogen bonding,hydrophobic interaction and electrostatic interaction may be the chemical adsorption mechanisms that exist in the TAP adsorption process of biochar.（3）The adsorption performance of biochar C800,which has the best adsorption effect,can be significantly improved by chemical co-precipitation modification.Ratio of raw material 2:1（mass ratio of C800 to iron oxide）,reaction temperature 60℃,reaction time 60 min,and water bath aging at 100℃for 2 h.FT-IR was used to compare the differences of biochar before and after modification.Compared with C800,Fe-C800 generated a new characteristic absorption peak of Fe-O vibration at 740 cm^-1 and 885 cm^-1,VSM analyzed the saturation magnetization of Fe-C800was 21.7 emu/g.Adsorption tests show that Fe-C800’s equilibrium adsorption capacity on TAP was 35.6 mg/g,slightly lower than the C800’s equilibrium adsorption capacity of 41.7 mg/g,but its magnetic stability was good,the recovering and recycling rate after five using times was84.65%,and the TAP can be completely absorbed and separated by magnet within 3 min.Therefore,the magnetic composite biochar material has potential application value in the treatment of antibiotic polluted water.