Study on tetracycline adsorption properties of modified sludge and chlorella copyrolysis biochar
Municipal sewage sludge and chlorella were co-pyrolyzed at high temperature and modified by FeCl2·4H2O,urea and KOH to prepare the original biochar(SCBC),iron nitrogen supported biochar(Fe2NSCBC)and al-kali secondary modified biochar(KFe2NSCBC),respectively,for the adsorption of tetracycline(TC).The results showed that KFe2NSCBC was superior to Fe2NSCBC and SCBC in terms of adsorption rate,adsorption capacity and removal rate.When pH=3,TC concentration is 200 mg/L and dosage is 2.0 g/L,the removal rate of TC by KFe2NSCBC is 98.51％.The characterization results show that KFe2NSCBC has a larger specific surface area and more abundant pore structure.Meanwhile,after modification the functional groups are increased,and the ferric oxy-gen functional groups(Fe3O4)and nitrogen oxygen functional groups are successfully loaded.The adsorption behav-ior of KFe2NSCBC is endothermic and active,and the mass transfer process meets the intra-particle diffusion type.The isothermal adsorption process is in good agreement with Langmuir and Freundlich models,and the saturation adsorption capacity at 45℃ is 315.75 mg/g.Comparative analysis of the characterization of TC before and after ad-sorption by KFe2NSCBC showed that pore diffusion,π-π bond,electrostatic reaction,hydrogen bond and complex reaction all affected the adsorption process of TC by KFe2NSCBC.
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