Preparation Of Camellia Oleifera Shells Based Biochar And Their Adsorption Performance To Tetracyclines

China is a major consumer and producer of antibiotic in the world,and a large number of antibiotics is excreted and accumulate in the form of original drugs or parent compounds to the environment,which cause the production of drug-resistant bacterial and the spread of antibiotic resistance genes,which seriously endangers public health safety.On the basis of the existing sewage treatment technology,it is very important to develop advanced treatment technology for antibiotic-containing wastewater.The adsorption method is expected to be used in the advanced treatment of antibiotic wastewater due to its simple operation and low cost.However,the application of adsorption method is limited due to the limitation of adsorption capacity of traditional adsorbents.In this work,phosphorus-containing biochar（PBC）were prepared from Camellia oleifera shells by the phosphoric acid activation method,and applied to efficiently adsorb tetracycline（TC）from aqueous solution.Systematic characterization and adsorption experiments were performed to determine the optimal preparation process,and the structure-function relationship between its physicochemical property and adsorption performance was also investigated.It was proposed that the chemisorption of the pyrophosphate surface functional groups（C-O-P bond）on PBC is the key to its excellent TC adsorption capacity.The main conclusions of the research are as follows:（1）Phosphoric acid is an excellent activator for activating C.oleifera shells based biochar.Compared with unactivated biochar,the TC adsorption capacity of PBC was increased by 27 times and reached 449.3 mg·g^-1,which was attributed to its abundant pyrophosphate surface functional groups（C-O-P bond）.（2）The pyrolysis temperature and impregnation ratio have a great influence on the physicochemical property and adsorption performance of PBC.Higher pyrolysis temperature will reduce the specific surface area of PBC;higher impregnation ratio will increase the phosphorus content of PBC,but the phosphorus content no longer increase when impregnation ratio greater than 2.Pyrolysis temperature of 600°C and impregnation ratio of1:2 is the optimal preparation process.（3）the PBC-2 exhibited superior TC adsorption rate,and the TC adsorption capacity and removal efficiency rapidly reached 315.48 mg·g^-1 and 59.1%at the first 5 min.Furthermore,PBC-2 also showed excellent applicability to the wide range p H value（1～9）,and the adsorption capacity remaining above 380 mg·g^-1.PBC-2 also exhibited selective removal ability toward TC.With the concentration of 1 mmol·L^-1,K⁺,Na⁺,NO₃^-,SO₄^2-and H₂PO₄^-shows negligible effect on TC adsorption.（4）The adsorption process was best depicted by Langmuir model,indicates that the adsorption of TC onto PBC-600 probably was monolayer adsorption that related to chemisorption.The kinetic experimental results show that the adsorption process was more matched by the pseudo-second order model.The thermodynamic results show that the adsorption process is spontaneous and endothermic and entropy decrease.