Preparation And Tetracycline Adsorption Of Modified Corn Cob Biochar

The use of tetracycline（TC）is not limited to human therapy,but is also widely used i-n veterinary medicine and agriculture.These compounds have been detected in the enviro-nment,especially in livestock farms,groundwater,surface water and so on,so it is vital th-at measures are taken to some extent to remove these compounds from the ecosystem.Tetr-acycline is the antibiotic detected in our environment in recent years,its usage is growing y ear by year to produce serious safety hazards.Biochar materials（CBC）were prepared by pyrolysis under three temperature conditions.The physicochemical properties of the materials were analysed by industrial analysis,SEM,BET,FTIR and XRD to investigate the effect of cracking temperature on the properties and adsorption effect of biochar.The biochar was also modified by impregnation-pyrolysis with silver nitrate and cobalt nitrate.The optimum preparation conditions for the cobalt-silver modified biochar(CS-CBC₈₀₀)were finally obtained by response surface modelling,which was used to improve the adsorption capacity of biochar as an adsorbent for tetracycline and to achieve the feasibility of farm waste treatment and recycling.The modified biochar was also characterised by means of morphological,structural and property analysis.A series of single-factor adsorption experiments were conducted to investigate the optimum adsorption conditions for tetracycline,and applied to the adsorption treatment of pollutants in farm wastewater.The results of the study are as follows.（1）The results of SEM and BET characterization showed that compared with CBC₄₀₀ and CBC₆₀₀,the biochar cleaved at 800°C(CBC₈₀₀)showed greater changes in morphological structure and comparative area,and the p H of the biochar improved greatly with the increase of the pyrolysis temperature.The adsorption of tetracycline from 5-10mg/L solutions reached more than 80%,and the adsorption capacity at 30 mg/L was 17mg/g,which was more than 1.5 times that of the biochar prepared at 400°C and 600°C.The adsorption experiments revealed that the adsorption effect of biochar on tetracycline increased significantly with the increase in pyrolysis temperature,which was probably due to the increase in alkalinity on the surface of the biochar.（2）The impregnation-cleavage modification of corn cob biochar(CBC₈₀₀)with two metal salts was used to obtain CS-CBC₈₀₀,and the optimal preparation process for CS-CBC₈₀₀ was obtained by response surface modelling as:m(CBC₈₀₀):m（cobalt nitrate）:m（silver nitrate）=2 g:0.25 g:0.375 g.The cleavage time was 2 h,the impregnation time was 6 h,and the cleavage temperature was controlled at 700°C.For 50 m L,the Tetracycline adsorption of 30 mg/L reached 81.257%.The CS-CBC₈₀₀ has a distinct porous structure with the presence of mesopores,and the high porosity provides more attachment sites for adsorption.（3）In the one-way adsorption experiments,the best adsorption effect of CS-CBC₈₀₀on tetracycline was achieved at a dosage of 20 mg and p H=4.In addition,the effect of different metal ion concentrations on the adsorption experiments showed that the presence of Na⁺,K⁺and Ca²⁺inhibited the adsorption of TC on CS-CBC₈₀₀,while the concentration of Cu²⁺in the range of（0.01 mol/L-0.1 mol/L）all promoted the adsorption of tetracycline by the modified biochar to varying degrees.（4）The adsorption of tetracycline on CS-CBC₈₀₀ can be described by a quasi-secondary kinetic model,where the adsorption is mainly chemisorption of a single molecular layer.The Langmuir model shows that the maximum adsorption capacity of CS-CBC₈₀₀ is 199.35 mg/g.The thermodynamic study shows that the adsorption of tetracycline on CS-CBC₈₀₀ is a spontaneous heat absorption process.The adsorpti-on rate can still reach 73.2%after four cycles.In order to avoid secondary pollution of the environment,the metal leaching rate of CS-CBC₈₀₀ was measured at different p H values for silver and cobalt ions,and the detected concentration of both ions w as below the environmental limit（GB5479-2006）of 0.5 mg/L.Therefore,CS-CBC₈₀₀ is a potential green adsorbent.（5）The surface adsorption and electrostatic interaction are the main mechanisms of tetracycline adsorption on corn cob biochar(CBC₈₀₀).The previous experimental results and the FTIR and XPS analyses of CS-CBC₈₀₀ before and after adsorption showed that the adsorption of tetracycline with the metal-bearing adsorbent was achieved by metal complexation,pore filling,hydrogen bonding and coordination bonding.The optimum treatment conditions in the culture wastewater were:adsorption time of 12 h,p H=4,dosing of 80 mg and 3 cycles still showed good results for TC and PO₄^3-Figure[42]Table[19]Reference[104]...