Influences Of Biochar On Adsorption-Desorption Of Tetracyclines In Soils

In this paper,the adsorption and desorption characteristics of four kinds of tetracycline antibiotics,such as chlortetracycline,tetracycline and oxytetracycline,were studied in order to reduce the concentration of tetracycline class of antibiotics to provide theoretical reference and technical support.The adsorption kinetics and thermodynamics of tetracycline antibiotics were studied by using OECD Guideline 106 batch balance method.The pseudo-first-order and pseudo-second-order kinetics equation and intra-particle diffusion model was fitted kinetic process.The thermodynamic process fitting with Freundlich and Langmuir equations.The main conclusions of this paper are as follows:1.Biochar on the tetracycline,oxytetracycline,chlortetracycline three tetracycline antibiotics have a good adsorption.By the pseudo-first-order kinetics equation and the pseudo-second-order kinetics equation fitting results,we can see that the pseudo-second-order kinetic equation correlation coefficient r is greater than 0.99,the fitting effect is better.The adsorption amount qe was positively correlated with the addition of biochar concentration.When the concentration of biochar was 5%,the adsorption capacity reached the maximum,the adsorption effect was the best,and the desorption was the least.2.The Freundlich equation and the Langmuir equation were used to fit the adsorption thermodynamics process of tetracycline,oxytetracycline and chlortetracycline on biochar soil.The results showed that the Freundlich equation had better fitting effect.When the concentration of biochar was increased from 1%to 5%,the lgKf of tetracycline increased from 1.3468 to 4.4003,and the IgKf of chlortetracycline increased from 4.7823 to 4.003,and the lgKf of oxytetracycline increased from 0.2802 to 3.4351.3.The temperature is also the main factor affecting the adsorption effect of tetracycline antibiotics on biochar soil.The experimental design 288 K,298 K,308 K three temperatures were used to study the adsorption of three tetracycline antibiotics at different temperatures.The results show that with the increase of temperature,the adsorption capacity increases gradually4.The desorption process of tetracycline antibiotics on the biochar soil is obviously hysteresis.The adsorption isotherm can not completely coincide with the desorption isotherm.The desorption process is not the reverse reaction of the adsorption process,and the desorption rate is less than the adsorption rate.