Study On The Adsorption And Catalytic Degradation Of Tetracycline In Water By Modified Watermelon Rind Biocha

With the rapid development of industrialization,the problem of contaminated water resources is becoming more and more serious.Among them,tetracycline,as the most widely used antibiotic,can stay in the water environment for a long time due to its hydrophilic and low volatility characteristics,therefore,it is of great strategic importance to remove antibiotic pollutants from the water environment efficiently and safely.Biochar,as a renewable resource with its own large specific surface area and rich pore structure,can be used as a carrier for adsorbent and catalyst,and its low cost and excellent effect can be regarded as an ideal material for the removal of antibiotics in the aqueous environment.This paper prepared watermelon rind biochar by modifying zinc chloride and melamine as the target pollutant with tetracycline and watermelon rind as the biomass raw material（ZMBC）and used as an adsorbent.On top of that,nitrogen and sulfur-doped biochar（NSBC）was prepared by adding thiourea and used as a catalyst.The research results obtained in the paper are as follows:（1）The effects of the impregnation ratio of Zn Cl₂,the addition ratio of melamine,and the activation temperature on the adsorption performance of the material were investigated,and the optimal preparation conditions of the material were determined by combining with the characterization,i.e.,the impregnation ratio of Zn Cl₂was 2,the addition ratio of melamine was 10%,and the activation temperature of the preparation was 600℃,and its adsorption efficiency for TC was97.8%.It was also demonstrated by BET,XRD,FTIR and other characterization means that ZMBC has a rich pore structure,large specific surface area(1138.681m²·g^-1),functional groups such as hydroxyl and amino groups on the surface,and good stability.The adsorption single-factor experiments showed that the adsorbent addition and temperature were beneficial to improve the adsorption efficiency;the adsorption efficiency of ZMBC decreased gradually with the increase of TC concentrations,but the adsorption amount increased;the adsorption efficiency was different under different p H conditions,but the best p H for TC adsorption was 7.（2）The kinetic,isothermal,and thermodynamic models were fitted to the adsorption process at different TC concentrations and temperatures,and the fitting results showed that the adsorption process of ZMBC on TC was more consistent with the Elovich model,which is mainly chemisorption and contains ion exchange.The adsorption isotherm simulation shows that the Redlich-Peterson model is the best fit,indicating that the adsorption of ZMBC on TC is a physicochemical adsorption;the adsorption thermodynamic results indicate that the adsorption process is a spontaneous heat-absorption reaction process dominated by chemisorption.The mechanism of the adsorption process is presumed to be pore filling,hydrogen bonding,electrostatic interaction andπ-πbonding,taking into account the changes of the material physical and chemical properties before and after adsorption.（3）Based on the material ZMBC,a high catalytic performance biochar material NSBC was successfully prepared by adding thiourea to introduce N and S atoms,and the removal effect of TC and XPS and Raman characterization showed that the addition of thiourea increased the defect degree of the material and provided a large number of active sites for activation of potassium monopersulfate（PMS）,but also destroyed the pore structure of NSBC,making the adsorption With the increase of the activation temperature,the catalytic performance of NSBC improved first and then increased,probably due to the higher temperature,which made the thiourea volatilized,so the best preparation conditions were the thiourea addition amount of 1and the activation temperature of 350℃.At this time,the degradation efficiency of NSBC-activated PMS on TC was 90.02%.（4）The single-factor experiments on degradation showed that the concentration of PMS was beneficial to the degradation of TC,and the optimal concentration was 1m M;the concentration of TC would inhibit the degradation reaction due to the limited active sites of NSBC,and the optimal concentration was 20 mg·L^-1;the catalyst dosage was not conducive to the degradation reaction due to the limited active sites and a small concentration of PMS,and the optimal dosage was 0.2 mg·L^-1;with the increase of p H,the degradation efficiency of NSBC on TC increased first and then decreased,and the optimal p H was 7;the increase of temperature was beneficial to the degradation reaction;the inorganic anion had a slight effect on the degradation reaction,and the NSBC prepared under optimal conditions had good stability.With the increase of p H,the degradation efficiency of NSBC to TC increased and then decreased,and the optimal p H was 7;the increase of temperature was beneficial to the degradation reaction;inorganic anions had a slight effect on the degradation reaction,and the NSBC prepared under the optimal conditions had good stability.By the burst experiment and EPR test,¹O₂and O₂^·-were the main oxides in the degradation processand were accompanied by electron transfer.By comparing the XPS patterns of NSBC before and after degradation showed that the active sites were mainly pyridine nitrogen,pyrrole nitrogen and thiophene sulfur.