Study On Adsorption Of Tetracycline In Aqueous Solution By Co-Pyrolysis Biochar Derived From Sludge And Microplastics

The use of antibiotics is increasing year by year worldwide,among which tetracyclines(TCs)are the most produced and used antibiotics,but the TCs ingested into animals cannot be completely absorbed and the unused part is excreted in urine and feces,leading to their widespread residues in the environment.Currently,biochar is a carbon-rich product obtained from high-temperature pyrolysis of agricultural wastes,which is widely used in environmental pollution treatment because of its large specific surface area,developed pore structure and abundant functional groups.In this study,we will use sludge(Sewage Sludge,SS)and polyvinyl chloride(PVC)co-pyrolysis biochar as adsorbent to investigate the removal effect of tetracycline to achieve the purpose of waste treatment.The biochar(PSBCs)was prepared by co-pyrolysis of SS with different mass fractions(5%,10%,20%,30%)of PVC using slow pyrolysis method.The physical and chemical properties of the biochar were characterized and analyzed using fully automatic specific surface area and porosity analyzer,Fourier infrared spectrometer,scanning electron microscope and X-ray diffractometer.Then measure total heavy metals(Zn,Cu,Pb,Cd)in PSBCs,BCR morphology and TCLP leaching capacity,The potential ecological risk index method was employed to evaluate the contamination risk posed by heavy metals in sludge and PSBCs.With TC in the water body as the removal target,using Batch processing test to investigatie the adsorption properties and mechanism of PSBCs.Dynamic adsorption study of PSBCs adsorption TC using fixed bed method.The main findings are as follows:(1)By analyzing the distribution of total heavy metals,BCR morphology and leaching amount in PSBCs,it was found that the enrichment effect of heavy metals occurred after the sludge was pyrolyzed,resulting in a significant increase of both total heavy metals and TCLP leaching amount in PSBCs,Among them,the total concentration of Zn increased the most,ranging from 48.49% to 109.03%.,while the four heavy metal chemical forms changed from the unstable state(F1,F2)to the stable state(F3,F4).For the potential environmental risk,PSBCs-600 all showed slight contamination,and with the increase of PVC addition,its total heavy metal decreased,the steady state heavy metal content decreased,and the potential environmental risk index RI increased,but its potential risk index and heavy metal leaching were within the safe range,indicating that PSBCs have certain application potential.(2)As the pyrolysis temperature increased,the surface defects of PSBCs increased,the pore structure increased,and the specific surface area increased.The results of batch adsorption tests showed that the adsorption of 5%PSBC-600,10%PSBC-600,20%PSBC-600,and 30%PSBC-600 on TC was consistent with Pseudo-second-order kinetics and Langmuir model,indicating that the adsorption process was chemisorption-dominated monolayer adsorption.the maximum adsorption amount of 20%PSBC-600 on TC was295.9mg/g,which was higher than the rest of the co-pyrolysis biochar.By analyzing the changes before and after TC adsorption onto 20%PSBC-600,it was revealed that the adsorption mechanism mainly involved electrostatic adsorption,hydrophobic interaction,surface complexation,hydrogen bonding and π-π interactions.(3)Using 20% PSBC-600 as the packing material,study the effect of different operating parameters on the adsorption performance of fixed bed columns,analyze the fitting of the penetration curve.The results showed that when the adsorbent addition,influent flow rate and influent concentration were 2g,10 m L/min and 20mg/L,respectively,the reaction column had the best adsorption effect on TC.The Thomas model exhibited a high correlation coefficient and predicted the maximum adsorption capacity of 42.31mg/g,which could effectively predict the performance of the adsorption column.