Removal Of Antibiotics From Aqueous Solutions By Modified Activated Carbon Derived From Lris Lactea

The residual antibiotics in water not only have toxic effects on animals and human bodies,but also make organisms resistant to drugs,which would pose a potential threat to the environment.The residual antibiotics in water are not biodegradable to some extent,which would remain for a long time in the environment.The adsorption has the advantages of simple operation,strong target selectivity,high adsorption efficiency with few secondary pollution compared with many other treatment technologies.Activated carbon is made up based on materials from a variety of sources.There is no study about Iris-based activated carbon.Iris,as a salt plant with large growth,drought tolerance and salt tolerance,has tough stems and leaves and high fiber content.In this study,iris-based activated carbon(ILAC)and crayfish-shell-modified activated carbon(CS-ILAC)were prepared by phosphoric acid activation with iris as carbon precursor and crayfish shell as modifier due to its high chitin and nitrogen element content.The adsorption capacity of ILAC and CS-ILAC of norfloxacin is researched.The other part of the research is the adsorption of cephalosporin by crayfish-shell-modified activated carbon with grinding processing(G-CS-ILAC)and iris-based activated carbon(ILAC).The physical and chemical characterization of ILAC,CS-ILAC and G-CS-ILAC were carried out by using specific surface area analyzer,FTIR and XPS.The results show that the activated carbon of iris is a kind of amorphous carbon.The specific surface area is 883.9611m~2/g and average pore size is 3.9 nm with well-developed micropores and mesopores.The surface functional groups are mainly carboxyl,hydroxyl and lactone.Isoelectric point is 5.84.After modification,CS-ILAC and G-CS-ILA are Indefinite structure.Specific surface area and total pore volume of CS-ILAC get enhanced to 1068.1098 m~2/g and 0.964 cm~3/g.The acid functional groups and nitrogen-containing functional groups on the surface of CS-ILAC increased obviously,isoelectric point is 5.32.G-CS-ILAC has larger specific surface area of1309.4581 m~2/g and lower isoelectric point of 3.42,with more functional group content and stronger acidity.The adsorption of norfloxacin on activated carbon was greatly improved by the modification of crayfish shell.The best modification conditions:the quality of crayfish shell powder accounts for 3.5%of the total quality of the powder,impregnation time is 10 h,solid liquid mass ratio is 1.25:1,heating temperature is 550?,incubation time is 1 h.Maximum adsorption capacity of CS-ILAC of is 373.73 mg/g compared with 227.37 mg/g of norfloxacin.The adsorption isotherm is fitted well with Freundlich model,and the adsorption kinetics accords with pseudo second-order kinetics model.The adsorption capacity of CS-ILAC and ILAC first increases and then decreases with the increase of pH,the peak appears at pH=7.5.Norfloxacin is mainly adsorbed in the form of amphoteric ions.The adsorption mechanism includes covalent binding of functional groups and electrostatic attraction.The nitrogen-containing functional groups introduced from crawfish shell can not only chemically adsorb with adsorbate,but also catalyze the adsorption of norfloxacin on activated carbon.The adsorption of cefalexin of G-CS-ILAC was 48.9474 mg/g,promoted by grinding.The adsorption isotherm is fitted well with Freundlich model,and the adsorption kinetics accords with pseudo second-order kinetics model.The adsorption capacity of CS-ILAC and ILAC first decreases slowly and then decreases rapidly with the increase of pH.Cefalexin is mainly adsorbed in the form of cation and zwitterion.The adsorption mechanism includes covalent binding of functional groups,electrostatic attraction and hydrophobic affinity.The main reason is that the content of oxygen-containing functional groups is high and the surface acidity of the activated carbon are increased,and the nitrogen-containing functional groups promote the adsorption of cefalexin on the activated carbon.