Effect Of Typical Manufactured Nanoparticles On The Adsorption Of Ciprofloxacin By Goethite

Excessive use of antibiotics has become a serious ecological problem worldwide.In recent years,studies on the adsorption of different antibiotics by goethite have been reported at home and abroad.However,as more and more manufactured nanoparticles are used in various fields,they have been detected in the environment,especially AgNPs and TiO₂ NPs.Antibiotics and manufactured nanoparticles can coexist in the environment,such as medical wastewater,sewage and sludge.Therefore,it is necessary to study the adsorption behavior of coexisting nanoparticles and antibiotics on goethite when entering the soil environment.In this study,citrate-coated silver nanoparticles?AgNPs?and titanium dioxide nanoparticles?TiO₂ NPs?were selected as typical manufactured nanoparticles,and ciprofloxacin?CIP?was selected as representative antibiotic.The difference of residual ciprofloxacin concentration after adsorption equilibrium in the circumstances that typical manufactured nanoparticles coexist with CIP or not was compared;the interaction between typical manufactured nanoparticles,ciprofloxacin and goethite was analyzed;finally,the mechanism of Citrate-AgNPs or TiO₂ NPs inhibit the adsorption of ciprofloxacin?CIP?by goethite was discussed through XPS,FTIR and other characterization methods.The main research results are as follows:?1?The kinetics of adsorption of CIP by goethite conforms to the pseudo-second-kinetic model;when Citrate-AgNPs or TiO₂ NPs coexist with CIP,the kinetics of CIP adsorption in the system still conforms to the pseudo-second-kinetic model.The interaction mechanism between goethite and CIP includes electrostatic interaction and complexation;TiO₂ NPs adsorb CIP mainly through electrostatic interaction and complexation.At pH=6.5,there is electrostatic attraction between Citrate-AgNPs and goethite,but the electrostatic interaction between TiO₂ NPs and goethite is weak.?2?The coexistence of Citrate-AgNPs inhibit the adsorption of CIP by goethite,which is mainly because citrate and citrate-coated AgNPs compete for CIP adsorption sites on goethite.The inhibitory effect of Citrate-AgNPs on the adsorption of CIP by goethite is weakened with the increase of pH?5⁹?.With the increase of ionic strength?0.01⁰.1 mol/L?,the inhibitory effect of Citrate-AgNPs on the adsorption of CIP by goethite is enhanced.As the concentration of magnesium ion?0.01⁰.1 mol/L?increases,the inhibitory effect of Citrate-AgNPs on the adsorption of CIP by goethite is also enhanced.?3?The coexistence of TiO₂ NPs also inhibits the adsorption of CIP by goethite,and the inhibition increases with the increase of TiO₂ NPs concentration.The main reason is that the competitive adsorption relationship between TiO₂ NPs and goethite makes the adsorption of CIP by goethite reduced.With the increase of pH?5⁹?,the inhibitory effect of TiO₂ NPs on the adsorption of CIP by goethite is firstly enhanced and then weakened.With the increase of calcium or magnesium ion concentration?0.01⁰.1 mol/L?,the inhibition of TiO₂ NPs on the adsorption of CIP by goethite is weakened.