Competitive Adsorption Between Ciprofloxacin And Flumequine On Goethite

Fluoroquinolone antibiotics have been widely used in personal care and thelivestock industry. Due to their absorption characteristics, Fluoroquinolones hasgradually become a hot academic research, because their potential risks on theecological environment cannot be ignored. Pollutants in soil and water generally donot exist alone, and have different physical and chemical properties. Thus, theiradsorption on mineral or soil will be inevitable differences. When there are multiplepollutants existing simultaneously on adsorption medium, the role between singlesubstances and adsorption medium cannot completely characterize the adsorptioncharacteristics of multiple pollutants and the interactions between multiple pollutants.In order to explore whether there will be competitive adsorption when a variety ofsubstances exist in the environment at the same time, this article selects two kinds offluoroquinolones (ciprofloxacin and flumequine) and goethite as the representative toresearch the adsorption characteristics. This article mainly achieved the followingresults:1) This article established a simple and effective method of simultaneousdetermination of ciprofloxacin and flumequine. The proportion of Mobile phase A(0.025mol/L phosphoric acid, adjusting pH=2.5by triethylamine) and mobile phaseB (acetonitrile) was equal to50:50. The injection volume was10μL. The flow ratewas1.0mL/min. The column temperature was40℃. The UV detection was dualwavelength detection wavelength (278nm&248nm). Under these conditions, theexperimental results agreed with the requirements.2） The adsorption of10.7μmol/L ciprofloxacin on goethite under pH of5conformed to the pseudo second-order equation. The adsorption of ciprofloxacin(between1and60μmol/L) on goethite conformed to Freimdlich isotherm. Theflumequine adsorption on goethite also reached a similar conclusion. Ciprofloxacinhad a faster initial adsorption rate, and Flumequine had more adsorption amount. 3） When flumequine and ciprofloxacin existed on the surface of goethite at thesame time, the adsorption of10μmol/L ciprofloxacin on goethite had a slightdecrease by changing the concentration of flumequine (between1to30μmol/L), butthe adsorption of10μmol/L flumequine on goethite remained unchanged by changingthe concentration of ciprofloxacin (between1to30μmol/L).4） pH was an important factor to affect the adsorption capacity of ciprofloxacinon goethite,which affected different molecular forms of ciprofloxacin and goethite.Phosphate ion could affect the adsorption of ciprofloxacin on goethite, whose essencewas also through the forms of coordination under different pH conditions. So wasflumequine.5） When10μmol/L ciprofloxacin and10μmol/L flumequine existed ongoethite at the same time, adsorption of flumequine on goethite trended unchangedwith the increase of pH. However, the highest values of adsorption of ciprofloxacin ongoethite reduced30%than ones without flumequine. Therefore，flumequine couldcompete part of the adsorption sites of ciprofloxacin, leading to the adsorptionquantity of ciprofloxacin on goethite decreased.