Study On Ofloxacin Sorption Characteristics To Attapulgite

The pollution of antibiotic medicines have become a more and more serious environmental problem.Adsorption is one of the main methods to remove contaminants from waste water.In this study,attapulgite,a typical clay mineral which is rich in China,was selected as a representative adsorbent to remove the fluoroquinolone antibiotics drugs in waste water.With ofloxacin?OFL?as representative compound,the characteristics of different forms of OFL?OFL+,OFL� and OFL-,respectively?sorbed to attapulgite were investigated by batch adsorption experiments.Furthermore,the competitive adsorption between cationic surfactant hexadecyl trimethyl ammonium bromide?HDTMA?and OFL to ATP was studied.The main conclusions are as follows:?1?Exchanging with Ca²⁺ and Mg²⁺ on the surface of the ATP was the main mechanism for OFL+ sorption.With increasing OFL+concentration,hydrogen bonding occurred between the Si-O-on the surface of ATP and carboxy group in OFL+.?2?OFL� and OFL-can form complexes with oxides of iron and aluminum on the surface of ATP.OFL-can first form complexes with Ca²⁺ and Mg²⁺ then adsorbed by electrostatic effect to ATP.But OFL� can only form complexes with Mg²⁺ and then adsorbed to ATP by electrostatic interaction.In addition,OFL� can exchange with Ca²⁺ on the surface of the ATP.?3?HDTMA depressed the adsorption of OFL to ATP by competing the exchangeable cations and covering the sites which used for adsorbing OFL.?4?The amount of OFL adsorbed on ATP decreased with the increase of initial pH in solution.When it coexisted with HDTMA,the HDTMA would adsorb to ATP firstly due to its stronger hydrophobicity and then resulting in the increase of the organic carbon content of ATP.At that situation,OFL would adsorbed to ATP by hydrophobic interaction,then the adsorption of OFL to ATP was almost not affected by the initial pH.?5?Relative to the background cation for Na⁺,When the background cation were K+,Ca²⁺and Mg²⁺,K+,Ca²⁺ and Mg²⁺ would compete adsorption sites with OFL,impede the cation exchange of Ca²⁺ and OFL and cause the electrostatic repulsion between [Mg²⁺-OFL]+ and ATP to depress the adsorption of OFL to ATP.And the inhibitory strength order was Mg²⁺ >Ca²⁺ ? K+.In the background of cations in the solution concentration was 0.01 M,0.5 CMC HDTMA adsorption coexist may inhibit OFL ATP cation exchange to compete with OFL,but this inhibition effect is not affected by the background intensity of cationic species.