不同形态的氧氟沙星在凹凸棒土上的吸附特征

通过控制反应体系的pH值,探究了阳离子、兼性和阴离子形态的氧氟沙星(OFL,3种形态分别记为OFL~+,OFL~±和OFL~-)在凹凸棒土(ATP)上的吸附特征.实验结果表明,OFL~+主要通过与ATP表面的Ca~(2+),Mg~(2+)进行阳离子交换吸附于ATP上,当其吸附量较高时,会存在少量的氢键;OFL~±和OFL~-可与ATP表面的铁氧化物、铝氧化物进行表面络合,也可与溶液中从ATP中溶解出的Ca~(2+)和Mg~(2+)形成络合物,再通过静电作用吸附于ATP上.在中性至微碱性(pH=7.10~7.70)条件下,由于Ca的电负性小于Mg,Ca~(2+)-OFL]+不能稳定地存在于溶液中,使得OFL±与Ca~(2+)进行阳离子交换而与Mg~(2+)形成络合物,再通过静电作用吸附于ATP上.当OFL主要以OFL~-形态存在于溶液中时(p H=9.00~10.00),Ca~(2+)和Mg~(2+)均可与OFL~-形成络合物,再通过静电作用吸附于ATP上.

Adsorption Characteristics of Different Forms of Ofloxacin to Attapulgite

By controlling the pH of reaction system, the adsorption characteristics of different forms of ofloxacin(i.e., OFL±, OFL+, and OFL-) to attapulgite(ATP) were investigated.The experimental results showed that exchanging with Ca2+ and Mg2+ on the surface of ATP was the main sorption mechanism for OFL+.When OFL+ adsorption quantity increased, there will be little amount of hydrogen bonding between OFL+ and ATP surface.OFL± and OFL-can form surface complexation with iron/aluminum oxide on the surface of ATP.Meanwhile, both OFL± and OFL-can form complexes with cations(Ca2+, Mg2+) dissolved from ATP and then adsorbed on ATP by electrostatic attraction.Because of the lower electronegativity of Ca than Mg, Ca2+-OFL]+ cannot exist stably in neutral to weakly alkaline(e.g., pH=7.10-7.70) solution, which results in the situation that OFL± exchange with Ca2+ but form complexes with Mg2+ then adsorbed to ATP by electrostatic attraction.When OFL-was the main form in solution(pH=9.00-10.00), both Ca2+ and Mg2+ can form complexes with OFL-and then adsorbed to ATP by electrostatic attraction.