Differential adsorption of zwitterionic PPCPs by multifunctional resins: The influence of the hydrophobicity and electrostatic potential of PPCPs

Zwitterionic pharmaceuticals and personal care products can interact with adsorbents in different ways due to their various properties. In this work, the effects of hydrophobicity and electrostatic potential were explored through the adsorption of ciprofloxacin (CPX) and tetracycline (TC) onto multifunctional resins. Nonionic surface interaction was dominant for the adsorption on high-surface-area resin GMA10. Thereinto, hydrophobic and pi-pi interaction dominant for hydrophobic CPX and hydrophilic TC, respectively. Electrostatic interaction played an important role for high-anion-exchange-capacity resin GMA90. Upon their adsorption onto GMA50 resin, the relatively separated positive and negative electrostatic potentials of CPX+- due to the greater distance (similar to 12.33 angstrom) between the anionic and cationic groups led to electrostatic attraction and interaction (Ea = 8.64 +/- 031 kJ/mol) and the vertical orientation of molecule on the surface. However, TC+-0 displayed nonionic surface interaction (Ea = 7.96 +/- 0.14 kJ/mol) due to its relatively neutral electrostatic potential arising from the adjacent functional groups. Hence, the surface of GMA50 was covered with TC+-0 molecules adsorbed parallel to the surface, thereby restricting TC+-0) adsorption. Coexisted with monovalent salts, CPX adsorption was facilitated due to the salting-out effect. By contrast, the salting-out effect for TC was extremely weak, and TC adsorption was restrained due to the competitive adsorption of salts. (C) 2019 Elsevier Ltd. All rights reserved.

两性离子药物和个人护理产品由于其各种特性会以不同方式与吸附剂相互作用。在这项工作中，通过环丙沙星（CPX）和四环素（TC）在多功能树脂上的吸附，探究了疏水性和静电势的影响。在高比表面积树脂GMA10上的吸附以非离子表面相互作用为主。其中，对于疏水性的CPX和亲水性的TC，分别以疏水作用和π - π相互作用为主。静电相互作用对高阴离子交换容量树脂GMA90起着重要作用。当它们吸附到GMA50树脂上时，由于CPX的阴离子和阳离子基团之间距离较大（约12.33埃），其相对分离的正负静电势导致静电吸引和相互作用（Ea = 8.64 ± 0.31 kJ/mol）以及分子在表面的垂直取向。然而，TC由于相邻官能团使其静电势相对中性，表现出非离子表面相互作用（Ea = 7.96 ± 0.14 kJ/mol）。因此，GMA50的表面被平行于表面吸附的TC分子所覆盖，从而限制了TC的吸附。与一价盐共存时，由于盐析效应，CPX的吸附得到促进。相比之下，盐对TC的盐析效应极弱，并且由于盐的竞争吸附，TC的吸附受到抑制。（C）2019爱思唯尔有限公司。保留所有权利。