Effect of neighboring groups on the pH responsive adsorption/desorption behaviors of carboxylate functionalized hollow polymer particles

Abstract

In this article, a serial of bi‐functionalized hollow polymer particles (BF‐HPPs), containing both carboxylate and different amide/amine groups [HPP‐NH2, HPP‐ethylenediamine (EDA), and HPP‐diethylenetriamine (DETA)], were specially designed and synthesized to investigate the effect of neighboring amino groups on their adsorption/desorption behavior. Due to the high density of carboxylate groups, these BF‐HPPs can serve as efficient adsorbents for selective removal of positively charged methylene blue (b‐MB). With increasing chain length of the neighboring amino groups, the maximum adsorption capacities (qmax) at pH 7 decrease dramatically from 606.1 mg g−1 for HPP‐NH2, to 404.9 mg g−1 for HPP‐EDA, and 332.2 mg g−1 for HPP‐DETA, due to increasing steric hindrance. Significantly, the equilibrium adsorption can be achieved within 15 min for HPP‐EDA and HPP‐DETA, while it takes more than 720 min for HPP‐NH2. Moreover, the qmax of HPP‐DETA exhibits remarkable pH‐sensitive property, which decreases sharply to 32.7 mg g−1 at pH 3 due to strong electrostatic repulsion between positively charged ammonium groups and b‐MB molecules. Accordingly, the desorption efficiency of HPP‐DETA reached up to 94% after one desorption step, which is much higher than that of HPP‐EDA (78%) and HPP‐NH2 (60%). The absorbed b‐MB can be facilely desorbed and the adsorption capacity of the regenerated HPP‐DETA keeps above 95% after five consecutive adsorption–desorption cycles. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1404–1413