Stimuli-responsive adsorption behavior toward heavy metal ions based on comb polymer functionalized magnetic nanoparticles

A novel type of poly(maleic anhydride)-graft-poly(vinyl alcohol) comb polymer functionalized magnetic nanoparticles was specially designed and prepared as an efficient adsorbent with stimuli-responsive reversible adsorption/desorption behavior for the controllable removal of heavy metal ions. The adsorption capacities of comb polymer functionalized magnetic nanoparticles toward Ag+, Ni2+, Cd2+, Pb2+ and Co2+, exhibiting good fits to Langmuir isotherm model and Pseudo-second order kinetic model with correlation coefficients of more than 0.98, were 0.8634, 0.8194, 0.8429, 0.6720 and 0.7682 mmol g(-1) respectively, which were 5 times greater than those of linear polymer functionalized magnetic nanoparticles due to the contribution of topology evolution. Furthermore, the uptake rate of comb polymer functionalized magnetic nanoparticles toward Ag+, Ni2+, Cd2+, Pb2+ and Co2+ increased significantly from 21.1%, 17.6%, 18.64%, 16.3% and 15.68% to 92.15%, 89.2%, 90.16%, 83.56% and 84.52% respectively when the solution pH increases from 4 to 7, showing a pH-responsive characteristic, the mechanism of which was elucidated as the pH-driven changes in electrostatic interaction and molecular morphology. Good sustainability and facile reusability were practically reflected by over 80% uptake efficiency after 5 consecutive absorption/desorption cycles. The innovation of this work is that changing molecular topological structure of the polymer can significantly contribute to excellent adsorption capacity and pH responsiveness to remove heavy metal ions in wastewater. The importance of this study is to offer a practical cleaner production process for an attractive adsorbent with stimuli-responsive adsorption behavior and good sustainable application through innovative molecular design. (C) 2019 Elsevier Ltd. All rights reserved.