Palladium ion-imprinted polymers with PHEMA polymer brushes: Role of grafting polymerization degree in anti-interference

Ion-imprinted polymers (IIPs) exhibit great potential as the adsorbent for adsorption of palladium from the industrial wastewater. However, co-existence of complicated water matrixes can readily block the imprinting cavities and disturb the adsorption of target ions. Therefore, it is meaningful to endow the IIPs with an excellent anti-interference ability toward practical applications. In this work, the polymer 2-hydroxyethyl methacylate (PHEMA) polymer brushes with different polymerization degree were successfully grafted on the IIPs. The polymerization degrees of PHEMA brushes are 43, 49, 73, 122, and 294 for the IIP-1, IIP-2, IIP-3, IIP-4, and IIP-5, respectively. Batch experiments reveal that polymerization degree has an inconspicuous effect on the adsorption capacity of IIPs. And their adsorption capacities are in the range from 42 to 46 mg/g, which is much higher than most adsorbents documented in literature. The kinetic constant has increased from 0.021 to 0.042 g/(mg.min) with the increase of polymerization degree from 43 to 294, respectively. This result implies that the highpolymerization PHEMA brush can accelerate the adsorption of Pd. More importantly, the anti-interference ability of IIP-3 significantly outperforms the ungrafted IIPs; and corresponding anti-interference mechanism has been proposed. This work provides a fundamental insight into the inter-relation between polymerization degree of polymer brushes and its anti-interference ability, which may facilitate the IIPs-based technology for the adsorption and recovery of valuable metals from complex wastewater.