Lithium ion-imprinted polymers with hydrophilic PHEMA polymer brushes: The role of grafting density in anti-interference and anti-blockage in wastewater.

Hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) brushes were modified onto the surface of ion-imprinted polymers (IIPs) via addition-fragmentation chain transfer (RAFT) polymerization. Four different grafting densities (1.43, 1.31, 1.17 and 1.06chains/nm) of IIPs were obtained, revealed by analysis using gel permeation chromatograph (GPC) and Brunauer-Emmett-Teller (BET). All the grafted IIPs had good anti-interference properties compared to the ungrafted IIPs, although the adsorption capacity of the ungrafted IIPs was higher than that of grafted IIPs in pure water. Among them, the grafted IIP3, with a grafting density of β=1.17chains/nm, exhibited superior anti-interference ability in silica and polymer flocculant simulated wastewater; moreover, it remained steady after 10 adsorption-desorption cycles. SEM-EDX and XPS data revealed anti-interference and anti-blockage mechanisms in which hydrophilic PHEMA brushes could effectively adhere to fine particles and flocculants through Van der Waals force interactions, which make the imprinted cavities well protected in a complex wastewater environment. Moreover, these grafted IIPs exhibit similar adsorption rate constants that are approximately 2 times greater than those of ungrafted IIPs, indicating that the PHEMA brushes increased the accessibility to Li(I) due to hydrophilic modification.