Molecularly imprinted nanoparticles (nanoMIPs): an efficient new adsorbent for removal of arsenic from water

Abstract

Geogenic contamination of arsenic in the groundwater of the Indian subcontinent and other parts of the world has been reported. Many methods have been developed to remove arsenic species from water. The most promising technology is adsorption for its merits such as simple in operation, low cost, and considerably insignificant by-product formation. In this study, a new polymer-based nano-adsorbent for As(V) has been prepared using a synergistic approach of molecular imprinting and metal–organic ligand chemistry. The nano-adsorbent was formulated with cost-effective polymethacrylate imprinted with fluorescein and As(V) complex. After polymerization, As(V) in the polymer matrix was removed from the polymer to create cavities with a specific affinity for As(V). The imprinted polymer with nanopores (nanoMIP) has shown high adsorption capacity, i.e., 49 ± 7 mg L−1; and the adsorption phenomena were studied by using theoretical Langmuir and Freundlich isotherms. The adsorption kinetics data were well fitted with the pseudo-second-order rate equation. The analyte As(V) was effectively adsorbed onto nanoMIP from real environmental samples. Infrared spectra of nanoMIP have shown that electrostatic interaction between surface functionalities (such as, –COOH and –C=O) of nanoMIP with As(V) would be responsible for high adsorption capacity of As(V). The mode of binding of As(V) onto the nanoMIP was further justified by molecular modeling. About 98% of adsorbed As(V) was removed from nanoMIP by washing with 0.1 M HNO3 solution, and the regenerated nanoMIP showed re-adsorption for ten cycles. The leachate of spent nanoMIP contains as low as 0.9 µg L−1 of As(V), which is lower compared with commercially used iron and aluminum oxide-based adsorbents.