Molecularly Imprinted Polymers for Removal of Metal Ions: An Alternative Treatment Method

Abstract

Aquatic and terrestrial environment and human health have been seriously threatened with the release of metal-containing wastewater by the rapid growth in the industry. There are various methods which have been used for removal of ions from the environment, such as membrane filtration, ion exchange, membrane assisted liquid extraction and adsorption. As a sort of special innovation, a polymerization technique, namely molecular imprinting is carried out by specific identification for the target by mixing it with a functional monomer. After the polymerization occurred, the target ion can be removed with suitable methods. At the end of this process, specific cavities, namely binding sites, are able to recognize target ions selectively. However, the selectivity of the molecularly imprinted polymer is variable not only because of the type of ligand but also charge, size coordination number, and geometry of the target ion. In this review, metal ion-imprinted polymeric materials that can be applied for metal ion removal from different sources are discussed and exemplified briefly with different metal ions.

Keywords: ion imprinting; metal pollution; metal removal; molecularly imprinted polymers.

Figure 1

The number of publications for metal ion-imprinted polymers.

Figure 2

Scanning electron microscope images of (A) mercury (II)-imprinted polymeric beads and (B) nonimprinted polymeric beads. Republished with permission of Elsevier, from [23]; permission conveyed through Copyright Clearance Center, Inc.

Figure 3

Scanning electron microscope images of (A) cadmium (II)-imprinted, (B) nonimprinted, (C) lead (II)-imprinted and (D) nonimprinted polymeric cryogels. Republished with permission of John Wiley & Sons, Inc., from [5]; permission conveyed through Copyright Clearance Center, Inc.

Figure 4

(A) Chemical structure of the N-methacryloyl-(l)-cysteine monomer and (B) pre-complex of template and monomer. Republished with permission of Elsevier, from [32]; permission conveyed through Copyright Clearance Center, Inc.

Figure 5

Scanning electron microscopy images of cadmium (II)-imprinted polymeric beads. (A) surface and (B) internal structure. Republished with permission of Elsevier, from [36]; permission conveyed through Copyright Clearance Center, Inc..

Figure 6

Preparation of chromium (III)-imprinted polymeric adsorbent. Republished with permission of Elsevier, from [39]; permission conveyed through Copyright Clearance Center, Inc.

Figure 7

Effect of nickel (II) concentration on the amount of adsorbed nickel (II). Republished with permission of Elsevier, from [43]; permission conveyed through Copyright Clearance Center, Inc.

Figure 8

Scheme of the pre-complex formation between imidazole groups and metal ions. Republished with permission of Elsevier, from [49]; permission conveyed through Copyright Clearance Center, Inc.