Surface Engineered Magnetic Biosorbents for Water Treatment


Water pollution is a matter of concern because of the adverse impact of contaminants on environment and human health. Common polymer-based sorbents are difficult to separate from treated water, a limitation that has restrained their use. Nanomaterials with magnetic features appear as advantageous alternatives to these conventional biosorbents offering the advantage of fast and easy magnetically-assisted separation. Moreover owing to reduced dimensions magnetic nanomaterials possess large specific surface area that favours adsorption. The surface modification with biopolymers enhances the adsorptive capabilities of magnetic nanoparticles without compromising the low-cost. However, in order to attain high-performance, a rational design of the surface of the magnetic biosorbents is essential. In this chapter we present an overview of the most recent developments on magnetic biosorbents for water treatment. Primary attention is given to the chemical strategies used for the surface modification of magnetic nanoparticles with biopolymers aiming to obtain highly effective, robust and reusable biosorbents with magnetic properties. Two different strategies are distinguished, the in situ functionalization and the post-synthesis surface functionalization. The later comprises two distinct stages, the synthesis of the magnetic nanoparticles and the surface functionalization, and allows a better control of each stage individually. Surface functionalization can involve the simple coating of magnetic nanoparticles with biopolymers or the covalent attachment of the biopolymer chains to the surface. Overall covalent immobilization of the biopolymer onto the particles surface, either by crosslinking or grafting approach, is recommended to ensure successful recycling and reuse of the biosorbents without significant loss of adsorption capacity. Appropriate selection of the biopolymer and the route for surface modification of magnetic nanoparticles are crucial to obtain effective magnetic biosorbents optimized and specialized in the targeted pollutants. The performance of several magnetic biosorbents in the uptake of heavy metal species and organic pollutants from water is discussed in this chapter


Soares S.F., Fernandes T., Trindade T., Daniel-da-Silva A.L.

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