Morphology, Modification and Characterisation of Electrospun Polymer Nanofiber Adsorbent Material Used in Metal Ion Removal

Among a wide range of technologies available to separate metal ions, adsorption is a major treatment technique for removing or recovering metals from aqueous solutions. Electrospun nanofiber adsorbents have attracted research consideration due to the distinctive properties such as their high surface area, high porosity and high adsorption capacity which makes nanofibers a good choice for selective metal recovery applications. Thus, the modification of electrospun nanofiber adsorbents by functionalisation with suitable ligands for selective metal extraction is a growing area of scientific research aiming to improve the selectivity of the adsorption process. This study reviews and summarises available information related to the different nanofiber modification processes for increasing adsorption efficiency, functionality and selectivity of modified nanofiber adsorbents as well as improving their durability and stability during use. The surface properties of an adsorbent is an essential control factor for its metal ion adsorption efficiency. The various techniques available for characterisation of specific properties of nanofiber adsorbents are also considered. Lastly, the recovery of the metal ions after adsorption by regenerating adsorbent materials and understanding the kinetics of nanofiber adsorption processes is summarised and recommendations made for further studies in order to address existing weaknesses of these materials.