Development of a novel MOF-based nanofiber for highly selective removal of cobalt from aqueous solutions†

Abstract

This study addresses the challenge of cobalt ion separation by developing novel MOF nanofibers, Co(II)-PIIMs. Co(II)-SIM-IIP was synthesized using zinc-based MOFs (SIM-1) as a matrix and tetraethylpentadiamine (TEPA) as a functional monomer through the ion-imprinting technique (IIT). These Co(II)-SIM-IIP particles were then incorporated as fillers into a polyacrylonitrile (PAN) substrate to fabricate Co(II)-PIIMs-x nanofibers via electrospinning, aimed at selective cobalt ion separation. The optimal performance was achieved at a 10% doping level of Co(II)-SIM-IIP, resulting in a maximum adsorptive capacity of 112.74 mg g⁻¹, a membrane flux of 1095 L m⁻² h⁻¹, and a retention rate of 43.49%. The material demonstrated excellent selectivity, exhibiting high selectivity factors for various ions, such as Ca²⁺ (7.42), K⁺ (55.98), Mg²⁺ (72.30), and Ni²⁺ (1.28). The adsorption mechanism revealed that cobalt adsorption onto Co(II)-PIIMs is primarily governed by chemisorption, facilitated by the uniform distribution of cobalt on the surface of the nanofibers. Importantly, after five cycles, Co(II)-PIIMs exhibited outstanding regeneration capability, retaining over 95% of their initial adsorption capacity. These remarkable selectivity factors underscore the material's potential for efficient cobalt ion separation and purification in environmental remediation applications.