Carboxyl and polyamine groups functionalized polyacrylonitrile fibers for efficient recovery of copper ions from solution

Heavy metals (e.g., Cu) in wastewater are attractive resources for diverse applications, and adsorption is a promising route to recovery of heavy metals from wastewater. However, high-performance adsorbents with high adsorption capacity, speed, and stability remain challenging. Herein, chelating fibers were prepared by chemically grafting amine and carboxyl groups onto the polyacrylonitrile fiber surface and used in the wastewater's adsorption of Cu2+. The adsorption behavior of Cu2+ on the fibers was systematically investigated, and the post-adsorption fibers were comprehensively characterized to uncover the adsorption mechanism. The results show that chelated fiber has a 136.3 mg/g maximum capacity for Cu2+ adsorption at pH = 5, and the whole adsorption process could reach equilibrium in about 60 min. The adsorption process corresponds to the quasi-secondary kinetic and Langmuir models. The results of adsorption, FTIR, and XPS tests indicate that the synergistic coordination of -COOH and -NH2 plays a leading role in the rapid capture of Cu2+. In addition, introducing hydrophilic groups facilitates the rapid contact and interaction of the fibers with Cu2+ in the solution. After being used five times, the fiber's adsorption capacity remains at over 90% of its original level.