High-density amino groups on polyacrylonitrile nanofibers via chemical grafting for selective Co(II) adsorption

To efficiently separate Co (II) from aqueous solutions and address the issues of difficult recycling and insufficient adsorption performance of traditional adsorbents, this study used polyacrylonitrile nanofibers (PAN/NFs) as the matrix and prepared an amino-functionalized adsorbent (PAN/NFs@NH ₂ ) via graft modification with triethylenetetramine (TETA). The structural characteristics and Co (II) adsorption performance of PAN/NFs@NH ₂ were investigated, and the material was characterized via SEM, EDS, FTIR, BET, XPS, and CA. PAN/NFs@NH ₂ exhibits advantages of easy recyclability, excellent physicochemical stability, and good hydrophilicity. Static adsorption experiments showed that the optimal conditions for Co (II) adsorption by PAN/NFs@NH ₂ are pH = 8 and a contact time of 12 h; under these circumstances, the equilibrium adsorption capacity reaches 48.30 mg/g, and the saturated adsorption capacity is 158.29 mg/g. The adsorption process is the Langmuir monolayer adsorption and it is an endothermic and spontaneous process. PAN/NFs@NH ₂ has superior selectivity for Co (II), with selectivity coefficients of 194.1 and 156.5 for Mn(II) and Li(I), respectively. Following 5 adsorption-desorption cycles, its adsorption capacity still retains around 70% of the initial value. XPS analysis confirmed that the adsorption mechanism involves the formation of coordination bonds between Co (II) and nitrogen atoms in amino groups (-NH ₂ , -NH-), where nitrogen atoms donate their lone pairs of electrons to Co (II). In conclusion, PAN/NFs@NH ₂ provides an efficient, stable, and easily recyclable fiber-based adsorbent for the treatment of Co (II)-containing wastewater.