Sulfonylcalix[4]arene functionalized nanofiber membranes for effective removal and selective fluorescence recognition of terbium(iii) ions

Abstract

An attractive sulfonylcalix[4]arene functionalized nanofiber membrane (sulfonylcalix-NFM) was fabricated by immobilizing the negatively charged sulfonylcalix[4]arene onto aminated polyacrylonitrile (APAN) nanofibers acting as an adsorbent and a sensor for the effective removal and naked-eye recognition of Tb³⁺ ions. Various factors affecting the adsorption capacities such as initial solution pH, concentration, membrane dosage, contact time and a series of foreign interfering ions were investigated in detail. The sulfonylcalix-NFM showed a maximum adsorption capacity of 123.92 mg g⁻¹ for Tb³⁺, and absorbed membranes could be well regenerated without obvious compromise of removal efficiency after three repeated adsorption–desorption cycles. Moreover, it was found that the co-existing cations K⁺, Mg²⁺, and Ca²⁺ hardly interfered with the adsorption of Tb³⁺, while Cu²⁺, Eu³⁺, and La³⁺ could markedly reduce the removal efficiency of Tb³⁺. The possible adsorption mechanism of Tb³⁺ ions onto the sulfonylcalix-NFM was mainly attributed to the complex of the loaded sulfonylcalix[4]arene ligand with Tb³⁺ ions. In addition, the Tb³⁺-loaded sulfonylcalix-NFM exhibited good photoluminescence performance with green fluorescence under 365 nm UV radiation due to the binding of Tb³⁺ ions with sulfonylcalix[4]arene, which has been successfully applied for selective fluorescence recognition of Tb³⁺ ions with a low naked-eye detection limit of 0.5 ppm.