Epichlorohydrin and triethylenetetramine functionalized electrosprayed Fe3O4/Chitosan magnetic microspheres for removal and separation of Congo red

Abstract

Aquatic ecosystem contaminated by organic dyes is one of the most crucial issues plaguing people worldwide, while water remediation through adsorption technology is the most sustainable option. Herein, two chitosan-based adsorbents were successfully fabricated by a facile one-step method under alkaline condition via electrospraying technology, then the above two materials were cross-linked with epichlorohydrin and grafted triethylenetetramine to prepare two kinds magnetic Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres for remediation of anion dyes namely Congo red (CR) in wastewater respectively. The morphology features, structure, composition, thermal stability, and pore diameter of the two adsorbents were acquired by SEM coupled with EDX, XRD, FTIR, TGA, and BET. The adsorption behavior of Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres towards CR from water was systematically evaluated. The determined isoelectric points (pHpzc) of Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 are orderly 7.4 and 7.8. The results confirmed that the CR remediation process can be simulated by PSO kinetic model (R2 > 0.995) along with Langmuir isotherm (R2 > 0.998) with maximal CR adsorption amounts by Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres of 1145.42 and 617.28 mg g−1 at pH = 7 and T = 25 °C, respectively. The negative ΔG0, positive ΔH0 (28.65 and 8.02 kJ mol−1), and positive ΔS0 (112.29 and 62.71 J mol−1 K−1) signified that the adsorption of CR onto Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres surface was spontaneous and endothermic in nature. After four consecutive cycles, both magnetic microspheres remained a superior CR removal performance, indicative of the stability and recyclability of the adsorbents.