Maghemite/alginate/functionalized multiwalled carbon nanotubes beads for methylene blue removal: Adsorption and desorption studies

Abstract

Magnetic alginate beads (A-Fe2O3) and magnetic alginate functionalized multiwalled carbon nanotubes beads (A-F-Fe2O3) were synthesized using citrate coated maghemite nanoparticles (γ-Fe2O3). Vibrating sample magnetometry analysis showed that the mass saturation magnetization of A-F-Fe2O3, A-Fe2O3, and γ-Fe2O3 is equal to 27.16, 29.06, and 42.63 emu·g−1, respectively. Compared with A-Fe2O3 beads, A-F-Fe2O3 beads showed a better adsorption performance for MB removal with a maximum monolayer adsorption capacity of qm = 905.5 mg·g−1. The adsorption studies revealed that the data of MB adsorption isotherm onto A-F-Fe2O3 were well fitted by Freundlich model. The adsorption was ionic strength and initial dye concentration-dependent. The beads presented high stability of MB adsorption capacity in a large domain of pH. Adsorption kinetic data followed the intraparticle diffusion model. Regeneration experiments were performed using five different desorbing agent. The findings reveal that magnetic A-F-Fe2O3 beads present an ideal and cost effective adsorbent in large-scale application as it demonstrated high affinity and reusability for methylene blue dye and facilitate an easy separation after treatment.