Synthesis and effective dispersion of Fe₃O₄ NPs on alfalfa as a green nanoadsorbent for the removal of cationic dyes from aqueous solutions

ABSTRACT

In this paper, Fe₃O₄ magnetic nanoparticles (Fe₃O₄ NPs) were successfully synthesised and dispersed on alfalfa to prepare Fe₃O₄/alfalfa nanocomposite for cationic dye removal from aqueous solutions. Characterisation of Fe₃O₄/alfalfa nanocomposite using FT-IR, FESEM, and EDX analyses showed that the Fe₃O₄ NPs were excellently dispersed on alfalfa. The results display that the Fe₃O₄/alfalfa as a green adsorbent have high removal ability for toxic cationic dyes, such as malachite green (MG) and crystal violet (CV). For Fe₃O₄-alfalfa, the average particle size of nanoparticles on alfalfa (around 20–30 nm) has decreased compared with alone Fe₃O₄. The experiments showed that the adsorption of dyes onto Fe₃O₄-alfalfa better described with pseudo-second-order kinetic and Freundlich isotherm models, suggesting the surface heterogeneity of the Fe₃O₄/alfalfa. Furthermore, Fe₃O₄-alfalfa with adsorption capacity of 62.68 mgg⁻¹ and 55.12 mgg⁻¹ towards MG and CV, respectively, was comparable with those of the reported adsorbents. The results indicated that the adsorption of both dyes onto Fe₃O₄-alfalfa was thermodynamically spontaneous and more favourable at lower temperatures. The results also confirmed that the removal of MG and CV by Fe₃O₄-alfalfa were remarkable after reusing five times. Therefore, the Fe₃O₄-alfalfa as a green and low-cost nanoadsorbent with an easy synthesis route could be used for purification of water and wastewater contaminated by pollutants.

KEYWORDS:

• Fe₃O₄ NPs
• alfalfa
• green adsorbent
• malachite green
• crystal violet

Acknowledgments

The authors are grateful to the Research Council of University of Guilan for financial support of this research work.

Disclosure statement

No potential conflict of interest was reported by the author(s).