Effective removal of crystal violet from aqueous solution by graphene oxide incorporated hydrogel beads as a novel bio-adsorbent: kinetic, isotherm and thermodynamic studies

Abstract

This study revealed the facile preparation of graphene oxide (GO) containing sodium alginate (SA) and hydroxyethyl cellulose (HEC) hydrogel beads that could be used as a low-cost and environmentally friendly bio-adsorbent for the removal of crystal violet (CV). The thermogravimetric analysis (TGA) and absorbency under load (AUL) test results demonstrated that the thermal stability and mechanical strength of SA-HEC hydrogel beads were enhanced by the existence of GO. The SA-HEC/GO bio-adsorbents displayed superior adsorption capability toward cationic CV dye molecules and the adsorption capacity increased from 123.16 mg g⁻¹ to 312.72 mg g⁻¹ at pH 5 by incorporation of 1 wt% GO. The CV adsorption is well-described by pseudo-second-order model and was mainly controlled by intra-particle diffusion. Also, the Langmuir and Temkin isotherm models confirmed the physical monolayer adsorption of CV. The calculated thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) indicated that the adsorption of CV onto SA-HEC/GO bio-adsorbents was spontaneous and it was favored at high temperatures. The bio-adsorbent retained its ability to adsorb CV with a removal efficiency of 79.4% for up to six cycles.

Graphical Abstract

Keywords:

• Sodium alginate
• hydroxyethyl cellulose
• graphene oxide
• hydrogel beads
• cationic dyes

Acknowledgements

The authors wish to thank Yaren Demirtemel and Kevser Kaya for their assistance in the synthesis of hydrogel materials.

Conflict of interest

The authors report there are no competing interests to declare.