Simultaneous adsorptive removal of cationic dyes from aqueous solution using graphene oxide-incorporated sodium alginate hydrogel beads

Abstract

In this study, we present a novel approach utilizing a graphene oxide (GO)-based sodium alginate (SA) composite for the efficient removal of hazardous cationic dyes Methylene Blue (MB) and Safranin O (SO) simultaneously from aqueous solutions. The composite material leverages the unique properties of both GO and SA, offering enhanced adsorption capabilities and eco-friendliness. The synthesis of the composite involved the dispersion of GO sheets in a sodium alginate solution, followed by cross-linking to form a stable composite matrix. The resulting GO-SA composite exhibited a high surface area and abundant functional groups, providing favorable sites for dye adsorption. Batch adsorption experiments were conducted to investigate the removal efficiency of MB and SO dyes from aqueous solutions at various initial concentrations(10ppm, 20ppm, 30ppm, 40ppm), contact times(5min, 10min, 30min, 45min, 60min, 75min, 90min, 120min, 180min, 1440min) and temperatures(308k, 318k, 328k).The adsorption kinetics followed the pseudo-second-order kinetics, indicating a chemisorption process, and the equilibrium data were well-described by the Langmuir isotherm model, suggesting monolayer adsorption onto a homogeneous surface. The maximum adsorption removal of the composite for MB and SO were found to be 97% and 95%, respectively, with condition 30ppm initial concentration, pH 8 and 5g beads. Furthermore, graphene oxide (GO)- based sodium alginate (SA) composite was elucidated through Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses, revealing the involvement of π-π interactions, electrostatic attractions, and hydrogen bonding between the dye molecules and the composite surface. Result of thermodynamic study for MB dye change in enthalpy(ΔH) 35455.8 J/mol, change in entropy(ΔS) 125.03 J/mol k and SO dye change in enthalpy(ΔH) 24817.29J/mol, change in entropy(ΔS) 90.58 J/mol k. After 2 cycles of regeneration of the adsorbent, a minor drop in removal efficiency was observed. The developed GO-SA composite demonstrates promising potential as an efficient and eco-friendly adsorbent for the removal of MB and SO dyes from aqueous solutions, contributing to the mitigation of water pollution and environmental remediation efforts. This study provides valuable insights into the design and application of graphene oxide-based composite materials for wastewater treatment.