A response surface methodology approach for the removal of methylene blue dye from wastewater using sustainable and cost-effective adsorbent

Abstract

Potable water availability is becoming increasingly challenging due to increasing level of global population and industrial revolution. The disproportionate use of methylene blue (MB), particularly in industrial applications, is a growing concern due to its high resistance to biodegradation and propensity to taint aquatic environments. In this study, we developed novel eco-friendly calcium oxide nanoparticles from eggshells and fishbones (CaONPs-ES and CaONPs-FB) and decorated them on graphene oxide (GO) surfaces. Both nanocomposites (CaONPs-ES@GO and CaONPs-FB@GO) were characterized using state-art-instruments and used for the removal of MB from aqueous solutions. transmission electron. Additionally, the adsorptive performance of CaONPs-ES@GO and CaONPs-FB@GO and their mechanisms of interaction with MB were investigated. BET, SEM/EDX, and XPS results revealed that the CaONPs-ES@GO and CaONPs-FB@GO were predominantly mesoporous, with surface areas of 112 m²/g and 108 m²/g, respectively. The temperature-dependent adsorption isotherms and kinetics of CaONPs-ES@GO and CaONPs-FB@GO towards MB were consistent with Redlich-Peterson and pseudo-second-order models, respectively. The Redlich-Peterson model demonstrated an adsorption similarity to the Freundlich model more than the Langmuir model, suggesting the dominance of a heterogeneous multilayer mechanism. The synthesized nanocomposites exhibited high reusability and stability for MB adsorption (>70%) even after 10 successive adsorption-desorption cycles. Thermodynamic evaluations revealed that the adsorption process was spontaneous, endothermic, and physically driven. The nanocomposites exhibited an outstanding selective adsorption behaviour towards MB from the mixture containing MB/RhB and MB/MO with separation efficiency of 99.10% and 77.34% for CaO-ES@GO, and 61.23% and 47.81% for CaO-FB@GO respectively. The particulate interaction mechanisms within the nanocomposites primarily involved π-π interaction, hydrogen bonding, pore-filling, and electrostatic attraction. The cost analysis revealed that the developed nanocomposites are more economical for treating MB in a large-scale application. Based on the statistical analysis using response surface methodology (RSM), the contributing effects of temperature and adsorbent dosage, as well as the single effect of pH, had the most significant impact on MB removal. The nanocomposites demonstrate a promising potential for sustainable MB treatment.