Effective removal of Malachite Green and Safranin O dyes from aqueous solution using nanoengineered lignocellulose

Abstract

Environment and public health are confronted with major challenges attributed to concurrent air and water pollution arising from the inadequate management of agricultural residues and the discharge of synthetic dyes into aquatic systems. To address these issues, this study aims to provide an advanced technique, through the application of a sequential chemical–mechanical treatment in a sustainable, cost-efficient and scalable framework. For the modification of rice straw into a competent nanobiosorbent to enhance its functionality and improve the efficient removal of cationic dyes from aqueous solutions. Comprehensive characterization portrayed fluorescence properties and the development of engineered lignocellulose nanostructures. Malachite Green (MG) and Safranin O (SO) colorants represent the basic dyes of interest. The developed biosorbent exhibited removal efficiency 99.54% ± 0.34 and 87.3% ± 0.94 for SO and MG respectively under adjusted parameters. At elevated temperature, the removal exceeded 90% for the two dyes in 30 min. Thermodynamic parameters confirmed a spontaneous and endothermic process with increased interfacial randomness. Based on nonlinear kinetic results, both SO and MG, were best described by pseudo-first-order kinetics while the overall adsorption rate was controlled by the combined contribution of film diffusion and intraparticle diffusion. Equilibrium data were evaluated by non-linear isotherm models; Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Redlich-Peterson whereas, Jovanović didn’t fit. The adsorption mechanism was elucidated through spectroscopic analysis and surface interaction studies. Results highlight the combination of favorable adsorption behavior, adsorbent regeneration, stability, and utilization of renewable biomass feedstock for nanomaterials advancement in water treatment.