Efficient adsorption of methylene blue from aqueous solutions using maize pith waste: Kinetic, isothermal and thermodynamic studies and mechanism analysis

Abstract

The increasing contamination of water bodies by dyes has raised the need for cost-effective and efficient treatment methods. Maize pith powder (PM) was studied for its potential to remove methylene blue (MB) from aqueous solutions, presenting an economical solution for environmental cleanup. The optimal biosorption conditions were determined for an initial dye concentration of 30 mg/L: 1.5 g/L biomass, pH 10, temperature of 25°C, and a contact time of 40 minutes. The biosorption process was evaluated using thermodynamic analysis, as well as adsorption isotherms and kinetic models. Functional groups involved in dye binding were identified using FT-IR, and surface morphology was examined through scanning electron microscopy (SEM). The thermodynamic study indicated that the biosorption process was exothermic, spontaneous, and increased randomness. The Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were best suited to describe the experimental data. The maximum biosorption capacity (qmax) was determined to be 20.22 mg/g. Kinetic analysis revealed that the biosorption followed pseudo-second-order kinetics, with intraparticle diffusion suggesting the presence of a boundary layer. SEM analysis showed a highly porous surface, enhancing the adsorption efficiency.Maize pith powder demonstrates significant potential as a low-cost and efficient biosorbent for dye removal from water. The favorable thermodynamic properties and high adsorption capacity, combined with its porous structure and functional groups, position maize pith as a promising material for water treatment applications.