Adsorption of cationic dye using a low-cost biowaste adsorbent: equilibrium, kinetic, and thermodynamic study.

In this study, papaya stem, an agricultural biomass abundantly available in Malaysia, was utilized as low-cost adsorbent for removing methylene blue from the aqueous solution. The textural and functional characterization was evaluated using the scanning electron microscopy and Fourier transform infrared analysis. The adsorption data were simulated using the nonlinear Langmuir, Freundlich and Temkin isotherm models. Kinetic modeling and adsorption mechanism were fitted to the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Thermodynamic parameters, enthalpy, entropy, and Gibb free energy changes were established. Equilibrium data were best described by the Langmuir isotherm equation, with a monolayer adsorption capacity of 260.95 mg/g. The results supported the potential use of papaya stem as an efficient adsorbent for the treatment of cationic dye. [ABSTRACT FROM AUTHOR]