A Kinetic, Thermodynamic, and Mechanistic Approach toward Adsorption of Methylene Blue over Water-Washed Manganese Nodule Leached Residues

The present study aims to investigate and develop a cheap adsorption method for color removal from wastewater using water-washed manganese nodule leached residues (WMNLR) as adsorbent. The method was employed for the removal of methylene blue (MB), and the influence of various factors such as adsorbent dose, adsorbate concentration, electrolytes (NaCl, Na 2 HPO 4, Na 2 SO 4, NaNO 3, and Na 2 CO 3 ), temperature, and pH was studied. The equilibrium of adsorption was modeled by using the Langmuir and Freundlich isotherm models; the kinetic parameters and intraparticle diffusion were also then determined for the MB−WMNLR system. Kinetic data were well described by the pseudo second-order model. The thermodynamics of the MB−WMNLR system indicates spontaneous and endothermic nature of the process. The results in this study indicated that WMNLR was an attractive candidate for removing MB (98%), which could be reused up to four times without significant loss in its adsorption capacity.