The easy and facile preparation of the Co-nanoparticles on the modified aluminum-silicate was reported for the adsorption of methyl orange (MO) from aqueous solution. The as-prepared nano-adsorbent was characterized by different techniques such as Fourier transform infrared (FTIR), UV-visible diffuse reflectance spectra (UV-vis DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). Cobalt nanoparticle (CoNP) with average size of about 5-10 nm were loaded successfully on the surface of modified aluminum-silicate and were widely dispersed. EPR and XPS data resulted that majority of CoNPs are in the form of Co(II) ions. The loaded Co(II) ions were demonstrated to be a potent adsorbent for the removal of MO from aqueous solution. The adsorption process was spontaneous and endothermic in nature and followed pseudo-second-order kinetic model. The electrochemical study of the mixture of CoNP and multi-wall carbon nanotubes (MWCNT) confirmed that the oxidation of loaded CoNPs took place at easier and lower potential in the presence of MO (the electron density at Co@Si/Al-MO is higher), this being in agreement with the FTIR result; where reduction of Co Si/A1 from (III) to (II) oxidation state was more favored. (C) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.