Comparative study of methylene blue dye adsorption onto activated carbon, graphene oxide, and carbon nanotubes

Three different carbonaceous materials, activated carbon, graphene oxide, and multi-walled carbon nanotubes, were modified by nitric acid and used as adsorbents for the removal of methylene blue dye from aqueous solution. The adsorbents were characterized by N2 adsorption/desorption isotherms, infrared spectroscopy, particle size, and zeta potential measurements. Batch adsorption experiments were carried out to study the effect of solution pH and contact time on dye adsorption properties. The kinetic studies showed that the adsorption data followed a pseudo second-order kinetic model. The isotherm analysis indicated that the adsorption data can be represented by Langmuir isotherm model. The remarkably strong adsorption capacity normalized by the BET surface area of graphene oxide and carbon nanotubes can be attributed to π–π electron donor acceptor interaction and electrostatic attraction.

► Three different carbonaceous materials were modified by nitric acid.
► The physico-chemical properties of three adsorbents were investigated and compared.
► The adsorption process was characterized by kinetics and isotherm analysis.
► Adsorption mechanism was attributed to the π–π interaction and electrostatic attraction.