Fe₃O₄-multiwalled carbon nanotubes-bentonite as adsorbent for removal of methylene blue from aqueous solutions

The contamination of water due to present of dyes, poses serious health problems. Therefore, treatment of contaminated water is necessary to resolve this problem. A tailored co-precipitation technique has been successfully used to prepare Fe₃O₄-multiwalled Carbon Nanotubes (MWCNTs)-Bentonite nanocomposite. The methylene blue present in aqueous solutions was removed using synthesized nanocomposite as adsorbent. The synthesized novel nanocomposite was analyzed by various characterization techniques. The scanning electron microscope analysis shows that Bentonite and Fe₃O₄ nanoparticles are well decorated with the MWCNTs matrix. The nanocomposite exhibited a high BET surface area of 204.01 m²/g with a pore volume of 0.367 cm³/g. The BJH adsorption average pore diameter was analyzed to be 7.2 nm. Moreover, the adsorption model was in agreement with the Redlich-Peterson model with adsorption capacity of 48.2 mg/g with a high nonlinear regression coefficient (R² = 0.985) and a low chi-square value (χ² = 6.18). Kinetics data were described well by pseudo-first-order and pseudo second order, models with a high non-linear regression coefficient (R² = 0.993). Adsorption of MB dye was determined to be a non-spontaneous and endothermic process since the values of ΔG, and ΔH were positive, and the entropy value was negative. Thus, the synthesized nanocomposite established itself as a promising candidate for the water treatment process.