Enhanced adsorption of Congo red dye by functionalized carbon nanotube/mixed metal oxides nanocomposites derived from layered double hydroxide precursor

• Novel CNT/Mg(Al)O nanocomposites were synthesized from a LDH precursor.
• The surface of the CNT is functionalized with abundant OH and COO groups without any further modification.
• The CNT/Mg(Al)O nanocomposites exhibit rapid adsorption rate and high adsorption capacity in the removal of Congo red with the maximum adsorption capacity enhanced to 1250 mg/g.
• Adsorption mechanism mainly involves complexation and electrostatic interaction.

Functionalized carbon nanotube/mixed metal oxides (CNT/MMO) nanocomposites composed of CNT and Mg(Al)O nanoparticles have been synthesized by pyrolysis of a terephthalic intercalated layered double hydroxide (LDH) precursor. The chemical composition and morphology of this nanocomposites were investigated by XRD, SEM, and TEM measurements. FTIR characterization shows that the surface of the prepared CNT is functionalized with abundant oxygen-containing groups without further modification. As a novel adsorbent, the as-prepared functionalized CNT/Mg(Al)O nanocomposites exhibit very high performance in the removal of Congo red (CR) dye from aqueous solutions. The initial pH of dye solution and dosage of adsorbent have an important influence on the adsorption property of the CNT/Mg(Al)O nanocomposites. The adsorption isotherm obeys the Langmuir model, with the maximum adsorption capacity greatly enhanced to 1250 mg/g, exhibiting potential applications in wastewater treatment. A adsorption mechanism that involves (i) strong interactions between the functional groups on the surface of CNT and CR molecules and (ii) electrostatic interactions between positively charged reconstructed LDH layer and negatively charged CR molecules, was proposed.