Synthesis of mesoporous rebar MWCNT/alumina composite (RMAC) nodules for the effective removal of methylene blue and Cr (VI) from an aqueous medium

Highlights: • Waste water treatment with no sludge formation and easy handling, scale up and reusable process developed. • Aqueous sol-gel route was employed in the synthesis of reusable Rebar Multiwalled CNT/Alumina Composite (RMAC) nodules. • Effective removal of Methylene Blue dye and Cr (VI) ion was achieved using RMAC nodules. • The mesoporous RMAC nodules were fully characterized using BET, XRD, SEM, TEM, FTIR and Raman techniques. • The kinetic and thermodynamic study of the adsorption process was carried out to examine the efficiency of RMAC nodules. -- Abstract: The distinctive and tuneable physical, chemical and configurational properties of carbon nanotubes (CNTs), has prompted their combination with metal oxides to contrive carbon composites showing entrancing adsorption property with incredible potential in water treatment. MWCNT/Alumina (RMAC) nodules with effective adsorption capacity were synthesized following aqueous sol-gel route. Batch sorption experiments examined the efficiency of removal of dyes and heavy metal ions from an aqueous solution on RMAC nodules. The factors affecting adsorption were studied for adsorption of methylene blue dye (MB) and hexavalent chromium by altering the MWCNT concentration from 1 wt.% to 5 wt.%. The adsorption experiment demonstrated an adsorption capacity of 187.5 and 597 mg g⁻¹ at 25 °C for MB and Cr (VI) respectively. Various characterization techniques such as XRD, BET, TEM, Raman, FTIR, TPD and CHN were employed to study the initial development of the material. Multiple adsorption interaction mechanisms (electrostatic interactions, hydrogen bonding, π−π electron-donor-acceptor interactions) may be credited for the remarkable adsorption capacity of these nodules. Results of this work are of great significance for environmental applications of Alumina/MWCNT composite as a promising adsorbent nanomaterial for organic pollutants from aqueous solutions. Apart from high sorption ability, these nodules offer ease of separation with splendid regeneration ability.