Enhanced Dye Adsorption on Cold Plasma-Oxidized Multi-Walled Carbon Nanotubes: A Comparative Study

Area of Science:

• Materials Science
• Environmental Science
• Chemistry

Background:

• Multi-walled carbon nanotubes (MWCNTs) are promising adsorbents but require surface modification for optimal performance.
• Conventional oxidation methods can be harsh and environmentally taxing.
• Cold plasma offers a tunable, low-temperature approach for surface functionalization.

Purpose of the Study:

• To investigate the cold plasma oxidation of MWCNTs for enhanced dye adsorption.
• To compare the adsorption performance of plasma-modified MWCNTs with pristine and chemically oxidized counterparts.
• To explore the physicochemical changes in MWCNTs induced by plasma treatment.

Main Methods:

• Dielectric barrier discharge (DBD) cold plasma generated by high-voltage nanosecond pulses was used for MWCNT oxidation.
• Modification parameters like processing time and pulse voltage were optimized.
• Physicochemical and morphological characterization (XPS, BET, TEM) evaluated oxidation extent and structural changes.
• Adsorption experiments using methylene blue (MB) determined removal efficiency and capacity.

Main Results:

• Maximum oxidation (O/C ratio increased from 0.02 to 0.09) was achieved after 60 min of nanopulsed-DBD plasma treatment.
• Plasma-modified MWCNTs demonstrated significantly higher MB adsorption capacity (~54% increase over pristine, ~9% over chemically oxidized).
• Adsorption followed pseudo-second-order kinetics and Langmuir isotherm models, indicating chemisorption.

Conclusions:

• Cold plasma oxidation is an effective and eco-friendly method to enhance MWCNT adsorbent properties.
• Plasma-treated MWCNTs offer superior performance for dye removal from aqueous solutions.
• This technology presents a viable, low-cost solution for water purification applications.