Polyelectrolyte-modified multi-walled carbon nanotubes for the adsorption of

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Chromium(VI) is a toxic heavy metal pollutant.
• Efficient methods for Cr(VI) detection and removal are crucial for environmental monitoring.
• Multi-walled carbon nanotubes (MWNTs) show promise as adsorbents due to their high surface area.

Purpose of the Study:

• To develop and characterize PDDA-MWNTs for Cr(VI) adsorption.
• To evaluate the performance of PDDA-MWNTs in a sequential injection system coupled with ETAAS for Cr(VI) determination.
• To assess the method's efficiency, selectivity, and applicability in real-world water samples.

Main Methods:

• Noncovalent wrapping of MWNTs with PDDA via π-π interactions.
• Characterization of PDDA-MWNTs using FT-IR and surface charge analysis.
• Adsorption of Cr(VI) in a mini-column packed with PDDA-MWNTs within a sequential injection system.
• Detection of Cr(VI) using electrothermal atomic absorption spectrometry (ETAAS).

Main Results:

• PDDA-MWNTs exhibited a 32% improvement in Cr(VI) adsorption efficiency compared to bare MWNTs at pH 6.
• Quantitative Cr(VI) recovery was achieved using 0.1 mol L-1 ammonium nitrate solution with 81% elution efficiency.
• The method showed no interference from Cr(III) at a 6:1 Cr(III)/Cr(VI) ratio.
• An enrichment factor of 8.6, a detection limit of 0.016 μg L-1, and a RSD of 3.9% were obtained.
• The procedure was validated using a certified reference material and real water samples.

Conclusions:

• PDDA-MWNTs are effective adsorbents for Cr(VI) removal and preconcentration.
• The developed sequential injection-ETAAS system offers a sensitive and selective method for Cr(VI) determination in water.
• This approach provides a reliable tool for environmental monitoring of chromium contamination.