Detailed Notes on the Detection of Bisphenol A Using Activated Fly Ash Modified Electrodes

Authors and Affiliations

• Authors: M. E. Ghanjaoui, S. Esserrar, M. Salmi, S. Ait Talhajt, A. Salhi, M. El Krati, S. El Ghachtouli, S. Tahiri
• Affiliations:
  • Laboratory of Water and Environment, Department of Chemistry, Faculty of Sciences, Research Team: Analytical Chemistry and Environmental Process Engineering, Chouaïb Doukkali University, Morocco
  • Laboratory of Interface Materials Environment, Faculty of Sciences Aïn Chock, Hassan II University, Casablanca, Morocco

Abstract Overview

• Title: Rapid and inexpensive method for Bisphenol A detection in water samples.
• Main Focus: Utilizing alkaline activated fly ash modified carbon paste electrode (MFA/CPE) for the electrochemical detection of bisphenol A (BPA) in water samples.
• Environmental Context: Fly ash, if not managed, can cause pollution; however, its reuse in a circular economy can mitigate these risks.

Key Concepts and Methods

Fly Ash (FA) and Its Modification

• Types of Fly Ash:
  • Class F: Derived from anthracite or bituminous coal (Fe₂O₃, Al₂O₃ exceed 70%).
  • Class C: Generated from sub-bituminous or lignite coal (Fe₂O₃ + Al₂O₃ exceed 50%, CaO > 20%).
• Modification: Alkaline activation process to enhance the electrochemical properties for detecting BPA.
• Characterization Techniques:
  • Scanning Electron Microscopy (SEM)
  • X-ray Fluorescence (XRF)
  • X-ray Diffraction (XRD)

Electrochemical Sensor Development

• MFA/CPE Construction:
  • Preparation uses a blend of activated FA (up to 30% w/w) mixed with graphite powder.
  • Cross-linking with paraffin oil and filling into CPE cavity (surface area 0.07 cm², diameter 3 mm).

Experimental Conditions and Optimization

Optimization Parameters for BPA Detection

• MFA Content: Optimal electrocatalytic activity for BPA oxidation achieved at 2.5% activated FA concentration.
• pH Optimization:
  • Best performance observed between pH ranging from 3 to 6.8; BPA is non-dissociated at lower pH.
• Time and Potential Accumulation:
  • Maximum peak current at 180 seconds accumulation; accumulation potential optimal at +0.2 V.

Analytical Performance of the MFA/CPE Sensor

• Linearity: Calibration plot exhibits a linear relationship from 2.5 to 125 µM of BPA with a detection limit (LOD) of 0.31 µM and quantification limit (LOQ) of 1.02 µM.
• Sensitivity: $1.12 ext{ µA} ext{M}^{-1}$.
• Interference Testing: Hydroquinone and catechol show no significant interference in BPA measurement.

Results and Discussion

Chemical Composition of Fly Ash

• Major oxides identified in Moroccan FA: SiO₂, Al₂O₃, and Fe₂O₃.
• Zeolite Characteristics: Zeta potential, reaction products noted under alkaline conditions indicating transformed fly ash into zeolite A.

Electrochemical Performance Assessment

• Surface Area: MFA/CPE shows a significantly larger effective surface area compared to unmodified CPE, enhancing detection sensitivity.
• Voltammetry Techniques:
  • Square Wave Anodic Stripping Voltammetry (SWASV) measurements used to analyze BPA concentrations in various water matrices (tap, river, well).

Field Testing with Water Samples

• Conducted recovery analyses with BPA spiked in different water samples yielding recoveries between 94% - 105% indicating efficacy and reliability.
• Standard Deviations: Ranges from 0.7% to 4.5% across sample types, reinforcing the method's reproducibility.

Conclusion and Future Directions

• Conclusive Findings: The MFA(2.5%)/CPE sensor provides a robust, inexpensive, and rapid method for BPA detection in aqueous environments.
• Future Applications: Explore the sensor's applicability for other environmental pollutants. Emphasis on the development of technologies for the practical deployment in real-world conditions.