Degradation of methylene blue dye and bisphenol‑a using expanded graphenec‑polypyrrole‑magnetite nanocomposite

Abstract

This work is focused on the synthesis of expanded graphene (EG), polypyrrole-magnetite (PPy/Fe₃O₄) and expanded gra- phene-polypyrrole-magnetite nanocomposite (EG-PPy/Fe₃O₄) electrodes and their application in the degradation of organic pollutants in water. The nanocomposites were synthesized through the co-precipitation method and characterized using ultra- violet–visible spectroscopy, Brunauer–Emmett–Teller surface area analyser, scanning electron microscope, energy dispersive X-ray, X-ray diffractometer and X-ray photoelectron spectroscope. The EG, PPy/Fe₃O₄ and EG-PPy/Fe₃O₄ electrodes were applied in a comparative photoelectrochemical degradation of 0.1 × 10−⁴ M methylene blue (MB) dye and bisphenol A (BPA) in 0.1 M Na₂SO₄ under visible light irradiation. The degradation was also performed through photolysis, electrochemical and photoelectrochemical processes. The results showed that the pure PPy and EG-PPy/Fe₃O₄ were present in the Anatase phase of PPy. The EG-PPy/Fe₃O₄ composite absorbed a noticeable amount of light in the entire visible light region compared to pure PPy and PPy/Fe₃O₄. The surface area and pore volume of pure PPy was observed to decrease after modification with the EG as a result of the interpenetration of the porous matrix of EG by the PPy nanoparticles. The EG-PPy/Fe₃O₄ electrode was the most effective in the degradation of both dyes. The order of efficiency was EG < PPy/Fe₃O₄ < EG-PPy/Fe₃O₄. The photoelectrochemical degradation process resulted in improved degradation efficiency of 92% (MB) and 88% (BPA) within 240 min and was observed to be greater than that of photolysis and electrochemical oxidation methods. The EG-PPy/Fe₃O₄ aterial for the degradation of MB and BPA in wastewater.