High-performance MnO2 embedded fly ash zeolite applied for effective mineralization of bisphenol-A and sorption of congo red: Mechanism, real water application, and toxicity assessment

Abstract

In this work, bisphenol A (BPA) and Congo red (CR) were eliminated using a hydrothermally produced flyash zeolite-embedded MnO2 (FAZ-MnO2) composite. Methods like X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-prepared composite. With a higher specific surface area of 384.85 m2/g, FAZ-MnO2 outperformed MnO2 and FAZ, which had surface areas of 46.84 and 28.46 m2/g, respectively. Likewise, the maximum adsorption capacity of FAZ-MnO2 towards BPA and CR was 172.19, and 293.91 mg/g respectively, which was higher than their pristine counterparts. The efficiency was observed to be enhanced due to inclusion of MnO2 into FAZ framework that served as active adsorption sites to remove BPA and CR. The removal of BPA occurs through adsorption followed by oxidation and mineralization due to presence of MnO2. Wheras, CR removal is dominated by adsorption process including covalent bonding, hydrogen bonding, and electrostatic interactions. Humic acid improved the elimination of BPA and CR, and FAZ-MnO2 showed good stability and recyclability with outstanding performance even after five cycles. FAZ-MnO2 can also effectively remove CR and BPA from various real water matrix. Eventually, the degradation byproducts were evaluated, and the lethality of those byproducts as well as the composite was assessed. The findings indicate that the eco-friendly composite studied has the potential to remove organic contaminants from water bodies.