Maia 3 lmh

The shape and surface morphology of MS were evaluated by scanning electron microscope (SEM) (TESCAN MAIA 3 LMH, Shanghai, China). The samples were mounted onto stubs using a double sided adhesive tape and were sputter-coated with gold prior to taking pictures.

The pH of the fly ash was measured using a calibrated pH meter (Thermo Orion, Waltham, MA, USA) and the morphology of the fly ash was characterized using a scanning electron microscope (TESCAN MAIA3LMH, Czech Republic). The physical and chemical properties of the fly ash, including the heavy metal content (Pb, Hg, Cr, Cd and As), were also determined. Heavy metal elements in the fly ash were measured by microwave digestion coupled with plasma mass spectrometry (ICAP6300; Mao et al., 2017 (link)).

The graphene used in this study was prepared in-house by an electrochemical method (Chen et al., 2022b ). In brief, graphite was used as both the anode and cathode with distilled water as the electrolyte. The graphite electrode was electrolyzed and oxidized by a high-frequency pulse current to prepare graphene oxide. Through the action of an electrochemical electric field, external electrolyte ions (molecules) were inserted into the layered materials, like liquid phase stripping, while an electric field force was applied to drive electrolyte molecules to intercalate into the graphite cathode directly in an electrochemical manner. Thus, the graphite layer spacing became larger, and the van der Waals forces between the layers became weaker. Graphene was thus prepared by electrochemical stripping of graphite using a nonoxidizing method. The characteristics of graphene were analyzed by UV-visible and Raman spectroscopy (Horiba, LabRAM HR Evolution). Raman spectra were obtained using a Renishaw inVia Qontor with a 532-nm excitation laser. Graphene morphology was examined by SEM (Tescan MAIA3 LMH) and transmission electron microscopy (TEM; Tecnai G2 F20 S-TWIN TMP).