Innovative Hematite-Incorporated Geopolymer Membrane from Coal Fly Ash through Direct Foaming Method

Abstract. Fly ash generation is a continuously growing waste or by-product resulting from the combustion of coal, which is potentially to explore for membrane materials. The addition of hematite as an antifouling agent allows for the utilization of fly ash as a geopolymer-based membrane. The objective of this study is to create a hematite/geopolymer membrane utilizing type C fly ash by the direct foaming technique in order to enhance the porosity of the membrane. A homogeneous mixture was obtained by combining 65 grams of fly ash and 0.85 grams of Al(OH)3 with a base activator. Subsequently, 3 grams of hematite were added to the mixture. Subsequently, hydrogen peroxide (H2O2) was added as a foaming agent and gradually blended with different percentages of 0, 2, 4, and 6 weight percent (wt.%) into the paste mixture. The paste mixture was put into the mould and left to undergo the process of curing for a duration of 7 days. The fly ash was analysed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and particle size analysis. Next, the membrane composite underwent characterization using XRD, FTIR, scanning electron microscope (SEM), and Archimedes techniques. The findings indicated that the fly ash from Pulang Pisau's Power Plant was officially identified and categorized as type C class. The diffractogram revealed the presence of mullite, quartz, and hematite phases in the hematite/geopolymer membrane. This finding was further verified by the FTIR analysis, which detected molecular vibrations indicating the existence of the T-O-T (T= Si or Al) and O-H components of the geopolymer structure. The scanning electron microscope images reveal that the membrane surface exhibits a rough texture and contains a limited number of microcracks resulting from the direct foaming process. Additionally, the measurements of porosity indicate that the porosity of the membrane increases proportionally with increased concentrations of H2O2. This research demonstrates the potential of coal fly ash as a sustainable raw material for developing advanced membranes for wastewater treatment.