SYNTHESES AND CHARACTERISTICS OF CALCIUM-BASED GEOPOLYMER FROM SOLAR-CELL PANEL-GLASS WASTE BY HYDROTHERMAL METHOD

Abstract

A calcium-based geopolymer was synthesized using a blend of recycled glass powder from solar panels (PV glass waste), limestone, and a sodium silicate solution, which underwent hydrothermal autoclaving at 180 °C for varying durations. This material is regarded as environmentally friendly and has garnered research attention worldwide. In this investigation, limestone served as the calcium source, while recycled glass from solar panels provided the SiO2 necessary for producing calcium-based geopolymer materials. Currently, solar-panel waste poses a significant environmental challenge that requires attention. The objective of this research was to develop a sustainable and high-performance calcium-based geopolymer using waste materials, specifically recycled glass from solar panels and limestone. The study aimed to evaluate the effects of hydrothermal autoclaving on the compressive strength, volume weight, porosity, and water absorption of the synthesized geopolymer, as well as to understand the microstructural transformations involved. The results revealed a remarkable 430 % increase in the compressive strength of the specimens following hydrothermal autoclaving for 24 to 96 hours compared to the unautoclaved samples. Concurrently, the volumetric weight had a substantial rise from 1.54 % to 2.31 g/cm3, with corresponding decreases in the porosity and water absorption from 38.1 % to 16.9 % and 10.26 % to 5.08 %, respectively. An X-ray diffraction (XRD) analysis of the mineral composition and a scanning electron microscope (SEM) examination of the microstructure demonstrated a transformation of all samples from an amorphous gel structure to needle- or spike-shaped fibrous, and then sheet-like CSH structures. These new structures exhibited dimensions of less than 10 µm in length, less than 2 µm in width, and less than 400 nm in thickness. The resulting CSH products constitute calcium silicate hydrate minerals, characteristic of calcium silicate materials, which are synthetic products arising from chemical reactions among SiO2, CaO, and H2O under hydrothermal conditions. This study underscores the potential of using recycled materials to produced high-strength geopolymers, offering a promising solution to the environmental challenge of solar-panel waste.