Groundnut Shell-Derived Amorphous Silica as a Sustainable Alternative to Quartz in Porcelain Stoneware: Phase and Microstructural Evaluation

Abstract

This study investigates the development of eco-friendly porcelain stoneware bodies using amorphous silica derived from groundnut shell ash (GSA) as a sustainable alternative to conventional quartz. Groundnut shells were subjected to controlled combustion and subsequent chemical precipitation to synthesize high-purity amorphous silica (GSASi). The extracted silica exhibited a high silica content of 93.7 wt.% and an amorphous structure confirmed by X-ray diffraction (XRD). Two stoneware compositions were formulated: one containing commercial quartz (PSWTSS) and the other incorporating GSASi (PSWTAS) as a complete replacement for quartz. The samples were prepared via conventional ceramic processing and sintered at 1050°C and 1100°C. Phase analysis revealed the presence of quartz, mullite, and albite in both compositions, indicating that the substitution did not adversely affect the essential phase formation. Microstructural evaluation using scanning electron microscopy (SEM) showed that the GSASi-based sample exhibited a finer, more homogeneous, and less porous structure compared to the quartz-based counterpart, especially at 1100°C. This improvement is attributed to the higher reactivity of amorphous silica, which enhances densification and promotes mullite formation. The findings demonstrate that groundnut shell-derived silica is a viable and sustainable substitute for conventional silica in porcelain stoneware production, with potential benefits in improving microstructural properties and reducing environmental impact.