Thermo-Chemical Modification of Gula Clay with Burnt Cow Bone for Ceramic Applications

Abstract

This study investigates the suitability of Gula clay for ceramic applications through chemical purification and reinforcement with burnt cow bone. Gula clay was treated with two reagents, oxalic acid and sodium dithionite, to reduce iron oxide impurities. X-ray fluorescence (XRF) analysis revealed that oxalic acid reduced Fe₂O₃ content from 3.01% to 2.64%, compared with 2.89% using sodium dithionite. Clay samples treated with oxalic acid were reinforced with varying amounts of burnt cow bone (0–10 wt.%), moulded, and fired at 1100 °C. The treated clay demonstrated superior refractoriness (>1100 °C) compared with untreated clay, which failed above 800 °C. Thermal resistivity improved to 3.8 W/mK, and compressive strength reached 1.26 g/mm³ at optimal conditions. Scanning electron microscopy (SEM) revealed block-like morphology, indicating high alumina and silica content, while X-ray diffraction (XRD) confirmed increased orthoclase (20%) in treated samples, enhancing refractoriness. Shrinkage analysis showed linear shrinkage of 24–24.3% and volume shrinkage of 25.2–26.3% for treated samples, while untreated clay displayed up to 27.8% volume shrinkage. These results confirm moderate shrinkage suitable for bricks, tiles, and refractory ceramics. The findings demonstrate that thermo-chemical modification with oxalic acid and burnt cow bone reinforcement improves the mechanical and thermal performance of Gula clay, positioning it as a cost-effective raw material for ceramic and refractory applications.