Effect of Transition Metal Ions on the Physicochemical Properties of Glass Produced from Rice Husk Based Silica and Periwinkle Shells

Abstract

Agricultural residues and biogenic wastes from food production are often poorly managed, contributing significantly to environmental pollution. This research repurposed such wastes as raw inputs for producing valuable products, thereby reducing pollution harmful to humans, animals, and plants. Rice husks, noted for their high silica content, and calcium-rich periwinkle shells were utilized. EDXRF analysis revealed silica (10.32 %W) and calcium (31.05 %W) in the mineralized rice husks and periwinkle shells, along with phosphorus (0.62 %W and 0.25 %W, respectively). Silicate glass samples were synthesized using alkali-extracted silica from rice husks and periwinkle shells with a flux, while transition metal-doped glasses were produced by adding Fe³⁺, Co²⁺, Ni²⁺ and Cu²⁺ salts. FT-IR analysis confirmed Si–OH and Si–O–Si groups in silica, and Ca–O and P–O bands in the periwinkle shells, with evidence of chelation through Si–OH interactions and M–O bonding. UV-visible spectra showed d–d transitions that affected absorbance, transmittance, colouration, and geometric structures of the doped glasses. SEM analysis revealed crystalline and semi-crystalline microstructures in the flint glass, which became more crystalline with transition metals doping. All glasses produced were stable, with flint glass showing the highest mechanical strength. Among the doped samples, Fe³⁺-doped glass exhibited the greatest stability, while Cu²⁺-doped glass showed the lowest strength and stability.