Upgrading of Tista River silica sand in Bangladesh using reverse flotation techniques for container glass applications

Silica sand is a critical raw material for glass manufacturing, but natural deposits often contain impurities such as iron oxides and alumina, which degrade the final product's quality. This study presents a comprehensive beneficiation approach to upgrade silica sand purity using a sequential process comprising gravity separation, magnetic separation, and froth flotation. The initial raw silica sand contained 68.09 ± 0.07 % SiO 2 , 7.92 ± 0.05 % Fe 2 O 3 , and 13.04 ± 0.06 % Al 2 O 3 . Shaking table separation increased the SiO₂ content to 73.36 ± 0.04 %, while magnetic separation and flotation further enhanced the purity to 95.85 ± 0.05 % and 96.52 ± 0.03 % in the + 125 µm and + 180 µm fractions, respectively. The flotation process achieved an overall silica recovery of 36.1 % based on three replicate analyses. Mineralogical characterization using X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) confirmed the efficient removal of feldspar, mica, and iron-bearing minerals. The purified silica sand was utilized to synthesize soda-lime-silicate glass via the melt-quenching method, followed by annealing for structural stability. The average chemical composition of the glass (core region) was obtained by X-ray Photoelectron Spectroscopy (XPS). The synthesized glass exhibited a density of 2.44 g/cm 3 , average micro-hardness value was 573 ± 12 kgf/mm 2 , and high transmittance (>90 %) in the UV-Vis-NIR range, indicating its suitability for container-type glass with enhanced chemical durability. These findings highlight the efficiency of an integrated beneficiation approach in producing high-purity silica sand, contributing to sustainable glass manufacturing and efficient resource utilization.