The silica washing process is used to remove impurities (such as iron, aluminum, clay, and organic matter) from silica sand or quartz to improve its purity for industrial applications like glassmaking, ceramics, electronics, and solar panels. Here’s a step-by-step overview:
1. Crushing & Grinding
– Raw silica ore is crushed and ground to liberate silica grains from impurities.
– Jaw crushers, cone crushers, or ball mills may be used.
2. Scrubbing & Attrition
– The crushed material is mixed with water in an attrition scrubber to break down clay and surface contaminants.
– High-speed rotating paddles create friction, removing adhered impurities.
3. Desliming (Removal of Fine Particles)
– Silica slurry is passed through hydrocyclones or settling tanks to remove ultrafine particles (slimes).
– This step reduces iron and clay content.
4. Gravity Separation (Optional)
– Heavy minerals (like iron oxides) are removed using spirals or shaking tables.
– Magnetic separation may also be used for iron removal.
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5. Acid Leaching (Chemical Washing)
– For high-purity silica (e.g., for solar-grade silicon), acid washing is done using:
– Hydrochloric acid (HCl) or sulfuric acid (H₂SO₄) to dissolve metal impurities.
– Oxalic acid or citric acid for iron removal.
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re is heated (~60–90°C) for better impurity dissolution.
6. Rinsing & Neutralization
– After acid treatment, the silica is washed repeatedly with deionized water to remove residual acids.
– pH is adjusted to neutral (~7) using alkaline solutions if needed.
7. Drying & Classification
– Washed silica is dried in rotary dryers or fluidized bed dryers.
– Sieving or air classification ensures uniform particle size distribution.
8. Final Quality Control
– Purity is checked via XRF (X-ray fluorescence) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry).
– Typical high-purity silica has >99.5% SiO₂ with low Fe₂O₃ (<0.05%).
Applications of Washed Silica:
– Glass manufacturing
– Semiconductor waf