Combined Process Route for Quartz Sand Purification

The preparation of high-grade quartz sand demonstrates that single mineral processing operations struggle to elevate low-quality quartz sand to ultra-white glass standards. A combined process route involving multi-stage linkage and sequential impurity removal is essential.

Addressing raw material characteristics with approximately 98% quartz content, iron impurities at 1000 μg/g, and aluminum impurities exceeding 10,000 μg/g, researchers designed a four-stage integrated technical solution: “scrubbing—grinding—magnetic separation—flotation.” First, the scrubbing operation—conducted at a pulp concentration of 60% with appropriate dispersant dosage—utilizes intense inter-particle friction to strip clay films and iron oxide layers from quartz surfaces. This single step reduces iron content to below 200 μg/g, achieving over 80% reduction. Coarse-grained products were then ground at an optimized concentration of 65% with precisely controlled grinding time. This not only adjusted particle size to the target range but also fully exposed impurities trapped within fractures, enabling their removal during fine-grained screening.

Magnetic separation employs a high-gradient magnetic separator with two passes at 1.0T and 1.2T field strengths respectively, specifically capturing weakly magnetic iron-bearing minerals like mica, tourmaline, pyroxene, and rutile, further reducing iron content to approximately 110 μg/g. The final flotation operation employs a staged reverse flotation strategy: “acid flotation of mica followed by alkaline flotation of tourmaline.” At pH 2.5, mixed amines collect mica, while at pH 7.8, sodium oleate collects tourmaline. These two reagents achieve selective separation of target gangue minerals through physical adsorption and chemical adsorption mechanisms, respectively.

This combined process ultimately yielded a high-quality concentrate with SiO₂ at 99.9% grade, Fe₂O₃ below 80 μg/g, and Al₂O₃ at 600 μg/g grade, fully meeting ultra-clear glass raw material standards. The core insight of this process lies in recognizing that refining low-grade quartz resources is not achieved through a single technological breakthrough, but rather through a systematic engineering approach involving coordinated multi-step operations and precise control of conditions. Scouring handles surface purification, grinding achieves particle liberation, magnetic separation removes magnetic minerals, and flotation eliminates non-magnetic silicates. These four steps are interdependent and indispensable.