Not sure about actual commercial applications, but you need to devise an adequate testwork program for your feed. (I would not rely on databases at all.)  Evaluate the impurities. If you have mainly iron and at low concentration (max. about 100 ppm), you may get away  with an oxalic leaching as a first step - test and see. If you have higher iron, not to mention other deleterious elements (Ba, Mg, Al, Ca, Ti, Zr, etc.) you may want to consider hydrochloric acid leaching. Sulfuric acid will not dissolve barium. If  no results, you may need to look at hydrofluoric acid leaching, which is essentially a health, safety and environmental  concern, potential liability. Try avoiding. In all scenarios, you will need to test at 2-3 grind sizes and eventually 2 temperatures. Try to get a concentration profile vs. time in each scenario. You will need to wash the leached product which open another can of worms due to process water treatment and recycling requirements. Reagent cost is also dependent on this stage. The leached and washed discharge may need some finishing touches before being directed to drying and product conditioning. As always with hydromet processes, nothing is simple and the risk to reward ratio  tends to be favored by the simplest approach, if effective. Otherwise, I would take a pass. Hope this helps. Cheers, Alex.

Hello

If the pollution is iron ore or another heavy mineral, you maybe don't need acid leaching but only density separation. 

Regards

Rheomet is exactly right - acid leaching could open up all sorts of problems (water balance, acid balance, water treatment, disposal of metals in solution, etc., etc.).  You need to look at the value of the final product vs. the cost of processing.  Unless this is a very high value sand you probably can't justify the hydromet cost.  Gravity separation or density separation could work if you know the liberation characteristics, the level of impurities, and the type of impurities involved.  If you could give us this information, along with estimated processing rates, we might be able to help you some more.

Best Regards

Andrew

Not so simple as impurities differ in silica sand sources. Start with customer specification and know what you need to produce. Size production quantity wanted including time for maintenance and off-line. Learn price and availability of acid delivered to your site. Confirm any reasonable conditions will result in product quality needed. Assume everything works and run proformas to confirm process would be viable with minimum leach, rinse, disposal of acid solubles flow sheet. If not, forget it. If economics and market look good do prefeasibility study. If this study looks good, follow-up with full feasibility study based on test results. Allow for EPA and other permit application time and cost constraints and .. . I've given you a starting point.