To fill up some time today, I have two photographs of the froth flotation at London Mill. The separation is based on there being a grain size after grinding where each grain is only iron sulfide, copper-iron sulfide, or zinc sulfide. The trick to separate these comes from the fact that all minerals have a native electric charge to their surface (usually balanced by soluble ions). Soaps also have charge. The most common bath soap is sodium lauryl sulfate where the organic part is negatively charged. On the opposite side of the spectrum, that soap that used to be called pHisohex has a positively charged organic part. Blends of soaps to be exactly opposite in charge to the charge on the grain of one of the three is turned to froth by air injection into a water slurry of the grains and the grains of that mineral float to the surface attached to bubbles where it is skimmed off. Since there were three concentrates produced at London Mill, there were three secret combination of soaps that did the work, each in a separate chamber as the slurry flowed from one air injection chamber to the next.
Posted on: Tue, 27 Jan 2015 00:40:34 +0000