Chromium sulfate solution to remove silica
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Dear experts: I have been recently purifying chromium sulfate in order to produce 99% chromium green. The raw material is difficult to filter after being dissolved in acid; even if filtration is possible at a slow pace, the filtrate cannot be filtered again quickly. If left for an extended period (more than 5 days), the solution becomes jelly-like. Testing revealed a high amount of silicon. Since my solution is acidic (pH 2.5–3.0), many methods for removing silicon in alkaline environments do not work. We have now tried using silicon-resin removers, silicon-removing agents, etc., but the results have been inconclusive. Is there anyone who can give some advice? Silicon removal technology under weak acid conditions. I am extremely grateful.
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Chromium sulfate – the raw material is chromium sulfate; what acid is used to dissolve it? There is also metasilicic acid in it, which reacts with the acid to form orthosilicic acid. The longer it is left like that, the worse the situation becomes. Is that the principle behind it? I also want to know what kind of system this is How is a weak acid environment determined?
The solution is prepared by dissolving chromium hydroxide in sulfuric acid, with a final pH of 2.5–3.0. Indeed, it behaves as you described: the longer it is left like this, the worse the situation becomes, until it eventually turns into a jelly-like substance. The original solution contains 60 g/l of chromium and 1.0 g/l of silica. Is there any way to reduce the silica level to below 0.01 g/l?
Silicon should exist in the form of metasilicic acid or silicic acid, right?