O/A Ratio
also known as organic-to-aqueous ratio · phase ratio
O/A ratio is the organic phase flow rate divided by the aqueous phase flow rate. In an extraction stage the loaded organic leaving the circuit is fixed by the metal mass balance and the organic's loading capacity, so the O/A ratio is really a consequence of the target concentration factor. In stripping the ratio is inverted and set by how concentrated the strip liquor must be.
Why it matters in practice
The O/A ratio determines the required settler area, the mixer energy density and the achievable concentration factor. In practice designers fix the ratio from loading data, then size the equipment to suit it — not the other way round.
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Related terms
Reference entry GL-O-A-RATIO. Definitions on this page describe engineering practice in hydrometallurgical process design; they are not a substitute for test work on your own material.