The column is split into 36 thin slices stacked from feed inlet to effluent outlet. Each slice tracks two numbers: the uranium concentration dissolved in the liquid passing through it, and how much uranium its resin has already picked up. Every animation step solves a small transport equation for the liquid (it is carried downward by the feed flow and spreads slightly the way a real flowing band does) and a separate uptake equation for the resin, which chases a Langmuir equilibrium — the more uranium already loaded, the less eager the resin is to take more.
Because uptake is not instant, a mass-transfer zone forms: a band of partially-loaded resin that travels down the bed ahead of the fully-saturated resin behind it. While that band is still inside the column, almost no uranium reaches the outlet — but the moment it reaches the bottom, effluent concentration climbs from near zero to the feed concentration, tracing the S-shaped breakthrough curve plotted on the right. A slow mass-transfer rate widens that band and softens the curve; a fast one sharpens it into an almost vertical step.
Once the bed is saturated, switching to elution keeps the flow direction the same but replaces the feed with a strong acid strip solution. Acid collapses the resin's affinity for uranium, so the same transport equation now runs in reverse: loaded resin dumps its uranium back into the liquid, which rides the flow down and out as a concentrated elution peak — the metallurgical step that turns a dilute leach solution into a small-volume, uranium-rich eluate ready for precipitation.
- Feed flow rate — how fast liquid moves through the bed, in bed volumes per hour. Faster flow gives the resin less contact time per slice.
- Feed uranium concentration — how much uranium is dissolved in the incoming pregnant leach solution.
- Resin capacity — the maximum uranium the resin can hold per litre of bed before it is fully saturated.
- Mass-transfer rate — how quickly the resin in a slice equilibrates with the liquid passing it; it sets how wide (and how gradual) the breakthrough band is.