2D Zinc Solvent Extraction: D2EHPA Mixer-Settler Cascade

This 2D companion to the 3D zinc SX lab strips the process to its real mixer-settler cross-section: two countercurrent extraction stages (E1/E2) feeding a spent-electrolyte strip stage (S1), driven by the same three process variables as the 3D scene — O/A phase ratio, D2EHPA (extractant) concentration and feed acidity. Underneath, it solves two independent cation-exchange distribution-coefficient equations for Zn2+ and Fe3+/Mn2+, so recovery and selectivity are not decorative numbers: D_Fe collapses faster than D_Zn as acidity rises because iron releases three protons per extraction event against zinc's two, exactly the chemistry a real Zn/Fe separation plant exploits. Watch the teal D2EHPA stream darken as it loads with zinc on its way from E2 to E1, rust-colored Fe/Mn-carryover dots thin out as you raise acidity, and gold zinc-rich electrolyte peel off at the strip stage once the spent-electrolyte acid reverses the exchange.