Waste solvent recovery — extractive distillation (IPA/water)

A pharmaceutical waste isopropanol/water stream (near the ~68 mol% IPA azeotrope) is fed to an extractive column with a high-boiling entrainer feeding in a few stages above it; a second column strips the entrainer back out of the bottoms for reuse. Honesty note: the brief's original entrainer, DMSO, doesn't have a pinned NRTL isopropanol binary in this codebase's databank (only DMSO-water is pinned), so this uses sulfolane instead — a real, industrially-standard extractive/physical solvent with a genuine pinned NRTL isopropanol binary. At this stage count and solvent-to-feed ratio the entrainer effect is real but modest (overhead reaches ~82 mol% IPA, up from the 68% feed) — a sharper, near-anhydrous cut would need more stages/reflux or a higher solvent ratio than what this session verified converges reliably.