Work

Mechanistic equilibrium-stage modeling and countercurrent recovery of dilute acetic acid by reactive extraction with TOPO in n-dodecane

Year: 2026

Type: article

Abstract: The recovery of dilute acetic acid (HAc) from aqueous streams remains an important separation challenge in established industrial processes and is gaining renewed importance in emerging sustainable routes, including gas fermentation for CO 2 utilization. Reactive extraction with trioctylphosphine oxide (TOPO) in hydrophobic diluents is promising, but process design is complicated by undesired H 2 O co-extraction and limited single-stage recovery. Here, HAc recovery using TOPO in n -dodecane is investigated by combining liquid–liquid equilibrium experiments, mechanistic modeling, and countercurrent extraction. A physically motivated complexation model is developed to quantify the competitive binding of HAc and H 2 O to TOPO in the organic phase, including (HAc ⋅ TOPO), (HAc ⋅ H 2 O ⋅ TOPO), and (H 2 O ⋅ TOPO) complexes. The model is parameterized over a broad experimental range covering aqueous HAc mass fractions up to 20 %, TOPO mass fractions from 5–30 %, and different phase ratios. At 298.15 K and 313.15 K, organic-phase HAc molalities are correlated with mean relative errors (MRE) of 4.8 % and 5.8 %, respectively, while the corresponding errors for H 2 O are 11.9 % and 23.0 %. The model is transferred to an equilibrium-stage countercurrent framework to evaluate solvent-to-feed ratio, number of stages, and TOPO concentration regarding HAc recovery and H 2 O co-extraction. Finally, countercurrent operation is demonstrated in a DN32 Kühni column. Simulated and experimental concentration profiles agree closely using a HETS of 450 mm, with maximum absolute deviations of only 2.8 % in extraction efficiency and 1.2 % in selectivity, confirming the model-based transfer from equilibrium data to countercurrent process design.

Source: Separation and Purification Technology

DOI: 10.1016/j.seppur.2026.139539

Authors: Janik Hense, William Graf von Westarp, Alea Frische, Andreas Jupke

Institutions: RWTH Aachen University, Forschungszentrum Jülich

Language: English

Topic: Phase Equilibria and Thermodynamics

Subfield: Physical and Theoretical Chemistry

Field: Chemistry

Domain: Physical Sciences

SDG: Responsible consumption and production

Open Access status: hybrid

Estimated APC paid: $4,060