CFD modelling and experimental analysis of aromatic amine extraction in a flat sheet supported liquid membrane contactor

Abstract

Supported liquid membranes (SLMs) using ionic liquids are effective for the extraction of aromatic amines. This experimental study employed a flat sheet SLM contactor with the ionic liquid trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P_6,6,6,14][N(Tf)₂]) as the solvent to investigate the separation of $\alpha$-methylbenzylamine (MBA) and 1-methyl-3-phenylpropylamine (MPPA) from isopropyl amine (IPA). A detailed process study was conducted to examine the effects of flow rate (5–10 L/h), feed concentration (0.5–2.5 g/L), and feed pH (9–11) on extraction performance. Under standard experimental conditions (10 L/h, 1.0 g/L, pH 10), MBA and MPPA demonstrated high solute fluxes of 2.39 and 5.47 g/(m²h), respectively, compared with IPA, which had a solute flux of 0.84 g/(m²h). However, after 24 h, the recoveries were relatively low, at 17.9 % for MBA, 32.6 % for MPPA, and 5.2 % for IPA. No significant velocity dependency was observed, with slight variations attributed to minor pH changes, while a linear flux increase was noted for higher feed concentrations. The feed pH had a significant impact on the extraction performance, with higher pH levels resulting in increased solute fluxes and recoveries. To complement the experimental results, computational fluid dynamics (CFD) simulations were employed using COMSOL Multiphysics 5.1. The model demonstrated satisfactory agreement across various conditions, but underestimated fluxes and recoveries at higher pH values. Consequently, a new mass transfer mechanism was proposed to explain the variations observed in the experimental results.