| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 145903 | Chemical Engineering Journal | 2016 | 8 Pages |
•Species distribution clearly described during acid partitioning in an absorptive polymer.•Effect of acid absorption on equilibrium pH well characterized.•High pressure CO2 (60 bar) can reversibly lower pH to facilitate acid absorption.•Amine-functionalized hydrogels achieve high acid recovery with low polymer fractions.
Strategies for extracting organic acids from aqueous solutions using polymeric absorbents are demonstrated and discussed in the context of two-phase partitioning bioreactor (TPPB) design. Experimental data and material balances for the uptake of butyric acid and benzoic acid by a poly(ether-block-amide) copolymer (Pebax 2533) establish the inherent limitations of unreactive absorbents for organic acid bioprocesses that operate at near-neutral pH. Improvements to TPPB performance are achieved by lowering pH temporarily with CO2 to enhance acid absorption, and removing the solute-rich polymer before restoring pH to fermentative values by releasing the CO2 pressure. Butyric acid removal by Pebax 2533 improved from 3% to 40% upon acidifying a pH 6 solution with 60 bar of CO2, while benzoic acid absorption increased from 1% to 80% using this pressure manipulation technique. A reactive extraction approach involving a newly-synthesized amine functionalized hydrogel is also described wherein acid/base reaction equilibrium governs the extent of solute uptake. Copolymerization of 2-(dimethylamino)ethyl acrylate (DMAEA) and trimethylolpropane triacrylate (TMPTA) yielded a thermoset material with sufficient basicity to remove 80% of both butyric and benzoic acid from aqueous solution using just 1 wt% polymer relative to the aqueous phase mass.
