Downstream Separation of Formic Acid with Anion-Exchange Resin from Electrocatalytic Carbon Dioxide (CO₂) Conversion: Adsorption, Kinetics, and Equilibrium Modeling

Journal Article · 05 February 2024 · Industrial and Engineering Chemistry Research

DOI: https://doi.org/10.1021/acs.iecr.3c02946 · OSTI ID:2413134

Hoque, Md A. ^[1]; Abad, Keemia  ^[2]; Kharel, Pom ^[2]; Omosebi, Ayo ^[2]; Thompson, Jesse  ^[2]

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1. University of Kentucky, Lexington, KY (United States); University of Kentucky
2. University of Kentucky, Lexington, KY (United States)

The electrocatalytic carbon dioxide reduction reaction (CO₂RR) that produces liquid formic acid (FA) is one potential route to minimize the CO₂ concentration in the atmosphere by utilizing CO₂ as a feedstock. However, one of the main disadvantages of this route is the high energy demand required for purification through conventional distillation. This method of purification has been shown to result in a large carbon footprint in life-cycle analysis (LCA). Therefore, finding an alternative purification technique that can integrate with an electrochemical CO₂RR process with the potential to lower the carbon footprint would be of great interest. Under the experimental conditions of the CO₂RR, FA remains in its basic form as the formate anion in the catholyte. Anion exchange resins with their basic properties can separate the formate anion from the catholyte mixture as an alternative to energy intensive distillation. In this work, three anion exchange resins with increasing basicity order: Amberlite IRA-96 < Amberlite IRA-910 < Ambersep 900 are tested to separate FA in the presence of aqueous solution of potassium bicarbonate catholyte with varying levels of resin and FA. Kinetics and equilibrium studies data for the FA adsorption are interpreted using several kinetics and isotherm models. The kinetics data fit well with a pseudo-first-order model at high initial FA concentrations and a pseudo-second-order model at low initial FA concentrations. The experimental data can be best explained with the Freundlich isotherm model. The fitted results show that strongly basic Ambersep 900 is more effective at separating FA, with a maximum adsorption capacity of 336.7 mg/g compared to Amberlite IRA-96 (275.2 mg/g) and Amberlite IRA-910 (209.2 mg/g) in neutral water. However, weakly basic Amberlite IRA-96 (110.8 mg/g) can separate FA more efficiently from potassium bicarbonate catholyte than Amberlite IRA-910 (99.9 mg/g) and Ambersep 900 (40.0 mg/g). As a result, competitive adsorption occurs in the presence of potassium bicarbonate catholyte, but the formic acid adsorption capacity is still sufficient for adequate separation.

• Research Organization: University of Kentucky, Lexington, KY (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: FE0031920
• OSTI ID: 2413134
• Journal Information: Industrial and Engineering Chemistry Research, Journal Name: Industrial and Engineering Chemistry Research Journal Issue: 6 Vol. 63; ISSN 0888-5885
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English