Activated carbon cloth as efficient microporous electrode for maleic acid recovery through electrical potential

Abstract

The purification of biobased organic acids poses considerable challenges due to the high energy demand and associated costs of conventional methods, which hinder the market potential of these renewable carbon sources. This study investigates the charging and electrosorptive behavior of activated carbon cloths for maleic acid as an alternative to the recently proposed particulate and monolithic electrosorptive systems for organic acid recovery. Characterization of the activated carbon cloth (ACC) revealed slightly acidic behavior with a point of zero charge (pHpzc) of 6.18, while Raman spectroscopy confirmed a highly amorphous structure. These features influence both adsorption capacity and charging behavior. Positive potentials increase maleic acid uptake to a maximum of 50.40 mg g⁻¹ at +1.00 V vs. Ag/AgCl, marking a greater than 5-fold improvement compared to open-circuit conditions. Conversely, negative potentials promote desorption, achieving recoveries of up to 93% at −1.00 V vs. Ag/AgCl. While applied potentials enabled precise control over the electrosorptive uptake and recovery of maleic acid, pore diffusion limitations resulted in prolonged kinetics for uptake (∼180 min) and recovery (∼60 min). For background electrolyte concentrations up to 20 mM NaCl, competition from inorganic ions was negligible and did not affect uptake behavior, while higher concentrations facilitated maleic acid release through electrodesorption. Our results demonstrate the potential of ACCs for the electrosorptive recovery of organic acids, even in media with elevated competing ion concentrations. Thus, ACCs offer a promising alternative to conventional purification methods, contributing towards sustainable bioprocessing and industrial applications.