Carboxylic acid recovery from aqueous solutions by activated carbon produced from sugarcane bagasse

This work explores the use of activated carbon (AC) synthesized from sugarcane bagasse (SB) to adsorb volatile carboxylic acids (VCA). Activation was performed by impregnation of SB with 20 and 35 % v/v H3PO4 (resulting P20 and P35 respectively) and by impregnation with 30 and 40 % v/v ZnCl2 (resulting Zn30 and Zn40 respectively). Since a low adsorption of VCA was expected in acid activated carbons, they were modified with KOH resulting P20 K and P35 K. Characterization of the produced ACs showed essentially microporous carbons, and points of zero charge between 8.4 and 9.2 that favor chemisorption of anions as VCA carboxylates. Zn40 showed the highest individual VCA molar adsorption percentages, followed by P35 K which also showed a highly microporous surface and sites of high adsorption energy on the N-2 adsorption isotherms. Desorption by sonication and heating was performed on Zn40 after acetic acid adsorption, obtaining the highest desorption percentage by sonication.