Recovery of carboxylic acids produced during dark fermentation of food waste by adsorption on Amberlite IRA-67 and activated carbon

• Two adsorbents are evaluated for the recovery of carboxylic acids from dark fermentation broth.
• Dark fermentation was performed on batch, without pH control, without addition of external inoculum.
• Lactic, acetic and butyric acids were recovered from fermentation broth.

Amberlite IRA-67 and activated carbon were tested as promising candidates for carboxylic acid recovery by adsorption. Dark fermentation was performed without pH control and without addition of external inoculum at 37 °C in batch mode. Lactic, acetic and butyric acids, were obtained, after 7 days of fermentation. The maximum acid removal, 74%, from the Amberlite IRA-67 and 63% from activated carbon was obtained from clarified fermentation broth using 200 gadsorbent/Lbroth at pH 3.3. The pH has significant effect and pH below the carboxylic acids pKa showed to be beneficial for both the adsorbents. The un-controlled pH fermentation creates acidic environment, aiding in adsorption by eliminating use of chemicals for efficient removal. This study proposes simple and easy valorization of waste to valuable chemicals.