Efficient Decolorization of Citric Acid Fermentation Broth using Carbon Materials Prepared from Phosphoric Acid Activation of Hydrothermally Treated Corncob

Citric acid, as an important organic acid, is largely used in aspects of food, beverage, chemical and pharmaceutical fields，and plays increasingly important role in the society. However, currently the downstream aspect of separating the citric acid is facing a tremendous problem——the decolorization of the citric acid fermentation broth. In order to costly and efficiently remove the pigments, a novel biomass-based carbon material, hydrochar, is put forward. During the preparation process, by adjusting the hydrothermal conditions (temperature, time) and feedstock type (food residue, agricultural, etc), we obtained an excellent hydrochar to be used in the decolorization of citric acid fermentation broth. Additionally, for further improving its adsorption performance, the post chemical activation is applied to optimize it textural characteristics. Meanwhile, the pigments adsorption process on the hydrochar-based carbon material (HBCM) was fully investigated. Meanwhile, the material was fully characterized by SEM, BET, FTIR, XPS and pH_pzc, and several mathematic models were used to analyze the adsorption mechanism involved in the adsorption process. Finally, the tailor-made HBCM had the excellence performance to achieve 99% decolorization ratio and no loss of citric acid at the optimum operating conditions. It could be a potential adsorbent for the removal of pigments in the citric acid fermentation broth.