Preparation of cationic modified graphene oxide and characterization of its adsorption for rhamnolipids from fermentation broth

Purification of rhamnolipids (RLs) from its fermentation broth has been thought as the main limitation for application of RLs at large-scale. In this work, cationic graphene oxide (C-GO) has been prepared by 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and graphene oxide for adsorbing rhamnolipids (RLs) from the fermentation broth. The adsorption capacity of C-GO for RLs was influenced by both the preparing conditions and the adsorption process. After optimizing the preparing parameters, the Zeta potential of the prepared C-GO was as high as + 23.01, and its corresponding adsorption capacity for RLs reached 2.0 g/g C-GO. The maximum adsorption capacity of C-GO reached within 2 min when the initial pH of RLs' fermentation broth was 4.0, the initial concentration of RLs was 16 g/L and the concentration of C-GO added was 4 g/L. Ethanol (99.5%) could recover 90% of RLs adsorbed on the surface of C-GO. The chromatographic purity of recovered RLs was above 90%. Based on the above results, C-GO, with quick, high specific adsorption and easy desorption property for RLs, has great potential in application of RLs' separation.