Design of folic acid based supramolecular hybrid gel with improved mechanical properties in NMP/H2O for dye adsorption

Folic acid (FA) supramolecular gel was prepared in a mixture solvent of N-methylpyrrolidone (NMP)/H2O at a 1/1 volume ratio by using FA as gelator with a concentration of 0.4% (w/v). In the mixture solvent, NMP was first of time used as a good solvent to tune the solvent properties in order to be able to induce formation of FA supramolecular gel. The folic acid-gelatin (FA-GA) hybrid gels were synthesized by adding different amount of gelatin (GA) into FA gelator. The gelation temperature (TGel) of the FA-GA hybrid gel is 30 °C which is much higher than that of FA gel (10 °C). The gel to sol transition temperature (TGS) is about 58 °C, which demonstrates that the hybrid gel has good stability at room temperature. The FT-IR and UV-vis spectra of FA-GA hybrid gel indicate that GA involves in the self-assembly process of FA via hydrogen bonding and π-π interactions with FA molecules. Owing to the π-π interaction happened between FA and GA molecules the fluorescence intensity of FA-GA gel is four times as high as that of FA gel. SEM images shows that the hybrid gel has a helical-fiber network structure which would enhance the gel strength to a great extent. Good stability, large specific surface and porosity in three-dimensional network structure of the FA-GA hybrid gel make it a highly promising adsorbent for dye adsorption. The FA-GA hybrid gel is able to absorb 63.5% of Congo red (CR), 68% of methyl blue (MB) and 44% of methyl orange (MO) respectively from their solutions.