Conversion of residual sugars from vinasses to 5-Hydroxymethyl furfural (5-HMF) and phenolic compounds using ion exchange resins and thermal treatment

Abstract

Due to its physicochemical composition, the final disposal of vinasses denotes a severe environmental problem. This work passed vinasses at 2.4 and 7.0 pH through ion exchange Amberlite FPX66 and Dowex Optipore SD2 resins and two thermal treatments (130 °C, 40 min, and 0.5% H2O2). Furanic and phenolic compounds increased, and sugar removal was determined using UPLC, HPLC, and FTIR analysis. The highest increase for 5-HMF was found using SD2 resin to 7.0 pH vinasses and two thermal treatments (494.87 mg/L). The resins did not adsorb in the case of furfural. The highest increase in phenolic compounds was observed in 3-hydroxybenzoic (9.22 mg/L), vanillic (5.02 mg/L), syringic (1.68 mg/L), and 2,4-di-tert-butylphenol (1.23 mg/L). The highest values were found at pH 7.0 and after a second thermal treatment. The highest removal of sugars and Chemical Oxygen Demand (COD) occurred in FPX66 resin using vinasses to 2.4 pH and two thermal treatments, with 66.9 and 54%, respectively. Xylose was reduced between 74.5 and 88% with the SD2 in both pH and with two thermal treatments, and FPX66 resin with vinasses to 7.0 pH and two thermal treatments. At the same time, sucrose was removed 99.5% after the FPX66 resins with two treatments and 2.4 pH. Inulin is reported in this work for the first time in tequila vinasse (4530 mg/L). Using vinasses to obtain compounds of economic importance helps to valorize this residue.