Detoxification of furanic aldehydes of the hemicellulosic hydrothermal hydrolysate of brewers' spent grains by continuous adsorption on a fixed-bed column

During the process of subcritical water hydrolysis of lignocellulosic compounds, such as brewers' spent grains, some toxic compounds can be formed due to the breakdown of the cellulose structure. These compounds are known as furanic aldehydes, and they are inhibitors of microorganisms that are used in different processes, such as fermentation and anaerobic digestion, among others. The detoxification and conditioning of these hydrolysates are required before their use in other processes that require low concentrations of toxins. One of the mechanisms that can be used to diminish those compounds is the adsorption process. For this reason, this study evaluated at-line and in-line purification strategies using different adsorbents in fixed-bed columns to remove furanic aldehydes from a model feed simulating hydrolysate from subcritical water hydrolysis. The model feed consisted of simple sugars and furanic aldehydes at appropriate concentrations. The selected adsorbents were silica-C18, hydrocarbons, and activated carbon. The results indicate that, among the adsorbents that were studied, activated carbon was the most efficient for the removal of both 5-hydroxymethylfurfural and furfural. The activated carbon removed >99% of furanic aldehydes in the experiments conducted in the at-line system. Sequential subcritical water hydrolysis followed by either at-line or in-line purification is promising for integrated inexpensive and efficient hydrolysate purification.