A process for purifying xylosugars of pre‑hydrolysis liquor from kraft‑based dissolving pulp production process

Ca(OH)₂ treatment in the first step of this process removed 41.2% of lignin and negligible amount of sugars, while notablely increased the concentration of acetic acid. Activated carbon (AC) adsorption of the second step at 1 wt% dosage led to additional 32% lignin and 5.9% xylosugar removals. Laccase assisted activated carbon treatment of the third step led to the removal of contaminants by 17.6%.Overall, 90.7% of lignin, 100% of furfural, 5.7% of xylose, and 12% of xylan were removed from PHL, while the concentration of acetic acid became twofolds in the PHL

A novel process via combining single state processes was designed for efficiently separating contaminants from PHL, while which can maintain xylosugars and acetic acid in the PHL for their possible utilization in downstream biochemical or chemical processes. Ca(OH)₂ treatment was effective in selectively removing lignin and furfural from PHL without influencing the concentration of xylosugars. The AC adsorption could remove lignin and furfural effectively and was ineffective in removing acetic acid. Xylan was more adsorbed on AC than xylose. Laccase assisted activated carbon treatment led to further removal of lignin via the polymerization tendency of laccase for lignin adsorbed on AC.

A process for removing contaminants of PHL include Ca(OH)2 treatment, AC adsorption, and laccase assisted AC treatment. Ca(OH)₂ treatment is the first step of this process, which removed 41.2% of lignin and negligible amount of sugars at the optimal Ca(OH)₂ dosage. In this step, a notable increase in the concentration of acetic acid was achieved. In the second step, the implementation of adsorption using activated carbon (AC) at 1 wt% dosage led to additional 32% lignin and 5.9% xylosugar removals. The aim of laccase assisted AC treatment of the third step is to polymerize the low molecular weight lignin of the Ca(OH)₂+AC treated PHL by laccase to improve their adsorption on AC. Laccase assisted activated carbon treatment led to further removal of lignin.