Effect of coagulating agents on lignin and oligosaccharide contents in pre-hydrolysis liquor obtained in the production of dissolving pulp from poplar residual slabs

Abstract

Pre-hydrolysis is an important step in the poplar residual slab dissolving pulp production process, as it aids in removing as much hemicellulose as possible from the cellulose fibers. In the pre-hydrolysis process, a portion of lignin also dissolves, along with the hemicelluloses. The presence of lignin in prehydrolysis liquor (PHL) is detrimental to the separation of xylo-oligosaccharide from the prehydrolysis liquor. This study researched lignin removal from PHL with three coagulating agents, namely aluminum sulfate (alum), polyaluminum chloride (PAC), and polydiallyldimethyl ammonium chloride (pDADMAC). It was found that the removal of lignin increased as the dosage of the alum, PAC, and pDADMAC increased. Additionally, the highest retention of xylo-oligosaccharide in the PHL occurred at dosages of 120 mg/L for alum and 160 mg/L for PAC and pDADMAC. The contents of the other oligosaccharides in PHL fluctuated irregularly with increasing dosages of the alum, PAC, and pDADMAC.