A process for producing lignocellulosic flocs from NSSC spent liquor

Area of Science:

• Biomass Valorization
• Pulp and Paper Chemistry
• Waste Management

Background:

• Neutral sulfite semi chemical (NSSC) pulping generates spent liquor (SL) requiring treatment.
• Current treatment methods for NSSC spent liquor are often energy-intensive and may not recover valuable components.
• Lignocelluloses present in SL are potential sources for valuable biomaterials.

Purpose of the Study:

• To develop and evaluate a new process for isolating lignocelluloses from NSSC pulping spent liquor.
• To optimize the removal of lignin and hemicelluloses from spent liquor using polymeric flocculants.
• To assess the impact of the process on spent liquor quality parameters like turbidity and COD.

Main Methods:

• Investigated the use of poly ethylene imine (PEI) for lignocellulose removal under varying conditions (pH, temperature, concentration).
• Evaluated a dual polymer system combining poly diallyldimethyl ammonium chloride (PDADMAC) and PEI for enhanced removal efficiency.
• Assessed parameters including lignin and hemicellulose content, turbidity, chemical oxygen demand (COD), and elemental analysis of flocs.

Main Results:

• Optimal conditions for PEI alone achieved 37% lignin and 37% hemicellulose removal.
• The dual system (PDADMAC + PEI) significantly improved removal rates to 47% lignin and 50% hemicellulose.
• Reductions in SL turbidity and COD were observed, with elemental analysis providing insights into floc composition.

Conclusions:

• A novel, effective method for lignocellulose recovery from NSSC spent liquor was demonstrated.
• The dual polymer system offers superior performance compared to single polymer application.
• This approach presents a promising avenue for valorizing NSSC spent liquor and improving wastewater treatment.