Utilization of corn stalk hemicellulose from KOH spent liquor as a wet-end additive

Abstract

The valorization of hemicellulose represents a sustainable pathway toward bio-based papermaking additives. In this study, hemicellulose was isolated from the black liquor of potassium hydroxide pulping of corn stalk. The recovered hemicellulose, which was predominantly xylan (89.3 % xylose), exhibited poor water solubility (2 %) and low nitrogen content (1.46 %), limiting its direct application as a wet-end additive. To overcome these limitations, the hemicellulose was cationized using (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHPTAC) under alkaline conditions. The cationization reaction was optimized by varying temperature, CHPTAC-to-hemicellulose molar ratio, and NaOH-to-CHPTAC molar ratio. Under optimal conditions, the cationic hemicellulose achieved a degree of substitution of 0.16 and a yield of 58.75 %. The cationic hemicellulose exhibited significantly improved water solubility (20 %) and increased nitrogen content (1.99 %). When applied to recycled pulp at doses up to 1.5 wt%, the cationic hemicellulose improved tensile, burst and tear indices. Furthermore, when used as a retention aid for precipitated calcium carbonate (PCC) at 10 % filler loading, cationic hemicellulose achieved an ash content of 8.38 % while maintaining superior mechanical properties compared to cationic starch. These findings demonstrate that cationized hemicellulose from KOH pulping black liquor is an effective, renewable wet-end additive for papermaking applications.