Opportunity for valorization of pulping by-product in production high performance sustaining release lignin-based gel.

This study focuses on optimizing the pulping by-product to produce effective hydrogels for controlling the release of salicylic acid (SA). In this regard, two routes are achieved: the first involves preparing black liquor (BL) composite hydrogels with various polymer macromolecules [polyacrylamide (PAM), polyvinyl alcohol (PVA), and chitosan (Cs), and the second involves carboxymethylation of BL and grafting with acrylamide. Hydrogels are evaluated using spectral analysis (ATR-FTIR), thermal analysis (TGA and DTG), and swelling measures. Encapsulation, release profile, SA release kinetics, as well as ATR-FTIR and SEM measurements, were used to evaluate the behavior of loaded hydrogels. According to the results, grafted carboxymethylated BL-gel had the maximum SA release (98.7 %), followed by PAM-BL (51.7 %) and PAM/PVA-BL (43.1 %). Over a 48-hour period, the hydrogels demonstrated a prolonged SA release pattern. The Ritger-Peppas and Higuchi models fitted to all examined hydrogels showed that SA release followed both Fickian and non-Fickian diffusion pathways.