Biodegradation process and yellowing mechanism of an ecofriendly superabsorbent based on cellulose from flax yarn wastes

A cellulose-based superabsorbent exhibits excellent water absorbency and retention performance as well as biodegradability. However, the detailed biodegradation process in soil has not been monitored yet. Yellowing is another important factor affecting its appearance and storage. In this work, cellulose from flax yarn wastes (FYW) was used as the skeleton material to synthesize a cellulose-g-P(AA-co-AM) (FYW/PAA) superabsorbent. The properties of the FYW/PAA superabsorbent were characterized, especially its biodegradation process and yellowing mechanism. The resultant FYW/PAA presented excellent water absorbency and retention capabilities of 886 g/g in deionized water and 73.2 wt% after being dried at 60 °C for 12 h, respectively. The fracturing of β-1,4-glycosidic bonds on the flax-cellulose macromolecules is the main reason for the biodegradation of FYW/PAA in soil. This causes a 70.8 wt% degradation after FYW/PAA has been buried in soil for only 60 days. The drying method and UV irradiation have important implications for the yellowing of FYW/PAA. They facilitate the generation of chromophore and auxochrome groups on the flax-cellulose macromolecules. 2,6-Di-tert-butyl-4-methylphenol (BHT) exhibits excellent antioxidant properties to inhibit the yellowing of FYW/PAA products.