Synthesis and Urea-Loading of an Eco-Friendly Superabsorbent Composite Based on Mulberry Branches

Mulberry branch, consisting of bark and stalk, was used as raw skeleton material without any chemical pre-treatment to synthesize an eco-friendly mulberry branch-g-poly(acrylic acid-co-acrylamide) (PMB/P(AA-co-AM)) superabsorbent composite. The synthesis conditions and properties of the PMB/P(AA-co-AM) superabsorbent composite were investigated. The results showed that under the optimal synthesis conditions, the water absorbency of the prepared PMB/P(AA-co-AM) reached 570.5 g/g in deionized water, 288.0 g/g in tap water, and 70.0 g/g in 0.9 wt% aqueous NaCl solution. The PMB/P(AA-co-AM) composite also exhibited excellent water retention capacity as well as a rapid water absorbency rate. The urea loading percentage of the PMB/P(AA-co-AM) composite was controlled by the concentration of aqueous urea solution. The release of urea from the loaded PMB/P(AA-co-AM) composite in deionized water initially exhibited a high rate of release for 60 min, followed by a rapid decline. Meanwhile, the PMB/P(AA-co-AM) superabsorbent composite with larger particle size achieved a better sustained release of urea.