Preparation and characterization of enzymatic hydrolysis lignin-based hydrogel.

In order to prepare a new type of high absorption resin with porous structure, enzymatic hydrolysis lignin-based composite hydrogel (EHL-g-PAA) was prepared by grafting using enzymatic hydrolysis lignin and acrylic acid. Free radicals of enzymatic hydrolysis lignin were formed by the system of Fe2SO4/H2O2; acrylic was performed with ammonium persulfate (APS) as initiator and N,N’-methylene double acrylamide (EMB) as crosslinking agent; EHL-g-PAA was prepared using the free radicals of enzymatic hydrolysis lignin and acrylic prepolymer. EHL-g-PAA was characterized by FTIR, SEM and TG, and the effects of mass ratio of enzymatic hydrolysis lignin and acrylic acid, pH value and temperature on the swelling properties of EHL-g-PAA were investigated. The results showed that the enzymatic hydrolysis of lignin had been successfully polymerized, and formed a new network structure of the enzymatic hydrolysis lignin-based hydrogel. Composite hydrogel had irregular hierarchical porous structure.When the mass ratio of EHL and AA was 0.4∶1, the water equilibrium absorption ability of EHL-g-PAA reached the maximum. Under room temperature of 20 ℃, water equilibrium absorption ability of EHL-g-PAA was 410.99 in distilled water, the adsorption equilibrium time extended 12 hrs, and its release rate to water was 93.88%. EHL-g-PAA showed good pH sensitivity. The ability to absorb water was lower in acid and alkaline solutions, and it reached the highest in neutral condition. Under low temperature conditions, the network diastole and water absorbing capacity of EHL-g-PAA increased; while under high temperature conditions, the network shrinkage and water absorption capacity of EHL-g-PAA decreased. Compared with PAA, EHL-g-PAA had better circulation ability and stability.