A novel Enteromorpha based hydrogel optimized with Box–Behnken response surface method: Synthesis, characterization and swelling behaviors

• Enteromorpha was used to prepare a novel hydrogel.
• Box–Behnken design was applied to find out the optimum synthesis parameters.
• Swelling kinetics and mechanisms of the Enteromorpha based hydrogel were studied.

A novel hydrogel consisted of Enteromorpha (EP) and acrylic acid (AA) was prepared by solution polymerization using a response surface methodology. This methodology was based on a three-level, three-variable Box–Behnken design (BBD) that was used to optimize the synthesis parameters. Influences of the three variables, (i.e. the mass ratio of AA to EP (AA/EP), neutralization degree (ND) of AA, and the mass ratio of crosslink agent methylene-bis-acrylamide (MBA) to AA (MBA/AA)) on water swelling capacity of the hydrogel were evaluated. The swelling properties, kinetics and mechanisms of the hydrogel achieved at different grain sizes, salt concentrations, pH values and temperature conditions were intensively investigated. The results indicated that optimal preparation parameters for the hydrogel were predicted as AA/EP of 8.4, ND of AA of 54.3% and MBA/AA of 0.33; under these conditions, a hydrogel was prepared and used to conduct water swelling experiments. The Schott’s pseudo second order model was effective in evaluating the swelling kinetics of hydrogel. In addition, hydrogel with the highest and fastest water swelling capacity was obtained at a condition of small grain size (40–60 mesh), low salt concentration (0%), weak acidity condition (pH = 5–6) and low temperature (20 °C).

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