Preparation of thermoresponsive alginate/starch ether composite hydrogel and its application to the removal of Cu(II) from aqueous solution.

A novel polysaccharide-based thermoresponsive hydrogel containing sodium alginate (SA) and 2-hydroxy-3-isopropoxypropyl starch (HIPS) was developed for removing Cu(II) from aqueous solution. HIPS/SA hydrogel showed network and porous structure, as well as the abundant carboxy groups inside the structure, endowed it with sufficient binding sites for adsorption of Cu(II). The reversible thermoresponsive swelling-shrinking behavior of HIPS/SA hydrogel was discussed. The effects of pH and initial Cu(II) concentration on adsorption capacity were investigated. The adsorption isotherms and kinetics of HIPS/SA hydrogel demonstrated that the adsorption of Cu(II) was subjected to Langmuir and pseudo-second-order models respectively, and the maximum adsorption capacity was 25.81 mg/g. Additionally, HIPS/SA hydrogel could be successfully desorbed by only small amounts of dilute hydrochloric acid within a short time for its thermoresponsive property, it also exhibited the feasibility of regeneration, because the adsorption capacity for Cu(II) was still higher than 15.23 ± 0.27 mg/g even after five cycles.