Thermoresponsive‐interpenetrating polymer network hydrogels for heavy metal ion recovery

Abstract

Thermoresponsive-interpenetrating polymer network (TR-IPN) hydrogels containing a large number of chelating groups were synthesized; the aim was to ensure the recovery of large amounts of heavy metal ions through temperature cycling across volume phase transition temperature of the hydrogel. The TR-IPN hydrogels were synthesized from poly(N-isopropylacrylamide) and alginate, and the ability of these hydrogels to adsorb a heavy metal ion, Cu(II), was investigated at different temperatures. In the experiment, the hydrogels were prepared using various alginate and crosslinker concentrations. Despite the incorporation of a large number of chelating groups, the TR-IPN hydrogels exhibited a large thermoresponsive volume change regardless of the presence of Cu(II). The Cu(II) adsorption experiment showed that the saturated adsorption amount of the hydrogels was larger at 50 than at 10 8C. In addition, we demonstrated that the difference between the amounts adsorbed at 10 and 50 8C, which we consider to be the amount of Cu(II) that the TR-IPN hydrogels can recover through temperature cycling, was greater than those obtained by other conventional copolymerized thermoresponsive hydrogels.

Synthesis of thermoresponsive copolymer/silica‐coated magnetite nanoparticle composite and its application for heavy metal ion recovery

“…From the result, it is observed that although the Cu(II) recovery amount in our adsorbent is somewhat smaller than that of the adsorbent reported by Ochi, 43 the time required for Cu(II) adsorption is significantly shorter. In their case, the adsorbent used was thermoresponsive interpenetrating polymer network hydrogel type adsorbent consisting of alginate and PNIPAM.…”

“…Then, the amount of Cu(II) recovery is plotted against the time required for adsorption (Figure 11). In the same figure, the results of other researchers were also plotted for comparison 5,43,44 . It should be noted here that although their adsorbent also consisted of thermoresponsive polymer, their forms were in gel.…”

Dual‐responsive shape memory hydrogels with self‐healing and dual‐responsive swelling behaviors

“…48 Considering the excessive consumption of nonrenewable resources and severe environmental pollution, the exploration of hydrogels from renewable resources has drawn significant attention. In recent years, as natural hydrophilic polymers, polysaccharides, including sodium alginate, [49][50][51] carboxymethyl cellulose, 52 chitosan, 53 starch 54 and carrageenan, [55][56] have been widely utilized as starting materials for fabricating hydrogels due to their non-toxicity, biocompatibility, biodegradability, and renewability. [57][58][59] Sodium alginate is a natural polymer with multiple carboxyl groups, which have outstanding coordination capability with divalent or polyvalent metal cations, 60 and is a suitable material for preparing SMHs and intelligent hydrogels.…”