3D-printed montmorillonite nanosheets based hydrogel with biocompatible polymers as excellent adsorbent for Pb(II) removal

Montmorillonite nanosheets (MMTNs), gelatin (GEL) and sodium alginate (SA) were used as the raw materials to synthesize the 3D porous hydrogel with high Pb(II) handling capacity and specific geometry via 3D-printing technology. MMTNs and GEL could bond with each other through the hydrogen bonding at the edge and electrostatic interactions on the surface of MMTNs, forming the stable organic-inorganic framework, and further forming the interpenetrating polymer network (IPN) with the crosslinking and intertwining interaction of SA. Characterizations shown that there were abundant macroporous and huge lamellas in hydrogel, offering an open access for Pb(II) to contact and react with the internal adsorption sites. The batch adsorption experiments shown that Pb(II) adsorption onto hydrogel was a monolayer chemisorption process, which was controlled by the number of adsorption sites in adsorbent. The maximal adsorption capacity for Pb(II) could reach 134 mg/g (C-0 = 1000 mg/L, T = 25 ?, M = 4 g/L, pH = 5), which was attributed to the coefficient of ion exchange, electrostatic interactions and surface complexation according to the XPS, FTIR and EDX tests. The hydrogel also has good filtering performance towards Pb(II) from aqueous solutions via the fix-bed column, showing the potential in practical application.