Novel Photocrosslinking Sulfhydryl Castor Oil–Gelatin Hydrogel for the Removal of Heavy Metals

As efficient and environmentally friendly adsorbents, a novel biomass hydrogel from methacrylated gelatin (Gel-MA) and sulfhydryl castor oil (HNBOE-SH) was developed by thiol–acrylate click photopolymerization in this study. By introducing a long-carbon chain HNBOE-SH, the tensile strength at break of P(HNBOE-SH/Gel-MA) (10.87 MPa) compared with that of P(Gel-MA) (1.79 MPa) has been improved significantly. The formation of cross-linked structures between HNBOE-SH and Gel-MA during photocuring gives P(HNBOE-SH/Gel-MA) a high decomposition temperature at 250 °C. The maximum adsorption capacities of P(HNBOE-SH/Gel-MA) for Cd(II), Cu(II), and Pb(II) were 82.34, 51.60, and 47.04 mg/g, respectively, and equilibrium could be reached within 12 h. The adsorption is well described by the pseudo-second-order (PSO) kinetic model and Langmuir isothermal model and follows an ion-exchange reaction. Various effects of conditions, such as the pH value, mass of the adsorbent, and contact time, were investigated. The results reveal the enormous potential of P(HNBOE-SH/Gel-MA) as an environmentally friendly adsorbent for the removal of heavy metal ions from wastewater.