Efficient removal of heavy metals from melting effluent using multifunctional hydrogel adsorbents

It is hard to balance high water permeability and good mechanical strength of hydrogel adsorbents. In this study, an enhanced double network hydrogel adsorbent of poly (vinyl alcohol)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PVA/PAMPS) was prepared via simple free-radical polymerization. Hydrophilic PAMPS guaranteed high swellability of the adsorbent, which made the sufficient diffusion of metal ions towards adsorbent inside. Meanwhile, the cross-linkage between PVA and PAMPS chains ensured good mechanical strength of the adsorbent. Significantly, the introduction of multifunctional groups (-NHR, -SO3H and -OH) endowed the adsorbent with both chelation and ion exchange function for enhancing heavy metal adsorption. The maximum adsorption capacities of Pb-2(+) and Cd-2(+) reached 340 and 155.1 mg/g, respectively. The adsorbent could efficiently remove heavy metals in melting effluent, especially Pb2+ and Cd2+. The removal efficiencies reached 88.1% for Pb2+, 91.4% for Cd2+, 70.4% for Zn2+, 77.4% for Cu2+, 42.5% for Mn2+, 45.1% for Ni2+ and 95.4% for Fe3+ using 2 g/L adsorbent in 2 h. Moreover, the adsorbent showed a good reusability, and the removal efficiencies maintained 94% for Pb2+ and 93% for Cd2+ in the fifth cycle (m/V =1 g dry gel/L). This work developed a highly practical hydrogel adsorbent for heavy metal removal from wastewater.