Synthesis of microgel‐reinforced double network hydrogel adsorbent and its adsorption on heavy metals

BACKGROUND The incompletely polymerized microgels play a crucial role during the formation of hydrogel. In this paper, a microgel (synthesized using Paecilomyces lilacinus and N‐isopropylacrylamide) was used as a cross‐linking agent to synthesize agar/poly (acrylamide‐co‐hydroxyethyl acrylate) double‐network (DN) hydrogel (NH2‐MRDN), which was further modified by triethylenetetramine. The physical and chemical properties of NH2‐MRDN were studied by SEM, FTIR, TGA, XPS, universal testing machine, and adsorption method. RESULTS The NH2‐MRDN has excellent mechanical properties and contains many hydroxy and amino groups. Adsorption experiments show that the NH2‐MRDN has better adsorption performance at pH 4 ~ 7 and that the interference ion has little effect on adsorption at low concentrations. In addition, the Kd for Pb(II) always had the highest values both in single component and mixed component for selective adsorption. The adsorption capacity values calculated by Langmuir model were 182.23 mg g−1 for Pb(II) and 118.36 mg g−1 for Cd(II), and they reached equilibrium in 160 and 240 min, respectively. Further, the mechanism and thermodynamic analysis showed that the adsorption process mainly relies on the hydroxyl and amine group, making it a spontaneous and endothermic adsorption process. CONCLUSION The NH2‐MRDN hydrogel reinforced by microgel overcame the poor stability of conventional adsorbents, and this is expected to provide a new method for the synthesis of hydrogel adsorbents. Meanwhile, this work supplies a theoretical basis and empirical evidence for the application and development of high polymer adsorbents. © 2023 Society of Chemical Industry (SCI).