In the paper, a green ultrasonic method was applied to prepare glucan-g-poly­(acrylic acid) (GL-g-PAA), sodium lignosulfonate-g-poly­(acrylic acid) (SLS-g-PAA), and glucan-g-poly­(acrylic acid) /sodium lignosulfonate (GL-g-PAA/SLS) hydrogels with the participation of initiator ammonium persulfate (APS) and cross-linker N′,N-methylenebis­(acrylamide) (NMBA), and these hydrogels were taken as absorbents to remove the Cu2+ ion from aqueous solutions. The structure, morphology, and stability of hydrogels were confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The various experimental conditions that influence the adsorption capacity were investigated such as temperature (25–50 °C), pH (1.0–6.0), adsorbent dosage (10–60 mg), foreign ions (300 mg·L–1), and contact time (0–180 min) as well as the initial concentration of the Cu2+ ion solution (100–600 mg·L–1). In addition, the experimental results indicated that the adsorption isotherms of the hydrogels for Cu2+ ions was in line with the Freundlich model, and the adsorption kinetics of the lyogels for Cu2+ ions were in good agreement with the pseudo-second-order model. The maximum adsorption capacities were 195.6, 188.5, and 221.4 mg·g–1 for GL-g-PAA, SLS-g-PAA, and GL-g-PAA/SLS, respectively. The thermodynamic parameters of Cu2+ ion adsorption onto preceding hydrogels were calculated. The positive ΔS° value reflected that adsorption is a process of entropy increase. The ΔG° was negative, revealing that the adsorption was a spontaneous process, and the ΔH° was positive value, suggesting that the adsorption was endothermic in nature.

Nowadays, the attention of both academic and industrial research is paid to the novel materials based on renewable organic resources. Sodium lignosulphonate (SLS) is selected in this study to synthesize novel superabsorbent hydrogels by ultrasonic polymerization. The structure, morphology and stability of SLS-based hydrogel were confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Under the optimal condition, SLS-based hydrogel possesses the water absorbency of 1328g·g in distilled water and 110g·g in 0.9wt% NaCl solution. In addition, the prepared SLS-hydrogel as an adsorbent was applied to remove Ni from an aqueous solution in virtue of its low cost and favorable adsorption capacity. The various experimental conditions that influence the adsorption capacity were investigated such as temperature (20-60°C), pH (2.0-7.0), contact time (0-360min) and initial concentration of the Ni solution (100-600mg·L). Then the adsorption capability could reach 293mg·g under optimal conditions. The results revealed that the adsorption behavior is spontaneous and endothermic. Furthermore, it was observed that the adsorption mechanism and adsorption equilibrium data obeyed pseudo-second-order kinetic and Freundlich models.

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