Abstract:

A new kind of cellulose-lignin composite hydrogel (UCHy) was prepared under ultrasonic irradiation using cellulose and lignin as raw materials. The resulting material was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) analysis. The swelling properties of UCHy were also investigated at a variety of different Pb(Ⅱ) concentrations, whilst its adsorption capacity was studied as a function of pH, reaction time, temperature, and concentration of the Pb (Ⅱ) solution under ambient conditions. The results showed that cellulose and lignin were beneficial to the formation of a denser structure, and that the ultrasonic treatment promoted the formation of the continuous pore microstructure of the hydrogel, resulting in a high swelling ratio and pollutant adsorption capacity. The swelling kinetics indicated that the initial solution intake of the composite hydrogel followed a non-Fickian type diffusion, and that the whole swelling process was fit for the Schott's model well. The adsorption capacity of Pb(Ⅱ) increased as the pH of the solution increased, and decreases with increasing temperature. The adsorption isotherm data followed the Langmuir and Freundlich models, with an optimum adsorption value of 786.16 mg·g^-1. The adsorption rate closely followed a pseudo-second order model. As a result, UCHy showed good responsive and adsorption properties towards heavy metal ions, and therefore represents a promising material for the detection and removal of heavy metal ions from aqueous solutions.

Key words: Composite hydrogel, Ultrasonic-assisted, Pb(Ⅱ), Adsorption, Heavy metal-responsive