Research On The Adsorption/Desorption Properties Of Salix Psammophila Power Based Hydrogel For Heavy Metal Ions

In recent years,salix psammophila power based hydrogel has good adsorption properties for heavy metal ions and has received extensive attention in the treatment of heavy metal wastewater.In this paper,polyaspartic acid/salix psammophila power(PASP/SPP)and polyaspartic acid/carboxymethyl salix psammophila power(PASP/CMS)hydrogels were prepared by aqueous solution polymerization using SPP and PASP as raw materials.The optimal preparation conditions of the hydrogels were determined.The microstructures of the hydrogels were characteried by Fourier transform infrared spectroscope(FTIR),X-ray diffraction(XRD),scanning electron microscope(SEM),and X-ray photoelectron spectroscopy(XPS).The optimal swelling conditions and adsorption conditions of the hydrogels were determined.The adsorption isotherms,adsorption kinetic models and adsorption thermodynamics of the hydrogels were further determined.The optimal desorption conditions of the hydrogels were determined.The main experimental results were as follows:1.Preparation and swelling properties of PASP/SPP hydrogelThe results of swelling experiments showed that,the largest swelling ratio of PASP/SPP hydrogel reached 7.2;FTIR result showed that graft copolymerization was developed between-COOH of PASP and-OH of SPP and formed PASP/SPP hydrogel,XRD result showed that the addition of PASP destroyed the order of SPP,reduced the crystallinity and formed PASP/SPP hydrogel.SEM result showed that the surface of PASP/SPP hydrogel has gap of varying size.2.Adsorption/desorption properties of PASP/SPP hydrogel for Pb2+,Cd2+The results of adsorption experiments showed that,the largest adsorption capacity of PASP/SPP hydrogel to Pb2+and Cd2+reached 936.5 and 539.5 mg/g,respectively.The adsorption processes of Pb2+ and Cd2 by PASP/SPP hydrogel fit very well with the Langmuire isotherm model and pseudo-second-order model.From the thermodynamic studies,it is seen that the adsorption is spontaneous,exothermic and decreased randomness.The characterization results showed that the hydrogel surface before adsorption was loose and porous,and the hydrogel surface after adsorption became dense.XPS proved more directly that heavy metal ions were adsorbed on the hydrogel surface.The results of desorption experiments showed that,the largest desorption capacity of Pb2+ and Cd2+on PASP/SPP hydrogel could achieved 497.28 and 269.76 mg/g,respectively.3.Adsorption/desorption properties of PASP/CMS hydrogel for Pb2+,Cd2+FTIR result showed that graft copolymerization was developed between-COOH of PASP and-CH2OH of CMS and formed PASP/CMS hydrogel,XRD result showed that the addition of PASP destroyed the order of CMS,reduced the crystallinity and formed PASP/CMS hydrogel.The results of adsorption experiments showed that,the largest adsorption capacity of Pb2+and Cd2+on PASP/CMS hydrogel reached 1657.6 and 719.6 mg/g,respectively.The adsorption processes of Pb2+and Cd2+by PASP/CMS hydrogel fit very well with the Langmuire isotherm model and pseudo-second-order model.From the thermodynamic studies,it is seen that the adsorption is spontaneous,exothermic and decreased randomness.The characterization results showed that the hydrogel surface before adsorption was loose and porous,and the hydrogel surface after adsorption became dense.XPS proved more directly that heavy metal ions were adsorbed on the hydrogel surface.The results of desorption experiments showed that,the largest desorption capacity of Pb2+and Cd2+on PASP/CMS hydrogel could achieved 580.16 and 382.16 mg/g,respectively.