Heavy Metal Ions And Dye Adsorption Of Modified-corn Stalk/PVP Semi-IPN Superabsorbents

Acrylic acid modified-corn stalk/PVP semi-IPN superabsorbents were prepared by graft copolymerization of acrylamide(AM)and acrylic acid(AA)with acrylic acid-modified corn stalk in an aqueous solution.Factors affecting absorption capacities of methene blue and lead ions of the superabsorbents,such as amount of acrylic acid modified-corn stalks,AA/ AM mass ratio,AA neutralization degree,crosslinker amount,PVP amount and initiator amount,etc,were investigated.Methene blue and lead ions adsorption thermodynamics and kinetics of the superabsorbents were studied..Application for the superabsorbents in the dye wastewater treatment and heavy metal pollution treatment in soils were discussed.Morphologies,structure and thermal properties of the superabsorbents were characterized by FTIR,XRD,optical microscope and TGA.Superabsorbents,having good absorption capacities for both heavy metal and cationic dye,have been synthesized.The main research findings are as follows.1.When the acrylic acid modified-corn stalk amount was 10%,the AA/AM mass ratio was 70:30,the ammonium persulfate amount was 1.6%,crosslinker amount was0.3%,AA neutralization degree was 70%,PVP amount was 9%,the adsorption capacities of lead ion and methene blue for superabsorbents was the best.2.To survey the initial concentration,pH,temperature which would may influence the superabsorbents adsorption.With increasing methene blue initial concentration,methene blue adsorption capacity for the superabsorbents increased steadily.However,methene blue adsorption capacity increased slowly and methene blue removal dereased rapidly when methene blue initial concentration exceeded 2000mg/L.When the absorption temperature increased from 25? to 45?,methene blue absorption capacities of superabsorbents increased.Methylene blue adsorption thermodynamic process of the superabsorbents accorded with Langmuir adsorption model,and methylene blue adsorption kinetic process are in line with the pseudo-second kinetic model.3.After absorbed by the superabsorbents,the color of the solution with 2000 mg/ L methylene blue changed from dark blue to nearly colorless,indicating that thesuperabsorbents had good absorption for methene blue.After immersed in DI water for a long time,methene blue-swollen superabsorbents had methene blue dye retention above 98%,indicating that the superabsorbents had very strong absorption of methene blue,leading to difficult desorption of methylene blue adsorbed.When the superabsorbents recycled up to 5 times.The superabsorbents has the excellent recycling properties for the superabsorbents.4.When the soil was added with 0.1%,0.3% and 0.5% superabsorbents,lead ions release rate in soil decreased from 86.1% to 67.8%,56.6% and 43.2%,respectively after 120 h,indicating that small amount of superabsorbents could significantly reduce release rate of heavy metal in soil.5.TGA and DTGA data showed that the thermogravimetric curve of the superabsorbents could be a good heat resistance of the superabsorbents.FTIR spectra preliminarily confirmed the target structure of the superabsorbents.XRD of the superabsorbents showed that the crystalline structure were further destroyed during the graft copolymerization between acrylic acid modified-corn stalk and functional monomerseared and the corn stalk structure was transformed from polycrystalline into amorphous structure.