Structure and properties of corn stalk-composite superabsorbent

A novel corn stalk-composite superabsorbent was prepared by graft copolymerization of corn stalk with acrylic acid, acrylamide and sodium 4-styrenesulfonate in aqueous solutions after the pretreatment of corn stalk, using N,N-methylenebisacrylamide as a crosslinker and ammonium persulfate and sodium bisulfite as redox initiators. Factors affecting water absorption rate of the superabsorbent composite, such as the amount of corn stalk, crosslinker, and initiator were investigated. Adsorption rates of Ni(II) and Cd(II) ions of the corn stalk-composite superabsorbent were also studied. Corn stalk-composite superabsorbent had equilibrium adsorption capacities of 210 mg g⁻¹ within 50 min and 505 mg g⁻¹ within 150 min for Ni(II) and Cd(II) ions, respectively. Fourier transform infrared spectroscopy indicated the structure of corn stalk-composite superabsorbent. X-ray diffraction indicated that the sharp diffraction peaks of corn stalks disappeared and transformed into a large and wide amorphous dispersion peak. The discontinuous sheet structure of corn stalks disappeared and gel aggregates with microporous holes and small capillary pores were formed after corn stalk graft modification. After absorbing water, the swollen composite superabsorbent formed a network-like structure filled with water. Thermal gravimetric analysis indicated that the composite superabsorbent had high thermal stability with three step degradations.