Synthesis, swelling and water-retention behaviors of phytic acid-modified corn stalk-composite superabsorbents

A novel phytic acid-modified corn stalk-composite superabsorbent (PACS-g-p(AA-AM-VP)) with water absorbency of 391 g/g, water retention around 30% at 200 min under 90 °C, adsorption capacities of 284 mg/g and 448 mg/g for Ni(II) and Cu (II), respectively, was synthesized by graft copolymerization of acrylamide(AM), vinyl pyrrolidone(VP) and itaconic acid(IA) with phytic acid-modified corn stalk (PACS) in aqueous solution, using N,N-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) and sodium bisulfite (SBS) as redox initiator. Factors influencing water absorbency and water retention of PACS-g-p (AA-AM-VP), such as PACS amount, initiator amount, crosslinker amount, neutralization degree of IA, IA/VP mass ratio and IA/AM mass ratio, were investigated. Morphologies and structure of PACS-g-p (AA-AM-VP) were characterized by FTIR and SEM. FTIR spectra indicate the structure of phytic acid-modified corn stalk graft-copolymer. SEM data shows that fiber structure of corn stalk is partially destroyed after phytic acid modification under ultrasonic wave. PACS-g-p (AA-AM-VP) has a coarse, fluffy and porous structure, facilitating the permeation of water and heavy metal ions into the polymeric network. Given these properties, PACS-g-p (AA-AM-VP) can be extensively applied in agriculture and horticulture as a water-retaining and soil remediation material which increases agricultural irrigation efficiency and remediates heavy metal-contaminated soil due to its low cost, environmental friendliness, high water retention and good adsorption for heavy metal ions.