pH-Responsive Nanocomposites From Methylcellulose and Attapulgite Nanorods: Synthesis,Swelling and Absorption Performance on Heavy Metal Ions

A pH-responsive methylcellulose-g-poly(sodium acrylate)/attapulgite (MC-g-PNaA/APT) nanocomposite superabsorbent was prepared by the free-radical solution polymerization of methylcellulose (MC), sodium acrylate (NaA) and nanoscale attapulgite (APT) in the presence of the crosslinker N,N′-methylene-bis-acrylamide (MBA). The structure and morphology of the nanocomposite were characterized by FTIR, FESEM, TEM, XRD and EDS techniques, and the effects of the amount of MBA, MC and APT nanorods on swelling behaviors were also evaluated. Results indicate that NaA has been grafted onto MC macromolecular chains and APT nanorods participated in polymerization by its active silanol groups, and APT led to a better dispersion in the MC-g-PNaA matrix. The incorporation of APT clearly enhanced the swelling capacity and rate of the superabsorbent. In addition, the nanocomposite exhibited excellent absorption capacity on heavy metal ions, and its absorption amounts on Ni²⁺, Cu²⁺ and Zn²⁺ ions reached 9.86, 7.66 and 21.86 times greater than active carbon (AC). The biopolymer-based nanocomposite superabsorbents can be used as a potential water-saving material and candidate of AC for heavy metal ion absorption.