Mechanochemical Preparation of Superabsorbent Materials from Okara and Itaconic Acid

In this study, a green technique of mechanochemistry was used to prepare superabsorbent polymers (SAPs) from soybean waste (Okara) and bio-based bifunctional itaconic acid (ItA) in a solventless melt-reactive esterification reaction using reactive extruder. SAPs were produced by reaction of ItA with Okara at 120 °C with and/or without the use of crosslinker N,N'-methylenebis(acrylamide) (MBA) in the presence or absence of free radical initiator, potassium peroxodisulfate (KPS). By varying the amounts of ItA and Okara, the effect of MBA and KPS was investigated on water absorption. The esterification of Okara with ItA was confirmed by attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopic measurements, while the structural characterization was done using X-ray diffraction, thermal gravimetric analysis, and scanning electron microscopy. Among the twelve SAPs formulations, the highest water absorption of 35.6 g/g of SAP was shown by SAP prepared from Okara/ItA in a ratio of 1 g/3.5 g and crosslinked with 0.5 wt% MBA. All the SAPs showed moderate centrifuge water retention (CWR) capabilities which show their potential for application in sustainable agriculture.