Structural Characteristics and Functional Properties of Corncob Modified by Hyperbranched Polyamide for the Adsorption of Cr (VI)

Corncob is a kind of agricultural waste, mainly composed of cellulose and hemicellulose. In this study, anion adsorbent hyperbranched polyamide-modified corncob was synthesized by glutaraldehyde cross-linking, which has abundant terminal groups. Then, the effect of modification conditions for the adsorption of Cr (VI) onto modified material was studied. The structural characteristics and the functional properties of modified corncob (HPMC) were revealed by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Experimental results show that the optimum modification conditions were as follows: oxidized corncob 1 g, glutaraldehyde 2.5 mL, hyperbranched polyamide 10 mL, and a reaction time of 4 h under 60 degrees C. The effect of reaction temperature (factor C) on the removal rate of HPMC for Cr (VI) was the largest and GA dosage was the least. The equilibrium adsorption capacity of modified corncob for Cr (VI) was 47.8 mg/g (pH = 2, initial Cr (VI) concentration 100 mg/L, dosage 2 g/L, 4.0 h). The content of functional groups (-NH2) on the surface of modified materials was obviously increased, the surface became rougher, and the thermal stability was improved. The adsorption mechanism was mainly electrostatic gravitation and oxidation-reduction reaction between HPMC and Cr (VI).