Optimization of the removal of reactive golden yellow SNE dye by cross-linked cationic starch and its adsorption properties

Abstract

In this study, cross-linked cationic starch was synthesized with corn starch as a raw material, epichlorohydrin as a cross-linked agent, and 3-chloro-2-hydroxypropyl trimethylammonium chloride as a cationic etherification agent, respectively, and it was characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, scanning electron microscopy, and thermogravimetry. The X-ray photoelectron spectroscopy results showed that cationic N appeared on the surface of cross-linked cationic starch; that is, a quaternary ammonium group was introduced. The X-ray powder diffraction results indicated that although the crystallinity of cross-linked cationic starch was lower than that of corn starch, cross-linked cationic starch still had an A-type crystal structure. The scanning electron microscopy results demonstrated that cross-linked cationic starch maintained a granular structure with small holes on the surface. Finally, the thermogravimetric results illustrated that the thermal stability of cross-linked cationic starch decreased. Before the adsorption experiment, the pHpzc of cross-linked cationic starch was obtained by the pH drift method, and it was 6.8. The optimal removal rate of reactive golden yellow SNE dye obtained by response surface methodology was 99.59%, and the optimal adsorption time, temperature, concentration of dye, and cross-linked cationic starch dosage were 14.3 min, 39°C, 100 mg/L, and 0.7 g/L, respectively. The adsorption of SNE by cross-linked cationic starch conformed to pseudo-second-order kinetics and the Langmuir isothermal adsorption model. The equilibrium adsorption capacity from pseudo-second-order kinetics and the maximum adsorption capacity from Langmuir isotherm model were 123.76 and 208.77 mg/g at 308.15 K, separately. In addition, this adsorption was an endothermic process.

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