Optimization of ultrasonic synthesis of N-succinyl-chitosan and adsorption of Zn²⁺ from aqueous solutions

Abstract

N-succinyl-chitosan (N-NSC) was prepared by reacting chitosan (CS) with succinic anhydride (SA) under an ultrasonic radiation. The influences of three parameters (ultrasonic radiation power, mass ratio of SA to CS, and ultrasonic radiation time) on the degree of substitution (DS) of N-NSC were discussed and optimized with a response surface modeling. The optimum values of the above parameters for maximum value of DS were 118 W, 1.8:1, and 108 min, respectively. The adsorption performance of N-NSC for removing Zn²⁺ from aqueous solution was investigated in a batch system. Kinetic experiments data of that adsorption of Zn²⁺ onto N-NSC were fitted by pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models and the equilibrium isotherm data were described by six different isotherm equations. The adsorption follows pseudo-second-order kinetic model. The results demonstrate that the Langmuir equation is the best-fit model to describe the adsorption process with a maximum monolayer adsorption value of 135.41 mg/g, and Sips equation to predicit experimental value at an initial concentration of 100–700 mg/L, pH 5.0, and temperature 298 K.

Keywords:

• Chitosan
• Succinylation
• Ultrasonic radiation
• Optimization
• Adsorption
• Zn²⁺

Acknowledgments

The authors gratefully acknowledge the financial support provided by the Natural Science Foundation of Anhui province (KJ2011B105).