Adsorption of lead ions from aqueous solutions by citric acid-modified celluloses

Abstract

In this study, citric acid was utilized to modify the surface of cellulose and the citric acid-modified cellulose (CAMC) was then used to remove Pb²⁺ from aquatic solutions. The surface characteristics of CAMC were determined by Fourier-transform infrared spectroscopy and zeta potential analyses. The exact effects of CAMC dosage, pH, and temperature on the adsorption of Pb²⁺ by CAMC were determined. After 180 min of reaction, the adsorption percentages of Pb²⁺ at 0.5, 1.5, and 2.5 g/L CAMC were 66, 87, and 94%, respectively. The Pb²⁺ removal efficiency of CAMC increased with CAMC dosage, pH, and temperature. Experimental results reveal that the pseudo-second-order model best represents the adsorption kinetics. The Freundlich model fits the experimental isotherms better than does the Langmuir model. ΔH° and ΔS° were 43.34 kJ/mol and 224.4 J/mol K, respectively. The value of ΔH° suggested that the Pb²⁺ was adsorbed onto CAMC via physisorption.

Keywords:

• Adsorption
• Citric acid
• Cellulose
• Lead ions
• Isotherm
• Kinetics
• Thermodynamics

Acknowledgment

The authors would like to thank the National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract No. NSC 101-2221-E-151-038-MY3.