Adsorption behavior of crystal violet from aqueous solutions with chitosan-graphite oxide modified polyurethane as an adsorbent.

ABSTRACT A series of chitosan (Ch)-graphite oxide (GO)-modified polyurethane foam (PUF) materials as adsorbents were synthesized by a foaming technique. The adsorbent was characterized through IR spectroscopy, scanning electron microscopy, and thermogravimetric analysis (TGA). Batch adsorption experiments of the cationic dye crystal violet (CV) were carried out as a function of the Ch-GO content (1.0-8.0 wt %), solution pH (2-10), dye concentration (100-300 mg/L), adsorbent dosage (10-60 mg/mL), and temperature (20-45°C). At a lower pH value, the surface of Ch-GO/PUF acquired positive charge by absorbing H⁺ ions; this resulted in a decreasing adsorption of the cationic CV dye because of electrostatic repulsion. As the pH of the aqueous system increased, the numbers of negatively charged sites increased by absorbing OH⁻ ions, and a significantly high electrostatic attraction existed between the negatively charged surface of Ch-GO/PUF and the cationic dye (CV) molecules. This led to maximum dye adsorption. The kinetics, thermodynamics, and equilibrium of CV adsorption onto Ch-GO/PUF were investigated. The equilibrium data for CV adsorption fit the Langmuir equation, with a maximum adsorption capacity of 64.935 mg/g. The adsorption kinetics process followed the pseudo-second-order kinetics model. Thermodynamic parameters analysis revealed that the adsorption of CV from an aqueous solution by a Ch-GO modified PUF material was a spontaneous and endothermic process. We concluded that Ch-GO/PUF is a promising adsorbent for the removal of CV from aqueous solutions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41828. [ABSTRACT FROM AUTHOR]