Synthesis of a bio-based polyurethane/chitosan composite foam using ricinoleic acid for the adsorption of Food Red 17 dye.

A novel bio-based polyurethane/chitosan foam (PU/chitosan) was synthesized using a polyol derived from castor oil and applied to remove Food Red 17 dye (FR17) from aqueous solutions. PU/chitosan foam presented better characteristics and adsorption potential than polyurethane foam (PU). PU/chitosan foam showed a semi-crystalline structure, with several functional groups, high porosity and good mechanical properties. These characteristics are adequate for adsorptive separations. Using identical adsorption conditions, PU/chitosan was able to remove >98% of FR17 dye from the solution, while, PU removed only 40%. The adsorption of FR17 on PU/chitosan composite foam was favored at pH 2. Pseudo-second order model was the most adequate to represent the kinetic data. The equilibrium data followed the Sips model, with a maximum adsorption capacity of 267.24 mg g-1. The adsorption process was spontaneous, favorable and endothermic. The results showed that polyurethane foams are capable to support chitosan, generating an adsorbent with better mechanical characteristics and high potential to remove anionic dyes from aqueous media.