Environmental Application of Chitosan-Supported Catalysts: Catalytic Hollow Fibers for the Degradation of Phenolic Derivatives

Abstract

:Hollow fibers made of chitosan were prepared and tested for the immobilization of palladium, a catalytic metal widely used for reductive reactions. Hollow chitosan fibers were prepared by extrusion of chitosan into a coagulating solution followed by a final conditioning step to increase the stability of chitosan in acidic solutions. The fibers were then contacted with palladium solution at pH 2; the Pd-loaded hollow fiber was finally chemically reduced with zinc powder in contact with sulfuric acid solution (in situ hydrogen production). The catalytic unit was designed as a two-compartment cell separated by the hollow fiber acting as a catalytic membrane. The solution to be treated was flowed through the lumen of the fiber, while the reductive medium was maintained outside the membrane. Two different reducing agents were used. The first was sodium formate, circulating outside the fiber. The alternative hydrogen donor was hydrogen gas maintained at a given pressure in the reductive compartment. The system was tested for the degradation of phenol derivatives. The efficiency of the catalytic process was evaluated in terms of experimental parameters such as the pH of the solution, the concentration (or pressure) of the reducing agent, the concentration of the phenol derivative, and the residence time in the fiber. The system proved to be of interest for the degradation of phenol derivatives under mild conditions (pressure, temperature, etc.).