Environmental remediation by chitosan-carbon nanotube supported palladium nanoparticles: Conversion of toxic nitroarenes into aromatic amines, degradation of dye pollutants and green synthesis of biaryls

Nitroarenes, organic dyes and solvents are recalcitrant pollutants commonly found in industrial effluents. These organic compounds are toxic to aquatic organisms, hence their removal from aquatic systems is of significance. Remediation systems based on metallic nanoparticles are superior to the conventional systems with respect to their efficiency. Biopolymers like chitosan are considered to be suitable support material because biopolymers are capable of forming gel and exhibit affinity for metal cations. Catalysis systems with palladium nanoparticles are efficient in reducing nitroarenes to aromatic amines through hydrogenation, degradation of dye molecules and forming C-C bonds in organic coupling reactions. This study reports the preparation of chitosan-carbon nanotube supported palladium catalyst and the results of characterization studies by FTIR, XRD, TGA and SEM-EDX. The catalyst system was effective in catalytic reduction of 4-nitrophenol, 2-nitroaniline, 4-nitro-o-phenylenediamine and 2,4-dinitrophenol, and in degradation of dyes i.e., Congo red, Methyl orange, Methylene blue and Methyl red. The heterogeneous catalyst system also showed an excellent activity in green and solvent-free synthesis of 18 different biaryl compounds simply by six-minute microwave irradiation. The study demonstrated that chitosan-carbon nanotube supported-Pd(0) nanoparticles can be used for environmental remediation and protection, and for green synthesis of biaryls through Suzuki-Miyaura coupling reactions.