Development of Chitosan Schiff base-Stabilized metal nanoparticles for the catalytic hydrodechlorination of 2-chlorophenol

Abstract

Catalytic hydrodechlorination (HDC) has been considered a promising method for treating chlorinated organic pollutants. The use of metal nanoparticles on biodegradable polymer support in catalysis has received tremendous interest due to their improved catalytic efficiency. Herein, we report a Schiff base of Chitosan-Benzothiophene-2-carboxaldehyde (CS-BTC) synthesized via a simple condensation approach for stabilizing zerovalent metal nanoparticles (CuNP, MnNP, and BiNP) as new nanocatalyst for the HDC of 2-chlorophenols (2-CP). The spectroscopic analyses revealed a good coordination between the biopolymeric Schiff base and the metal nanoparticles. In addition, the microscopic studies of the metal nanoparticles revealed rough surfaces with heterogeneous features with irregular roughly packed surfaces and openings that could assist the diffusion of reactants and products. Under optimized conditions, 0.1 g of the nanocatalysts could convert 2-CP to phenol in 20–30 min; meanwhile, both phenol and cyclohexanone were produced for 40–60 min of reaction. The bases introduced to the reaction system neutralized the hydrochloric acid (HCl) created during the reaction process, preventing catalyst toxicity. The kinetic studies reveal good catalytic performance of the nanocatalysts and the results highlight the importance of the type of metal and the catalytic state in impacting reaction kinetics in zeroth-order catalysis.