Silver nanoparticles decorated polydopamine-coated pure silica zeolite as an efficient nanocatalyst for organic pollutants removal

An efficient catalyst, composed of silver-decorated polydopamine coatings on pure silicon zeolite (PSZN/PDA/ Ag), capable of removing organic pollutants in water effectively, was synthesized using an economical in-situ reduction approach. The polydopamine (PDA) coating facilitates the stable dispersion of silver (Ag) nanoparticles and offers numerous catalytic active sites. This can be attributed to the ability of PDA in acting as a redox medium, via the interchange between its catechol group and the benzoquinone structure, thereby decreasing impediments to electron transfer among reactants, and consequently promoting the catalytic reaction. The porous structure of PSZN aids in embedding the PDA elements inside the pores, preventing the coating from peeling off and providing additional adsorption to transport reactants to the catalytic center for cooperative catalysis. Leveraging these properties, it demonstrates excellent efficiency and reusability in the catalytic reduction of waste methylene blue (MB) and 4-nitrophenol (4-NP), achieving reaction rates of 41.23 x 10-2 min-1 across five cycles respectively, with a minimum average conversion rate of 96 %. Moreover, the impressive performance is primarily due to the significant load (wt = 30.7 %) and small size (11.85 nm) of Ag nanoparticles, which boast a large number of reaction centers.