Stabilization of zero-valent Au nanoparticles on carboxymethyl cellulose layer coated on chitosan-CBV 780 zeolite Y sheets: assessment in the reduction of 4-nitrophenol and dyes

Performance of polymer-based Au catalysis depends on the size of Au particles and the structure of polymer host materials. In the current studies, the carboxymethyl cellulose-chitosan (CMC-CH) sheet was synthesized by layering CMC on CH sheet, while CMC-CH-CBV 780 zeolite Y (CMC-CHZY) sheet was synthesized by coating the CMC layer on a sheet of CH-incorporated CBV 780 zeolite Y (ZY). The CMC-CH or CMC-CHZY sheets were individually immersed in Au(III) salt solution, which was converted to Au⁰ NPs by treating with NaBH₄ to synthesize Au/CMC-CH or Au/CMC-CHZY catalysts respectively. Both the synthesized Au catalyst activities were compared against the discoloration of methylene blue (MB) and Congo red (CR) dyes as well as the reduction of 4-nitrophenol (4-NP). It was revealed that Au/CMC-CHZY catalyst showed excellent catalytic performance against all the pollutants. Furthermore, the apparent rate constant k_app (3.3 \(\times\) 10⁻¹ min⁻¹), of Au/CMC-CHZY catalyst was found higher against MB dye discoloration as compared to CR and 4-NP. It was also observed that MB discoloration followed pseudo-first-order while CR and 4-NP followed the zeroth-order kinetics. The catalyst alters the mechanism of a chemical reaction and so does the order of the reaction, therefore, observed different orders of reaction in the current study.