Synthesis of zero-valent Au nanoparticles on chitosan coated NiAl layered double hydroxide microspheres for the discoloration of dyes in aqueous medium

The catalyst activity of the nano Au was largely dependent on the particle size and the structure of the supported matrix to avoid particle agglomeration. Chitosan (CS) and CS coated layered double hydroxide of NiAl (LDH) microsphere were designed through a simple and an economic casting method. The CS and LDH microsphere were used for the impregnation and support of Au NPs and represented as Au/CS and Au/LDH and used for the sole and concurrent discoloration of methylene blue (MB) and rhodamine B (RB) dyes. The aim of the incorporation of NiAl-LDH to the CS host polymer is to increase the binding capacity of CS with Au NPs to make it more stable. The Au/LDH displaying stronger catalyst activity for both dyes discoloration, while found highly selective for MB dye. The high catalyst activity of Au/LDH is due to their small crystallite size which is 1.02 nm compared to 6.75 nm in Au/CS derived from Scherer's equation. The k(app) value based on zero-order kinetics was higher with Au/LDH against MB and RB dyes which are 3.5 x 10(-1) and 1.4 x 10(-1) min(-1) respectively. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The research paper investigates the discoloration of methylene blue and rhodamine B dyes by incorporating gold nanoparticles into chitosan and Nickel-Aluminum Layered Double Hydroxide microspheres, where Au/LDH shows stronger catalytic activity and high selectivity due to its small crystallite size, enhancing the stability of Au NPs.