Chitosan coated NiAl layered double hydroxide microsphere templated zero-valent metal NPs for environmental remediation

Microspheres of pure chitosan polymer (CH) and CH-LDH composites were synthesized via a simple casting method to stabilize the metal nanoparticles (NPs). The CH-LDH composites comprising NiAl layered double hydroxide (LDH) incorporated in CH host polymer. The CH or CH-LDH microspheres template were impregnated with Cu, Ag and CuAg metal ions and investigated through ICP-OES where the distribution coefficient (K-d), of CH-LDH was highest towards Cu(II) ions (3.35 x 102 mL g(-1)), suggesting the greatest selectivity of CH-LDH for Cu(II) compared to Ag(I). The adsorbed metal ions on CH or CH-LDH microspheres were converted to their corresponding zero-valent metal NPs (ZVM), and then assessed their catalytic properties in the degradation of dyes, nitrophenols, and concurrent removal of a mixture of dyes and nitrophenols by using NaBH4 as a reductant. Furthermore, the rate constant value k(app) based on pseudo -first-order kinetics was highest for CH-LDH@Cu catalyst against Congo red (CR) and 4-nitrophenol (4-NP) which was 3.9 x 10(-1) and 3.6 x 10(-1) min(-1) respectively. The slowest k(app) rate (8.9 x 10(-2) min(-1)) was observed for 2,4-dinitrophenol (2,4-DNP). Moreover, the turnover frequency (TOF) were determined for the degradation of all the pollutants, where the highest TOF found for CR as 0.448 h(-1). Furthermore, for the practical applications, the CH-LDH@Cu NPs was also used for the concurrent removal of dyes and nitrophenols. The current study applications is general and the synthesized catalyst can be applied in other potential applications because of their strong catalytic activities. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Microspheres of pure chitosan polymer and CH-LDH composites were synthesized to stabilize metal nanoparticles. The composites showed high selectivity for Cu(II) ions and exhibited excellent catalytic properties in the degradation of dyes and nitrophenols.