Polyacrylic acid@zeolitic imidazolate framework-8 nanoparticles for detection and absorptive removal of cyanide from aqueous media with high efficiency

Abstract

A strategy for sensing of cyanide anion by analyte-induced displacement of a preloaded fluorescent molecule from a cage-like structure is developed. For this purpose, the polyacrylic acid@zeolitic imidazolate framework-8 nanoparticles (PAA@ZIF-8 NPs) were synthesised and a fluorescent molecule, fluorescein isothiocyanate (FITC), was loaded in its cavity. On loading, the fluorescence of FITC was quenched, then upon addition of CN− into the PAA@ZIF-8-FITC, the CN− replaced the doped FTIC, the fluorescence of which was then regenerated and it was then used as a highly sensitive signal transduction for detection of CN- in aqueous media. The process was optimized with parameters such as pH, incubation time etc. for best sensitivity and quantification. The kinetics and mechanism of cyanide adsorption have been studied in detail. The PAA@ZIF-8 NPs has been tested for removal of CN- from aqueous media by adsorption and it exhibited remarkable uptake efficiency of 61 and 85 mg g-1 for NaCN and CuCN, respectively. The kinetic adsorption data exhibits good agreement with the pseudo-second order kinetic fit, while the equilibrium data fitted perfectly with the Langmuir adsorption equation. The PAA@ZIF-8 can be used as a packing material of a column for removing cyanide anion. This study demonstrated a viable and sustainable solution for detection and removal of cyanide from contaminated water.