Development and characterization of chitosan functionalized dialdehyde viscose fiber for adsorption of Au(III) and Pd(II).

A highly efficient fiber-based adsorbent (DAVFs-CS) was developed via decoration of chitosan (CS) on the dialdehyde viscose fibers (DAVFs) substrate, and employed to selective separation of precious metals from simulated contaminated water. The surface functionalization of the solid material was probed using the Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR) technique. The batch characteristic results showed that the maximum uptake capacities of DAVFs-CS were higher up to 322 mg/g and 207 mg/g for Au(III) and Pd(II) at optimal pH 2.0 and 3.0, which exhibited competitiveness with the majority of the reported adsorbents. Meanwhile, the adsorption data were in accordance with Langmuir and PSO equations, which indicated that the monolayer chemisorption dominated the adsorption process. The competitive adsorption study showed that the removal efficiency of Au(III) was not susceptible to the co-existing impurities. Adsorption mechanism study revealed that the negative Au(III) or Pd(II) species were firstly adsorbed on DAVFs-CS via the protonated amino groups, subsequently the partially reduction of them to zero-valent gold and palladium with the help of reductive functional groups. Thus, DAVFs-CS could be as a promising adsorbent to recovery of precious metals owning to its unique adsorption mechanism and excellent adsorption performance.