Chitin hydrogel reinforced with TiO2 nanoparticles as an arsenic sorbent

Abstract

In this work chitin hydrogels were reinforced with TiO2 nanoparticles acting as fillers. The mechanical and physicochemical characteristics of these hydrogels were studied by oscillatory rheology, infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Small Angle X-ray Spectroscopy (SAXS). Adsorption showed to be higher at pHs below the TiO2 point of zero charge (pH≈6.9). The equilibrium was achieved within 4h following an Elovich kinetic model. The equilibrium assay showed a maximum capacity of 3.1mg/g with better fitting for the Langmuir model. Moreover, the homogeneity/heterogeneity parameters of the Sips, Toth and Redlich-Peterson models were close to a value of 1, indicating a homogeneous sorbent/sorbate interaction. Typical natural water ions competed with As(V) for the sorption sites, being sulfate the most relevant interference. This interference was also evidenced in As(V) adsorption from natural water samples where the sorption capacity varied depending the anion composition of the sample. The reutilization of the hybrid gel was assessed up to five adsorption cycles.