Fibrous Cerium Phosphate and its Intercalated-Urea Product as Versatile Adsorbents for Mercury (II) Removal

Abstract

Fibrous Nano cerium Phosphate was achieved by reacting Cerium Sulphate solution with phosphoric acid at 80°C for several hours.  Furthermore, Urea was intercalated into the prepared f-cerium phosphate. Techniques like Fourier Transform Infra-Red spectroscopy, X-ray diffraction, Scanning Electron Microscope, and Thermogravimetric analysis were used to characterize these products. Under various conditions, the products were examined to their adsorption capability to extract mercury (II) ions from aqueous solution. The semicrystalline nature of the phosphates was demonstrated by XRD, and the interlayer d-spacings for the cerium phosphate and urea-intercalated compounds were 10.6 and 11.3 Å, respectively. The FTIR spectra of the intercalated phosphate showed an additional peak at 1400 cm⁻¹ corresponding to C-N stretching confirming the presence of urea. The SEM showed a fibrous morphology of the cerium phosphate with a particle size of 16mm. The optimum adsorption conditions were at pH values 3.0 at a reaction time interval of 30 minutes. Pure cerium phosphate behaved differently from intercalated cerium phosphate, which consistently showed a decrease in adsorption percentage as the initial ion concentration increased. Both phosphates showed a systematic increase in adsorption percentage as the adsorbent amount increased, however, pure cerium phosphate showed greater adsorption ability than its intercalated analogue. Both Freundlich and Langmuir isotherm models were used, and their linearity curves are comparable. For pure and intercalated chemicals, the Langmuir model yielded R² values of 0.5351 and 0.7283, respectively. According to the Freundlich model, the pure and intercalated phosphates R² values were 0.5823 and 0.8649 respectively. Although a low correlation is observed, the intercalated material fit both isotherms and showed a slightly better behaviour.