Phosphate Imprinted Polythia longifolia Cellulose:A Promising Biosorbent for the Removal of Heavy Metal Ions in Water

摘要

Cellulose isolated from the seed of Polythia longifolia was imprinted with phosphate functional group to produce Cell-Phosphate in order to remove Ni~(2+), Cu~(2+), Pb~(2+) and Cd~(2+) ions from the water. Characterization of Cell-Phosphate included the use of Fourier Transform Infrared spectrometer (FTIR), X-ray Diffraction analysis (XRD), Thermogravimetric analysis (TGA-DTA), zeta potential, Scanning Electron Microscopy (SEM) and Particle Size Dispersion (PSD). The FTIR revealed the different functional groups in Cell-Phosphate while the XRD showed a crystallinity index of 30.15%. The corresponding DTA data confirmed the assigned degradation temperature ranges. The zeta potential increased with increased pH while SEM revealed the surface of Cell-Phosphate to be homogeneous with fibre structure. Cell-Phosphate removed Ni~(2+), Cu~(2+), Pb~(2+) and Cd~(2+) ions with an adsorption capacity (40.00-49.40 mg g~(-1)) that compares favourably with other known agricultural-based adsorbents in the literature. The metal ions removal fitted well for pseudo-second-order model. The Gibb's free energy change (△G~o) suggested a spontaneous sorption process while entropy change (△S~o) suggested that the metal ions are stable on Cell-Phosphate. Conclusively, Cell-Phosphate is a promising material for the sorption of Ni~(2+), Cu~(2+), Pb~(2+) and Cd~(2+) ions through a mechanism reaveled by Density Functional Theory (DFT) to be ionic interaction with a des-orption capacity above 70% for the metal ions in the first regeneration cycle.