Biosorption of toxic metal ions (Cr, Cd) and nutrients (PO) from aqueous solution by diatom biomass.

This paper evaluates diatom biomass as a biosorbent for removing Cr, Cd, and PO ions from water. The diatom was characterized by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Scanning Electron Microscopy (SEM-EDS) for its crystallinity, functional groups, and morphology. A batch sorption study was conducted to evaluate the parameters influencing Cr, Cd, and PO ions adsorption, and the mechanisms were explored. The FTIR spectra revealed Si-O, O-H, N-H, and C-O as the main functional groups present on the surface of the adsorbent. The SEM showed a rough and irregular-shaped morphology, while the EDS indicated that the diatom biomass is an aluminosilicate material. The rate-limiting steps for Cr and Cd were pseudo-first order, and pseudo-second order sorption favored PO based on their R values. Moreover, the dominant adsorption model that best described the equilibrium data was the Freundlich isotherm. The maximum adsorption capacities obtained for Cr was 5.66 (mg/g), and Cd was 5.27 (mg/g) at 313 K while PO was 19.13 (mg/g) at 298 K. The thermodynamic data revealed that the reaction was endothermic for Cd and exothermic for Cr and PO respectively. Diatom biomass was observed to be a promising bio-sorbent for removing Cr, Cd and PO from wastewater.