Date of Award
Master of Science (MS)
Yaser E. Greish
Dr. Kyrikai Polychronopolo
Water pollution due to the presence of soluble metal ions is one of the greatest challenges to environmental scientists. Different methods have been explored to the removal of these soluble ions. Among these methods, elimination by sorption into/onto solid materials has been considered one of the successful approaches. Sorbent materials usually chemically interact with soluble ions and eliminate them by bond formation between the ions and the sorbent molecules. On the other hand, soluble ions can be also exchanged with inorganic sorbents in which other environmentally friendly ions can exchange with the soluble metal ions. In the current study, the sorption of metal ions through chemical adsorption and ion exchange mechanisms were explored. Apatitic calcium phosphate solid sorbents with various Ca/P molar ratios were synthesized and characterized after being prepared and after thermal treatment at 800oC. Additionally, a stoichiometric HAp with a Ca/P molar ratio of 1.67 was also evaluated in three forms, synthetic, commercial in the nm scale and commercial in the nm scale, as a component in a composite with cellulose acetate fibrous sorbents. In this regard, the proportion of the stoichiometric HAp powders was maintained at 5 and 10% by weight. All sorbents were evaluated for their efficiency to remove Cd2+ ions, as a model soluble metallic ion pollutant, from a simulated aqueous media. A batch study was utilized in this regard where the effect of varying the pH of the medium, the weight of the sorbent material, the initial concentration of the sorbate (Cd2+) ions and the contact time between the sorbent and the sorbate solution were thoroughly studied and evaluated. Results showed the high crystallinity of the prepared and purchased calcium phosphate sorbents and the homogeneity of distribution of the stoichiometric apatitic sorbent particulates within the fibrous membrane of CA. An optimization was carried out for the sorption process where an optimum pH of 5.5 was selected in all experiments in the presence of 0.1 g of the sorbent material and 1 mmol of the sorbate ions for a maximum of 3 contact hours. Comparatively, pure calcium phosphate sorbents were found more efficient than CA fibrous sorbents containing a maximum of 10 wt% of the stoichiometric apatite particulates. In addition, the relatively lower affinity of the CA fibrous membrane towards Cd2+ ions is based on its chemical structure, where the ester and -OH functional groups of the CA is inferior in its interaction with Cd2+ ions, compared with the exchange mechanism between the Cd2+ ion in solution and the Ca2+ ions within the apatite structure.
Charnetskaya, Eleanora, "Development of Hydroxyapatite-Polymer Sorbents for the Removal of Heavy Metal Ions from Waste Waters" (2018). Chemistry Theses. 6.