Date of Award

11-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Yaser E. Greish

Second Advisor

Dr. Fathalla Hamed

Third Advisor

Kyriaki Polychronopolou

Abstract

Sorption is one of the most efficient techniques for the removal of heavy metal ions from waste water. It involves the use of solid materials, known as sorbents, which can be natural of synthetic in origin. Recently, synthetic nanomaterials of various compositions have been used as sorbents. Among these materials, calcium phosphate; also known as hydroxyapatite (HAp), and magnetite were previously investigated as potential sorbents. In the current study, commercial HAp, and magnetite nanoparticles as well as their physical and chemical mixtures were investigated as potential sorbents for the removal of Cd2+ ions from simulated wastewater. A comparison is made between the structure, morphology and properties of physically prepared HAp: magnetite and HAp chemically grown onto magnetite nanoparticles. A detailed characterization of all sorbents was carried out, both as prepared and after thermal treatment at various temperatures. A batch study was used to study the effect of different parameters on the efficiency of Cd2+ ions sorption. The effects of changing the solution pH, initial sorbent weight, initial sorbate concentration and contact time were studied. Moreover, the effect of thermal pretreatment of the sorbents at temperatures up to 600°C on their sorption capacities were evaluated. Results showed phase purity of both HAp and magnetite starting materials, while their physical and chemical mixtures were varied in composition and properties. Physically mixed HAp and magnetite (1:1) showed the partial conversion of magnetite to hematite when heated at 600°C, unlike pure magnetite which showed a complete conversion to hematite at the same temperature. In contrast, chemically prepared HAp-on magnetite (1:1 and 2:1) mixtures showed the formation of HAp layers onto the surfaces of the magnetite seeds. This was reflected on a maintained magnetization even after heating to 600°C due to the inhibited conversion of magnetite to hematite. The later chemical mixtures showed better sorption capacities than the physical mixture and pure magnetite, but close to pure HAp sorbents. The main mechanism of sorption is dominated by the ion exchange capability of HAp, and with the magnetite in the core, a magnetic-based HAp sorbent is highly believed to be effective for the removal of Cd2+ ions from aqueous media.

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