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Title: Feasibility of polymer enhanced ultrafiltration (PEUF) for heavy metals retention under competitive conditions
Author: Almutairi, Fahad M.
Awarding Body: Swansea University
Current Institution: Swansea University
Date of Award: 2009
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Heavy metals are valuable resources for the modern world; however, they are potentially hazardous. Contamination exists in aqueous waste streams of many industries, such as metal plating facilities, mining operations, and tanneries. The soils surrounding many military and industrial sites are also contaminated and pose a risk of metals groundwater and surface water contamination. Some metals associated with these activities are cadmium, chromium, lead, and mercury. Heavy metals are not biodegradable and tend to accumulate in living organisms, causing various diseases and disorders. However, heavy metals have a high commercial value if they can be recovered in pure form. Polymer enhanced ultrafiltration (PEUF) was investigated because it offers the potential to selectively recover metals rapidly from solutions containing low concentrations. However, the major drawback (complex solutions containing other chelators and competitors) of these processes have not been investigated in detail and a fundamental understanding of these processes in real systems is required to truly assess and exploit their potential. The aim of this project was to investigate the performance of PEUF for metal ions filtration in batch mode and continuous feeding using metals, individual and in mixtures, metal binding chelator and competitor. A variety of feed compositions were used, and metal ions retention profiles were determined. The competition from other chelators or competitors for metal ions was investigated in the presence of PEI. The binding mechanisms of metal ions were explored and the ability of the Langmuir isotherm model to describe these systems using a batch and continuous feed was determined. Based on the principal of mass balance and Langmuir adsorption isotherms, a mathematical model describing the continuous feed of PEUF was developed. Ultrafiltration experiments were carried out in the stirred dead-end ultrafiltration cell and cross flow ultrafiltration systems. The metals investigated were: Cu2+, Zn2+, Ni2+, Cr6+, Co2+ and Cd2+. The results showed that adding PEI to metal ion solutions significantly increases the retention of the metal ions in the solution to greater than 90% at its best. However, the addition of the polymer significantly reduces the flux of the process (by approximately 50%) for equivalent solution conditions. Membrane surface charge is also a factor which is critical to the process performance. In general, the highest retention of metal ions occurred when the membrane had its highest negative charge. The results of the binding studies showed that the Langmuir isotherm offers a better description of the binding process than the Freundlich isotherm. The work reported here showed that competition for ions from other chelators or competitors is possible and change the performance compared to ideal simple systems. It also showed some potential advantages of this approach by changing capacity and selectivity of the separation based on PEUF processes. Under competitive conditions with chelators and competitors, maximum capacities of metal ions bind to PEI using Langmuir isotherm in continuous feed of PEUF were greater than those obtained from batch system, they were similar for Cu2+-PEI complex in single and mixed metals solutions of both systems. The model developed in this project showed good predictions of the experimental results with minor exception in the case of strongly competitive situations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available