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Abstract

The necessity to find efficient and economic methods of treating waste water which contains heavy metals has led to this work. The properties of several natural zeolites, specifically clinoptilolite, mordenite and ferrierite have been examined with a view to their use in the removal of lead and cadmium from both fresh water and for saline environments.

Binary equilibrium studies were performed using either sodium forms of the minerals (which were then exchanged with lead cadmium or ammonium) or the ammonium zeolites which were similarly exchanged with either lead or cadmium. In the case of experiments involving cadmium, two different co-ions were used, the nitrate and the chloride. Most binary exchanges were carried out at a total external solution concentration Of 0.1 equiv.dm and at 25°C, but some exchanges involving lead in the sodium zeolites were performed at higher concentrations (0.5 equiv.dm ). The thermodynamic parameters were calculated where possible, but some of the exchanges turned out to be ternary in nature. The overall affinities indicated that lead was preferred over cadmium in the presence of all the sodium zeolites while the ammonium forms of the minerals were less selective for both lead and cadmium.

In addition some ternary equilibrium studies were carried out for the systems Pb/Cd/Na and Pb/Cd/NH^ Clinoptilolite has been found to effectively remove lead and cadmium in the presence of sodium or ammonium, while for mordenite the ammonium ion inhibits the exchange of the heavy metals. Ferrierite shows no selectivity for either lead or cadmium and can only be used to a limited degree.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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