Date of Award

1-1-1968

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Abstract

Leonardite has been considered as a substitute for bentonite as an iron ore pellet binder since it would impart less undesirable impurities to the iron ore. In the case of leonardite, pellet binding strength is believed to be derived from the formation of leonardite- water gel systems. In this respect, the gels formed by addition of sodium hydroxide ("sodium gels") or sodium hydroxide and calcium hydroxide ("calcium gels") to leonardite-water slurries are of interest. Procedures were developed giving reproducible results in the preparation and study of these gel systems. The effects of variable composition, temperature, time and order of reagent addition on gel viscosity was determined. Viscosities, as measured by a Brookfield Viscometer ranged from 10 to greater than 8,000,000 cp. for both systems studied.

Maximum sodium gel viscosities were achieved at sodium hydroxide:leonardite ratios between 0.08 and 0.12. Increased leonardite:water ratios resulted in increased viscosities.

Calcium gels had high viscosities over a broader range of compositions and at lower leonardite:water ratios.

Both gel systems studied were non-Newtonian, thixotropic and became more viscous at lowered temperatures.

The gelling phenomena in both systems were attributed to the formation of a lattice network of humic acid molecules linked by divalent calcium ions.

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