A study of the relationship between the chemical structure of some carboxylic acids and their capacity to inhibit the crystal growth of calcium fluoride

Flotation Selectivity of Novel Alkyl Dicarboxylate Reagents for Calcite-Fluorite Separation

A series of amino acid-based surfactants with a fixed alkyl chain length and with two carboxyl groups separated by a spacer of one, two or three carbon atoms have been synthesized and evaluated as potential collectors for flotation of calcite and fluorite. A monocarboxylate amino acid-based surfactant having the same length of the hydrocarbon tail was also included for comparison in the study. Experiments using a Hallimond flotation tube showed that although the flotation reagents solely differ in terms of spacer, their efficacy in terms of flotation recovery varied very much. Whereas on calcite at pH 10.5 only the monocarboxylate collector gave a high yield, on fluorite at the same pH both the monocarboxylate and the dicarboxylate collectors with one carbon between the carboxyl groups gave good results. On calcite at the natural pH the monocarboxylate collector was most efficient but the dicarboxylate collectors with a two- and a three-carbon spacer also gave a reasonable recovery. On fluorite at the natural pH the dicarboxylate collectors with a two- and a three-carbon spacer were most efficient. The ζ-potential and the flotation recovery of the mineral particles as a function of added collector were assessed and the adsorption was also monitored by diffuse reflectance infra-red spectroscopy. Taken together, the results showed that small changes in the head group region of the collector can radically affect flotation recovery. This type of knowledge is important to understand flotation selectivity in a mixture of similar minerals.

Impact of Heat Treatment on the Performance of Polymers as Ferric Ions Stabilization Agents for Aqueous Systems

The impact of heat treatment on the performance of various polymers as ferric ions stabilization agents in an aqueous system at pH 7.00, 23 °C has been investigated. The polymers evaluated include: (a) homo-polymers of acrylic acid, methacrylic acid, maleic acid, 2-acrylamido-2-methylpropane sulfonic acid, sulfonated styrene; (b) co-polymers of acrylic acid: 2-acrylamido-2-methylpropane sulfonic acid and maleic acid: sulfonated styrene, and (c) ter-polymers of acrylic acid: 2-acryalamido-2-methylpropane sulfonic acid: sulfonated styrene, acrylic acid: methacrylic acid: t-butylacrylamide, and acrylic acid: 2-acrylamido-2-methylpropane sulfonic acid: t-butylacrylamide. It has been found that all polymers lose performance to a varying degree when exposed to thermal treatment (150 °C, 200 °C, 240 °C, 20 hr). The performance data collected before and after thermal treatment suggest that sulfonated styrene containing co- and ter-polymers are better ferric ions stabilization agents than the co- and ter-polymers containing 2-acrylamido-2-methylpropane sulfonic acid and t-butylacrylamide. In addition, it has been found that heat treatment exhibits positive influence on the performance of homo-polymer of 2-acrylamido-2-methypropane sulfonic acid. The results have been explained in terms of loss of 2-acrylamido-2-methylpropane sulfonic acid and t-butylacrylamide in the co- and ter-polymers during thermal treatment.