Synergistic Mechanism And Application Of Cationic Collector Mixture In Steam Coal Reverse Flotation

Flotation is one of the prime mineral processing methods that have found wide application in the separation of coal slimes. However, for some hard- toseparate coals such as oxidized coal and low rank coals, conventional flotation process is not suitable. The gangue minerals in comparison to coal have consistent chemical nature and well defined structures which impart them uniform floatability. The coal reverse flotation process has some obvious advantages over forward flotation. Meanwhile, some problems still exist in coal reverse flotation such as weak collecting ability of collectors, huge dosage of collectors and the expensive price of the collector used in coal reverse flotation process.For the efficient using of the cationic collector, and decreasing the reagent dosages, this paper proposed a combination of cationic surfactant and fatty acids aiming for the collector efficiency improvement. Mixture of dodecanamine hydrochloride(DAH) and fatty acids is proposed as collector in coal reverse flotation process. Reverse flotation behaviors of raw coal slime and kaolinite in the presence of collector mixture or DAH were researched in the paper. The synergistic mechanism of the mixture collectors were studied by means of contact angle measurement, IR spectra, micro electrophoresis, surface tension measurement and molecular dynamics calculation. In summary, following conclusions can be drawed according the paper:1. Mixtures of amine collector-DAH and comment anion collectoroleic acid(OA) were prepared. And the effects of the mixture collector on coal reverse flotation behavior were studied. It is indicated that the collector mixtures have much stronger collecting ability than DAH. And the collecting ability improves with the increase of the ratio of OA and DAH in the mixture. But, the collector mixtures showed weak selectivity. During the reverse flotation process, the addition of OA could greatly reduce the volume of the froth product.2. Effects of collector mixture of different cationic amine collector(DAH, DTAC, CTAB) and different fatty acid(R-COOH, R=7, 9, 11, 13, 15, 17) on coal reverse flotation were studied systematically. And the effect of the molar ratio of the cationic amine collector and fatty acid was researched. Experimental results showed that the collector mixture have stronger collecting ability than pure cationic amine collector. The collecting ability improved with the increase of the R and the molar ratio of fatty acid in the collector mixture.3. Reverse flotation results of kaolinite in the presence of different collector were compared with each other. It is indicated that the collecting ability of collector mixtures to kaolinite improved with the decrease of the R and the decrease of the molar ratio of fatty acids in the mixtures. The recovery of the kaolinite increased with the decrease of the pH. Finer coal slimes were more easily collected and floated into froth product.4. Molecular dynamics results showed that the functional group of the DAH molecule was absorbed vertically onto the 001 surface of the kaolinite. The hydrophobicity of kaolinite 001 surface was further improved by the interaction of carbon chain between fatty acids molecules and DAH molecules. Molecular dynamics in the presence of water environment revealed that the relative concentration of water molecules near kaolinite 001 surface decreased with the addition of DAH or collector mixtures. The relative concentration of N atom in DAH molecules and the O atom in fatty acids molecules near kaolinite 001 surface indicated that kaolinite 001 surface mainly interacted with DAH molecules.It is well known that steam coals show poor floatability. Coal reverse flotation technology may produce an alternative method for the separation of hard-to-float coals. This study has a certain guiding significance to reduce processing costs, and improve the effect of coal reverse flotation.