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2 Physicochemical Problems of Mineral Processing

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Effect of pH and time on hydrodynamic properties of dodecylamine

Zhou X., Tan Y. H., Finch J. A.

Physicochemical Problems of Mineral Processing

2018

Vol. 54, iss. 4

1237--1244

Gas holdup and froth height in the presence of dodecylamine (DDA, pKa = 10.63) are reported at three pH values. The results revealed a strong time effect for DDA: stability was reached at pH 3; not at natural pH, for example, gas holdup declining to the water only value; and at pH 11, while stability was reached quickly gas holdup was now less than in water alone indicating coalescence. In the first two cases, the time effect is attributed to loss of amine from the system as molecular amine, observed at natural pH as precipitates on the column wall. An argument for precipitation at pH < pKa is presented. At pH 11, coalescence is attributed to the oily nature of the molecular amine present as colloidal aggregates. Noting a difference in literature steady state gas holdup data at natural pH, it is speculated that varying steady states can be reached that corresponds to different levels of amine loss.

Flotation separation of cervantite from quartz

Wang J., Hua Y., Yu S., Xiao J., Xu L., Wang Z.

Physicochemical Problems of Mineral Processing

2017

Vol. 53, iss. 2

1119--1132

Flotation separation of cervantite (Sb2O4) from quartz was investigated using dodecylamine (DDA) as a collector. Experiments were conducted on single minerals and on a synthetic mixture of quartz and cervantite. Flotation separation mechanisms were investigated using the zeta potential technique, solution chemistry principles, density functional calculations and Fourier Transform Infrared (FT-IR) spectroscopy. The results indicated that DDA, primarily in the form of molecules, exhibited excellent performance in flotation of cervantite and quartz at pH 10.5. The adsorption energy of the DDA molecules on the cervantite surface was greater than the adsorption energy of water molecules, while the adsorption energy of DDA on the quartz surface was less than the adsorption energy of water molecules. DDA molecules can be adsorbed on the quartz surface to a certain extent, but it was difficult for the same molecule to be adsorbed on the cervantite surface in the pulp. This resulted in flotation of quartz. DDA molecules were adsorbed on quartz not only through physical adsorption but also by hydrogen bonding. However, cervantite could not be floated at pH 10.5 since adsorption of DDA molecules occurred through weak physical bonds on cervantite.