Abstract
The chemical nature of the interaction of starch and dodecylamine (DDA), which generally act as depressant and collector, respectively, in the reverse flotation of bauxite, was investigated using starch-iodine tests. The results obtained from the blue-value measurements for starch+DDA+iodine system indicate the formation of the inclusion complex for amylose-DDA system at low DDA concentration (<2 mmol/L). However, it is less likely for amylopectin-DDA system with short helix. UV-Vis spectra of starch-iodine complexes show that each helix of amylose can accommodate two DDA molecules locating separately at its two ends, and in the helical cavity there is room available for the upcoming iodine. When concentrated DDA is tested, amylose-DDA system exhibits no characteristic starch-iodine color, owing to the presence of a compact coating of DDA molecules on starch via hydroxyl/amine hydrogen bonding. 1H NMR spectroscopy and surface tension determination help to clarify the interaction mechanism of amylose with DDA.
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