Abstract
The purpose of fhe present papaer is to examine fundamentally the separation and recovery of gyp sum by means of the flotation process from the so-called“Scale”obtained in the salt-making plants.
The wettability of the saturated solutions of the gypsum together with or without the other salts for the gypsum particles, at first, are studied qualitatively to determine the most suitable collector and experimental conditions when the flotation is applied. From the experiments in which the various surface active agents was tested as the collector, it was indicated that oleic acid was the best collector for the crystal gypsum and “Auxide”(alkyl pyridinium salts) for the gypsum in the scale.
The simple flotation tests with an apparatus described by Knoll & Leaf were carried out for the two cases; the one is the mixture of NaCl and CaSO4·2H2O (both commercial grade), and the other being the scale. In the former, it was observed thet the rate of flotation upon the CaSO4·2H2O became greater if the ratios of amounts of initially presented CaSO4·2H2O to those of NaCl were made smaller. In the latter, moreover, it was acertained that the rate of flotation was up to arround 86%, with the results that the concentrate contained about 40-48% gypsum, in which dihydrate was 88.3%, and NaCl and magnesium salts as the remainder.
According to the results abovementioned, the possibility on the separation of gypsum by the flotation process could be expected. Especially, from the views of separation and recovery of gypsum, the following treatment would be recommended which the concentrates risen by flotation were well washed by water, because of the greater solubility of such coexisting salts as NaCl, MgSO4, MgCl2 and so on than that of gypsum in water.
