人工微細ヘマタイトの加圧浮上に関する基礎的研究

抄録

Dissolved-air pressure flotation of fine hematite particles has been investigated as functions of pH, amount of collector or flocculant added, solid concentration in feed and volume of air bubbles, using sodium oleate, Separan NP 20 and aluminum sulfate as collector, polymeric flocculant and inorganic flocculant, respectively. In addition, the efficiency of dissolved-air pressure flotation has been compared with that of dispersed-air flotation (using a Denver type flotator), in the case that a collector was used.
The results obtained are as follows:
1) When the suspended particles are in a flocculation state at pH region near the zero point of charge, the flotation recoveries of them are about 80% and 30% in a pressure type cell and a Denver type cell, respectively, in the absence of collector or flocculant.
2) Maximum flotation is obtained at a collector concentration where flocculation occurs the most remarkably in either case of a pressure type and a Denver type cell. In order to obtain sufficient flotation recovery in Denver type cell, it is, however, necessary to make the particle surface more hydrophobic than in a pressure type cell.
3) In pressure type cell using polymeric flocculant, flotation efficiency reaches a maximum at a certain concentration of polymeric flocculant. The lowering of flotation efficiency beyond this concentration may be caused by the reason that the ability of the floc structures formed to trap air bubbles decreases as the floc overgrows and becomes hydrophilic.
4) In pressure type cell using inorganic flocculant (aluminum sulfate), Maximum flotation is obtained at neutral pH region, where aluminum hydroxide is precipitated. It is assumed from the values of the zero point of charge that aluminum hydroxide and hematite particles flocculates each other in this pH region. In this case a large volume of air bubbles are required for obtaining sufficient flotation, so use of inorganic flocculant is unfavorable in the case of high solid concentration in feed.