黄鉄鉱浮選における石灰の抑制作用について

抄録

The depression of pyrite with lime in xanthate flotation was investigated by means of flotation tests, adsorption studies and electrokinetic potential measurements.
The results obtained are summarized as follows: 1. In xanthate flotation of pyrite, lime is more effective than sodium hydroxide as a depressant.
2. Ca²⁺ions do not affect the adsorption of xanthate on pyrite; the adsorption amount of xanthate decreases with increasing pH of solutions.
3. The adsorption of Ca²⁺ions on pyrite is relatively small in the range of pH5 to 7, while the adsorption of Ca²⁺ions increases rapidly as the alkalinity of solutions increases. The adsorption of Ca²⁺ions are not affected by the presence of xanthate.
4. The pH value at which the zeta-potential of pyrite bacomes zero is found to be 7.6; above and below which pyrite is negatively and positively charged, respectively. It is observed that the sign of the zeta-potential of pyrite is reversed by the addition of Ca²⁺ions in the range of pH above 7.6, i. e. the range where pyrite is negatively charged. This may be interpreted in terms of the specific adsorption of Ca²⁺ions on pyrite surfaces.
5. MgCl2 is more effective depressant than CaCl2 under the conditions in which the-pH of solutions was adjusted by NaOH. As in the case of Ca²⁺ions, the adsorptions of xanthate on pyrite is not affected by the presence of Mg²⁺ions.
6. The adsorption of Mg²⁺ions on pyrite becomes significant with increasing pH of solutions, while no appreciable change in the adsorption amount of Mg²⁺ions takes place in neutral pH regions. Based on the above results the following conclusions may be obtained.
A. The adsorption of Ca²⁺ions is responsible for the depression of pyrite. The depression of pyrite may be caused not by the formation of calcium sulfate or calcium carbonate of pyrite surfaces but by the adsorption of Ca²⁺ions asscciated with OH^-ions.
B. The adsorption of xanthate and Ca²⁺ions takes place independently on the surfaces of pyrite. The floatability of pyrite depends upon the relative adsorption amounts of xanthate and Ca²⁺ions; the former makes the surfaces of pyrite hydrophobic, while the latter makes them hydrophilic.