CRYSTALLIZATION PHENOMENA AND THE FLOATABILITY OF SYLVINE AND HARD SALT

For various reasons, difficulties arise in the flotation of sylvinite and kieseritic hard salt, resulting in considerable quality losses in potash production. High carnallite amounts in the crude salt and as a consequence different MgCl2 concentrations in the brine are the most i mportant reasons for the difficulties. The aim of this study was to ch aracterize the nature of the surface of sylvine in brines of different MgCl2 concentrations, i.e. to prove the existence of time-dependent p artial solution effects on the salt surface and/or of crystallization phenomena leading to the formation of new mineral phases as centres of selective adsorption of surface-active substances, and to examine the influence of these alterations on floatability. By means of a compari son between laboratory flotation results, adsorption measurements, rad iotracer measurements, and measurements of adhesion forces as well as scanning electron microscopy investigations, it was shown that the pro blems in the kieseritic hard salt (Rossleben, Germany) are mainly caus ed by the so-called red variety of sylvine. The conclusions of these i nvestigations are, firstly, that improvement of flotation characterist ics is possible by conditioning the flotation feed in the brine for a period of time, depending on the MgCl2 concentration, before the addit ion of reagents to the brine and before the floatation. Secondly, the flotation-improving effect of the clay depressant Amysed-W is caused b y the interaction of this reagent with the red sylvine and with the co llector Rofamin by forming an inclusion compound of Amysed-W with the amine.