Research Information System
PHYSICOCHEMICAL PROBLEMS OF MINERAL PROCESSING, vol.61, no.3, pp.1-11, 2025 (SCI-Expanded)
Clay minerals are mainly composed of aluminum hydrosilicates. In some
minerals, aluminum is completely or partially replaced by Fe or Mg.
Alkaline minerals or alkali metals are present as major constituents of
clay minerals. While some clay sources may contain a single clay
mineral, they often contain different minerals such as quartz, calcite,
feldspar, pyrite, etc. as impurities. They also contain organic matter
and water-soluble salts. Halloysite is a clay mineral belonging to the
kaolinite group and USA Environmental Protection Agency (EPA 4A)
declared it as an innocuous/adaptable material to human health and the
environment. Halloysite ore deposits are mainly found together with
kaolinite and quartz minerals, but can also be found as a pure source.
The degree of purity of halloysite ore determines the industrial area
where it will be used and therefore its economic value. Since clay
minerals are naturally composed of fine particles, it is necessary to
disperse the clay particles in suspension to separate halloysite and
kaolinite minerals. In addition, there are also fine-grained quartz
minerals, and to recover pure halloysite minerals, it is necessary to
determine their properties in the fine size fraction. In this study,
the dispersion properties of halloysite, kaolinite, and quartz minerals
in the presence of sodium silicate (SS), sodium tripolyphosphate (STPP),
and sodium hexametaphosphate (SHMP) dispersants in fine-size fraction
(-38 μm) were researched by particle size measurements and mineral
separation properties were investigated by sedimentation experiments at
different acidic, neutral, alkaline pH values. In dispersion
experiments, the d90 values of halloysite, kaolinite, and quartz
minerals were 74.0, 50.7, and 61.3 μm without any dispersant addition,
and such values decreased to 54.7, 26.3, and 57.1 μm as SHMP increased
to 10 kg/ton, respectively. d50 and d10 values showed a significant
change for halloysite, while no important change was observed for
kaolinite and halloysite. SHMP had the most effect on the particle size
change in the dispersants especially on halloysite minerals. The least
effect on particle size change was observed in the quartz sample with
dispersant addition. The sedimentation experiments aimed to investigate
the effects of pH on halloysite, kaolinite, and quartz recoveries in
binary systems as settled products. Kaolinite settled more at acidic pH
and halloysite at basic pH. There was no pH-dependent change in the
settling behavior for halloysite and quartz. In the quartz-kaolinite
system, quartz mineral settled more than kaolinite for all pH values.
The settling experiments showed the importance of morphological
differences between tubular halloysite and lamellar kaolinite minerals.