701
A Determination of the Effect of Changing Collector Chain
Length Under Varying Water Quality
Taonga Sinjani, Resoketswe M. Manenzhe, Malibongwe S. Manono, Kirsten C. Corin
Centre for Minerals Research, Department of Chemical Engineering, University of Cape Town
ABSTRACT: Xanthate collectors are required in flotation to enhance the hydrophobicity of valuable minerals,
resulting in higher concentrate grades and recoveries. Under typical flotation conditions, longer chained
collectors achieve higher solids and water recoveries due to the increased adsorption onto mineral surfaces owing
to the presence of a longer hydrophobic chain, whilst shorter chained collectors have been found to achieve
higher grades. However, once the pulp chemistry is altered by changes in water quality e.g., the concentration of
ions, there may be a change in the efficacy of the collector in separating the valuable minerals from the gangue.
Therefore, to provide more knowledge into the optimisation of reagent usage in flotation, this study investigates
differences in collector performance under varying water quality. A two-phase factorial design of experiments
used three ionic strengths of synthetic plant water and three dosages of collectors, SEX and SIBX in the batch
flotation of a Merensky ore. The longer chained collector, SIBX, behaved atypically, achieving lower solids
and recoveries than SEX in water with low ionic strengths. The factor with the largest impact on the flotation
response was the ionic strength of the water. The findings provide plant operators with more control over the
process performance as reagent control may compensate for changes in water quality.
Keywords: collector chain length, flotation performance, water quality
INTRODUCTION
Xanthate collectors contain a non-polar end that consists of
a hydrocarbon chain that can contain one to six carbons. It
is known that an increase in the number of carbon atoms
increases the hydrophobicity of the molecule (Feng et al.,
2012). This affects the characteristics of the collector such
as the strength, stability, and selectivity (Mielczarski et. al,
1998). These factors affect the recoveries and grades achiev-
able by the collector and the dosages required. A study uti-
lised micro-flotation to compare collectors, namely, sodium
ethylxanthate (SEX) to potassium amyl-xanthate (PAX) on
the flotation of multiple sulfide minerals (Goktepe, 2001).
According to Goktepe (2001), the order of the strength was
found to be amyl isobutyl isopropyl ethyl xanthates.
This was explained by an increase in hydrophobicity that
increases the efficiency of air bubble-particle attachment as
there is a larger contact angle (Mielczarski et al., 1998). In
the flotation of pyrite, PAX resulted in the highest recover-
ies due to this increased hydrophobicity at pH levels above
8. At low pH levels, SIBX recovered the most pyrite, oppos-
ing the previously observed pattern. SEX, however, consis-
tently performed poorly at recovering the pyrite at all pH
levels, remaining the weakest collector.
Eh/pH diagrams in a study by Janetski et. al (1977)
explained that this decrease in the floatability of pyrite
was due to the pyrite surface oxidising more readily than
the shorter chained xanthate. Goktepe (2001) found in
the flotation of chalcopyrite, at a pH level of 4, sodium
A Determination of the Effect of Changing Collector Chain
Length Under Varying Water Quality
Taonga Sinjani, Resoketswe M. Manenzhe, Malibongwe S. Manono, Kirsten C. Corin
Centre for Minerals Research, Department of Chemical Engineering, University of Cape Town
ABSTRACT: Xanthate collectors are required in flotation to enhance the hydrophobicity of valuable minerals,
resulting in higher concentrate grades and recoveries. Under typical flotation conditions, longer chained
collectors achieve higher solids and water recoveries due to the increased adsorption onto mineral surfaces owing
to the presence of a longer hydrophobic chain, whilst shorter chained collectors have been found to achieve
higher grades. However, once the pulp chemistry is altered by changes in water quality e.g., the concentration of
ions, there may be a change in the efficacy of the collector in separating the valuable minerals from the gangue.
Therefore, to provide more knowledge into the optimisation of reagent usage in flotation, this study investigates
differences in collector performance under varying water quality. A two-phase factorial design of experiments
used three ionic strengths of synthetic plant water and three dosages of collectors, SEX and SIBX in the batch
flotation of a Merensky ore. The longer chained collector, SIBX, behaved atypically, achieving lower solids
and recoveries than SEX in water with low ionic strengths. The factor with the largest impact on the flotation
response was the ionic strength of the water. The findings provide plant operators with more control over the
process performance as reagent control may compensate for changes in water quality.
Keywords: collector chain length, flotation performance, water quality
INTRODUCTION
Xanthate collectors contain a non-polar end that consists of
a hydrocarbon chain that can contain one to six carbons. It
is known that an increase in the number of carbon atoms
increases the hydrophobicity of the molecule (Feng et al.,
2012). This affects the characteristics of the collector such
as the strength, stability, and selectivity (Mielczarski et. al,
1998). These factors affect the recoveries and grades achiev-
able by the collector and the dosages required. A study uti-
lised micro-flotation to compare collectors, namely, sodium
ethylxanthate (SEX) to potassium amyl-xanthate (PAX) on
the flotation of multiple sulfide minerals (Goktepe, 2001).
According to Goktepe (2001), the order of the strength was
found to be amyl isobutyl isopropyl ethyl xanthates.
This was explained by an increase in hydrophobicity that
increases the efficiency of air bubble-particle attachment as
there is a larger contact angle (Mielczarski et al., 1998). In
the flotation of pyrite, PAX resulted in the highest recover-
ies due to this increased hydrophobicity at pH levels above
8. At low pH levels, SIBX recovered the most pyrite, oppos-
ing the previously observed pattern. SEX, however, consis-
tently performed poorly at recovering the pyrite at all pH
levels, remaining the weakest collector.
Eh/pH diagrams in a study by Janetski et. al (1977)
explained that this decrease in the floatability of pyrite
was due to the pyrite surface oxidising more readily than
the shorter chained xanthate. Goktepe (2001) found in
the flotation of chalcopyrite, at a pH level of 4, sodium