2
widely produced or desired to be the primary solution to
mitigating acid mist for copper electrowinning.
New alternatives are needed to efficiently suppress acid
mist without employing fluorocarbon based solutions and
has been a focus of study recently in the industry. When
considering any new chemical additive in hydrometal-
lurgical processes, the compatibility with adjacent unit
operations must be considered along with the targeted
performance of the additive. The electrowinning process
shares a common aqueous phase with the solvent extrac-
tion operation and must be considered. Surface active addi-
tives are known to have negative impacts on the solvent
extraction process which presents a unique challenge when
finding a suitable acid mist suppressant. The acid mist sup-
pressant cannot negatively impact the physical or metal-
lurgical performance of the solvent extraction circuit and
should not transfer or accumulate in the organic phase. In
electrowinning, the additive should not negatively impact
copper deposition, cathode quality or cathode stripping
performance.
A suitable chemical alternative should provide the
desired acid mist suppression at economic concentrations
and cost while demonstrating compatibility with both the
electrowinning and solvent extraction operations.
A New Chemical Additive for Acid Mist Suppression
A newly developed chemical additive, ACORGA ® EW98,
has been introduced by Syensqo to mitigate the forma-
tion of acid mist in copper electrowinning operations. The
additive is an aqueous solution which is dosed in-line with
the electrolyte prior to the electrowinning tankhouse. The
additive remains soluble in the aqueous phase and is not
transferred to the organic phase. A series of laboratory and
pilot plant tests have been completed and studied during
project development showing promising results.
RESULTS
A three phase strategy was used to develop and evaluate a
new acid mist suppressant. Phase 1 consisted of a quali-
tative assessment of potential chemistries to suppress acid
mist against the industry standard fluorosurfactants. Phase
2 evaluated solvent extraction compatibility to ensure the
physical and metallurgical performance of the solvent
extraction process was not impacted. Phase 3 evaluated elec-
trowinning compatibility including cathode plate quality
and lab scale qualitative analysis of acid mist suppression.
Phase 1—Candidate Pre-Screen
All candidates were pre-screened for acid mist suppres-
sion effectiveness using an identical bench top apparatus.
A synthetic lean electrolyte was made consisting of 30 g/L
Cu and 180 g/L acid. A flask was filled with 1 liter of lean
electrolyte and dosed with the acid mist additive. A plas-
tic tube with an air sparger was inserted into the flask and
attached to a pump to supply air. Filter paper was placed on
top of the flask to collect acid mist generated by the air sup-
ply. The test was operated for 120 minutes with consistent
air flow, solution volume and electrolyte conditions for all
candidates.
To quantify the acid mist accumulation at the end of
the test, the filter paper was added to 50 mL of DI water in
a beaker and mixed for 5 minutes. The pH was then mea-
sured and compared to the starting pH. Figure 1 shows the
method used for pre-screening of various acid mist suppres-
sant candidates.
All candidates were initially measured at a dosage of
40 ppm to access acid mist suppression with a relatively
high concentration. If insufficient acid mist suppression
was measured at 40 ppm, the candidate was failed and not
considered for phase 2 or 3 evaluations.
Through extensive screening, failures and learnings,
a suitable chemistry was developed, ACORGA ® EW98.
Figure 2 shows the phase 1 pre- screen result of ACORGA
EW98 compared to a standard fluorosurfactant.
To evaluate mist suppression over a range of concentra-
tions, the pre-screening method was repeated at concentra-
tions of 3 -40 ppm. Figure 3 shows the mist suppression
at these concentrations compared to a baseline acid mist
formation without a chemical additive.
Acid mist suppression is seen with low concentrations
of ACORGA EW98. 90% of the acid mist accumulation
was prevented with a concentration of 10 pm and over
95% at concentration of 15 ppm or higher. A target con-
centration of 10 -20 ppm is concluded from the results.
Additional work is ongoing to discuss the stability of the
additive and required make-up dosages, which initially
indicate low degradation and make-up needs.
Figure 1. Schematic of the pre-screening apparatus used to
evaluate additives for acid mist suppression
widely produced or desired to be the primary solution to
mitigating acid mist for copper electrowinning.
New alternatives are needed to efficiently suppress acid
mist without employing fluorocarbon based solutions and
has been a focus of study recently in the industry. When
considering any new chemical additive in hydrometal-
lurgical processes, the compatibility with adjacent unit
operations must be considered along with the targeted
performance of the additive. The electrowinning process
shares a common aqueous phase with the solvent extrac-
tion operation and must be considered. Surface active addi-
tives are known to have negative impacts on the solvent
extraction process which presents a unique challenge when
finding a suitable acid mist suppressant. The acid mist sup-
pressant cannot negatively impact the physical or metal-
lurgical performance of the solvent extraction circuit and
should not transfer or accumulate in the organic phase. In
electrowinning, the additive should not negatively impact
copper deposition, cathode quality or cathode stripping
performance.
A suitable chemical alternative should provide the
desired acid mist suppression at economic concentrations
and cost while demonstrating compatibility with both the
electrowinning and solvent extraction operations.
A New Chemical Additive for Acid Mist Suppression
A newly developed chemical additive, ACORGA ® EW98,
has been introduced by Syensqo to mitigate the forma-
tion of acid mist in copper electrowinning operations. The
additive is an aqueous solution which is dosed in-line with
the electrolyte prior to the electrowinning tankhouse. The
additive remains soluble in the aqueous phase and is not
transferred to the organic phase. A series of laboratory and
pilot plant tests have been completed and studied during
project development showing promising results.
RESULTS
A three phase strategy was used to develop and evaluate a
new acid mist suppressant. Phase 1 consisted of a quali-
tative assessment of potential chemistries to suppress acid
mist against the industry standard fluorosurfactants. Phase
2 evaluated solvent extraction compatibility to ensure the
physical and metallurgical performance of the solvent
extraction process was not impacted. Phase 3 evaluated elec-
trowinning compatibility including cathode plate quality
and lab scale qualitative analysis of acid mist suppression.
Phase 1—Candidate Pre-Screen
All candidates were pre-screened for acid mist suppres-
sion effectiveness using an identical bench top apparatus.
A synthetic lean electrolyte was made consisting of 30 g/L
Cu and 180 g/L acid. A flask was filled with 1 liter of lean
electrolyte and dosed with the acid mist additive. A plas-
tic tube with an air sparger was inserted into the flask and
attached to a pump to supply air. Filter paper was placed on
top of the flask to collect acid mist generated by the air sup-
ply. The test was operated for 120 minutes with consistent
air flow, solution volume and electrolyte conditions for all
candidates.
To quantify the acid mist accumulation at the end of
the test, the filter paper was added to 50 mL of DI water in
a beaker and mixed for 5 minutes. The pH was then mea-
sured and compared to the starting pH. Figure 1 shows the
method used for pre-screening of various acid mist suppres-
sant candidates.
All candidates were initially measured at a dosage of
40 ppm to access acid mist suppression with a relatively
high concentration. If insufficient acid mist suppression
was measured at 40 ppm, the candidate was failed and not
considered for phase 2 or 3 evaluations.
Through extensive screening, failures and learnings,
a suitable chemistry was developed, ACORGA ® EW98.
Figure 2 shows the phase 1 pre- screen result of ACORGA
EW98 compared to a standard fluorosurfactant.
To evaluate mist suppression over a range of concentra-
tions, the pre-screening method was repeated at concentra-
tions of 3 -40 ppm. Figure 3 shows the mist suppression
at these concentrations compared to a baseline acid mist
formation without a chemical additive.
Acid mist suppression is seen with low concentrations
of ACORGA EW98. 90% of the acid mist accumulation
was prevented with a concentration of 10 pm and over
95% at concentration of 15 ppm or higher. A target con-
centration of 10 -20 ppm is concluded from the results.
Additional work is ongoing to discuss the stability of the
additive and required make-up dosages, which initially
indicate low degradation and make-up needs.
Figure 1. Schematic of the pre-screening apparatus used to
evaluate additives for acid mist suppression