Key Take-Aways

  • Nanocoatings can influence the properties of sensor reference junctions
  • To achieve the desired effects, applying the nanocoating must consider electrolyte retention
  • Use of nanocoatings to mitigate fouling of sensors shows promise but precise placement is required during the manufacturing process

Details of Paper

  • Title:  Efficacy of Nanocoatings in Reducing pH Sensor Maintenance in Froth Flotation Cells
  • Author:   Mark Fitzpatrick
  • Date:   November 16, 2022
  • Event:   Copper 2022 Santiago Chile
  • Program link:   link

Introduction

In froth flotation, pH sensors need to work in abrasive slurry, fine solids, oily films, and process reagents. That makes the reference junction one of the most important – and most vulnerable – parts of an electrochemical pH sensor.

A mining symposium paper comparing wood, nanocoated wood, and PTFE juntions in a copper flotation circuit produced a useful engineering lesson. The particular nanocoated configuration tested did not show a long-term performance advantage under the conditions studied. At the same time, the results suggest that hydrophobic and oleophobic surface treatments may still have promise if they are integrated with junction structure and electrolyte management in the right way.

That is an important distinction for plant engineers. The real design question is not simply whether a sensor uses a coating. It is whether the full reference junction system stays fast, stable, and recoverable under real process conditions.

What The Study Tested

The paper compared three combination pH sensors that were identical except for the reference junction design: uncoated wood, nanocoated wood, and porous PTFE. The sensors were exposed in a copper flotation conditioning tank and then evaluated using SEM/EDS imaging and standard buffer response testing.

  • SEM/EDS was used to examine how far process constituents penetrated into each junction structure.
  • Response testing compared T90 (response time) and peak response rate before service, after service, and after an extended soak.
  • The objective was to understand whether the tested nanocoating approach could reduce fouling and extend useful service life.

 

 

What Made The Result Interesting

The original expectation was that a hydrophobic and oleophobic nanocoating would help the wood junction resist contamination. Instead, the evidence suggested a more complicated outcome. The coated junction appeared to permit deeper movement of process material into the porous structure and may also have allowed electrolyte to leave the junction more readily.

In other words, a surface treatment that may help resist plugging or surface buildup can still create a long-term tradeoff if it also changes how species move through the junction. For pH measurement, anti-fouling behavior at the surface is only one part of the design challenge.

 

SEM/EDS evidence indicated deeper penetration of process-related material into the nanocoated wood junction. Adapted from the source paper.

 

What The Results Suggest About Junction Design

This study reinforces a practical principle for flotation measurement: good pH sensor performance depends on the whole electrochemical design, not just on the presence of a coating or a single material claim.

  • The nanocoated wood junction showed deeper ingress of mineral elements than expected in this trial.
  • After soaking, the nanocoated junction was the only design that clearly deteriorated relative to its original response performance.
  • The standard wood junction showed the best overall balance of response and recoverability after contamination in this study.
  • PTFE remained a credible option, although the wood junction appeared more recoverable after cleaning or soaking under the tested conditions.

T90 response results from the source paper. The tested nanocoated junction showed the greatest post-soak deterioration in this comparison.

 

Why This Matters For Flotation Operations

For engineers and operators, the takeaway is straightforward. A good flotation pH sensor junction must do more than resist surface fouling. It must balance permeability, protection, electrolyte retention, and recoverability after contamination. In this study, the standard wood junction delivered the strongest overall balance, while PTFE also remained a credible option for harsh slurry service.

Just as importantly, the nanocoating result should not be read as the final word on hydrophobic or oleophobic coatings. It should be read as evidence that coatings must be matched carefully to pore structure, electrolyte strategy, and fabrication method. That is exactly the kind of engineering detail that determines whether a promising idea becomes a durable field solution.

Seen that way, the study supports a broader point: credible pH sensor suppliers in mining should understand not only how to resist fouling, but how to preserve junction chemistry and response characteristics over time. That is where robust sensor design earns its value.

 

QUESTIONS AND ANSWERS

Q: Did the nanocoating improve long-term performance in this study?

A: Not in the tested configuration. The study suggests the coated junction did not show a long-term advantage under the conditions evaluated, likely because improved surface resistance was offset by unwanted transport through the porous structure.

Q: Does this mean hydrophobic or oleophobic coatings have no place in pH sensors?

A: No. The study leaves room for future use of coatings, but suggests they must be engineered carefully alongside junction structure, electrolyte retention, and fabrication method.

Q: What should engineers look for in a flotation pH sensor?

A: A junction design that balances anti-plugging behavior with electrolyte retention, stable response time, and recoverability after contamination. Also, the available volume within the junction to act as a “reservoir” for contaminants can influence maintenance intervals. If the reference junction’s capacity to accumulate contaminants is not exhausted, the sensor should continue to function. As deposits collect on or in the junction, the sensor’s responsiveness will gradually decline.

 

About the Author

  • Mark Fitzpatrick, P.Eng., is President and General Manager of IC Controls, a Canadian manufacturer of industrial pH, ORP, conductivity, and related analytical measurement equipment. He presented “Efficacy of Nanocoatings in Reducing pH Sensor Maintenance in Froth Flotation Cells” at the Copper 2022 technical symposium, drawing on IC Controls’ field and laboratory work with pH sensors in copper flotation service. Mark regularly travels on behalf of IC Controls to mine sites and refining operations, where he works with plant teams to understand demanding process conditions and improve the reliability of online analytical measurements.
  • Mark Fitzpatrick – LinkedIN – link
  • IC Controls – LinkedIN – link
  • IC Controls Management Team – link
  • IC Controls Corporate Profile – link

 

Related Links:

Share This Story, Choose Your Platform!