The Zetasizer uses electrophoretic light scattering to find the charge of particles. This charge can mean the difference between dispersed particles and flocculated sediment. That is why Zeta potential in water treatment is important to get cleaner H2O: we want all particulate matter to settle out. In order to achieve this, we aim for eliminating charge on particles. These (almost) neutral particles then stick together and settle to the bottom. The top is clean water.
Why zeta potential?
There are different methods to optimize coagulants used in the water treatment industry. For example, in jar testing, we observe the effect of polymer/coagulant addition overtime on a small scale. Another case is in turbidity tests. Here one can relate the transmitted light to the amount of organic matter. The big advantage of using zeta potential in water treatment plants is
- no calibration
- objective data independent of the operator
- fast, typically less than 1 minute per run.
Because the method is quite easy to use it has become more popular over the years. And it can even be integrated “live” online into a plant control system. So how do you select good settings for the measurement?
Measurement settings for zeta in water treatment
Since the measurement is fast, we typically look at least at three repeated runs. Select the Auto Mode for the analysis settings. It’s a good idea to limit the upper number for zeta sub-runs to 40. But that is not a requirement. You can also just leave it in the default.
Example SOP for the classic Zetasizer Nano
The Zetasizer Nano software can accept a “standard operating procedure” or SOP. This SOP contains all the settings. For water, the monomodal analysis provides the mean zeta, and we use automatic measurement duration. Just unzip the file Water-3xZeta-at-25C-recommended-settings.zip and place the extracted Water-3xZeta-at-25C-recommended-settings.sop into the folder C:\Users\username\Documents\Malvern Instruments\Zetasizer\SOP . For clarification, below is a screen image of these settings in the Nano software:
Example method for the Zetasizer Advance series
Simply unzip Water-3xZeta-at-25C.zip and place the extracted Water-3xZeta-at-25C.zskd method file into the folder C:\Users\username\Documents\Malvern Instruments\ZS XPLORER\Methods. To show this graphically, here is a screen snippet for these settings in the ZS Xplorer software:
In conclusion, for both the classic Nano and the new Advance series we can pre-program the measurement settings. Then all there is to do is to run that method or SOP.
Zeta cell still OK to use? Find out how to detect whether to re-use the capillary cell.
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