The isoelectric point (pI) of ZnO nanoparticles significantly affects the photodegradation of MB (Methylene Blue) dye. Here’s how:

To calculate the isoelectric point of ZnO nanoparticles using the acid-base titration method:

• Disperse ZnO nanoparticles in deionized water to create a suspension.
• Determine the initial pH of the ZnO suspension.
• Slowly add either acid (e.g., HCl) or base (e.g., NaOH) to the suspension while monitoring the pH.
• Measure and record the pH after each addition of acid or base.
• The isoelectric point is reached when the pH remains constant despite additional acid or base being added. This pH value corresponds to the isoelectric point of ZnO nanoparticles

or

The isoelectric point (pI) is identical to the point of zero charge (pzc). The determination of pzc is detailed in this manuscript.

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The isoelectric point of ZnO nanoparticles influences their surface charge and thereby affects their adsorption capacity and photocatalytic activity towards MB dye. Understanding and controlling the isoelectric point is crucial for optimizing ZnO nanoparticle-based systems for efficient photodegradation of MB dye pollutants.

I hope this helps. Regards, Pramod