In my view there is no clear answer on this, but I can give recommendations.

For one, when selecting for added ions (say you just want to add nitrate) you'll need to ensure you are selecting a species that does not interact negatively with your solution (e.g. adsorbing to substrate itself, chemical reactions, etc.). For example, I've had times where I introduced copper in the form of copper sulfate, and found that the adsorption was in the form of a co-precipitate between copper and sulfate (posnjakite, a basic copper sulfate, see my 2022 publication if interested). If you have too much chloride in solution though, this changes precipitation form, with different thermodynamics. I really like Tong Wen et al. 2019, Effect of anions species on copper removal from wastewater by using mechanically activated calcium carbonate.

As a second point, I think the question you more have to ask is what other ions are in solution in the industrial application you are looking at. From this, make synthetic wastewaters with ion concentrations set at levels which would be observed in those industrial effluents (e.g. many mines see acid mine drainage, here, the drainage is a sulfate rich solution so look at what those concentrations are). So I'd start with a review of your objective and tie in norms from industrial wastewaters to assess the effectiveness of your adsorbent, starting from a single metal solution and then adding in other cations/anions depending on what is typically there. Hope that helps!

Why Do Researchers Focus on Coexisting Ions?

The motive is to simulate real-world conditions.

• Natural waters (like groundwater, wastewater, or seawater) always contain a variety of ions.
• These coexisting ions can interfere with or compete with the target adsorbate for the same adsorption sites.
• By studying their effect, researchers can understand: How selective an adsorbent is. How performance might change in practical applications.
• So find the interest of your research idea domain and get your answer
• Best luck

Sandip Kuthe Hello sir!

I would like to ask the adsorbent to eluent ratio for reusability experiments. What is the common ratio used? for example 1:10 (1mg adsorbent : 10 mL MeOH)

And which one is better, shaking incubator or sonication?

I personally prefer sonication because it's more effective and I might just need shorter time using this.

Thank you!

Yes

About sonikation

That is effectively used