[Joskafiser]

Hello guys,

I'm in grade 11, i.e. second-last year of highschool. I am doing my extended essay in chemistry and I am doing it on coagulation/flocculation. What I have discovered in some of my tial runs is that when I added 5ml of 0.2M copper(ii) sulfate solution to a 50ml sample of river water, the coagulation process occured almost instantly. I was not expecting this and was a bit confused at the start.

But I did some extra research and I found out that there is not much literature on transition metal compounds as coagulants/flocculants (except for iron obviously) and I want to change the direction of my research. What I want to do is maybe compare copper/nickel sulfate, etc. in terms of flocculation and how effective they are or maybe even try to deduce some optimum conditions for their function, i.e. pH, stirring intensitiy, dosage, etc.

However, I don't really know/am not sure how to measure the process effectively. I was thinking about changes in mass, like amount of matter removed or changes in absorbance in terms of turbidity, but that's also kinda confusing because transition metal compounds are all coloured.

I would really appreciate you help guys, esepcially if any of you are experienced in this area or have an idea of how I could investigate these things mentioned above.

Thanks!

[Enthalpy]

Welcome, Joskafiser!

To measure the turbidity with light, maybe you could:

• Use several wavelengths and avoid the ones absorbed by the transition metal or correct them by computation?
• Fill the measure cell successively with clear water, clear water +metal, river water, river water +metal, and deduce the effect?
• Or instead of absorption, measure the diffusion of light by the particles?

My impression (poorly substantiated) is that light will give only measures to be calibrated by other means, and that you will need some absolute measure for that anyway, so you might do everything without light altogether. What about sampling after coagulation the water that hasn't settled, pass it through some kind of filter, dry the filter and weigh it before and after?