New guy, please be gentle. I might ask questions not according to conventions, I am not a chemist nor do I study chemistry. Feel free to adapt the question and the tagging.
I am preparing a solution for Fenton's reagents according to [1], mixing 0.750 g $\ce{FeSO4 * 7 H2O}$ (blueish green, cyan almost) to 50 ml deionized (milli-q) $\ce{H2O}$ ([1] uses a slightly higher concentration, but we adapted it according to another publication). This solution needs to be adjusted to $\mathrm{pH}~3$, which, according to [1], can be done with $\ce{H2SO4}$. Now, even if I adjust the solution to well under $\mathrm{pH}~3$, let's say $\mathrm{pH}~1.5$, I still get fallout (presumably a ferrous(III) compound) and a generally turbid solution.
I don't understand what might be falling out and why the solution is turbid in general. What might be happening here? Is the solution somehow reacting with the surrounding air? Could it be further reacting with the water?
2. Fenton’s Reagent
This reagent has two components: $30\%$ (v/v) $\ce{H2O2}$ with an iron catalyst. The catalyst solution was composed of 20 g of iron(II) sulfate heptahydrate in 1 l of filtered RO water. Tagg et al.(34) tested this reagent within the context of extracting microplastics from wastewater. The authors identified this as the optimum concentration. The catalyst solution was adjusted to $\mathrm{pH}~3.0$ using concentrated sulfuric acid.
References
- Hurley, R. R., Lusher, A. L., Olsen, M., & Nizzetto, L. Validation of a method for extracting microplastics from complex, organic-rich, environmental matrices. Environmental science & technology, 2018.