Hi all, I came across various sources of articles that discuss the activation of PMS and PDS via the use of transition metals as listed below. While some sources suggest that PMS is better while others suggest that PDS is better. I have a few questions for those that have tried these methods of activation below. I am relatively new to this form of AOP, so do excuse my ignorance.

1) Are reduced metals (ie Fe2+) better than their oxidised counterparts (Fe3+)? some articles do suggest the use of ferric ions as activators

2) what are some of the differences in terms of selectivity for the oxidation pathway of PDS vs PMS. While the review article did discuss some key factors "PMS is more effectively activated to yield SO4•– by transition metals (e.g., Co(II), CuFe2O4, Fe2O3) than PDS due to the unsymmetrical molecular structure' I would like to know if anyone did a direct comparison for such a case and are there documented papers on this?

3) Am I am able to perform this combination PMS+oxdidised form of transition metals or PDS+oxidised form of transition metals? (since there are conflicting literature that suggest that oxidsed form of activation is still possible, where most literature report only the reduced form)

4) Are there any oxidation byproducts that are of particular concern when using PMS/PDS?

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