How to inhibit Mn2+ autocatalysis in the oxalate-permanganate reaction?

It is well known that permanganate in acidic solution can oxidize oxalate ions (or oxalic acid). The reaction produces $\ce{Mn^2+}$, which catalyzes this very reaction.


$$\ce{2MnO4^- + 16H^+ + 5C2O4^2- -> 2Mn^2+ + 8H2O + 10CO2}$$


As a part of a demonstration on chemical kinetics, I want to inhibit this autocatalysis somehow. (I intend to perform three reactions: one with normal autocatalysis, one with $\ce{Mn^2+}$ added, which will run faster, and one preventing the $\ce{Mn^2+}$ from catalyzing the reaction.)


At first I thought I might use EDTA to complex the manganese ions. Alas, it didn't help. Maybe the environment is too acidic. (The reaction was actually faster with EDTA, I don't know why.)


Perhaps I should try a different chelating agent? Perhaps I could precipitate the $\ce{Mn^2+}$ ions? What do you suggest?




At first the reaction is slow. But when we heat up, the reaction gets catalyzed due to formation of $\ce{Mn^2+}$ ions. It happens due to the fact that $\ce{Mn^2+}$ gets oxidised to $\ce{Mn^3+}$ ions. ([Source](https://www.google.co.in/url?sa=t&source=web&rct=j&url=http://www.chemsheets.co.uk/Chemsheets%2520A2%2520039%2520(Catalysis).pdf&ved=0ahUKEwi1p5KG853RAhVDuo8KHWGyB-cQFgg8MAU&usg=AFQjCNFI9z1hup6xjKZu4W09HVWZMmJqsA&sig2=Fy9DsrDw0IoEK2kja9m62w)).


$$\ce{4Mn^2+ + MnO4- + 8H+ -> 5Mn^3+ + 4H2O}$$


So, we have to inhibit the formation of $\ce{Mn^3+}$ ions so as to inhibit the autocatalysis reaction. For this, we have to use [phosphonate and carboxylate based chelating agent](http://pubs.acs.org/doi/full/10.1021/es7032668?src=recsys) that solubilize (hydr)oxide-bound $\ce{Mn(III)}$ . The following is some relevant information from the site:



> 
> **phosphonate-based chelators that solubilize (hydr)oxide-bound
>  Mn(III) via ligand-promoted and/or reductive dissolution at
>  circum-neutral pHs.**
> 
> 
> pyrophosphoric acid (PP), methylenediphosphonic acid (MDP), and
>  phosphonoacetic acid (PAA), ligand-promoted dissolution is
>  predominant: from pH 6−8, initial dissolution rates and plateau
>  concentrations for dissolved Mn(III) decrease in the order PP > MDP >
>  PAA, and at pH 5, MDP reacts equally well (with birnessite) or more
>  efficiently (with manganite) than PP, and PAA remains the least
>  reactive chelator. For manganite reacting with an excess concentration
>  of aminophosphonate/carboxylate-based chelators, the
>  aminophosphonate-containing iminodimethylenephosphonic acid and
>  glyphosate yield appreciable amounts of dissolved Mn(III), but the
>  aminocarboxylate-based methyliminodiacetic acid yields solely
>  dissolved Mn(II) via Mn(III) reduction.
> 
> 
> 


 1