Hello everybody, so I'm trying to synthesize graphene oxide using solvent free mechanochemical synthesis. So I use KMnO4 as oxidizing agents and graphite flakes but the problem is rinsing, after washing permanganate with H2O, the problem is translating MnO2 to Mn2+. I've been using:
a) HCl (wash it out few times, neutralized it back by washing it out with H2O and then apply ultrasound)
b) after washing it out with water, i acidified it with acedic acid and add little portions of H2O2 (to translate all Mn to MnO2), then HCL and H20 at the end
but nothing works out, does anybody have some good advice or ideas to solve this problem??
Dear Magdalena,
What exactly do you mean by "nothing works out"? That you cannot reduce MnO2 to Mn2+ with HCl, or/and something else?
Magdalena,
If you want to convert MnO2 to its lower valence state, Mn2+, you can try dissolve it in concentrated HCl and slightly heat the solution. The concentrated HCl is able to react with MnO2.
Hi, Martin - im using centrifugation in every step and at the end of washing it out i ultrasonically disperse it to get GO solution. Tianyu Liu, thank you for advise but i'm trying to bypass usage of konc HCl, but i tried with 10% HCL washed it 2 times.
Dear Vladimir, so i suspect that reduction od MnO2 to Mn2+ is the problem. Either that or the problem can be product after ball milling. To explain myself, after getting graphene oxide im doing hydrothermal reduction of GO to rGO but im trying to get hydrogels (when im using bought GO the hydrothermal procedure is easy but with mc-GO it doesnt work out=.
After washing it out, when i ultrasonically disperse it im getting really little concentrations of GO solution im not using settled sample but solution. Whats your procedure? Any of you using mechanochemical ball milling? Maybe the problem is with milling conditions (vibration mill, GO:KMnO4=1:2 or 1:2,5 ;;12mm ZrO2, 4h). Thanks for fast answers :D
Hi Magdalena,
MnO2 is certainly not ideal. It doesn't really get reduced by hydrogen peroxide but catalyses its decomposition instead. Like Tianyu said, you could attempt to reduce the MnO2 with conc. HCl but if this is not possible then perhaps dialysis could be an option if the MnO2 is very small? But this is unlikely.
yeah it is unlikely, so beside konc HCl, is there any other acid that would work out?
The function of HCl is not acidity: it is a reducing agent. To work well, it has to be concentrated. So there are not "too many" options.
What happens if GO:KMnO4=1:1?
I got that but in other articles people used 5-10% HCL. Thank you for that. if it's 1:1 all KMnO4 expend, as well as if the ratio is 1:2 there is really little KMnO4 left.. , its only the start so i have to get the right conditions.
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