I have been using green solvents for reduction of graphene oxide . I have used two different green solvents for reduction but I am unable to filter it. I have changed filter papers from 0.22micrometer to 11 micro meter also, .initially filtration was taking place but then it stopped even after changing the filter paper .kindly suggest me what can be done
Dear Hameem Habib , probably your problem is due to the graphene flat shape. Graphene (or graphene oxide) layers can be packed closely so that they block the flow of solvent through the filter. It happens with 0.22um and 11um pores specially if your graphene flackes are "big". The thing is like when you are washing lettuce in the kitchen sinc, if some pieces are released, they tend to clog the sinc and the water is retained there.
Vacuum filtration can help, but if your flackes are sinking they will clog the filter anyway. Stirring the solution/suspension while filtering can help, because in this way it is avoided the stacking of flackes and so they do not clog the filter. Applying vacuum while stirring the solution would help because the flow will be increased.
If you use vacuum with a Büchner funnel or a glass frit funnel, my advice is that place a filter paper. In Büchner is always necessary, frits don´t need it, but if your flackes are small enough they can anyway clog the pores.
Depending on the solvent type and volume you could also try to evaporate the solvent, in a rotovapor for instance.
Hope it helps.
The problem is most probably because of aggregated nano particles in the dispersion. You can try to first prepare a homogenized dispersion which you can easily produce through ultrasonic probe sonication.
Dear Manuel Gómez I tried doing what you have suggested but still there is no affect
Dear Hameem Habib , you could try centrifugation of your dispersion, the graphene layers will go to the bottom of the centrifuge tube and the solvent will be the supernatant. Gently dispose the solvent and then with the help of a spatula remove the solid (still wet) and filter it under vacuum or /and dry it on a disicator under vacuum. In this way you minimize the volume of solvent to filter and reducing the filtration problems.
Another option could be to lyophilize your sample (freezing your dispersion and then under vacuum sublimate the solvent... usually water... (be careful, other solvents could damage the machine or the rubber joints, so read the machine
specifications or ask to a experienced user for advice).
Hope it helps.
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