It is true that polyacrylamides are very efficient flocculants, but it is only when the particles are not dissolved. Since your pH is very low, if your carbonaceous materials are dissolved flocculation is not a suitable way to separate them.

If the materials are in suspension, then you can try flocculate them. However, there are a wide portfolio of polyacrylamides and you must select one at lab scale by jar test flocculation trials, for example, and optimize the dose.

The efficient one and the rquired dose depends on the surface characteristics of the suspended materials and the molecular weight and charge density of the polyacrylamide.

At such low pH, all the cationic groups of the polymer will be charged, but it is possible that all your carbonaceous material is cationic instead of anionic. Therefore, I would start trying the cheapest polyacrylamides, with low charge, but high molecular weigh to form bridges among particles. If it does not work, you can try branchedpolyacrylamides and higher mollecular weigth polyacrilamides.

You can also consider polyethylene oxide as a flocculant, in case of unsucess of polyacrylamide.

Sincerely yours,

Elena

Thanks Elena for your suggestions. I have tried to flocculate it with polyacrylamide (although don't know the molecular weight of it). It seems to form some floc but after high dilution of acid only.