[Sly_Mudaly]

Hello guys, I am having a problem precipitating ettringite. I have a saturated CaSO4 solution and add lime to take pH sufficiently high enough. I also add aluminium hydroxide to 1.5 x stoichiometric amount required to reduce SO4 concentrations from about 1800 ppm down to 200 ppm...

Agitation seems to be fine as the impellor blades are pritched and pick the solids of the both of the reactor ... however it is not stirring at too fast a speed that it does not impeed any precipitate from forming.

Is anyone familiar and has precipitated ettringite before so that they may be able to tell me what I am doing wrong because I have no clue what I could be missing in the recipe