• To participate in the 911Metallurgist Forums, be sure to JOINLOGIN
  • Use Add New Topic to ask a New Question/Discussion about Thickening, Filtering or Tailings and Water.
  • OR Select a Topic that Interests you.
  • Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent).
    Using Add Reply allows you to Attach Images or PDF files and provide a more complete input.
  • Use Add Comment = to comment on someone else’s Reply in an already active Topic/Discussion.

Milk of Lime Dosage (1 reply)

Carmen Ibanz
9 months ago
Carmen Ibanz 9 months ago

I am doing a correlation between the pH and the theoretical Ca(OH)2 requirement in mg per liter of acid drainage to reach to neutral Zone and precipitate Fe and Al.

The expression has the following form: mgCa(OH)2/L acid = k pH ^( -n). Where k is a constant and n is an exponent. This expression is supported by lab tests and titration simulations in PHREEQC.

I need to validate this expression to adjust the automatic feed. Does anyone know a better way to do that?

Bob Mathias
9 months ago
Bob Mathias 9 months ago

Sounds like a pH stat titration may suit your requirements first on a closed system to determine optimum dosing rates then on a flow through system to demonstrate dynamic system control. By undertaking the flow through titration at a range of discharge rates I think you should be able to correlate the volumetric dispensing requirements of Ca(OH)2 with influent flow and initial pH. Obviously in the field if there is a lot of variability in Fe and Al flux you may get some over shoot or under dosing, but if the free Fe and Al concentrations correlate well with pH then I think you would probably achieve reasonable pH control. The H+-Fe-Al system will also be dependent on other major ion water chemistry which would dictate which phases precipitate as pH is increased and could influence the overall buffering capacity (H+ stoichiometry) so maybe validating the choice of phases used in your phreeqc model with some mineralogical characterisation of the precipitate could help. This may be particularly useful if you anticipate there are secondary mineralisation reactions occurring over time (i.e. assessing the geochemical stability of the initially precipitated phase).

Please join and login to participate and leave a comment.