Diphosphonic Acid and Orthophosphates

[Miniguy77]

Is it known how long it takes for the phosphate components of diphosphonic acid as used in many scale inhibitors to degrade into orthophosphates?

 

[the_sphynx]

I am able to read those words but have no idea what they are but I think you can summon @JoyfulNoise and this sounds like his language.

 

[JoyfulNoise]

I don’t have a definitive answer but it is a continuous process. The lifetime of a maintenance dose is days which is why you add weekly. Effective doses are 25ppm and higher (depending on hardness levels) but that maintenance dose is only about 12ppm or so. So if I had to guess, you’re probably losing 8-10ppm per week.

 

[Miniguy77]

I don’t have a definitive answer but it is a continuous process. The lifetime of a maintenance dose is days which is why you add weekly. Effective doses are 25ppm and higher (depending on hardness levels) but that maintenance dose is only about 12ppm or so. So if I had to guess, you’re probably losing 8-10ppm per week.

Do orthophosphates have any sequestering capability?

 

[JoyfulNoise]

Do orthophosphates have any sequestering capability?

Not really. If orthophosphate levels are high enough, calcium phosphate will scale out of solution at high pH. But you need very high PO4 and Ca ion concentrations for that to happen.