How a TI performs?

Actually Ti function is not scientifically documented. A TI is acting by increasing the oversaturation concentration. That’s all.  In early 1985 I proposed an explanation of this activity based to the observation of the known TIs.

All TI have a strong acidic end (normally Phosphonates) and a less acidic (PBTC) or non-ionic (HEDP) or even cationic (ATMP) part. So they present a bi-ionic function, having negative and positive sites at the same molecule. Those sites are prevented to react between them by stereochemistry.

Having bi-ionic nature at the same molecule, according to my theory, they are offering themselves as the basic crystallite for the crystallization start-up. But they are hybrid, not real crystallization nuclei of CaCO3 or CaSO4 etc, and this crystallite cannot go further.

If the capability of the TI is overpasses, due to the creation of normal basic crystallites, water ignores the false crystallites of the TI and precipitation starts. The presence or the overfeed of the TI cannot avoid that.

My theory even explaining the action of TIs, but it was rejected for two reasons:

• All known TI have this structure. But there are many other substances having this structure without any TI activity.
• I m Greek and Not US or UK or even German. So I have not the right to make serious scientific proposals.

Another explanation for Organo-Phosphonates, which are typical (and most in use) Threshold Inhibitors, has proposed by Professor J.P. Phellan. This mechanism is similar the CD type antiscalents mechanism.

According to J. P. Phellan, the Phosphonates functional group is far more anionic than carbonate and sulfate ions, and has higher affinity to combine with Calcium.

So, as the crystal grows, they participate and are taking key positions into the crystal growth. This position into the crystal structure is creating stresses for further growth, while at the same time are strongly electrostatically repulsing the other scale forming anions and disturbing more Calcium to participate to the crystallization, due to their bi-ionic nature.

This theory can easily explain while Threshold Inhibitors are partially performing to a scaled system and why if overfed are performing as sequestrant. The sequestrant action can explain the gradually cleaning of a scaled system, if the T.I. is overfed.

But cannot give acceptable answers why the system ignores completely its presence, if underfeed or overpassed its capabilities. It should loose partially its control, according to the level of underfeed or the percentage of maximum capabilities overpassed.

As long as the mechanism of scale inhibition through T.I. is not yet explained, we have to take under consideration all relative options, but also take too much care in the application design.

According to proposed mechanism, a TI has to be present in any case, as to lower the amount of the basic crystallites when the system start to precipitates, and to give to CD the time to diffuse at the growing crystallites and to catch them. I don’t know if I m right or wrong, but it works.

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