Abstract
Mineral scale inhibitors are used in many industries and are ubiquitous in biological systems. Yet, no molecular theory of inhibition exists that can explain field observations and be used to optimize inhibition. A common source of complication in understanding the mechanism of inhibition is potential for precipitation of metal salts of inhibitors, either calcium or iron and possibly other heavy metals. A new molecular theory of scale inhibition is presented that can be used to explain most empirical observations of inhibition of sparingly soluble minerals such as calcite and divalent metal sulfates. It is proposed that the primary driving force for adsorption is related to simple hydrophobic repulsion from solution of a macro neutral molecule and not, as is generally presumed some specific inhibitor-surface interaction. From the nucleation study, it is observed that the inhibitor needed to completely inhibit barite formation is approximately equal to 16% surface coverage. Equation to predict minimum inhibitor need is proposed based upon this model and compared with field observations. The range of predicted inhibitor concentrations is quite similar to what is observed in the field as a minimum effective dose, even though it was arrived at by a completely independent method of calculation.
