New methodology based on static light scattering measurements for evaluation of inhibitors for in bulk CaCO3 crystallization

• A new procedure for scale inhibitor evaluation and classification is proposed.
• This method follows changes in particle size distribution by laser diffraction technique.
• The method differentiates between nucleation and growth inhibitor.
• Variation of pH gives additional information on CaCO3 “in bulk” crystallization.

In the present work a new procedure for evaluation of scale inhibitor for calcium carbonate is proposed based on continuous measurement of particle size distribution by laser diffraction technique and simultaneous pH recording. From data obtained during real-time monitoring of the homogeneous nucleation and growth of CaCO3 particles formed in the bulk phase after the addition of carbonate ions to synthetic formation water (AF-W2), it was possible to evaluate the performance of four inhibitors classified in two groups: phosphonates (ethylenediamine tetramethylene phosphonic acid, EDTMP; diethylenetriamine pentamethylene phosphonic acid, DETPMP) and polymeric inhibitors (phosphino poly carboxylic acid, PPCA; polyvinyl sulfonate, PVS). The comparative bulk crystallization inhibition efficiency for the evaluated inhibitors, under the experimental conditions used in this work, increases in the following order: EDTMP < DETPMP < PVS ≅ PPCA. Moreover, this methodology allowed the deduction of the main mechanism of their inhibiting action: nucleation inhibition or crystal growth retardation.

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