Effect of anionic surfactants on crystal growth of calcium hydrogen phosphate dihydrate

The effect of anionic surfactants (single-chained sodium n-dodecyl sulfate (SDS), asymmetric double-chained sodium bis(2-ethylhexyl) sulfosuccinate (A OT), and two-headed disodium oleoamido PEG-2 sulfosuccinate) on the crystal lization process of calcium hydrogen phosphate dihydrate (DCPD) was investi gated. All surfactants, depending on the type and actual concentration, sho wed inhibitory effects on the overall crystallization process. Below the cr itical micelle concentration (cmc), electrostatic adsorption, of surfactant anions on lateral crystal faces inhibited crystal growth and changed cryst al morphology. Above the cmc, SDS and AOT caused phase changes; that is, a mixture of DCPD and octacalcium phosphate was formed.