Sodium chlorate is a model material for studying chiral symmetry breaking and deracemization, as it being optically inactive in a solution and forming optically active L-form and D-form crystals via crystallization. According to our previous study, crystal size was identified as one of the determining factors for deracemization of sodium chlorate since the deracemization was always readily for proceeding to enantiomer of large crystal size via the sacrifice of small-size enantiomer crystals, as like a process of Ostwald ripening. Meanwhile, they were not deracemized when crystal size was greater than a certain criterion. As a consequence, the rapid increase of crystal size caused by agglomeration of small crystal significantly influenced on the deracemization. In the present study, the crystal size changes of enantiomeric pure sodium chlorate crystals in turbulent flow were systematically investigated using seed crystal by varying initial crystal sizes, agitation speed and magma density of suspension. Increment rate of crystal size was enhanced as reducing the initial crystal size (seed size). As such, the crystal size increased rapidly and reached 160 µm when using 13 µm of seed at an agitation of 600 rpm. Correspondingly, the crystal population was significantly reduced. From this experimental result, it could be inferred that the agglomeration and dissolution of crystals were involved in changes of crystal size and population. As increasing the seed size above 100 µm, the crystal dissolution little occurred. So, the crystals were hardly agglomerated, resulting in little change of crystals size. The crystal agglomeration also depended on agitation speed of impeller. As increasing agitation speed, the shear force inhibited the crystal agglomeration, resulting in decrease of agglomerates size. Thus, the agglomerates size decreased to 110 µm at agitation speed of 900 rpm when using 13 µm of seed crystals. In addition, when increasing the magma density, the agglomeration was enhanced due to the promotion of crystals collision.

Crystal agglomeration of sodium chlorate in turbulent flow

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