Lactose Crystal Growth in Centrifugal Field
Abstract: Centrifugation is a normal separation unit in crystallization industry, while this operation may affect the crystals’ size and shape when the solution is still in supersaturated condition. Observation and theoretical analysis on crystal growth under different centrifugation speed (varied from 0 to 25,000 rpm), centrifugation temperature, centrifugation time and degree of supersaturation are presented in this paper. Digital video-microscope and scanning electron micrographs were used to observe the shape changes of these crystals. It is demonstrated that centrifugation leads to a favorable condition of super-saturation and high pressure, thus promoting lactose crystal growth along the centrifugal force direction and induces forming acicular and quadrate crystal other than the normal tomahawk-shaped. Mutarotation of lactose between αandβanomers was also identified. It is also found that the existence of surface active agents such as sodium fatty alcohol ether sulfate (AES) and glycerol, etc, significantly affects the crystal growth in centrifugal field. This research shows that crystallization in centrifuges (i.e. high gravitational acceleration) may be developed as a promising practical method for growing special shape crystals (larger or longer).
Key words: lactose, crystal growth, centrifugal field