Influence of supersaturation level on the morphology of α-lactose monohydrate crystals

Abstract

To crystallise alpha-lactose monohydrate (αLM) crystals with shorter nucleation time, four different experimental processes were adopted: (i) conventional slow evaporation, (ii) fast evaporation, (iii) slow cooling and newly introduced (iv) swift cooling. By adopting these processes, different levels of supersaturation (S) were generated within the system and the effect of this on nucleation control and morphology of αLM crystals was analysed. αLM crystals were nucleated with tomahawk, triangular, pyramidal and needle-like morphologies at S = 0.97–1.62, S = 1.62–2.34, S = 2.34–3.46 and S = 3.46–5.65, respectively. Growth on different crystal faces of αLM was analysed based on the interaction of solute molecules with different protruding molecular structure of the respective crystal planes. Size and morphology of αLM crystals depend on the level of supersaturation generated and the possibility of H–bond formation between the solute molecules in their corresponding solution environment. Among four different processes employed, the swift cooling process produces crystals within a short period of time.