Removal of contaminants in wastewater, such as heavy metals, has become a severe problem in the world. Numerous technologies have been developed to deal with this problem. As an emerging technology, nanotechnology has been gaining increasing interest and many nanomaterials have been developed to remove heavy metals from polluted water, due to their excellent features resulting from the nanometer effect. In this work, novel nanomaterials, including carbon-based nanomaterials, zero-valent metal, metal-oxide based nanomaterials, and nanocomposites, and their applications for the removal of heavy metal ions from wastewater were systematically reviewed. Their efficiency, limitations, and advantages were compared and discussed. Furthermore, the promising perspective of nanomaterials in environmental applications was also discussed and potential directions for future work were suggested.

The pre-nucleation clusters played a key role in the process of crystallization of organic small molecules, indicating that the dynamics of nucleation could be regulated by changing the structure and size of the pre-nucleation clusters.

Effectively manipulating crystal nucleation and growth is an essential issue for controlling the crystal morphology. In this work, the effect of additives on promoting crystal nucleation and growth was investigated from both thermodynamic and kinetic perspectives by using p-methylacetanilide as the model compound. Two additives with amide-terminal and halogen-terminal were selected, and it was found that they can promote the nucleation and crystal growth of p-methylacetanilide. It was found that the existence of 4-bromoacetanilide or 4-chloroacetanilide could decrease the solubility and the interfacial energy of p-methylacetanilide in ethanol, thus leading to an easier nucleation process. Furthermore, by measuring the growth rates of the (1 1 0) and (0 1̅ 1) faces of p-methylacetanilide in the absence and presence of additives, it was found that the raised supersaturation was not the only factor for crystal growth intensification. Molecular simulations revealed that the promotion effect was because the amide-terminal of additives bring the halogen-terminal to the proximity of the p-methylacetanilide surface and disrupt the absorbed ethanol layer, thus eliminating the negative influence of solvent on the surface diffusion of p-methylacetanilide.

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Hydrates are common in pharmaceutical development, and the formation of hydrates affects the performance of the final product. However, the role that water plays in crystal packing remains unclear. In this study, Avibactam sodium, which has one dihydrate (Form E), one monohydrate (Form A), and two anhydrous forms (Form B and D), was chosen as the model compound to understand this subject. Single crystal structures of four solid forms were obtained and characterized by single X-ray diffraction. The dynamic vapor sorption experiments revealed the moisture-dependent stability increased in the order: Form B < Form D < Form A < Form E. It can be envisaged that the integration of water molecules could noticeably compensate the potential intermolecular interactions, thereby significantly improving the crystal stabilities of hydrates. Furthermore, the hydration of Form B was investigated to understand the integration of water molecules by measuring the critical hydration water activities (a w). The results indicated that both water activities and temperature are vital factors to determine the amount of water molecules existing in crystal lattice. Moreover, to probe the disintegration of water molecules, the dehydration of dihydrate was investigated in detail by solid-state transformation and solvent-mediated transformation experiments. Finally, two-step dehydration and one-step dehydration + recrystallization mechanisms of these different pathways were proposed by analyzing the transformation experiment results and the crystal structure of various solid forms.