**8. Conclusion**

Good mining practices have shown bentonite as environmentally not hazardous provided dust abatement mask used. Bentonites demonstrate good performance as sealant and absor-

Environmental concern in the extraction, use, and application of clay can range over the environmental characteristics of clay type and its minerals (=minerals present in clay sample). Montmorillonite particles, depending upon the size range, may come in contact with living species. The health and safety concern related to montmorillonite particles received interest

The nature and distribution of inorganic contaminants, such as metals and metalloids like arsenic, iron, and lead, in clay-bearing rocks, may introduce the environmental concerns. These environmental factors may influence the use of clays in natural and industrial applica-

Information obtained on environmental effects for industrial minerals, including various clay types, sand, gravel, and crushed stone may not be applicable to montmorillonite composition, and studies will be more useful that is clearly based on any montmorillonite structure.

Information on occupational exposure to bentonite dust in mines, processing plants, and user safety is limited [5]. Varying amount of silica is present in bentonite and kaolin clays; however, there are no reported cases of marked diffuse/nodular pulmonary tissue fibrotic reaction to montmorillonite containing no free silica. Bentonite comprising montmorillonite as major fraction, and kaoline have not shown local or systematic adverse effects in cosmetics.

Particle size and the chemical structure of montmorillonite are two obviously different aspects. The increased concerns in the toxicity of airborne fine (0.1–2.5 μm) and ultrafine (<0.1 μm) particles received research interest. Epidemiological studies indicated an increase in morbidity, and mortality was associated with the rise in airborne particles, particularly in ultrafine size range. The decreasing potencies of quartz, kaolinite, and montmorillonite to introduce lung damage were related to their known relative active surface areas and surface chemistry. Therefore, handling of ultrafine particles requires more vigilant control to abate health effects. Natural clay particles are smaller than 0.004 mm in diameter; however, manufactured nanoclay particles are in ultrafine size range and have shown toxic properties [1]. These nanoparticles

However, these were indicated to cause reduced toxicity toward aquatic organisms.

bent and used as barrier for landfill and toxic waste repository.

18 Current Topics in the Utilization of Clay in Industrial and Medical Applications

**Figure 2.** Green chemistry effects in organic synthesis using montmorillonite as catalyst.

for study.

tions [50].

Clay minerals have long been benefiting the human and society. Montmorillonite, an important clay type, has received growing interest in utilization as an additive in polymer and products for enhanced effects. Bentonite is an important source of montmorillonite in nature.

The basic molecular structure comprises silica tetrahedron and aluminum octahedral. The cation Si+4 is fourfold and possesses tetrahedral coordination with oxygen, while the cation Al+3 occurs in sixfold or octahedral coordination. Chemical composition, ionic substitution, layer structure, and particle size of natural clay minerals are important to introduce the functional properties and effects in the application of montmorillonite. Sheet structure was used to classify the clay minerals, and chemical composition was used for nomenclature.

Important applications of montmorillonite include uses additive for food, health, and stamina, for antibacterial activity, improved polymer performance; as sorbent for nonionic, anionic, and cationic dyes; and as green chemistry catalyst in organic synthesis, and so on.
