Activated charcoal and zeolites are both categorized by having pores equal to or smaller than what size?
Nanoporous materials Nanoporous materials consist of a regular organic or inorganic framework supporting a regular, porous structure. The size of the pores is generally 100 nanometers or smaller. Most nanoporous materials can be classified as bulk materials or membranes. Activated carbon and zeolites are two examples of bulk nanoporous materials, while cell membranes can be thought of as nanoporous membranes.
Refined grains Refined grains, in contrast to whole grains, refers to grain products consisting of grains or grain flours that have been significantly modified from their natural composition. The modification process generally involves the mechanical removal of bran and germ, either through grinding or selective sifting. Further refining includes mixing, bleaching, and brominating; additionally, thiamin, riboflavin, niacin, and iron are often added back in to nutritionally enrich the product. Because the added nutrients represent a fraction of the nutrients removed, refined grains are considered nutritionally inferior to whole grains. However, for some grains the removal of fiber coupled with fine grinding results in a slightly higher availability of grain energy for use by the body. Furthermore, in the special case of maize, the process of nixtamalization (a chemical form of refinement) yields a considerable improvement in the bioavailability of niacin, thereby preventing pellagra in diets consisting largely of maize products.