Natural clay-based particles

For all processes that involve the adsorption step, such as physical processes of separation or catalytic transformations, the usage of solid materials with optimised activity as adsorbents and catalysts is necessary. Various solids, such as porous materials (zeolites—molecular sieves with hierarchical porosities and natural clays), activated carbons, mesoporous silica-based materials, pillared clays and metal oxides, have shown the ability to act as adsorbents or as catalysts for the conversions of previously mentioned atmospheric pollutants. Solid materials are also used for the removal of pollutants that can be found in wastewaters. The possibilities to remove polyaromatic hydrocarbons (PAHs) and heavy metal particles using the adsorptive characteristics of activated carbon and porous materials from wastewaters have been proven [15-17]. The same classes of solids are used for the elimination of organic pollutants form wastewaters by heterogeneous catalytic oxidation processes one of the most important tasks is to eliminate phenolic compounds [13]. 

Other studies use soil or sediment samples for a more accurate indication of microbial activity in natural environments. In these samples, organic matter and clay particles play a role in metal toxicity.76112113 Both organic material and clay particles in soil can bind metals and reduce their bioavailability. For example, Pardue et al.87 demonstrated that much less solution-phase cadmium was required to inhibit trichloroaniline (TCA) dechlorination in a mineral-based soil than in a soil containing a higher concentration of organic matter. Other studies have shown that adding clay minerals to a medium mitigates toxicity. Clay minerals, such as kaolinite, montmorillonite, bentonite, and vermiculite, can bind to metals to decrease the amount that is bioavailable.112 115... 

There are two basic types of nanocomposites, in which particles are intercalated or exfoliated. In an intercalated composite the nanodispersed filler still consists of ordered structures of smaller individual particles, packed into intercalated structures. Exfoliated particles are those dispersed into practically individual units, randomly distributed in the composite. Layered silicates, such as montmorillonite clays or organoclays, can be used in nanocomposites. Because clays are hydrophilic and polyolefines are hydrophobic, it is not easy to make a nanocomposite based on polyethylene or polypropylene because of their natural incompatibility. 

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