Kaolinite-montmorillonite

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... 

Some of the clays that enter the ocean are transported by river input, but the vast majority of the riverine particles are too large to travel fer and, hence, settle to the seafloor close to their point of entry on the continental margins. The most abundant clay minerals are illite, kaolinite, montmorillonite, and chlorite. Their formation, geographic source distribution and fete in the oceans is the subject of Chapter 14. In general, these minerals tend to undergo little alteration until they are deeply buried in the sediments and subject to metagenesis. 

Photolytic. Mathew and Khan (1996) studied the photolysis of metolachlor in water in the presence of kaolinite, montmorillonite, and goethite and fulvic acid under neutral and acidic conditions at 22 °C. Metolachlor degraded in all the treatments at both pH conditions. The rate of photolysis and degradation products formed was dependent on the duration of UV exposure, the initial pH of the solution, and the composition of the suspended/dissolved material. The following photoproducts identified included 2-hydroxy-A-(2-ethyl-6-methylphenyl)-A-(2-methoxy-l-meth-ylethyl)acetamide, 4-(2-ethyl-6-methylphenyl)-5-methyl-3-morpholine (major product forming at 74-84% yield), 8-ethyl-3-hydroxy-A-(2-methoxy-l-methylethyl)-2-oxo-l,2,3,4-tetrahydroquino-line, 2-chloro-A -(2-(l-hydroxyethyl)-6-methylphenyl)-7V-(2-hydroxy-l-methylethyl)acetamide, and 2-chloro-A -(2-ethyl-6-hydroxymethylphenyl)-A-(2-methoxy-l-methylethyl)acetamide. 

Based on these rate laws, various equations have been developed to describe kinetics of soil chemical processes. As a function of the adsorbent and adsorbate properties, the equations describe mainly first-order, second-order, or zero-order reactions. For example. Sparks and Jardine (1984) studied the kinetics of potassium adsorption on kaolinite, montmorillonite (a smectite mineral), and vermiculite (Fig. 5.3), finding that a single-order reaction describes the data for kaolinite and smectite, while two first-order reactions describe adsorption on vermiculite. 

Lee SY, Jackson ML, Brown JL (1975a) Micaceous occlusions in kaolinite observed by ultrami-cotomy and high resolution electron microscopy. Clays Clay Miner 23 125-129 Lee SY, Jackson ML, Brown JL (1975b) Micaceous vermicuUte, glauconite and mixed-layered kaolinite-montmorillonite by ultramicotomy and high resolution electron microscopy Proc Soil Sci Soc Amer 39 793-800... 

Figure 2. pK for equilibrium between Ca-beidellite and kaolinite plotted as a function of Na content of Sierra Nevada spring waters. Arrow ABC is the path of water evolution calculated for the reaction from Na0 62Ca038 plagioclase to kaolinite in a closed system with an initial dissolved C02 of 0.0006 moles per liter. Arrow ABD is the expected path if evolution is also controlled by the two-phase equilibrium kaolinite-montmorillonite... 

Typical clays include kaolinite, montmorillonite, and illite (Keller, 1985). They are found in most natural soils and in large, relatively pure deposits, from which they are mined for applications ranging from adsorbents to paper making. 

Kaolinite seldom occurs interstratified with 2 1 clay minerals although Sudo and Hayashi (1956) described a randomly interstratified kaolinite-montmorillonite in acid clay deposits in Japan. On the basis of the chemical analysis (Si02 = 41.94, A1203 = 30.12, Fe203 = 2.42, FeO = 0 21, MgO = 1.52, CaO = 0.32, Ti02 = 0.40, H20+ =... 

Schultz, L.G., Shepard, A.O., Blackmon, P.D. and Starkey, H.C., 1969. Mixed-layer kaolinite-montmorillonite from the Yucatan Peninsula. Clay Miner. Soc. Abstr., 18th Conf, p. 33. 

Of special significance with respect to their properties as sorbents are the clay minerals (e.g. kaolinite, montmorillonite, vermiculite, illite, chlorite), mainly due to their high exchange capacity. 

Manning B. A. and Goldberg S. (1996) Modeling arsenate competitive adsorption on kaolinite, montmorillonite and illite. Clays Clay Min. 44, 609-623. 

Adsorption of aniline on minerals, such as kaolinite, montmorillonite and vermiculite as well as on a-alumina and iron powders, has been studied in order to better understand the interaction of the adsorbate with natural adsorbents154-157. However, the results, similarly to those obtained on a smooth polycrystalline platinum electrode158, are not useful for the removal of aniline from waste water. The commonly used activated charcoal is also deficient owing to slow kinetics of the removal of dissolved pollutants. In this situation, activated carbon fibers, woven as a C-cloth, seem to be the ideal adsorbents for removal of aniline from waste streams. The reports of Niu and Conway159,160 explained the adsorptive and electrosorptive behavior of aniline on C-cloth electrodes and suggested a methodology for clean-up of industrial waste waters. 

Available forms Kaolinite, montmorillonite, ata-pulgite, illite, bentonite, halloysite. 

Aggregation of dissolved humic substances can also occur with particulate materials in the estuarine water column. Preston and Riley (1982) showed that the adsorption of riverine humic substances onto kaolinite, montmorillonite, and illite increased with increasing salinity and dissolved humic substance concentration. Adsorption increased in the order kaolinite < illite < montmorillonite, which they ascribed to increasing cation-exchange capacity of the clays. They found considerable quantitative differences between the extent of adsorption of riverine versus extracted sedimentary humic substances, indicating the importance of using materials of proper origin in experiments of this type. 

Calcite-quartz 1467 Illite-kaolinite 1410 Illite-montmorillonite 662 Illite-montmorillonite 1212 Illite-pyrite 1519 Illite-quartz 1450 Kaolinite-montmorillonite 1403 Kaolinite-pyrite 1445 Kaolinite-quartz 1220 Montmorillonite-pyrite 1053 Montmorillonite-quartz 1492 Pyrite-quartz 1571... 

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