Adsorption onto minerals

This paper contributes to the literature by quantifying anionic polymer adsorption onto the clay minerals kaolinite, feldspar, mica and quartz by X-ray photoelectron spectroscopy (XPS). XPS measures the sorbed amount directly rather than by a subtraction technique. This enables an insight into how effective selective flocculation is for obtaining kaolinite from a mineral mixture. Atomic force microscopy (AFM) is also used to image polymer adsorption onto mineral surfaces and the effectiveness of this technique applied to mineral surfaces is discussed here. 

XPS can be used to quantify HPAM adsorption onto minerals at various polymer bulk concentrations. It is seen here that kaolinite has twice the affinity for HPAM than feldspar at pH 9.0 and 50 ppm. Little or no adsorption was monitored on the surface of quartz or mica. Imaging XPS to monitor selective adsorption of mineral mixes proved difficult. Flocculating a mineral mixture of kaolinite, mica and quartz caused the kaolin floes to encapsulate the other minerals. This created a layer of kaolin on the quartz and mica prohibiting polymer mapping on their surfaces. It is shown that the effectiveness of the kaolin recovery is more strongly affected by encapsulation of other minerals during flocculation rather than the selective adsorption process. 

The retardation of subsurface transport of TNT arises from this compound s absorption into NOM and adsorption onto mineral siloxane surfaces covered with weakly hydrated cations like potassium (but not sodium and calcium). While components of feldspars exhibit some siloxane surfaces, here we anticipate that most of the silox-anes occur in the aluminosilicate clay minerals (e.g., illite) because these particles have such high specific surface areas (Table 11.3). Hence, the total for TNT may be found at this site ... 

We observed from the column data that uranium in solution is not very mobile when the solution contacts the sediments used in the experiment. We expected that the oxidized uranium [U(VI)] in the pregnant lixiviant would be reduced and immobilized by solu-tion/sediment interactions, and this is what happened in the experiments after two to three pore volumes were eluted. The actual removal of uranium from solution may occur by adsorption onto mineral surfaces, which produces localized high concentra-... 

The first comprehensive study of fluoride adsorption onto minerals and soils was published in 1967 [57], Since that time, several workers have investigated the adsorption of fluoride on various substrates. These studies include the use of Ando soils of Kenya [58], Illinois soils of USA [59], Alberta soil Luther [60], il-lite-goethite soils in China [2] clay pottery [61,62], fired clay [63], fired clay chips in Ethiopia [12], kaolinite [64], bentonite and kaolinite [65,66] and fly ash [17],... 

Other reactions leading to NH4 removal from soil solution besides microbial nitrogen assimilation, metal-ammine formation, or adsorption onto mineral surfaces, involve NH3 fixation by incorporating it as NH2 in aromatic rings of humic acids (quinone) followed with aromatic ring condensation. 

Although the concept that sedimentary organic matter is strongly associated with mineral surfaces has stood the test of time, the monolayer-equivalent hypothesis has not. It has been deduced from the energetics of gas adsorption onto minerals from continental margin sediments that generally less than 15% of the surfaces of typical sedimentary minerals are coated with organic matter (Mayer, 1999). 

Grimaldi, G.O., M.S. Thesis. Texas University, College Station, TX, 1999, cited after Hur, J. and Schlautman. M. A.. Molecular weight fractionation of humic substances by adsorption onto minerals. J. Colloid Interf. Sci., 264, 313, 2003. 

However, when considering uranium transport at the same site, we need to consider a different set of chemical reactions. Uranium is a trace component in groundwater. The consideration of the interactions between the chemical components, both in the aqueous phases and between the aqueous and solid phases, is different from sulfate, the major component. Uranium transport is most likely controlled by surface adsorption onto mineral surfaces. So the surface adsorption reactions that are safely ignored in the sulfate case are now important. Surface reactions concerning other trace metals, for example, Ni and Cd, are ignored in the sulfate transport case, but now they need to be included because of competitive adsorption. Furthermore, even though our concern is about a trace component, i.e., uranium, we need to know the major components of groundwater to study uranium transport because the iron oxide surface sites may be mostly occupied by sulfate at low / H. 

F. Belaib, A. H. Menial, M. B. Lehocine, Elimination of phenol by adsorption onto mineral/polyanihne composite solid support. Enrgy Proced 2012, 18,1254-1260. 

In soils and clays the most generally present biopolymers that naturally occur in the adsorbed state on mineral and clay particles are humic substances , or humic acids these are decomposition products of lignin, whidi is the major non-cellulosic polymer in wood and other plant debris. Humic acids (also called allomelanins (Merck Index, 1989)) are for the greater part polyphenolic compounds, usueJly anionic polyelectrolytes, which can complex metal ions, and are surface active and thus capable, upon adsorption onto mineral particles, to enhance their suspension stability in aqueous media (Chheda and Grasso, 1994). 

Inorganic reactions in the soil interstitial waters also influence dissolved P concentrations. These reactions include the dissolution or precipitation of P-containing minerals or the adsorption and desorption of P onto and from mineral surfaces. As discussed above, the inorganic reactivity of phosphate is strongly dependent on pH. In alkaline systems, apatite solubility should limit groundwater phosphate whereas in acidic soils, aluminum phosphates should dominate. Adsorption of phosphate onto mineral surfaces, such as iron or aluminum oxyhydroxides and clays, is favored by low solution pH and may influence soil interstitial water concentrations. Phosphorus will be exchanged between organic materials, soil inter-... 

The thermodynamic properties of U-Th series nuclides in solution are important parameters to take into account when explaining the U-Th-Ra mobility in surface environments. They are, however, not the only ones controlling radionuclide fractionations in surface waters and weathering profiles. These fractionations and the resulting radioactive disequilibria are also influenced by the adsorption of radionuclides onto mineral surfaces and their reactions with organic matter, micro-organisms and colloids. 

Adsorption on Inorganic Surfaces. McCarty et al. (55) and Karickhoff (1 ) proposed a two-phase model for sorption onto mineral surfaces and organic matter partitioning. This model hypothesizes that sorption to inorganic surfaces may occur simultaneously with the accepted partitioning into the organic matter. Assuming additivity of these two contributions, Kj can be estimated from... 

The immobilization of dissolved chemical species by adsorption and ion exchange onto mineral surfaces is an important process affecting both natural and environmentally perturbed geochemical systems. However, sorption of even chemically simple alkali elements such as Cs and Sr onto common rocks often does not achieve equilibrium nor is experimentally reversible (l). Penetration or diffusion of sorbed species into the underlying matrix has been proposed as a concurrent non-equilibration process (2). However, matrix or solid state diffusion is most often considered extremely slow at ambient temperature based on extrapolated data from high tem-... 

It has been established that plutonium hydrolysis products exhibit colloidal behaviour (147-151) and may adsorb onto minerals and other surfaces to form radiocolloids. However, it is difficult to determine whether a radiocolloid is a true colloid or a pseudocolloid formed by adsorption of the plutonium species onto other colloidal impurities in the solution (152). In some cases both forms may be present... 

Both the refractory and labile fractions of HMW DOM can be lost from seawater through formation of macrogels that aggregate into marine snow. The labile fraction that is known to participate in marine snow formation are the TEPs, such as mucopolysaccharides found in the mucus sheaths surrounding fecal pellets and plankton colonies. HMW DOM is also lost from seawater via (1) adsorption onto sinking POM and minerals, (2) conversion into POM at the sea surfece by turbulence associated with bursting bubbles, and (3) photochemical degradation. 

Abiotic, for example by adsorption of reactants onto mineral surfaces, distinguished from biotic catalysis by the absence of a temperature optimum. 

Superplasticizers operate by adsorption onto the initial hydrates of C3A, C2S and C3S. In the case of C3A there is evidence that this is more than just a physical effect, and that an organo-mineral compound may be formed. 

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