Adsorbate solubility

Davies (20) used powdered activated carbon in conjunction with ultrafiltration of activated sludge to adsorb soluble organic constituents which might otherwise pass through the membrane until the biomass can metabolize them. The reduction in effluent COD is shown in Figure 42. 

The degree of adsorption increases as adsorbate solubility decreases. 

The modification of the sand surface allows the grains to simultaneously adsorb soluble heavy metals and remove particulate metals by filtration in a column packed with the media. Important factors to the performance of the adsorbent include pH of the solution to be treated, empty bed detention time (EBDT), and the presence of complexing agents, oil, surfactant, and biodegradable substances. 

Cs occurs in crater ejecta and fallout debris as a surface-adsorbed, soluble radionuclide, owing to its gaseous precursor. The behavior of... 

In this chapter, we have so far discussed the adsorption of gases in solids. This section gives a brief description of the adsorption process from liquid solutions. This adsorption process has its own peculiarities compared with gas-solid adsorption, since the fundamental principles and methodology are different in almost all aspects [2,4,5], In the simplest situation, that is, a binary solution, the composition of the adsorbed phase is generally unknown. Additionally, adsorption in the liquid phase is affected by numerous factors, such as pH, type of adsorbent, solubility of adsorbate in the solvent, temperature, as well as adsorptive concentration [2,4,5,84], This is why, independently of the industrial importance of adsorption from liquid phase, it is less studied than adsorption from the gas phase [2],... 

Solubility of the adsorbate Solubility is an important factor affecting adsorption. In general, the extent of adsorption of a solute is inversely proportional to its solubility in the solvent from which adsorption... 

Powdered activated carbon (PAC) is used in water and wastewater treatment facilities to adsorb soluble organic materials and to aid in the clarification process. PAC is fed to a treatment system using chemical feed equipment similar to those used for other chemicals that are purchased in dry form. The spent carbon is removed with the sludge and can then be discarded or regenerated. Regeneration can be accomplished in a furnace or wet air oxidation system. There are seven types of physicochemical PAC process systems (21-24,36,37,45,46,52) ... 

Olsen s extractant has a minor disadvantage it tends to dissolve organic matter resulting in coloured extracts which interferes in colorimetric estimation. Thus activated charcoal is used with the soils to adsorb soluble organic matter. The charcoal must be phosphate free totally. Also carbon dioxide bubbles are formed during colour development which must be completely removed by allowing time or else the COg bubbles interfere with colorimetry. 

UV absorption spectra of wastewater are not easy to understand in view of their featureless shapes, partly due to the effect of suspended matters. The latter are very heterogeneous and responsible for diffuse absorbance more intense in the UV region than in visible. Actually, UV responses of particulate and colloidal matter are often the result of both chemical and physical responses related to their nature (organic for a great part and able to adsorb soluble compounds such as surfactants). For example, in case of slate particles (mineral) of a few micrometers, the spectrum is flat. The absorbance is uniform and higher for smaller particles. The chemical absorbance related to the presence of suspended solids of organic nature seems to emphasise spectrum slope and to create shoulders (Fig. 6). 

A drawback of this approach is that the chiral support can provide the necessary chiral environment only for the neighboring metal atoms (metal-support interface). Note that the chiral environment induced by a chiral support is much more rigid than that created by an adsorbed soluble chiral modifier (see below). The stability... 

The abilily of activated carbon to remove a broad spectrum of orj nic compounds from wastewater is well documented. The Freundlich single-solute isotherm constants, as tabulated in [32], are reproduced in Table 2. These data illustrate clearly the wide range of organic compounds of different structures, sizes, functionality, etc. that can be adsorbed by an activated carbon. It can also be observed that these compounds exhibit different adsorption characteristics. Indeed, the adsorption behavior is affected by various factors related to molecular structure [33], like the adsorbate solubility, the kind of substituent groups of aromatic compounds, the size of tire molecule, its polarity and its hydrophobicity. 

In 1960, Blair (94) published findings obtained on an elastic membrane, whieh when eompressed, developed wrinkles and thiek striations about the point of disturbance for several erude oil/water interfaees. He found that in time the striations disappeared by an annealing process, and the interface then finally assumed a more uniform appearance. After using a surfaee film balanee to measure the spreading forees (from 16 to 31 dyne/em) for several crude oils on water with and without demulsifiers, he eoncluded that stability arises from the formation of a eondensed and viscous interfacial film of adsorbed soluble material from the petroleum phase. Specific demulsifiers have spreading pressures sufficient to displace the petroleum film, leaving a thin film with little resistance to coalescence. 

When two metal nanoparticles covered by a layer of adsorbed soluble polymer chains approach to a distance less the total thickness of adsorption layers, the polymer layers start to interact (Fig. 1). The interaction brings about steric stabilization and leads, in a majority of cases, to repulsion between the colloidal particles. It was repeatedly attempted to clarify its nature and determine its magnitude. Most frequently the problem is studied in terms of changing the Gibbs s energy when two particles are covered by an adsorbed polymer that are approaching one another from irffinity. 

Holt and King discovered in 1955 that when powdered quartz was added to water, the concentration of dissolved silica, SifOH), increased rapidly at first but thereafter very slowly. This was traced to a form of silica that amounted to 16% of a monolayer on the crystal surface and that dissolved rapidly. Furthermore, when this material was removed by treatment with alkali, the cleaned surface then adsorbed soluble silica from solution, to reestablish the layer. Using Si(OH)4 containing radioactive Si, they found that at pH 5 it did not exchange with the surface at pH 9 it exchanged with adsorbed Si(OH)[Pg.34]

It is probably for this reason that lime and magnesia are commonly used for removing silica from water. They flocculate colloidal silica along with other su.s-pended or precipitated matter and combine with and adsorb soluble silica. A suitable granular magnesia adsorbent for silica, made from magnesite, worked best at pH... 

Compo- nents Concentration in clean, dry air (vppm) Concentration in industrial air (vppm) Retention in molecular sieve adsorbers (%) Solubility in LOX at-183°C Lower explosion limit (%volume fraction) [2.40]... 

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