Adsorption humic materials

Tomaic, J., and V. Zuti6 (1988), "Humic Material Polydispersity in Adsorption at Hydrous Alumina Seawater Interface", J. Colloid and Interface Sci. 126, 482-492. 

Large pores are desirable but not always possible when high surface area is also demanded. Therefore, a compromise is necessary. This compromise is evident in the choice of XAD-8, with its lower surface area, over XAD-7 when humic acids are accumulated from environmental waters (143, 167, 319-321). The same, but more subtle, considerations apply to XAD-2 and XAD-4. The 780 m2/g for XAD-4 will be available for the adsorption of intermediate weight organic solutes only if the water is relatively free of humic material that can block many of the pores. Therefore, a situation can exist for environmental waters for which the lower surface area XAD-2 is more effective than the XAD-4 polymer. 

Water Samples. Nine monthly MRR samples were collected at 11 sampling points throughout the pilot plant. The sample collector (Concentreur S656, SERES Co., Aix en Provence, France) enabled a composite sample to be collected over several days (8) and is based on adsorption of organics on resins (XAD-2 and XAD-8, Rohm and Haas). Factors that influence adsorption capacity in sampling were considered in the design of a two-bed resin column XAD-8 is more efficient to adsorb humic materials than XAD-2. Thus, an XAD-2 resin bed in series with an XAD-8 resin bed is appropriate to concentrate... 

A residual CP concentration is often observed after soil bioremediation. The leveling-off of degradation is not due to decreased microbial activity, since freshly added CPs are rapidly degraded (Harmsen, 1993 Salkinoja-Salonen et al., 1989). The residual concentrations are explained by the gradual diffusion of pollutants deep into micropores, as well as by their adsorption onto soil organic matter (Harmsen, 1993). Lagas (1988) observed that the nonextractable fraction of CPs in sterile soil increased according to the square root of time as a consequence of diffusion into humic material. 

Humic Materials. Adsorption studies of model compounds have been primarily directed toward single compound classes rather than mixtures, even simple... 

Factors that influence the adsorption of humic materials onto mineral surfaces are listed in Table 3.1. 

Analytical methods used for determining DNOC in environmental samples are given in Table 6-2. Most of the methods for products, waters, soils, and sludges rely on extraction of DNOC from an acidified matrix acidification minimizes dissociation of the phenolic hydrogen and thus facilitates extraction into an organic solvent or adsorption onto a solid phase extraction medium. The influence of pH on the adsorption of DNOC to humic materials in coal waste waters has been studied (Porschmann and Stottmeister 1993) and significant adsorption was found to occur at pH 7 but not... 

This last point is one of the most significant and challenging areas in the development of adsorption technology today, at least with respect to field applications of the technology. In one approach, adsorption data are modeled in term of target organics, treating other compounds such as humic material as an unspecified but... 

The techniques that have been used to determine the approximate molecular weights of humic materials are often those used to study biological macromolecules. Such techniques are often prone to artifacts arising from adsorption, precipitation, and degradation. Many of the methods suffer from one common problem, the lack of appropriate standards. Only colligative properties are free of this problem however, they yield number-averaged molecular weight, with no indication of the polydispersity of the humic material. 

The chemical and biochemical behaviors of humic substances can also be changed by GPC. Frimmel and Sattler (1982) studied the complexation/ adsorption of trace metals by dissolved humic substances and discovered that the affinity of humic substances for metals markedly increased following GPC. Similarly, Stewart and Wetzel (1982) observed that all Sephadex G-lOO fractions of dissolved humic material obtained from the aquatic macrophyte Typha were more stimulatory to C assimilation by algae than were the same humic substances that had not been fractionated. The observations indicated that the gel, eluent, or processing procedure (e.g., lyophilization, reconstitution, cleavage during separation) either reduced the toxicity of the humic substances or enhanced its stimulatory nature or affinity toward trace substances. 

Kunin, R. and Suffet, I. H. (1980). Removal of humic material from drinking water by anion-exchange resins. In Activated Carbon Adsorption of Organics from the Aqueous Phase, Vol. 2 (M. J. McGuire and I. H. Suffet, eds.). Ann Arbor Science, Ann Arbor, MI, pp. 425-442. 

Tomaic, J. and Zutic, V., Humic material polydispersity in adsorption at hydrous alumina/seawater interface, 7. Colloid Interf. Sci.. 126,482, 1988. 

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