Effect of sorption

Ogram AV, RE Jessup, LT On, PSC Rao (1985) Effects of sorption on biological degradation rates of (2,4-dichlorophenoxy)acetic acid in soils. Appl Environ Microbiol 49 582-587. 

Subba-Rao RV, M Alexander (1982) Effect of sorption on mineralization of low concentrations of aromatic compounds in lake water samples. Appl Environ Microbiol 44 659-668. 

O Reilly et al. (2001) studied the effect of sorption residence time on arsenate desorption by phosphate (phosphate/arsenate molar ratio of 3) from goethite at different pH values. Initially, desorption was very fast (35% arsenate desorbed at pH 6.0 within 24 hrs) and then slowed down. Total desorption increased with time reaching about 65% total desorption after 5 months. These authors found no measurable effect of aging on desorption of arsenate in the presence of phosphate. Furthermore, desorption results at pH 4.0 were similar to the desorption behaviour at pH 6.0. On the contrary, Arai and Sparks (2002) demonstrated that the longer the residence time (3 days-1 year), the greater was the decrease in arsenate desorption by phosphate from a bayerite. 

Scow KM, Johnson CR (1997) Effect of sorption on biodegradation of soil pollutants. Adv Agron 58 1-56... 

Column studies employ the same general techniques as flask studies, except glass tubes are packed with aquifer matrix, and groundwater, with or without amendments, is percolated through the column. Sterile and nutrient-amended columns are used as controls. Leachate is tested to determine the rate and type of chemical change that occurs in the column. While column studies do not accurately reflect the actual subsurface environment, they do provide an indication of the likely effects of sorption and precipitation within the aquifer. 

The isotopic effects of sorption remain relatively unknown, with disparate interpretations of its significance during DIR. An important avenue of future research will be to quantify the rates of isotopic exchange between sorbed Fe(II) and Fe(II)3q, and to investigate a range of ferric oxide/hydroxide substrates. Because traditional sorption experiments generally... 

Regardless of the transport equation considered, the major effect of sorption on contaminant breakthrough curves is to delay the entire curve on the time axis, relative to a passive (nonsorbing) contaminant. Because of the longer residence time in the porous medium, advective-diffusive-dispersive interactions also are affected, so that longer (non-Fickian) tailing in the breakthrough curves is often observed. 

The hydrolysis of pesticides which are sorbed to sterilized natural sediments has been investigated in aqueous systems at acid, neutral and alkaline pH s. The results show that the rate constants of pH independent ("neutral") hydrolyses are the same within experimental uncertainties as the corresponding rate constants for dissolved aqueous phase pesticides. Base-catalyzed rates, on the other hand, are substantially retarded by sorption and acid-catalyzed rates are substantially enhanced. A large body of evidence will be presented which substantiates these conclusions for a variety of pesticide types sorbed to several well-characterized sediments. The significance of our results for the evaluation of the effects of sorption on the degradation of pesticides in waste treatment systems and natural water bodies will also be discussed. 

Esters of 2,4-D. Studies of the alkaline hydrolysis of the methyl and n-octyl esters of 2,4-D in sediment/water systems (24), though less detailed than the chlorpyrifos studies, show similar effects. Results from Investigations using EPA-13 at pH s near 10 for the methyl and octyl esters of 2,4-D are summarized in Figure 7. Under the conditons in these experiments, the fractions of the methyl and octyl esters which are sorbed to the sediment are 0.10 and 0.87, respectively. The aqueous hydrolysis half-lives of the methyl and octyl esters at pH=10 are 3.6 and 27 minutes, respectively. In the sediment/water system, the methyl ester, which is mainly in the dissolved phase, hydrolyzes at a rate similar to that expected for the sediment-free system at the same pH. The octyl ester, on the other hand, hydrolyses at a rate which is considerably retarded (and non-first-order) when compared to the expected aqueous phase rate. Though the data are less detailed and do not permit calculations similar to those conducted for chlorpyrifos, it is clear that the effect of sorption is to considerably slow the alkaline hydrolysis rate. 

Inadequate understanding of the kinetics of the sorption/desorption process detracts from our ability to completely understand the effects of sorption on hydrolytic rates, and more research is needed in this regard. 

Porous media have much larger solid-to-solution phase ratios (rsw) than surface waters (lakes and rivers). Therefore, even the transport of a chemical with moderate to small solid-water distribution ratios (/Q may be influenced by sorption processes. The basic mathematical tools which are needed to quantify the effect of sorption on transport are described in Section 18.4 and summarized in Box 18.5. 

Explain the effect of sorption on the transport of a chemical in an aquifer. 

Ainsworth, C. C., Frederickson, J. K. Smith, S. C. (1993). Effect of sorption on the degradation of aromatic acids and bases. In Sorption and Degradation of Pesticides and Organic Chemicals in Soil, ed. D. M. Linn, T. H. Carski, M. L. Brusseau F-H. Chang, pp. 125-44. Madison, WI Soil Science Society of America, American Society of Agronomy. 

In most wastes and wastewater, polychlorinated biphenyls (PCBs) and particulate matter are found in the aqueous phase. The fraction of PCBs associated with each phase depends on the hydrophobicity. The congeners containing more chlorine substituents have a stronger tendency to associate with particulate. PCBs sorbed to surfaces such as diatomaceous earth are not oxidized by aqueous OH at an appreciable rate relative to the reaction rate of OH with solution-phase PCBs. Sedlak and Andren (1994) performed a quantitative evaluation of the effect of sorption to particulate matter on the rate of PCB oxidation by OH. The transformations of three PCB congeners — 2-monochlorobiphenyl (MClBp) 2,2, 5-trichlorobiphe-nyl (TrCIBp) and 2,2, 4,5,5 -pentachlorobiphenyl (PeCIBp) — were studied at an initial concentration of 1 pM of PCB solution. Data from the experiments were compared with predictions from quantitative kinetic models that used independently determined data on reaction rates and OH concentrations. 

Aksoy, A., and Culver, T. B. (2000). "Effect of sorption assumptions on the optimization of aquifer remediation designs." Ground Water, 38(2), 200-208. 

Butler, E. C Hayes, K. F. Micellar Solubilization of Non-Aqueous Phase Liquid Contaminants by Nonionic Surfactant Mixtures Effects of Sorption, Partitioning and Mixing, Water Research, 1998, 32, 1345-1354. 

TABLE II Combined Effects of Sorption on Biofilms and Microbial use on DOC Concentrations, Shown as Retention of DOC (Sorbate) in Perfused Cores (Sorbent)... 

One can attempt to overlay the effects of sorption on this scenario. It is apparent that strong sorption of radionuclides will tend to depress the equilibrium concentration of the element in... 

Results for C4 products (Table 6) indicate that, whilst the totel C4 yield is slightly higher with ZSM-5 (due to the greater conversion compared to KEHY), the ratio of paraffins to olefins is significantly lower, and is particularly so with the iso compounds. This reflects the greater facility for hydrogen transfer in KEHY, as opposed to ZSM-5, vdiich can be explained in terms of the influence of site proximity [12], or the effects of sorption preference [13] both of which favour hydrogen transfer in more alumina-rich zeolites. 

Sedlak DL, Andren AW. The effect of sorption on the oxidation of polychlorinated-biphenyls (PCBs) by hydroxyl radical. Water Res 1994 28 1207-1215. 

In this chapter, the relationship of geological origins and interfacial properties of bentonite clay will be reviewed first. Then we will discuss the migration of water-soluble substances in rocks and soil, and the effect of sorption on the migration. A linear model will be derived by which the quantity of ion sorbed on rocks can be estimated when the mineral composition and sorption parameters of the mineral components are known. Surface acid-base properties of soils will be discussed, and the sorption of an anion (cyanide ion) will be shown on different soils and sediments. 

Migration of water-soluble substances is a common process occurring in rocks and soils (Chapter 1, Section 1.3.6.2). This process is the net result of different hydrological and sorption processes. Hydrological processes (Chapter 1, Equation 1.127), that is, the movement of water, are governed by the water levels. Sorption processes can decrease the rate of water movement via interfacial processes (Chapter 1, Equations 1.128-1.131). In this chapter, the effect of sorption will be shown on the migration rate of water-soluble substances. 

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