Heavy metal sorption and desorption capacity of soils containing endogenous contaminants

Soils on serpentinites in some regions of northwestern Spain have been the subject of agricultural management practices involving the use of fertilizers and various types of organic waste containing heavy metals. Although such practices have facilitated crop growth, they have also raised the natural contents in heavy metals of the soils. In this work, three ferralic Cambisols and another three mollic Leptosols with high Cr and Ni contents were used to study competitive sorption and desorption of six heavy metals via K(d100), which was employed as a measure of the ability of the soils to adsorb and retain each metal. Lead was found to be the metal sorbed and retained to the greatest extent, and Cd, Ni and Zn those sorbed and retained in the smallest amounts. Although the ferralic Cambisols were found to contain greater amounts of natural heavy metals, they exhibited an increased ability to adsorb and retain the body of metals relative to the mollic Leptosols by effect of their increased contents in clay and Fe, Mn and Al oxides, in addition to their higher ion-exchange capacity. Based on the results, Pb and Cu are strongly bound, and Zn, Cd and Ni weakly bound, to the soils. The ferralic Cambisols exhibited an increased capacity to adsorb and retain Cd, Ni, Zn and--especially--Cr than the mollic Leptosols; the latter, however, proved more effective in adsorbing and retaining Cu and Pb by virtue of their increased organic matter contents. Copper sorption and retention, and Pb retention, were found to be correlated with the content in organic matter and that in vermiculite--which was only present in the mollic Leptosols--in the clay fraction.     

Influence of Fenton oxidation on soil organic matter and its sorption and desorption of pyrene

The influences of Fenton oxidation on the content and composition of soil organic matter (SOM) and the consequent change of its sorption and desorption of pyrene were investigated using three soil samples. The results showed that both the content and the composition of the SOM changed, with total SOM content decreasing. The content of humic acid (HA) was reduced, while the content of humin did not change significantly, however the content of fulvic acid (FA) had a tendency to increase. Correlation analysis of soil-water distribution coefficient (K(d)) and different parts of the SOM reveals that humin and HA are the key factors controlling the sorption of pyrene. Organic carbon normalized K(d) (K(OC)) varied to different extents after Fenton oxidation due to the change of SOM composition. The reduction of K(OC) is significant in Soils 1 and 2 where large part of HA was reduced to FA, whose sorption ability is low. The change of K(OC) by oxidation in Soil 3 is not so significant due to that the percentage of humin and HA in Soil 3 did not change greatly after oxidation. Desorption was hysteretic in all cases, and humin percentage was found to be the key factor on the extent of desorption hystersis. Oxidation made desorption more hysteretic due to the elevated proportion of humin.     

Competitive sorption and desorption of heavy metals by individual soil components

Knowledge of sorption and desorption of heavy metals by individual soil components should be useful for modelling the behaviour of soils of arbitrary composition when contaminated by heavy metals, and for designing amendments increasing the fixation of heavy metals by soils polluted by these species. In this study the competitive sorption and desorption of Cd, Cr, Cu, Ni, Pb and Zn by humified organic matter, Fe and Mn oxides, kaolinite, vermiculite and mica were investigated. Due to the homogeneity of the sorbents, between-metal competition for binding sites led to their preferences for one or another metal being much more manifest than in the case of whole soils. On the basis of k(d100) values (distribution coefficients calculated in sorption-desorption experiments in which the initial sorption solution contained 100mgL(-1) of each metal), kaolinite and mica preferentially sorbed and retained chromium; vermiculite, copper and zinc; HOM, Fe oxide and Mn oxide, lead (HOM and Mn oxide also sorbed and retained considerable amounts of copper). Mica only retained sorbed chromium, Fe oxide sorbed cadmium and lead, and kaolinite did not retain sorbed copper. The sorbents retaining the greatest proportions of sorbed metals were vermiculite and Mn oxide, but the ratios of k(d100) values for retention and sorption suggest that cations were least reversibly bound by Mn oxide, and most reversibly by vermiculite.     

Effect of desorption and sorption processes occurring in a dry soil layer on the variation of water evaporation

The effect of desorption and sorption processes accompanying temperature changes in a dry layer of natural soil on the transport of vapor in the soil is discussed and the temporal variation of the evaporation of water from the soil is explained.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.21, No. 6, pp. 1025–1032, December, 1971.     

Detection and quantification of aromatic contaminants in water and soil samples by means of laser desorption laser mass spectrometry

The combination of laser desorption of untreated soil samples and subsequent selective laser ionization followed by time-of-flight mass analysis results in an ultrafast technique for the quantitative detection of aromatic contaminants in soil samples. The method allows for high sample throughput, because the complete measurement is finished within about 1 min. Although the different types of soil investigated (sand, humus, clay) showed differences in the desorption efficiency, none of them produced mass spectrometric interferences when an ionization laser wavelength of 266 nm was used. Quantification was carried out by relative measurement with respect to an internal standard and gave satisfactory results over 4 orders of magnitude of analyte concentration. Although the detection of polycyclic aromatic hydrocarbons could successfully be carried out using nanosecond laser pulses, the quality of the mass spectra obtained for labile substances, for example, nitrotoluenes, could be greatly improved by the use of ultrashort pulses in the subpicosecond range. With the preliminary setup, detection limits in the low micrograms-per-gram range were achieved. The identical setup can be used for the analysis of liquids, in particular, water, when the soil sample is replaced by a solid, porous adsorber medium onto which the sample is applied. Activated carbon proved to be a useful adsorber for IR laser desorption, whereas for the UV, granular clay or lime/sand mixtures are preferable.     

Combined effects of DOM extracted from site soil/compost and biosurfactant on the sorption and desorption of PAHs in a soil-water system

The combined effects of DOM and biosurfactant on the sorption/desorption behavior of phenanthrene (PHE) and pyrene (PYR) in soil water systems were systematically investigated. Two origins of DOMs (extracted from soil and extracted from food waste compost) and an anionic biosurfactant (rhamnolipid) were introduced. The presence of DOM in the aqueous phase could decrease the sorption of PAHs, thus influence their mobility. Desorption enhancement for both PHE and PYR in the system with compost DOM was greater than that in the soil DOM system. This is due to the differences in specific molecular structures and functional groups of two DOMs. With the co-existence of biosurfactant and DOM, partitioning is the predominant process and the desorption extent was much higher than the system with DOM or biosurfactant individually. For PHE, the desorption enhancement of combined DOM and biosurfactant was larger than the sum of DOM or biosurfactant; however desorption enhancement for PYR in the combined system was less than the additive enhancement in two individual system under low PAH concentration. This could be explained as the competition sorption among PAHs, DOM and biosurfactant. The results of this study will help to clarify the transport of petroleum pollutants in the remediation of HOCs-contaminated soils.     

Water sorption and desorption isotherms of some naturally occurring zeolites

Water sorption/desorption isotherms of some naturally occurring zeolites (more appropriately, zeolitic tuffs), such as chabazite, clinoptilolite, erionite, mordenite, and phillipsite, as measured by a volumetric method are reported. As expected, all the zeolites showed the Brunauer Type I isotherms with upward deviation at higher pressures, the latter as a result of multilayer sorption and liquid condensation in mesopores. The desorption branch of the isotherms exhibited small hystereses in all the samples. The micropore-filling capacities of the different zeolites were calculated from the Dubinin equation in order to delineate the effects of mesopores, impurities, crystallinity, and particle size. The Dubinin micropore-filling capacities were more or less found to be coincident to the Langmuir monolayer capacity.     

Development of the theory and methods for calculating the dynamics of sorption and desorption

A system of equations of heat and mass transfer, phase transformations, and deformation of porous bodies in sorption and desorption are derived and substantiated. Formulas for the area of contact between a liquid and gas in a unit volume of a porous body, for the intensity of phase transition, heat of phase transformations, equilibrium partial vapor pressure, and for the thickness of adsorbate layer on the surfaces of capillaries with allowance for the influence of adsorption forces are presented. The results of a comparison between calculated and experimental data are given.     

乙醇分子在PPES,PPEK,PPESK膜中动态吸收和解吸实验研究

用重量吸收法测定了298.15,303.15,308.15K下乙醇蒸气在PPEK,PPES,PPESK膜中吸收和解吸动力学数据.结果表明,随着温度的升高,乙醇在膜中的吸收/解吸行为由Non-Fick扩散向Fick扩散转变,乙醇蒸气在三种膜中吸收速度v(PPES)>v(PPESK)>v(PPEK),解吸速度v(PPEK)>v(PPESK)>v(PPES).     

Water sorption/desorption in polyacid-modified composite resins for dentistry

The water sorption and desorption behaviour of three commercial polyacid-modified composite resins used in clinical dentistry have been studied in detail. Cured specimens of each material were subjected to two successive water uptake cycles in an atmosphere of 93% relative humidity, with one intervening desorption cycle in a desiccating atmosphere over concentrated sulfuric acid. Specimens were found to absorb and desorb water according Fick’s law until M_t/M_∞ values of approximately 0.5. Diffusion rates for uptake varied between cycles, ranging from 2.37–4.53 × 10⁻⁹ cm² s⁻¹ for 1st cycle to 0.85–2.72 × 10⁻⁸ cm² s⁻¹ for 2nd cycle. Desorption rates were similar to those for 2nd cycle sorption, and ranged from 0.86 to 5.47 × 10⁻⁸ cm² s⁻¹. Equilibration times for 1st cycle water uptake were greater than for 2nd cycle sorption and for desorption and overall the behaviour of polyacid-modified composites in a high humidity atmosphere was similar to that of conventional composites in water. It is concluded that the hydrophilic components of the former do not bring about an enhanced rate of water transport.     

Helical sorbent for fast sorption and desorption in solid-phase microextraction-gas chromatographic analysis

A new technique for solid-phase microextraction (SPME) of analytes using a helical solid sorbent followed by thermal desorption into a gas chromatographic injector is reported. The main factors that affect the mass transport of analytes in sorption and thermal desorption process using a poly(dimethylsiloxane) (PDMS) helical sorbent are described. The sorption and thermal desorption were achieved in a few seconds, being very close by the theoretical prediction. Both processes were very fast by the reduction of the thickness of boundary layer between sorbent and gaseous sample as a result of a turbulent rotational flow of the headspace air on the surface of sorbent, which is generated by the helical configuration of the sorbent. The thermal desorption was also reduced by improving heat transfer into a thin boundary layer and by increasing the temperature of the heat transporter (carrier gas). The sorption and desorption with PDMS helical sorbent were compared with those of the PDMS silica rod. The extraction time was as much as 15 times faster with the PDMS helical sorbent than with the PDMS silica rod. The desorption with the PDMS helical sorbent was very fast, giving narrow peaks without tailing and a high efficiency of separation in comparison with PDMS silica rod.     

Influence of sequence of chemical reactions on kinetics and solid state behavior for bisphenol A diglycidyl ether – bisphenol A – sulfanilamide ternary blends

The kinetics of reaction of ternary blends based on Bisphenol A diglycidyl ether, Bisphenol A and sulfanilamide curing agent was investigated using FTIR, HPLC, SEC following two different synthesis paths. Four the same initial composition prepolymers differing by the cross-link point distribution and the chain length between cross-links have been synthesized and their solid state behavior has been studied. For the formulation DGEBA:SAA:BA = 4.0:1.25:1.5 mol (catalyst - 0.005 e.e.w. DGEBA), though the schedules have different kinetics, finally the prepolymers with equal conversion of epoxy groups and mass-average molar mass were obtained by both schedules. The dynamic mechanical spectroscopy performed in the glass transition region displays the evolution of the viscoelastic characteristics as a function of cross-link density. For similar formulations networks obtained by schedule 1 have higher values of T _g and σ _y than networks obtained by schedule 2, perhaps due to a higher real cross-link density. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

Corrugated fibreboard in modified atmospheres: Moisture sorption/desorption and shock cushioning

Corrugated fibreboard, the most used material for transport packaging, is moisture sensitive and therefore its performance is highly influenced by the moisture content. This paper examines the shock absorption under a range of humidity and temperature conditions and the appropriateness of a model for moisture sorption/desorption isotherms for corrugated fibreboard. A range of corrugated fibreboard materials was investigated by first conditioning samples using proximity cells, testing samples for impact absorption using a small scale cushion tester and modelling moisture sorption/desorption isotherms. Results show that the shock absorption is directly influenced by static loading, humidity and temperature and that isotherms can easily fit a widely accepted model.     

Effects of carbonate and organic matter on sorption and desorption behavior of polycyclic aromatic hydrocarbons in the sediments from Yangtze River

The role of carbonate and organic matter in the sorption and desorption process of polycyclic aromatic hydrocarbons (PAHs) was studied by using a sequential separation procedure, which sequentially removed carbonate and organic matter from the natural sediment. Five PAHs were used as multi-sorbate and their sorption and desorption characteristics in separated samples were investigated. The Linear, Freundlich and Langmuir models were applied to correlate the experimental data to reveal sorption characteristics of PAHs. The results showed that the sorption mechanism was neither complete adsorption nor partition procedure. The desorption mass of PAHs was very low for all the three sediment samples, especially for higher ring PAHs. It was discovered that carbonate mainly affected sorption and desorption process of lower ring PAHs due to its influence on the physical characteristics of sediment. Organic matter remarkably affected the behavior of higher ring PAHs in the sorption and desorption procedure by determining the dominating partition process.     

Effect of soil organic matter chemistry on sorption of trinitrotoluene and 2,4-dinitrotoluene

The sorption of organic contaminants in soil is mainly attributed to the soil organic matter (SOM) content. However, recent studies have highlighted the fact that it is not the total carbon content of the organic matter, but its chemical structure which have a profound effect on the sorption of organic contaminants. In the present study sorption of two nitroaromatic contaminants viz. trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT) was studied in different SOM fractions viz. a commercial humic acid, commercial lignin and humic acid and humin extracted from a compost. ¹³C-DP/MAS NMR studies indicated that the structural composition of the organic carbon in different SOM fractions was different. The order of sorption of the nitroaromatics in the different sorbents was: humic acid-commercial > humic acid-compost > humin ～ lignin. Among the aliphatic and aromatic carbon fractions (representing bulk of SOM matrix), adsorption parameter K_f(1/n) for nitroaromatics sorption correlated well with the aliphatic carbon (r = 0.791 for TNT and 0.829 for 2,4-DNT) than the aromatic carbon (r = 0.634 for TNT and r = 0.616 for 2,4-DNT). However, among carbon containing functional groups, carbonyl carbon showed strong positive correlation with sorption of TNT (r = 0.991) and 2,4-DNT (r = 0.967) while O-alkyl carbon showed negative correlation (r = 0.832 for TNT and r = 0.828 for 2,4-DNT). The study indicates that aliphatic domains in the SOM significantly affect the non-specific sorption of both the nitroaromatic contaminants.     

Influence of temperature on the sorption properties of rocks from the Nizhnekansky massif

The kinetics of radionuclide sorption onto finely divided samples of rocks from the Nizhnekansky massif, taken from the level of the planned arrangement of deep radioactive waste repository, was studied, and the times in which the sorption equilibrium was attained at 20 and 90°С were determined. The distribution coefficients of actinides (²³³U, ²³⁹Pu, ²⁴¹Am) and fission products (¹³⁷Cs, ⁹⁰Sr) were determined. Increasing the temperature from 20 to 90°С intensifies the sorption of the radionuclides studied, except cesium for which the sorption slightly decreases.     

Temperature-jump investigation of alkyl chain length effects on sorption/desorption kinetics at reversed-phase chromatographic interfaces

The influence of the alkyl chain length on the kinetics of solute retention at reversed-phase chromatographic surfaces is examined. A Joule-discharge temperature-jump relaxation experiment was used to monitor reversible sorption/desorption kinetics at C4- and C8-modified silica/solution interfaces. Biexponential sorption/desorption relaxation kinetics were observed for a charged fluorescent probe, 1-anilino-8-naphthalenesulfonate (ANS), on both C4- and C8-silica surfaces. Both relaxation rates on C4 surfaces were sufficiently slow to be measured and increased linearly with solute concentration. One of the relaxations on a C8 surface is too fast to be resolved from the heating rate, similar to behavior of the solute on a longer chain C18-silica. These observations suggest that sorption kinetics on the intermediate chain length surfaace, C4-silica, are different from kinetics on longer chain length surfaces, C8- and C18-silica. From a fit of the data to a two-step kinetic model, the rates of both adsorption and partition of the ionic probe on the C4 chain are estimated; both rates exhibit significant influence over the equilibrium constant. The relaxation rate of a neutral probe, N-phenyl-1-naphthylamine, is also measured; the results indicate a fast (diffusion-controlled) adsorption step, followed by a detectable barrier to partition that is similar to the partition barrier for ANS on the C4-silica surface. These results show that the alkyl chain length of modified silica strongly influences retention kinetics.