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1.
Riccardo Riffaldi Renato Levi-Minzi Gian Franco Soldatini 《Water, air, and soil pollution》1976,6(1):111-118
Pb adsorption for 12 soils from Tuscany was studied. The data fitted the Langmuir and the Freundlich isotherms over a large range of concentrations. Results showed that organic matter and clay content were responsible for adsorption maxima. The effect of Mn oxides, explained independently of organic matter and clay, was negligible. The adsorption maxima were generally found to be greater than CEC; the possible mechanisms are discussed. 相似文献
2.
The precipitation and adsorption of pentachlorophenol (PCP) on allophane was confirmed by adsorption experiments carried out at various pll values. The precipitation of PCP took place around base-unsaturated clay particles when the concentration of PCP exceeded solubility. The adsorption of PCP involves anion exchange reaction as well as physical adsorption due to van der Waals' force, and the PCP adsorbed as anions is released with greater when washed with deionized water. Allopbane of Andosols appears to adsorb PCP largely as anions, while humus, balloysite, and allophane (molar SiO2/Al2O3 ratio about 2) seem to adsorb PCP mostly as molecules. The precipitation of PCP in mlcell might participate in the adsorption. PCP mixed with layer silicate day minerals such as illite, montmorillonite, and kaolinite sublimated by about 200°C. In contrast to this, PCP mixed or adsorbed on allophane did not sublimate by 200°C but burnt out between 250 and 500°C showing a strong exothermic reaction. 相似文献
3.
In a previous communication we1) reported the adsorption and subsequent release of adsorbed Cu++ by two soils and a compost sample using fairly high concentrations of Cu++ ions in the form of copper sulphate solution. 相似文献
4.
The mineralogies of ‘Tirs’ (Typic Pelloxererts), and ‘Debs’ (Typic Haploxerolls and Typic Xerochrepts) soils of the Gharb plain in north-western Morocco are investigated, with special attention given to the determination of the nature of the smectitic phase using the lithium test (Li test) and the alkylammonium method. The sand and silt mineralogy of Tirs soils is dominated by quartz with small amounts of feldspars and kaolinite. The sand and silt fractions of Dehs soils also contain significant amounts of mica, chlorite, and interstratified phyllosilicates. The clay minerals of Tirs soils are predominantly a high-charge smectite. The estimated interlayer charge for this phase is 0.61 mol(c)/O10(OH)2 and the fraction of tetrahedral charge varies from 38 to 44%. Although the percentage tetrahedral charge is less than 50%, the smectitic phase behaves as beidellite with the Li test. Dehs clays are more heterogeneous, consisting of smectite, vermiculite, illite, kaolinite, chlorite, and interstratified illite/smectite and illite/vermiculite. The Li test and the alkylammonium method demonstrate that a high-charge smectite or vermiculite is interstratified with illite. A low-charge montmorillonite is also present both in Tirs and in Dehs soils. The high-charge beidellitic phase is believed to be a transformation product of mica, whilst the low charge montmorillonite is thought to be inherited from the parent material. 相似文献
5.
A low-swelling smectite exhibiting little intra-crystalline swelling even after saturation with Na was found in paddy soils derived from marine alluvium of Ariake Bay in Kyushu, Japan. The low-swelling smectite was considered to be beidellite-nontronite mineral containing as much as 10% Fe2O3. The low-swelling characteristics of this smectite are ascribed to the considerable substitution of Fe2+ for Al3+ in the ochtahedral layer which depresses the dissociation of unit layers of smectite. Transformation of low-swelling to high-swelling smectite is believed to be due to the oxidation of Fe2+ to Fe3+ in the octahedral layer. 相似文献
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8.
O. K. BORGGAARD 《European Journal of Soil Science》1987,38(2):229-238
Eleven soils from Denmark and Tanzania were extracted with ammonium acetate (controls), EDTA, and dithionite-EDTA (DE) to fractionate iron (and manganese) oxides. The amounts of cobalt adsorbed and acidity desorbed by the extracted soils as well as by two synthetic iron oxides were determined, using 0.85 mM cobalt in 0.2 m NaNO3 .
No significant correlations were found between cobalt adsorption and the contents of extractable manganese or organic matter, presumably because of their low contents. The major part of the cobalt adsorption (by DE-extracted samples) was due to the clay fraction and was associated with the release of approximately one proton per adsorbed Co. The remaining cobalt adsorption was attributed to the iron oxides. This portion of adsorbed cobalt was well described by considering soil iron oxides composed of only two fractions, an EDTA-extractable fraction of high reactivity and a less reactive fraction corresponding to the difference between DE-extractable iron and EDTA-extractable iron. Approximately 1.7 protons were released per Co adsorbed by these iron oxide fractions and by the synthetic iron oxides.
The amounts of cobalt adsorbed by the soil iron oxides were well predicted from the contents and specific surfaces of the two iron oxide fractions together with the specific cobalt adsorption of synthetic iron oxides. 相似文献
No significant correlations were found between cobalt adsorption and the contents of extractable manganese or organic matter, presumably because of their low contents. The major part of the cobalt adsorption (by DE-extracted samples) was due to the clay fraction and was associated with the release of approximately one proton per adsorbed Co. The remaining cobalt adsorption was attributed to the iron oxides. This portion of adsorbed cobalt was well described by considering soil iron oxides composed of only two fractions, an EDTA-extractable fraction of high reactivity and a less reactive fraction corresponding to the difference between DE-extractable iron and EDTA-extractable iron. Approximately 1.7 protons were released per Co adsorbed by these iron oxide fractions and by the synthetic iron oxides.
The amounts of cobalt adsorbed by the soil iron oxides were well predicted from the contents and specific surfaces of the two iron oxide fractions together with the specific cobalt adsorption of synthetic iron oxides. 相似文献
9.
A two-parameter mathematical model based on some physical assumptions was developed for the adsorption of water vapor by soils:
W = W
mh[(p/p
0) − (p/p
0)3 + (p/p
0)6] + W
res. It was shown that one of the model’s parameters is close to a conventional soil-hydrological constant, namely, the maximum
hygroscopic moisture, or maximum hygroscopicity W
mh. The second parameter reflects the residual water content W
res as the content of immobilized water, which is bound to the most active part of the adsorbing surface, is adsorbed at the
initial stage of adsorption (0 ≤ p/p
0 ≤ 0.05), and later does not participate in the adsorption processes. Methods were proposed for the differential calculation
of singular points and parameters of the model corresponding to the characteristic physical phenomena of water vapor adsorption
in soils. The model was tested for the quantitative assessment of the interaction between the soil solid phase and the water
vapor in different soils (a soddy-strongly podzolic soil, an ordinary chernozem, a chestnut soil, and a medium-columnar solonetz).
A method was proposed for calculating the integral adsorption energy E
max of the soil solid phase-water vapor interaction. It was shown that the E
max values are determined by the physicochemical properties of the soils and characterize the capacity of the separate soil horizons
for adsorbing water vapor. The relationship of the integral adsorption energy of the soils with the relative pressure of the
water vapor and the water content was studied. 相似文献
10.
《Communications in Soil Science and Plant Analysis》2012,43(6):493-504
Abstract The influence of reaction time and ionic environments, on phosphate adsorption were studied using one calcareous soil from India, and one calcareous and two latosols from Hawaii. Phosphorus adsorption by soils has a initial rapid phase followed by a slow process. For plant nutrition studies, where emphasis is on P concentration of solutions from which plants derive P, isotherms should be constructed using data obtained after near‐equilibration has been attained. This condition does not obtain in a few hours and may require 6 days or more. Calcium chloride as suspending electrolyte always gave lower phosphate solubility than when KC1 was used as electrolyte. Phosphate retention increased with increasing ionic strength. The necessity for obtaining clear supernatant solutions and the desirability for maintaining reasonable constant equilibrium conditions make 0.01 M CaCl2 a reasonable choice for constructing P sorption isotherms, even though 0.01 M CaCl2 is not representative of Ca concentrations in many soil solutions. Saturation extracts of soils investigated here were in the range 0.0002 to 0.005 M Ca. Adsorption of calcium by highly weathered soils was high suggesting specific adsorption. Calcium adsorption was increased by phosphate additions to a Hydrandept. 相似文献
11.
The adsorption curves for four soils were divided into segments I, II and III. Segment I () and segment II (2–150 μg P/ml equil. concentr.) conformed to the Langmuir equation similar to that of pure materials like gibbsite, pseudoboehmite and kaolinite, whereas segment III conformed to the Freundlich equation and was unlike the previous finding of linear relationship for pure materials. 相似文献
12.
Arsenic has recently received increasing attention due to its high toxicity and to the possible risks for human and environmental health associated with As-polluted soils. The present work deals with the kinetics and reversibility of As sorption by Fe-oxide-coated sand (IOCS) and soils with different chemical and physical characteristics. Soils and IOCS were equilibrated for five different periods of time with solutions containing As (III) and/or (V) in order to study the kinetics of As adsorption. After 1, 10 and 30 days of equilibration soils and IOCS were sequentially extracted to assess the effect of aging on the binding forms of As. The kinetics of arsenite and arsenate adsorption varied among the soils as a result of differential soil characteristics. The conversion of As to less mobile forms was demonstrated using a sequential extraction. The amount of As extracted with weaker extractants decreased with time whereas the amount of As in more recalcitrant fractions increased. This conversion is expected to render As less mobile and toxic with time after addition to the soil. 相似文献
13.
A previous study with a range of soils indicated that adsorption of copper could not be adequately described by the Freundlich equation. Adsorption curves for all but a highly calcareous soil could be divided into two straight lines with a marked increase in slope at low solution concentrations. A computer program (QELIOS) has now been used to calculate the effects of pH, CO, partial pressure and different inorganic anions on the chemical equilibria of the systems used in the adsorption experiments. At pH 6–8.5, hydrolysed species play a major role in Cu speciation whereas CO2?3 species become important only at pH > 8.0. The sensitivity of Cu hydrolysis to pH changes and to total Cu concentration in solution provides a possible explanation for the two surface Freundlich curves for soils of pH 6–7, and for the lack of such double surfaces for soils of pH > 7. 相似文献
14.
Studies on selenium adsorption were conducted on seleniferous and non‐seleniferous soils of north‐west India. Soils were equilibrated with graded levels of Se ranging from 1 to 100 μg ml—1 tagged with 75Se in the presence of sulphate, nitrate and phosphate ions, generally being applied to soils as inorganic fertilizers. The adsorption of Se on different soils, both in the presence and absence of competing anions, increased with increase in the level of Se added. Adsorption of Se conformed to Langmuir equation. In the absence of any competing anions, adsorption maxima of Se for different soils ranged from 270 to 461 μg g—1. The corresponding values decreased appreciably in the presence of competing anions; per cent decrease ranged from 3 to 21 at 10 μg SO4‐S ml—1, from 8 to 40 at 60 μg NO3‐N ml—1 and 32 to 56 at 15 μg H2PO4‐P ml—1. The bonding energy of Se in different soils decreased by 33 to 66 per cent in the presence of only phosphate ions. The changes in bonding energy were inconsistent in the case of nitrate and sulphate ions. At equal concentration of added P and Se, the amount of P adsorbed was 2 to 3 times the amount of Se adsorbed. With increasing concentration of Se, greater amounts of S were released in the equilibrium solution. The distribution coefficients (Kd) decreased significantly in the presence of different anions; the effect was conspicuous in the case of phosphate ions. 相似文献
15.
Extractability and adsorption of sulphate in soils 总被引:8,自引:0,他引:8
Virtually all of the indigenous sulphate (SO4) in a range of UK soils with moderately high pH values (> 6) was found to be present in the soil solution and, as a consequence, was highly susceptible to leaching. For acid soils containing adsorbed SO4, the extractability of SO4 in NaCl and CaCl2 solutions was dependent on both the ionic strength and cation species. Addition of small amounts (<~ 10?2M) of either NaCl or CaCl2 actually decreased the amount of SO4 extracted, but SO4 extractability increased sharply with concentrations of NaCl or CaCl2 higher than about 0.1 M. At a similar ionic strength, more SO4 was extracted by NaCl than CaCl2. Sequential extraction with 1 M NaCl removed essentially all of the absorbed SO4. The release characteristics of SO4 were very different to those of phosphate and this difference in behaviour is not easily reconciled with the view that SO4 is chemisorbed, as is phosphate. Except for a few acid soils with high oxide contents, the capacity of the soils to adsorb added SO4 was quite small. None of the soils with pH values higher than 6 adsorbed a significant amount SO4. The results raise questions regarding the efficiency of SO4-containing fertilizers in correcting and preventing S deficiency in situations where leaching is important. 相似文献
16.
The effect of liming the A and B horizons of a number of acid soils on the subsequent adsorption of phosphate by soils retained moist or allowed to dry was investigated. Air-drying increased the phosphate adsorption capacity but the reason was not clear. When A horizons were maintained moist, incubation with lime for six weeks increased phosphate adsorption by four samples and had no effect on another. When A horizons were air-dried, the effect was considerably reduced or reversed. For B horizons, which had considerably greater phosphate adsorption capacities than A horizons, liming decreased phosphate adsorption irrespective of whether the soils remained moist or were dried. The relative decrease in adsorption was, however, greater when the soils were dried. In a more detailed study using one acid soil it was shown that incubation of the soil with lime for six weeks had no effect on phosphate adsorption by moist A and B horizons but after 36 weeks incubation liming decreased adsorption by the moist samples. If soils were dried then liming decreased phosphate adsorption after six or 36 weeks incubation. Such relative effects of liming on phosphate adsorption were confounded by the fact that air-drying greatly increased the phosphate adsorption capacity of the unlimed soil. The drying effect was at least partially reversible following rewetting of the soil. Results were interpreted in terms of the lime-induced increase in soil pH causing (i) the surface charge conferred on soil oxide surfaces to become more negative (thus decreasing phosphate adsorption) and (ii) the precipitation of exchangeable Al as hydroxy-Al polymers resulting in the formation of new, highly active, adsorbing surfaces (thus increasing phosphate adsorption). Phosphate adsorption by moist limed soils can, therefore, be increased, decreased or unaffected depending on the relative magnitudes of these two processes. It is suggested that after liming, and/or air-drying, crystallization of amorphous materials progressively decreases their surface area and adsorbing capacity. Thus, liming tends to decrease phosphate adsorption when the soils are dried. 相似文献
17.
Aspects of transport processes in aggregated soils 总被引:4,自引:0,他引:4
The way in which water and solutes move in aggregated soils depends on the mode of saturation of the pore space that is made up of the micropore region within the aggregates and the macropores surrounding them. When both regions are saturated, a hydraulic-head gradient causes water to flow preferentially in the macropores with little flow within the aggregates, so that movement of solutes into or out of the aggregates is mainly by diffusion caused by the difference between the solute concentrations of the water in the two regions. When macropores full of water surround unsaturated aggregates, water is imbibed by the aggregates giving rise to convective movement of solutes with the moving water. When the macropores are empty, the aggregates become almost isolated so that redistribution of water and solutes occurs only within the aggregates with very little transport of water and solutes between them. The movement of water and solutes in the micropore region within the aggregates can be considered to behave as if in a continuum, and can be described by Darcy's law and the dispersion equation, with boundary conditions imposed by conditions in the macropores. These physical considerations of transport behaviour in aggregated soils can be used to give guidance on soil management practices concerning drainage and leaching. 相似文献
18.
Phosphorus adsorption by surface samples of five ironpan soils (Kumayili, Kpelesawgu, Nyankpala, Wenchi and Changnalili series) within the Guinea Savannah zone of Ghana were studied. The samples differed in their capacity to adsorb added inorganic P. Per cent adsorbed P decreased as P additions and equilibrium P concentrations increased. P adsorption isotherms obtained were in two parts, and approximately 25 and 40% of the total adsorption was represented by the first lower part of the Langmuir isotherm. Phosphorus adsorbed correlated with percentage organic matter, oxalate-extractable Al and dithionite-HCl-extractable Fe but not with percentage clay, pH and dithionite-citrate-extractable Fe. Fractionation following six days of equilibration showed that added inorganic P was retained mostly as Al-P rather than as Fe-P. It was found that samples of three of the ironpan soils, the Kumayili, ?Kpelesawgu and Nyankpala series, have low P adsorption capacities. 相似文献
19.
硫酸盐对锌和镉在可变电荷土壤上吸附的影响 总被引:8,自引:1,他引:8
SO4^2- and Zn^2 or Cd^2 were added to three variable charge soils in different sequences.In one sequence sulfate was added first ,and in the other,Zn^2 or Cd^2 first.The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added,with the effect more remarkable whn the soil reacted with the sulfate prior to the metal.the shift in pH50 for both Zn and Cd adsorption was aslo comparatively larger in the first sequence of reactions .It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd,and the formaiton of the ternary surface complex-S-SO4-M might also play a role in the effect. 相似文献
20.
Prediction of the adsorption of ionizable pesticides in soils 总被引:1,自引:0,他引:1