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1.
Studies of Cd(II)-sulfate interactions at the goethite-water interface by ATR-FTIR spectroscopy 总被引：1，自引：0，他引：1
G.Y. Zhang 《Geochimica et cosmochimica acta》2007,71(9):2158-2169
A combination of macroscopic experiments and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to study Cd(II)-sulfate interactions on the goethite-water interface. The presence of SO4 dramatically promoted Cd adsorption at lower pH (pH 5.5-6.5) and had a smaller effect at higher pH. ATR-FTIR studies indicated sulfate adsorption on goethite occurred via both outer- and inner-sphere complexation. The relative importance of both complexes was a function of pH and sulfate concentration. ATR-FTIR spectra provided direct evidence of the formation of Cd-SO4 ternary surface complexes on goethite. In addition to ternary complexes, Cd specifically sorbed on goethite promoted SO4 adsorption via changing the surface charge, and caused additional SO4 adsorption as both inner- and outer-sphere complexes. The relative importance of ternary complexes versus electrostatic effects depended upon pH values and Cd concentration. Ternary complex formation was promoted by low pH and high Cd levels, whereas electrostatic effects were more pronounced at high pH and low Cd levels. A portion of SO4 initially sorbed in inner-sphere complexes in the absence of Cd was transformed into Cd-SO4 ternary complexes with increased Cd concentration. 相似文献
2.
3.
《Geochimica et cosmochimica acta》1999,63(19-20):3059-3067
In order to test the ability of a surface complexation approach to account for metal-bacteria interactions in near surface fluid-rock systems, we have conducted experiments that measure the extent of adsorption in mixed metal, mixed bacteria systems. This study tests the surface complexation approach by comparing estimated extents of adsorption based on surface complexation modeling to those we observed in the experimental systems. The batch adsorption experiments involved Ca, Cd, Cu, and Pb adsorption onto the surfaces of 2 g positive bacteria: Bacillus subtilis and Bacillus licheniformis. Three types of experiments were performed: 1. Single metal (Ca, Cu, Pb) adsorption onto a mixture of B. licheniformis and B. subtilis; 2. mixed metal (Cd, Cu, and Pb; Ca and Cd) adsorption onto either B. subtilis or B. licheniformis; and 3. mixed or single metal adsorption onto B. subtilis and B. licheniformis. %Independent of the experimental results, and based on the site specific stability constants for Ca, Cd, Cu, and Pb interactions with the carboxyl and phosphate sites on B. licheniformis and B. subtilis determined by Fein et al. (1997), by Daughney et al. (1998) and in this study, we estimate the extent of adsorption that is expected in the above experimental systems.Competitive cation adsorption experiments in both single and double bacteria systems exhibit little adsorption at pH values less than 4. With increasing pH above 4.0, the extent of Ca, Cu, Pb and Cd adsorption also increases due to the increased deprotonation of bacterial surface functional groups. In all cases studied, the estimated adsorption behavior is in excellent agreement with the observations, with only slight differences that were within the uncertainties of the estimation and experimental procedures. Therefore, the results indicate that the use of chemical equilibrium modeling of aqueous metal adsorption onto bacterial surfaces yields accurate predictions of the distribution of metals in complex multicomponent systems. 相似文献
4.
Humic acid adsorption onto the bacterial surface of Bacillus subtilis was measured with and without Cd, as a function of pH and humic–bacteria–Cd ratios. These experiments tested for the existence of ternary interactions in a bacteria–humic–metal system. We determine both the effects of humic acid on the bacterial adsorption of Cd, as well as the effects of the aqueous metal cation on the bacterial adsorption of humic acid. The presence of Cd does not affect the extent of humic acid adsorption onto the bacterial surface, indicating that there is no competition for sorption sites between humic acid and Cd under the experimental conditions, and that changes in the charging properties of the bacterial surface, as a result of the Cd adsorption, are not significant enough to affect humic acid adsorption.
The presence of humic acid does diminish Cd adsorption onto the bacterial surface, suggesting the presence of an aqueous Cd–humate complex under mid to high pH conditions. However, we also observe that the solubility of humic acid is unaffected by the presence of aqueous Cd. This apparently inconsistent behavior of an aqueous Cd–humate complex affecting Cd adsorption but not affecting humic acid solubility is not observed with simpler ionizable organic molecules. We propose that the solubility of humic acid is controlled by the solubility of a less soluble fraction of the acid. Cd forms an aqueous complex with the more soluble fraction of humic acid and there is no interdependence between the aqueous activities of the more and less soluble fractions. That is, the solubility of one humic acid fraction is unaffected by the presence of an aqueous Cd–humate complex involving another humic acid fraction. These experimental results constrain the relative importance of surface ternary and aqueous metal–humate complexes on the bacterial adsorption of both humic acid and metal cations. 相似文献
5.
《Applied Geochemistry》2001,16(5):503-511
The use of adsorption data from single sorbate systems to model metal adsorption in SO4-rich waters, such as acid mine drainage, can lead to inaccurate predictions of metal speciation. The adsorption of Cu and Zn on ferrihydrite, for example, is enhanced at low pH values in the presence of SO4. This effect can only be accurately modeled using the diffuse layer model and surface complexation theory if ternary surface complexes, ≡FeOHCuSO4 or ≡FeOHZnSO4, are taken into consideration. Intrinsic adsorption constants for the formation of these ternary complexes on ferrihydrite have been derived from experimental data. When included in the model, Cu and Zn adsorption in the presence of SO4 is accurately predicted for a wide range of metal, ferrihydrite and SO4 concentrations. Adsorption of Cu and Zn onto the SO4-rich Fe oxyhydroxide, schwertmannite, could also be accurately predicted and is indistinguishable from adsorption onto ferrihydrite in the presence of high solution SO4 concentrations (e.g. 0.01 mol kg−1 SO4). 相似文献
6.
《Applied Geochemistry》2005,20(3):529-536
Freshly precipitated hydrous oxides of Al (flocs) are important sorbents of heavy metal ions and are used in water treatment processes. The addition of chelating agents or polyelectrolytes can increase the efficiency of heavy metal removal by flocs. The polymer polyethylenimine is commonly used as a flocculant aid in water treatment and has been modified with phthalic acid. Adsorption studies have shown that the addition of millimolar concentrations of polyelectrolyte increases the removal of Cd ions from a 29.7 μM aqueous solution by aluminium flocs from ca. 40% to up to 75%. Experiments in which the pH was varied demonstrated that the observed enhancement of Cd adsorption is caused by a shift of the pH edge to lower pH values in the presence of polyelectrolyte. Maximum polyelectrolyte adsorption occurs between pH 6 and pH 7, corresponding to the point of enhanced Cd adsorption in the presence of polyelectrolyte. The enhancement of Cd adsorption observed below pH 7 is therefore likely to be due to the formation of a ternary surface complex. At pH values above pH 8 the polyelectrolyte forms a stable complex with Cd and Al ions in solution causing floc dissolution and decreased Cd adsorption. 相似文献
7.
Sorption of copper and sulfate onto goethite (-FeOOH) in aqueous solution is examined in Cu---SO4 binary-sorbate systems and in Cu-SO4-organic acid (either phthalic acid or chelidamic acid) ternary-sorbate systems. Compared to single-sorbate systems, sorption of Cu onto goethite was enhanced at low pH values in the presence of sulfate. Sorption data for Cu and SO4 in Cu---SO4 binary-sorbate systems were described with the Generalized Two Layer Model by proposing formation of a Cu---SO4 ternary surface complex. Addition of sulfate to a Cu-phthalic acid binary sorbate system had little effect on Cu sorption. However, addition of sulfate to Cu-chelidamic acid binary-sorbate systems resulted in significant reduction of Cu sorption at low pH values, primarily due to competition for surface sites between sulfate and Cu-chelidamic acid ternary surface complexes. While organic acids such as humic substances can potentially influence sorption of metal ions, results from this study suggest that the extent of such influence may be strongly dependent on the presence of other sorbing anions, such as sulfate. Sorption of Cu and SO4 in Cu---SO4-organic acid ternary-sorbate systems was predicted reasonably well, based on surface reactions and equilibrium constants derived from fitting of sorption data from single- and binary-sorbate systems. These modeling results provide a validation of the extrapolation of sorption from simple systems to multicomponent systems through surface complexation modeling. 相似文献
8.
The complexation of Cd(II) and Cd(II)-phthalate at the goethite/water interface were investigated by EXAFS and IR spectroscopy, by batch adsorption experiments and by potentiometric titrations at 298.15 K. The EXAFS spectra showed Cd(II) to form only inner-sphere corner-sharing complexes with the goethite surface sites in the presence and absence of phthalate. EXAFS spectra also showed the presence of Cd(II)-chloride complexes in 0.1 mol/L NaCl. IR spectra also showed phthalate to form (1) an inner-sphere complex with adsorbed corner-sharing Cd(II) surface complexes in the pH 3.5 to 9.5 and (2) an outer-sphere complex with the same type of corner-sharing Cd(II) complex however at pH > 6, in addition to the inner- and outer-sphere complexes of phthalate reported in a previous study. The potentiometric titration and the batch adsorption data were used to constrain the formation constants of the different Cd(II)-phthalate surface complexes on the dominant {110} and the {001} planes of the goethite. The models were carried out with the Charge Distribution Multisite Complexation model coupled to the Three Plane Model and can predict the molecular-scale speciation of cadmium and phthalate in the presence of goethite. Cd(II) adsorption models calibrated on a 90 m2/g goethite also could accurately predict experimental data for a 37 m2/g goethite of slightly different basic charging properties. 相似文献
9.
高岭石对重金属离子的吸附机理及其溶液的pH条件 总被引：14，自引：0，他引：14
高岭石对Cu^2+,Pb^2+离子的吸附实验及高岭石的溶解实验表明,高岭石对重金属离子的吸附有别于石英单一表面配位模式,离子交换和表面配位模式并存,并随溶液pH由酸性往碱性的变化发生规律性的演替：pH<6.5时主要表现为外圈层配位的离子交换吸附,且在pH<4时由于受到高岭石表层中铝的高溶出及溶液中较高离子强度的影响,高岭石对Cu^2+,Pb^2+离子的吸附率较低,pH为5～6时由于高岭石端面的荷电性为近中性,吸附率则有明显的提升并且表现为一个吸附平台;pH>6.5时离子交换和表面配位均为重要吸附机制,pH再升高时沉淀机制则起着重要作用。研究表明,pH调控高岭石-水界面溶解与质子化-去质子化反应过程,并影响着Cu^2+,Pb^2+离子的吸附行为。最后采用Sverjensky(1993)表面配位的物理模型对吸附结果作了描述。 相似文献
10.
Several recent studies have applied surface complexation theory to model metal adsorption behaviour onto mesophilic bacteria. However, no investigations have used this approach to characterise metal adsorption by thermophilic bacteria. In this study, we perform batch adsorption experiments to quantify cadmium adsorption onto the thermophile Anoxybacillus flavithermus. Surface complexation models (incorporating the Donnan electrostatic model) are developed to determine stability constants corresponding to specific adsorption reactions. Adsorption reactions and stoichiometries are constrained using spectroscopic techniques (XANES, EXAFS, and ATR-FTIR). The results indicate that the Cd adsorption behaviour of A. flavithermus is similar to that of other mesophilic bacteria. At high bacteria-to-Cd ratios, Cd adsorption occurs by formation of a 1:1 complex with deprotonated cell wall carboxyl functional groups. At lower bacteria-to-Cd ratios, a second adsorption mechanism occurs at pH > 7, which may correspond to the formation of a Cd-phosphoryl, CdOH-carboxyl, or CdOH-phosphoryl surface complex. X-ray absorption spectroscopic investigations confirm the formation of the 1:1 Cd-carboxyl surface complex, but due to the bacteria-to-Cd ratio used in these experiments, other complexation mechanism(s) could not be unequivocally resolved by the spectroscopic data. 相似文献
11.
James A. Davis 《Geochimica et cosmochimica acta》1984,48(4):679-691
The adsorption behavior and solution speciation of Cu(II) and Cd(II) were studied in model systems containing colloidal alumina particles and dissolved natural organic matter. At equilibrium a significant fraction of the alumina surface was covered by adsorbed organic matter. Cu(II) was partitioned primarily between the surface-bound organic matter and dissolved Cu-organic complexes in the aqueous phase. Complexation of Cu2+ with the functional groups of adsorbed organic matter was stronger than complexation with uncovered alumina surface hydroxyls. It is shown that the complexation of Cu(II) by adsorbed organic matter can be described by an apparent stability constant approximately equal to the value found for solution phase equilibria. In contrast, Cd(II) adsorption was not significantly affected by the presence of organic matter at the surface, due to weak complex formation with the organic ligands. The results demonstrate that general models of trace element partitioning in natural waters must consider the presence of adsorbed organic matter. 相似文献
12.
盐岩矿的水溶法开采是获得人类生活必需品和重要工业原料——盐的重要途径之一。在水溶法开采中,岩盐矿中的水溶性重金属会随着母液到达地表环境和后续的岩盐产品中,可能对地表环境造成污染和危害人体健康,故对岩盐矿中水溶性重金属的检测非常重要。岩盐矿中的水溶性铜铅锌镉含量较低,而盐分含量过高,过高的盐分含量会影响ICP-OES的雾化效率,故很难用ICP-OES直接测量重金属含量。本文以巯基棉为吸附材料,从溶液pH、洗脱液浓度、洗脱液体积等方面研究了分离富集岩盐矿中水溶性铜铅锌镉的实验条件。结果表明,在pH=7的介质中,巯基棉对铜铅锌镉有良好的吸附性能,被吸附的铜铅锌镉可用7 m L盐酸(15%)定量洗脱,溶液中的钠对吸附无明显影响。对解吸后的溶液,铜铅锌镉的回收率均≥92.2%,钠回收率仅0.04%,基本实现了铜铅锌镉与钠的分离,达到了ICP-OES检测要求。 相似文献
13.
The adsorption of five toxic metallic cations, Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II), onto montmorillonite was investigated as a function of pH and ionic strength and a two-site surface complexation model was used to predict the adsorption data. The results showed that in the lower pH range, 3∼6 for Cd, Cu, Ni and Zn, and 3∼4.5 for Pb, the adsorption was greatly affected by ionic strength, while in the higher pH range, the adsorption was not. In the lower pH range, the metallic cations were mainly bound through the formation of outer-sphere surface on the permanently charged basal surface sites (≡X−), while in the higher pH range the adsorption occurred mainly on the variably charged edge sites (≡SOH) through the formation of inner-sphere surface complexes. Acid-base surface constants and metal binding constants for the two sites were optimized using FITEQL. The adsorption affinity of the five metallic cations to the permanently charged sites of montmorillonite was Pb > Cu > Ni ≈ Zn ≈ Cd, while that to the variable charged sites was Pb ? Cu > Zn > Cd > Ni. 相似文献
14.
Apparent overall equilibrium constants for the adsorption of Cd, Cu, Ni, Pb and Zn onto natural iron oxyhydroxides have been calculated from the partitioning of these trace metals in oxic lake sediments and the in situ measurement of trace metal concentrations in the associated pore waters. Such values obtained from lakes of various pH located on the Precambrian Shield, in the area of Sudbury, Ontario, are compared with equilibrium constants obtained for the adsorption of the trace metals onto iron oxyhydroxides in well-defined media.The field data are consistent with laboratory experiments reported in the literature and with theory. Both the influence of pH upon adsorption and the binding strength sequence observed for the field data agree with theory. At high sediment pH values, the partitioning of Cd, Ni and Zn between the pore waters and the natural iron oxyhydroxides is similar to those reported in the literature for the adsorption of these metals at low surface coverage onto amorphous iron oxyhydroxides in a NaNO3 medium; deviation from this simple model is however observed for Cu and Pb, presumably due to the competitive action of dissolved ligands. At low sediment pH values, the adsorption is much higher than predicted by the simple model and can be explained by the formation of ternary complexes with the iron oxyhydroxide surface. 相似文献
15.
The adsorption of Cu, Pb, Zn, and Cd on goethite (αFeOOH) from NaNO3 solutions and from major ion seawater was compared to assess the effect of the major ions of seawater (Na, Mg, Ca, K, Cl, and SO4) on the adsorption behavior of the metals. Magnesium and sulphate are the principal seawater ions which enhance or inhibit adsorption relative to the inert system. Their effect, as determined from the site-binding model of Davis et al. (1978), was a combination of changing the electrostatic conditions at the interface and decreasing the available binding sites.The basic differences between the experimental system of major ion seawater and natural seawater were examined. It was concluded that: 1) although the experimental metal concentrations in major ion seawater were higher than those found in natural seawater, estimates of the binding energy of Cu, Zn, and Cd with αFeOOH for natural seawater concentrations could be made from the data, 2) Cu, Pb, Zn, and Cd showed little or no competition for surface sites on goethite, and 3) the presence of carbonate, phosphate, and silicate had little or no effect on the adsorption of Zn and Cd on goethite. 相似文献
16.
Susana Serrano Peggy A. O’Day Maria Teresa García-González 《Geochimica et cosmochimica acta》2009,73(3):543-558
The bioavailability and fate of heavy metals in the environment are often controlled by sorption reactions on the reactive surfaces of soil minerals. We have developed a non-electrostatic equilibrium model (NEM) with both surface complexation and ion exchange reactions to describe the sorption of Pb and Cd in single- and binary-metal systems over a range of pH and metal concentration. Mineralogical and exchange properties of three different acidic soils were used to constrain surface reactions in the model and to estimate surface densities for sorption sites, rather than treating them as adjustable parameters. Soil heterogeneity was modeled with >FeOH and >SOH functional groups, representing Fe- and Al-oxyhydroxide minerals and phyllosilicate clay mineral edge sites, and two ion exchange sites (X− and Y−), representing clay mineral exchange. An optimization process was carried out using the entire experimental sorption data set to determine the binding constants for Pb and Cd surface complexation and ion exchange reactions.Modeling results showed that the adsorption of Pb and Cd was distributed between ion exchange sites at low pH values and specific adsorption sites at higher pH values, mainly associated with >FeOH sites. Modeling results confirmed the greater tendency of Cd to be retained on exchange sites compared to Pb, which had a higher affinity than Cd for specific adsorption on >FeOH sites. Lead retention on >FeOH occurred at lower pH than for Cd, suggesting that Pb sorbs to surface hydroxyl groups at pH values at which Cd interacts only with exchange sites. The results from the binary system (both Pb and Cd present) showed that Cd retained in >FeOH sites decreased significantly in the presence of Pb, while the occupancy of Pb in these sites did not change in the presence of Cd. As a consequence of this competition, Cd was shifted to ion exchange sites, where it competes with Pb and possibly Ca (from the background electrolyte). Sorption on >SOH functional groups increased with increasing pH but was small compared to >FeOH sites, with little difference between single- and binary-metal systems. Model reactions and conditional sorption constants for Pb and Cd sorption were tested on a fourth soil that was not used for model optimization. The same reactions and constants were used successfully without adjustment by estimating surface site concentrations from soil mineralogy. The model formulation developed in this study is applicable to acidic mineral soils with low organic matter content. Extension of the model to soils of different composition may require selection of surface reactions that account for differences in clay and oxide mineral composition and organic matter content. 相似文献
17.
基于硫酸根自由基的高级氧化技术能有效降解水中磺胺类药物残留。由于在自然环境中共存重金属会对环境修复效果产生一定影响,文中重点研究了不同pH环境条件下不同重金属离子对针铁矿活化过硫酸盐(PS)去除水中磺胺吡啶(SPY)的影响。不同类型重金属离子(Cu^2+、Pb^2+、Cd^2+,0.2mmol/L)在反应体系(初始条件:针铁矿,1.0g/L;PS,4mmol/L;SPY,10mg/L;pH=8.2)中对SPY的降解对比研究发现:在无重金属共存的条件下,针铁矿/PS体系降解SPY的去除率为25.2%;Pb^2+和Cd^2+对针铁矿/PS体系的影响较弱,去除率分别为30.8%和34.8%;Cu^2+的促进作用很大,可以使SPY被完全降解(100%)。机理分析认为,在针铁矿/PS体系中Pb^2+和Cd^2+主要通过影响吸附作用导致磺胺吡啶被去除,而Cu^2+主要通过自身活化PS的作用。不同pH条件(3.0,8.0,12.0)实验证实弱碱性条件下,Cu^2+/针铁矿/PS能够发挥较高的活性从而降解SPY。本文结果为采用针铁矿活化过硫酸盐技术修复类似复合污染地下水环境提供了实验依据。 相似文献
18.
Conditional surface binding constants and complexation capacities for Zn, Pb, Cd, and Cu were determined from surface titration experiments of heterogeneous natural aquatic particulate matter of different origin and composition. Metals and particles were evaluated in naturally occurring concentration ranges in river water.The adsorption of trace metals can be adequately described with a single conditional binding constant over a wide range of metal : particle ratios. Binding constants for aquatic particles at pH 8.0 are remarkably independent from particle composition and are specific for each metal: log Kads
Zn = 8.39, log Kads
Pb = 9.67, log Kads
Cd = 8.61, log ads
Cu = 9.84. From competition experiments with Ca and Pb we extracted a sorption coefficient for Ca of log Kads
Ca = 2.5 (pH 8.0). Maximum surface binding capacities for all metal ions were found for particles containing high fractions of Mn-oxides which are associated with large specific surface areas. Generally, we found sorption capacities to decrease in the sequence Cu Pb, Zn > Cd.The experiments suggest that the conditional surface binding constants and complexation capacities are applicable to model trace metal adsorption in the concentration ranges of natural waters under conditions similar to the experiments. Results also imply that the chemical nature of particle surface sites is rather uniform in the intermediate concentration range or that the array of binding sites averages out differences in sorption strength over the prevailing concentration range of metal ions, respectively. 相似文献
19.
利用XRD和SEM测试方法表征了热活化胶状黄铁矿结构和微观形貌,考察了溶液pH、溶解氧和热活化温度对热活
化胶状黄铁矿去除水中Cd（Ⅱ）的影响,并探讨了除Cd（Ⅱ）反应动力学和作用机理。胶状黄铁矿在N2氛围下650℃热活化
5 min可完全分解生成多孔结构化单斜磁黄铁矿（PMPyr）。在pH 2~6的无氧水溶液中PMPyr除Cd（Ⅱ）效率均达到88%以
上,除Cd（Ⅱ）效率受pH影响较小;PMPyr表面氧化会抑制其与Cd（Ⅱ）的反应。PMPyr除Cd（Ⅱ）动力学可用准二级动力学模型拟合（R2> 0.9992）,结合溶液pH变化趋势、Fe（Ⅱ）和SO42-浓度变化推测,PMPyr除Cd（Ⅱ）机理主要是Fe1-xS和CdS溶度积差异推动了PMPyr与Cd（Ⅱ）交换反应,表面络合属于次要作用。 相似文献
20.
A. Gélabert O.S. Pokrovsky J. Schott A. Feurtet-Mazel 《Geochimica et cosmochimica acta》2007,71(15):3698-3716
This work is devoted to the physico-chemical study of cadmium and lead interaction with diatom-water interfaces for two marine planktonic (Thalassiosira weissflogii, TW; Skeletonema costatum, SC) and two freshwater periphytic species (Achnanthidium minutissimum, AMIN; Navicula minima, NMIN) by combining adsorption measurements with surface complexation modeling. Adsorption kinetics was studied as a function of pH and initial metal concentration in sodium nitrate solution and in culture media. Kinetic data were consistent with a two-step mechanism in which the loss of a water molecule from the inner coordination sphere of the metal is rate limiting. Reversible adsorption experiments, with 3 h of exposure to metal, were performed as a function of pH (2-9), metal concentration in solution (10−9-10−3 M), and ionic strength (10−3-1.0 M). While the shape of pH-dependent adsorption edge is similar among all four diatom species, the constant-pH adsorption isotherm and maximal binding capacities differ. Measurements of electrophoretic mobilities (μ) revealed negative surface potential for AMIN diatom, however, the absolute value of μ decreases with increase of [Pb2+]aq suggesting the metal adsorption on negative surface sites. These observations allowed us to construct a surface complexation model (SCM) for cadmium and lead binding by diatom surfaces that postulates the Constant Capacitance of the electric double layer and considers Cd and Pb complexation with mainly carboxylic and, partially, silanol groups. In the full range of investigated Cd concentration, the SCM is able to describe the concentration of adsorbed metal as a function of [Cd2+]aq without implying the presence of high affinity, low abundance sites, that are typically used to model the metal interactions with natural multi-component organic substances. At the same time, Cd fast initial reaction requires the presence of “highly reactive sites” those concentration represents only 2.5-3% of the total amount of carboxylic sites. For reversible adsorption experiments, the dominating carboxylic groups, whose concentration is allowed to vary within the uncertainty of experimental acid-base titrations, are sufficient to reproduce the metal adsorption isotherms. Results of this study strongly suggest that laboratory experiments performed in a wide range of metal to biomass ratios, represent robust and relatively simple method for assessing the distribution of metals between aqueous solution and planktonic and periphytic biomass in natural settings. 相似文献