Single Sorption Research Articles

Degree of phosphorus saturation threshold for minimizing P losses by runoff in cropland soils of Southern Brazil

Abstract The objective of this work was to assess the risk of phosphorus losses by runoff through an index based on the degree of P saturation (DPS), in cropland soils of Southern Brazil. Sixty-five highly representative cropland soils from the region were evaluated. Three labile P forms were measured (Mehlich-1, Mehlich-3, and ammonium oxalate), and four P sorption indexes were tested (phosphorus single sorption point and Fe+Al determined with the three extractors). Water-extractable P (WEP) was used as an index of P susceptibility to losses by surface runoff. The DPS was determined from the ratio between labile P and each sorption index. DPS values obtained from the ratio between Mehlich-1 P and the single P sorption point ranged from 1 to 25%, whereas those from Mehlich-1 P and Fe+Al (ammonium oxalate) ranged from 1 to 55%. All DPS types were highly correlated with WEP. From a practical stand point, the DPS obtained with both P and Fe+Al extracted with Mehlich-1 can be used to estimate the risk of P losses by runoff in soils of Southern Brazil.

Characterizing the kinetics of free and bound water using a non-isothermal sorption technique

ABSTRACTThis article presents novel techniques for characterizing the kinetics of the free and bound water in a specimen by performing only one single sorption experiment. By monitoring the time variation of the residual water in a specimen that undergoes a controlled non-isothermal sorption over the range of temperatures of interest, the initial mass of the free and bound water in the specimen, the Arrhenius constants of diffusivity of the free water, and the Arrhenius constants of the rate of dissolution of the bound water can be extracted through a combination of time–temperature transformation and regression.

Modeling influence of hysteretic moisture behavior on distribution of chlorides in concrete

Aggressive environmental conditions, such as exposure to the sea climate or use of de-icing salts, can have a considerable influence on the durability of reinforced concrete structures due to corrosion-induced damage of reinforcement. Recently, the coupled 3D chemo-hygro-thermo-mechanical (CHTM) model for simulation of processes related to the chloride induced corrosion of steel reinforcement in concrete was developed. In the model, it is assumed that for wetting and drying of concrete, the transport of water is controlled by a single sorption curve. However, it is well known that concrete exhibits a hysteretic moisture behaviour, which significantly influences the distribution of moisture and chlorides. To account for the hysteretic moisture behaviour of concrete and for simulating a more realistic time and space distribution of moisture, the CHTM model was further improved. The proposed hysteretic model is implemented into a 3D finite element code and it is validated using a numerical example, which shows reasonably good agreement with the available test results. Similar to what is observed in the experimental tests, it is shown that due to the wetting and drying of the concrete surface, the peak concentration of chloride moves progressively deeper into the concrete specimen.

Joint antibacterial activity of soil-adsorbed antibiotics trimethoprim and sulfamethazine

Trimethoprim (TMP) and sulfamethazine (SMZ) are two antibiotics that are often administered in combination. We investigated the sorption and desorption behaviors of TMP and SMZ individually as single solute and in combination as co-solute in three representative soils, and evaluated joint antibacterial activity of the soil-adsorbed antibiotics to a reference strain Escherichia coli ATCC 25922. Comparative sorption tests showed that co-solute sorption of TMP and SMZ was not considerably different from their single sorption. Soil-adsorbed TMP was found to effectively inhibit the growth of E. coli at environmentally relevant concentrations in all three soils, and moreover co-presence of SMZ enhanced the antibacterial effects on bacteria both in its dissolved form and soil-adsorbed form. Overall, the results from this study suggest that various soil-adsorbed antibiotic residues could play a joint influencing role in soil bacterial community activity.

Sorption of radionuclides by cement-based barrier materials

This paper investigates the sorption of radionuclide ions, 137Cs+ and 90Sr2+, by cement-based barrier materials for radioactive waste disposal. A mortar with ternary binder is prepared and powder samples are ground from the hardened material following a predetermined granulometry. After pre-equilibrium with an artificial pore solution, the sorption behaviors of powder samples are investigated through single sorption and blended sorption. The results show that: (1) no systematic difference is observed for single and blended sorptions thus the interaction between 137Cs+ and 90Sr2+ sorptions must be weak; (2) the sorption kinetics is rapid and all characteristic times are less than 1d; (3) the sorption capacity is enhanced by C–A–S–H hydrates and the measured Kd values can be predicted from C–S–H sorption data with Ca/Si ratio equal to Ca/(Si+Al) ratio.

Effect of dye auxiliaries on chemical oxygen demand and colour competitive removal from textile effluents using Posidonia oceanica

The use of an abundant and widely distributed seagrass species, Posidonia oceanica, as a biosorbent for the direct dye Yellow 44 was successfully shown. The studies were performed on the single dyestuff dissolved in water and in a dyebath containing agents commonly used in the textile industry, i.e. a surfactant (Lavotan TBU), a sequestring agent (Meropan DPE), a softening agent (Eurosoft CI10) and a salt (NaCl). The colour reduction results showed that P. oceanica was found to be more efficient for removal of Yellow 44 from an aqueous solution (162 mg g−1) than from a dyebath solution (135 mg g−1), according to the Langmuir isotherm model. For the single dyestuff sorption, Fourier transform infrared and X-ray photoelectron spectroscopy studies highlighted chemical sorption between the dye alcohol function and the sorbent acid function. The chemical oxygen demand removal percentages were found to be 54.9 and 76.6% for Yellow 44 dissolved in aqueous solution and in dyebath solution, respectively. This confirmed the both sorption of the chemical auxiliaries and the dye on P. oceanica.

Competitive adsorption of phenol and resorcinol onto rice husk ash

The present study deals with the adsorptive removal of phenol and resorcinol from aqueous solution onto rice husk ash. The competitive adsorption equilibrium of the binary mixtures (phenol/resorcinol) was determined by conducting batch experiments with initial concentration varying in the range of 50 to 1000 mg/L. In order to evaluate multicomponent adsorption isotherm parameters, individual adsorption equilibrium studies were also carried out. Langmuir, Freundlich and Redlich-Peterson equilibrium isotherm models were used for single compound equilibrium sorption data modeling. All three models almost similar fit for single compound equilibrium data. Binary equilibrium adsorption data and the parameter evaluated from single adsorption data were fitted to various multicomponent isotherm models by minimizing the sum of square of error. The extended Langmuir model gave the better fit to the experimental adsorption data of phenol and resorcinol from binary systems onto rice husk ash. It seems that both phenol and resorcinol compete for the same adsorption sites on rice husk ash. The net interactive effect of phenol and resorcinol on the adsorption of resorcinol by rice husk ash was found to be antagonistic.

Evaluation of the endotoxin binding efficiency of clay minerals using the Limulus Amebocyte lysate test: an in vitro study

Endotoxins are part of the cell wall of Gram-negative bacteria. They are potent immune stimulators and can lead to death if present in high concentrations. Feed additives, which bind endotoxins in the gastrointestinal tract of animals, could help to prevent their negative impact. The objective of our study was to determine the potential of a bentonite (Bentonite 1), a sodium bentonite (Bentonite 2), a chemically treated smectite (Organoclay 1) and a modified attapulgite (Organoclay 2) to bind endotoxins in vitro. Polymyxin B served as positive control. The kinetic chromogenic Limulus Amebocyte lysate test was adapted to measure endotoxin activity. Firstly, a single sorption experiment (10 endotoxin units/mL (EU/mL)) was performed. Polymyxin B and organoclays showed 100% binding efficiency. Secondly, the adsorption efficiency of sorbents in aqueous solution with increasing endotoxin concentrations (2,450 – 51,700 EU/mL) was investigated. Organoclay 1 (0.1%) showed a good binding efficiency in aqueous solution (average 81%), whereas Bentonite 1 (0.1%) obtained a lower binding efficiency (21-54%). The following absorbent capacities were calculated in highest endotoxin concentration: 5.59 mg/g (Organoclay 1) > 3.97 mg/g (Polymyxin B) > 2.58mg/g (Organoclay 2) > 1.55 mg/g (Bentonite 1) > 1.23 mg/g (Bentonite 2). Thirdly, a sorption experiment in artificial intestinal fluid was conducted. Especially for organoclays, which are known to be unspecific adsorbents, the endotoxin binding capacity was significantly reduced. In contrast, Bentonite 1 showed comparable results in artificial intestinal fluid and aqueous solution. Based on the results of this in vitro study, the effect of promising clay minerals will be investigated in in vivo trials.

A pressure and concentration dependence of CO2 diffusion in two Australian bituminous coals

Gas diffusion in coals plays an important role in enhanced coalbed methane production, fugitive gas emissions from coal, and gas release in coal mines. However, a consistent picture of diffusion behaviour in coals is yet to emerge. For example, the adequacy of describing diffusion by a single coefficient is debated. Moreover, some researchers have reported diffusion coefficients as increasing with rising pressure, others report the opposite. This variation may be due to the choice of the model, coal, or experimental conditions. In this study, experimental CO2 kinetic sorption data was obtained for two Australian bituminous coals over a range of pressure conditions and analysed using three different models. We found that the unipore model, which uses only one characteristic diffusion coefficient, does not adequately capture the sorption kinetics. Using a bidisperse model, two characteristic coefficients can describe the diffusion process. The pressure dependence of the fast diffusion coefficient decreases as the system pressure rises. However, the slow diffusion coefficient is not solely dependent on pressure, but is influenced by additional sorption by the coal, which is introduced during the pressure step. Depending on the amount of gas sorbed in a single sorption step, the magnitude of the slow diffusion component will change. This diffusion coefficient exhibits concentration dependence; it varies depending on whether small or large pressure steps are applied. This suggests that the bidisperse model used is inappropriate for examining the pressure dependence of diffusion coefficients at these conditions. Experiments were repeated using a microporous activated carbon, where CO2 uptake displayed rapid kinetics, with no evidence of a slower component. This indicates that the slower uptake of CO2 observed in coal is due to specific properties of the coals. A Fickian diffusion-relaxation model (FDR) developed for studying anomalous diffusion in glassy polymers is proposed instead, ascribing the diffusion in the primary stage to Fickian diffusion, and in the second stage due to slow rearrangement of the coal structure possibly associated with swelling. Additionally, the rapid uptake of gas by the coals (investigated by the model fits) is found to be very sensitive to measured sorption values immediately after gas exposure. This affects the magnitude of calculated diffusion coefficients.

A new method for predicting sorption isotherms at different temperatures using the BET model

A new methodology to predict sorption isotherms at different temperatures is proposed in this work. The classical BET model is used coupled with the Clausius–Clapeyron equation, and an Arrhenius temperature dependency is assumed for the BET energetic parameter C. When compared to the usual procedure based solely on the use of a model for the sorption isotherm, this methodology presents two main advantages: (i) a single set of parameters may be used to predict isotherms at different temperatures and (ii) fewer experimental data are required to estimate this set of parameters, using only one single sorption isotherm and one single value of differential enthalpy of sorption, at a specific and arbitrary humidity. The new methodology was tested with different food materials and the predicted results were in good agreement with experimental data, attesting the potential of this new approach.

Competitive sorption and desorption of cadmium and lead in paddy soils of eastern China

To assess the competitive sorption and desorption of cadmium (Cd) and lead (Pb), batch equilibrium experiments were performed using single- and binary-metal solutions in surface samples of three paddy soils from eastern China. Sorption isotherms were well fitted with one-metal and competitive Langmuir equation for single- and binary-metal system, respectively. The distribution coefficient (Kd) values were Kd single (Pb) > Kd binary (Pb) > Kd single (Cd) > Kd binary (Cd), indicating that Pb was stronger sorbed by these soils than Cd in binary metal system. Soils with high pH and clay content had the greatest sorption capacity as estimated by the maximum sorption parameter (Q). The co-existence of both metals reduces their tendency of sorption, whereas Cd sorption was affected to a greater extent than that of Pb. The Langmuir binding strength parameter (b) in binary sorption system was greater than that in single sorption system for all soils (b < b1), indicating that competition for sorption sites promote the retention of both metals into more specific sorption sites. Sorption of Cd and Pb decreased soil pH by 1.61 U for YRS, 1.39 U for PCS, and 0.91 U for SLS. The decreases of pH in binary metal system were greater than in single-metal system for three soils. Cadmium and Pb desorption increased with increasing Cd and Pb sorption saturation for all soils; however, Cd desorption ratio in binary metal system (dCd*) was much greater than Pb (dPb*), indicating that under the competitive sorption conditions, the sorbed Cd was more readily desorbed from the soils than the sorbed Pb.

Binary Adsorption of a Zn(II)-Cu(II) Mixture onto Egeria densa and Eichhornia crassipes: Kinetic and Equilibrium Data Modeling by PSO

The adsorption of Zn(II) and Cu(II) ions onto two dry macrophytes used as biosorbents was investigated in batch systems. All single and binary metal sorption experiments using Egeria densa and Eicchornia crassipes biomasses as biosorbents were performed under constant shaking, at pH 5, with mixed grain size, and drying and sorption temperatures of 30°C. A 20–45 min equilibrium time range was attained with E. densa, whereas a 30–60 min equilibrium time was achieved with E. crassipes. It was also found that the overall adsorption kinetic data was best described by the pseudo second-order kinetic model, and that the intra-particle diffusion model was involved in the sorption process. An extended-to-multi-component Langmuir-type isotherm model and a parameter identification procedure based on the PSO method have been effectively used for the reproduction of the experimental data and the prediction of the maximum adsorption capacities of Zn(II) and Cu(II) ions in a binary metal ion solution. Finally, E. densa and E. crassipes biomasses exhibited opposite metal adsorption affinity order in the Zn(II)-Cu(II) binary system.

Adsorption of Zn(II) and Cd(II) ions in batch system by using the Eichhornia crassipes

In this work, the displacement effects on the sorption capacities of zinc and cadmium ions of the Eichornia crassipes-type biosorbent in batch binary system has been studied. Preliminary single metal sorption experiments were carried out. An improvement on the Zn(II) and Cd(II) ions removal was achieved by working at 30 °C temperature and with non-uniform biosorbent grain sizes. A 60 min equilibrium time was achieved for both Zn(II) and Cd(II) ions. Furthermore, it was found that the overall kinetic data were best described by the pseudo second-order kinetic model. Classical multi-component adsorption isotherms have been tested as well as a modified extended Langmuir isotherm model, showing good agreement with the equilibrium binary data. Around 0.65 mequiv./g maximum metal uptake associated with the E. crassipes biosorbent was attained and the E. crassipes biosorbent has shown higher adsorption affinity for the zinc ions than for the cadmium ones in the binary system.

Competitive sorption of Cu and Cr on goethite and goethite–bacteria complex

Sorption of Cu and Cr in single and binary sorbate systems on goethite and goethite– Bacillus thuringiensis complex was studied. It was observed that the initial sorption rate and sorption capacity of heavy metals on goethite– B. thuringiensis complex were greater than that on goethite in single system at studied pH. The competitive ability of Cr in the sorption on both goethite and goethite– B. thuringiensis complex was stronger than that of Cu in binary system. Greater intensity of competitive sorption between heavy metals was found on goethite– B. thuringiensis complex than on goethite. The percentage of sorbed metals desorbed by Ca(NO 3) 2 from goethite was lower than that from goethite– B. thuringiensis complex, conforming the higher sorption affinity of heavy metals for goethite than that for goethite– B. thuringiensis complex. For each sorbed heavy metal, the desorption ratio was slightly higher from single sorption system than from binary sorption system, indicating the release of loosely sorbed metal and the retention of tightly bound cation during competitive sorption. The results obtained in this study are of significant importance for the assessment and remediation of multi-heavy metal pollution.

Measuring and Modeling Adsorption of PAHs to Carbon Nanotubes Over a Six Order of Magnitude Wide Concentration Range

Understanding the interactions between organic contaminants and carbon nanomaterials is essential for evaluating the materials' potential environmental impact and their application as sorbent. Although a great deal of work has been published in the past years, data are still limited in terms of compounds, concentrations, and conditions investigated. We applied a passive sampling method employing polyoxymethylene (POM-SPE) to gain a better understanding of the interactions between polycyclic aromatic hydrocarbons (PAHs) and multiwalled carbon nanotubes (CNTs) over a 6 orders of magnitude wide concentration range. In the low-concentration range (pg-ng L(-1)), sorption of phenanthrene and pyrene was linear on a nonlogarithmic scale. Here, sorption could thus be described using a single sorption coefficient. Isotherm fits over the entire concentration range showed that (i) monolayer sorption models described the data very well, and (ii) the CNTs sorption capacity was directly related to their surface area. Sorption coefficients for 13 PAHs (11 of which have not been reported to date) were also measured at environmentally relevant low concentrations. No competition seemed to occur in the low-concentration range and sorption affinity was directly related to the solubility of the subcooled liquid of the compounds.

Fluorescence Spectral Characteristics and Sorption Behaviors of Acenaphthene to Surface Sediment in Chongqing Section of Yangtze River

3-D Fluorescence Spectrometry analysis and sorption experiments of Acenaphthene (Acp), one of the polycyclic aromatic hydrocarbons (PAHs), were carried on in this paper. Under the experimental conditions, the optimized excitation/emission wavelength (λex/λem) was 280/320nm. The correlative coefficient of 0.998 and the relative standard deviation of 4.03%(n=5) could be obtained over the linear ranges of 0.025mg/L~1mg/L for the calibration curve. The sorption tests of Acp to surface sediment in Chongqing Section of the Yangtze River showed that the sorption isotherms were fitted with different types of model, including traditional linear partition model and Freundlich model. According to the fitted value of model, the sorption behaviors of Acp to the surface sediment was not affected by the single sorption mechanism but the combined action of linear partition process and surface sorption.

Pyrene and Phenanthrene Sorption to Model and Natural Geosorbents in Single- and Binary-Solute Systems

Sorption of pyrene and phenanthrene to model (illite and charcoal) and natural (Yangtze sediment) geosorbents were investigated by batch techniques using fluorescence spectroscopy. A higher adsorption of phenanthrene was observed with all sorbents, which is related to the better accessibility of smaller molecules to micropores in the molecular sieve sorbents. In addition, pyrene sorption in binary-solute systems with a constant initial concentration of phenanthrene (0.1 μmol L(-1) or 2 μmol L(-1)) was studied. A 0.1 μmol L(-1) concentration of phenanthrene causes no competitive effect on the pyrene sorption. A 2 μmol L(-1) concentration of phenanthrene significantly suppresses the sorption of pyrene, especially in the low concentration range; nonlinearity of the pyrene sorption isotherms thus decreases. The competitive effect of 2 μmol L(-1) phenanthrene on the pyrene sorption is overestimated by the ideal adsorbed solution theory (IAST) using the fitted single sorption results of both solutes. An adjustment of the IAST application by taking into account the molecular sieve effect is proposed, which notably improves the IAST prediction for the competitive effect.

Sorption and desorption characteristics of the dye tracer, Brilliant Blue FCF, in sandy and clay soils

Abstract Dye tracers are widely used for tracing and visualising hydrological flow paths in soils. Despite evidence of non-conservative behaviour (i.e. sorption) in recent years, Brilliant Blue FCF continues to be used extensively for dye tracing in soil. However, previous studies have not considered hysteresis in the sorption mechanism. The objectives of this study were (1) to test the hypothesis that sorption of Brilliant Blue FCF on soils with widely contrasting textures could be described with a single sorption isotherm based solely on sorption by the clay fraction and (2) to determine whether desorption hysteresis is likely to confound the estimation of retardation factor in modelling dye transit through soil. We measured the sorption and desorption of Brilliant Blue on four soils of contrasting texture, ranging from a light sand to a heavy clay, and resolved a single Freundlich sorption isotherm for the clay fraction in all soils. An attempt to include silt and humus fractions as additional adsorbents with independent Freundlich parameters was unsuccessful. The sorption of Brilliant Blue FCF on the four soils studied was not fully reversible; there was apparent sorption–desorption hysteresis in all cases. Therefore, even though the sorption strength of Brilliant Blue in soils might be less than that of other dye tracers, it is possible that the visualised flow pathways may not accurately reflect those of water in soil. From this we suggest that Brilliant Blue may not be well suited for all forms of dye tracing in clay soils and it is therefore crucial that the specific environmental conditions, soil type, dye concentration and objectives of the study are considered each time when choosing the appropriate dye tracer.

Evaluation of Textile Dye Sorption on GAC Produced from Almond Shells Based on Optimized Isotherm Models

ABSTRACT Single component sorption of three basic dyes used by the textile industry (rhodamine b, malachite green oxalate, and methylene blue) from aqueous systems was evaluated for granular activa...

Uptake of Polycyclic Aromatic Hydrocarbons by Insoluble Dietary Fiber

The sorption isotherms of polycyclic aromatic hydrocarbons (PAHs) by insoluble dietary fiber (IDF) were measured in artificial gastric juice (AGJ) and artificial intestinal juice (AIJ) at 37◦C and then the sorption behavior of IDF was examined. Benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo[a]pyrene were used. It was suggested that the uptake of PAHs by carboxymethyle cellulose (CMC), agar, and IDF from powdered young barley leaves (YBL) involved not single sorption behavior, but complex sorption behavior. YBL had an extraordinarily high sorption capacity (60.7–147.3 nmol/g in AGJ and 76.7–162.7 nmol/g in AIJ), as compared with CMC (1.5–3.6 nmol/g in AGJ and 1.1–2.7 nmol/g in AIJ) and agar (0.1–0.4 nmol/g in AGJ and 0.3–0.7 nmol/g in AIJ) at a residual concentration of 5.0 nM. The sorption of PAHs in AGJ and the desorption of PAHs from IDF in both AGJ and AIJ indicate that the sorbed PAH molecules are held firmly by IDF while it passes through the digestive tract in vivo. From the results on sorption capacity and the removability of PAHs from IDF, YBL would be expected to be more useful than CMC and agar.