Langmuir Sorption Research Articles

Removal of the metal ions from aqueous solutions by nanoscaled low molecular pectin isolated from seagrass Phyllospadix iwatensis

Pectins from sea grasses are considered as promising substances with pronounced metal-binding activity. Due to the high molecular weight and heterogeneous structure, the use of pectins for removal of metal ions is difficult. Technology of directed pectin degradation was developed and homogenous degraded nanoscaled pectin polymers were synthesized. Experimental samples of degraded pectin isolated from Phyllospadix iwatensis were tested for their metal binding activity in comparison with native pectin from this seagrass and commercial citrus pectin. The metal uptake of all pectin compounds was highest within the pH range from 4.0 to 6.0. The Langmuir, Freundlich and BET sorption models were applied to describe the isotherms and constants. Results showed that depolymerized pectin exerts highest lead and cadmium binding activity with pronounced affinity. All pectin compounds were suggested to be favorable sorbents. Therefore, it can be concluded that degraded pectin is a prospective material for creation of metal-removing water treatment systems.

Comparative evaluation of arsenate sorption–desorption in two soils of North India

A sandy loam (Typic Ustochrept) and a clayey (Typic Hapludalf) soil from two north Indian states, Punjab and Himachal Pradesh, respectively, were used to study sorption–desorption behaviour of arsenate. Arsenate sorption by the soils was studied from a range of added concentrations (50–100 mg arsenate kg−1) in the presence of background electrolyte, 0.01 M KNO3. Arsenate sorption was found to increase with each increment in added arsenate concentration in both the soils. However, the magnitude of sorbed arsenate decreased. The sorption was rapid initially followed by gradual retention behaviour. The amount and pattern of arsenate sorbed over a period of time (2–512 h) differed between the two soils. The sorption was higher and quicker by clayey soil as compared to sandy loam soil, which could be due to difference in their pH, AEC, organic matter, Fe and Mn oxide content. Arsenate sorption data were well explained by Langmuir and Freundlich sorption isotherms. Desorption of arsenate was carried out by six successive washings with arsenate free 0.01 M KNO3 solution. At all levels of added arsenate, most of the sorbed arsenate could not be desorbed back into the solution and a marked hysteresis between arsenate sorption and desorption isotherms was observed in both soils which became greater with increasing reaction period. Relatively lesser amount of arsenate could be desorbed back from clayey soil than from sandy loam soil.

Removal of levofloxacin from aqueous solution using rice-husk and wood-chip biochars

The potential for rice husk (RH) and wood chip (WC) biochars to remove levofloxacin (LEV) from aqueous solution was evaluated. The physical and chemical properties of the biochars were characterized using various tools and techniques. Furthermore, batch sorption experiments were conducted to determine the sorption ability of the biochars to LEV. The pseudo-second order kinetic model described the sorption kinetic data better than the pseudo-first order kinetic model and the Elovich equation because the process involved both surface adsorption and pore diffusion. For the isotherms, the Langmuir equation fitted the data better than the Freundlich equation. The maximum Langmuir sorption capacities of the biochars to LEV ranged from 1.49 to 7.72 mg g−1. Thermodynamic parameters obtained from the experiments showed that the adsorption of LEV onto the WC biochar was spontaneous and exothermic, while its adsorption onto the RH biochar was spontaneous and endothermic under tested conditions. A mixture of 0.025 M phosphate buffer (80%, pH 3.0) and acetonitrile (20%) effectively desorbed the LEV from the biochars with a recovery rate up to 80%. Findings from this work indicate that biochars can be used as an alternative adsorbent to effectively remove emerging contaminants including LEV from aqueous solutions.

Mass transfer and kinetic studies on mercury adsorption by titania nanofibers

The stringent laws and tight regulation on heavy metal bearing wastewaters being discharged into the water stream lead to emergence of technically advanced and super effective treatment methods. Heavy metal contaminated aqueous streams have become a global concern due to their carcinogenicity and delirious effects on human health. In particular, the health hazards of mercury include adverse effect on central nervous system, pulmonary and kidney functions, etc. Having a maximum discharge limit of 0.001 mg/L, which is the lowest amongst other heavy metals, mercury contamination has become a matter of global concern. In the present study, TiO 2 having a proven track record for its affinity for heavy metals was lab synthesized in the form of fiber mats and tested for its adsorptive behaviour towards Hg(II) in aqueous system. The electrospinned nanofibers possessed smooth morphology and very high surface area ≈ 740 m 2 /g. The batch adsorption experiments showed titania nanofibers possessed great affinity towards Hg(II). At the most optimized conditions the removal percentage went remarkably high to 95.5% with initial Hg(II) concentration of 0.01 mg/L. Since the rate limiting steps in adsorption are of vital importance in order to define the rate parameters for design purposes, the present study takes into account External mass transfer, Weber and Morris and Boyd mass transfer diffusion models for Hg(II) adsorption on lab synthesized titania nanofibers. The equilibrium data were then analyzed using Langmuir, Freundlich and Temkin sorption models and the characteristic sorption parameters for each isotherm were determined. The Mass transfer mechanism appeared to be film diffusion controlled and data fitted best to Freundlich isotherm with regression value of 0.991. The discussion also focuses on few of the recently used adsorbents for Hg(II) uptake and their comparison with the present study on the basis of removal percentage and kinetics involved. Promising adsorbent characteristics and rapid Hg(II) uptake makes this process a convenient one.

Phosphorus Modeling in Tile Drained Agricultural Systems Using APEX

Phosphorus (P) losses through tile drained systems in agricultural landscapes may be causing persistent eutrophication problems observed in surface water. The purpose of this paper is to evaluate the state of the science in the Agricultural Policy/Environmental extender (APEX) model related to surface and tile P transport. This was accomplished using data from a monitored corn-soybean rotation field in the St. Joseph River watershed, IN. The estimation of soluble phosphorus (SP) in surface runoff and tile flow in APEX includes a user defined linear (based on GLEAMS) and nonlinear (Langmuir) sorption option. The results suggest that the inclusion of the Langmuir isotherm improved (18%) SP sorption estimates in surface runoff during the corn year only when P inputs were added, whereas the linear method was more appropriate during the soybean year when no fertilizers were applied. Similarly, SP estimates in tile flow were improved (30%) when using the Langmuir option during the corn year, though the overall model performance predicting this variable were very poor. Modeling improvements of P partitioning processes in APEX can help predict more realistic outputs. Yet to achieve this in tile flow, water percolation processes need to be improved to reflect preferential flow conditions often found in long-term no-till fields and in soils with high clay content. Greater accuracy in the estimation of the effect of artificial drainage systems, common in the US Midwest, should result in the improved evaluation of agricultural conservation practices in order to examine strategies that could reduce P losses for water quality purposes.

Sepiolite functionalized with N-[3-(trimethoxysilyl)propyl]-ethylenediamine triacetic acid trisodium salt. Part II: Sorption of Ni2+ from aqueous solutions

sorption of Ni2+ on the sepiolite functionalized by covalent grafting of N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt, MSEAS, was studied in batch experiments as a function of the initial metal concentration, the equilibration time, pH value, and temperature. The modification of sepiolite resulted in an enhanced Ni2+ retention with a capacity of 0.261 mmol/g at 298 K. The retention of Ni2+ ions occurred dominantly by specific sorption and exchange of Mg2+ ions from the sepiolite structure. The sorption process followed pseudo-second-order kinetics. The sorption equilibrium results were best described by the non-linear form of the Langmuir Sorption Equation. The values of the thermodynamic parameters (enthalpy, free energy and entropy) were calculated from temperature dependent sorption isotherms and these values showed that the sorption of Ni2+ onto modified sepiolite was endothermic.

PAHs in Household Floor Dust Collected in Amman, Jordan

PP-g-MAA oil sorption materials were synthesized by graft polymerization method of methacrylic acid (MAA) onto polypropylene fibers (PP) using divilylbenzene (DVB) as cross-linking agent. The virgin and grafted PP fibers were characterized by FT-IR, SEM, TGA, and DSC analysis. The results revealed that MAA was grafted onto PP fibers successfully. Factors affected the grafting yield (GY) were examined such as monomer concentration, initiator concentration, effects of temperature as well as reaction time. At the DVB and MAA concentrations of 1.5% and 2%, respectively, the maximum GY was obtained (73.1%). The obtained correlation coefficient (R2) from well-known Langmuir sorption isotherms suggested well-fitting of the experimental data, which is assumed that at maximum coverage with identical sorption sites, there is monomolecular layer sorption on the PP-g-MAA surface. Oil sorption capacity of PP-g-MAA fibers was investigated which revealed a maximum oil sorption capacity (qmax) of 20.833 g/g. SEM pictures and FTIR results were taken for these materials under test.

Polypyrrole/cobalt ferrite/multiwalled carbon nanotubes as an adsorbent for removing uranium ions from aqueous solutions.

A novel rod-like, dual-shell structural adsorbent of polypyrrole/cobalt ferrite/multiwalled carbon nanotubes (PPy/CoFe2O4/MWCNTs) was successfully synthesized by a hydrothermal method, which could easily separate uranium(vi) ions with an external magnetic field. The structure and morphology of PPy/CoFe2O4/MWCNTs were characterized by VSM, XRD, XPS TEM and FT-IR. The results proved that the dual-shell structure was obtained in which a shell of cobalt ferrite and polypyrrole formed around the MWCNTs core. In batch adsorption experiments, including pH, equilibrium time and temperature on uranium adsorption, were investigated. The main results show that the PPy/CoFe2O4/MWCNTs composite has a higher affinity towards the uptake of uranium(vi) from aqueous solutions. The highest adsorption capacity reached was 148.8 mg U per g at pH 7. A kinetic analysis showed that the adsorption process was best described by a pseudo-second-order kinetic model. The uranium sorption equilibrium data correlated well with the Langmuir sorption isotherm model in the thermodynamic analysis. 0.5 mol per L NaHCO3 was used as the desorbent and good adsorption properties were shown after the desorption procedures were repeated three times. Thus, PPy/CoFe2O4/MWCNTs was an excellent adsorbent for removing uranium(vi) ions.

In-situ synthesis of magnetite acrylamide amino-amidoxime nanocomposite adsorbent for highly efficient sorption of U(VI) ions

A new in-situ magnetite nanoparticles inserted into crosslinked poly (acrylamido-amineamidoxime-co-2-acrylamido-2-methylpropane sulfonic acid (AO/AMPS) were prepared and used as novel uranium adsorbents. The prepared composites were applied as adsorbents to remove U(VI) from aqueous solutions that could be separated by a simple magnetic separation method. The removal of U(VI) was evaluated by spectrophotometric method using arsenazo-III as complexing agent. The results showed that, the sorption process strongly depended on pH and the sorption equilibrium can be reached within 150min. The Langmuir sorption isotherm model correlated well with the uranium sorption equilibrium data for the concentration range of 50–500mg/L.

Langmuir slip-Langmuir sorption permeability model of shale

Darcy law has been widely used in high permeability formations; however, it fails to realistically describe different flow processes other than the viscous flow. Several permeability models have been developed to describe gas flow in shale nanopores due to various processes, and relevant processes other than viscous flow include Knudsen diffusion, slip flow and desorption. To include these processes, all the current models need some empirical coefficients which are not easily available for shale formations. We propose a permeability model that – (1) does away with the shortcomings of Maxwell slip condition, (2) uses readily available Langmuir sorption data to determine slip coefficient for gas flow, and (3) includes the higher-order slip effects on gas flow. This model also includes the effect of pore enlargement due to pressure-depletion sorption. Our model, represented by a single analytical equation depends only on pore size, pressure, and Langmuir sorption isotherm data of shale sample. We validated our model using a set of in-house detailed experimental data on Eagle Ford shale samples and also using data from the literature on shale gas permeability versus pore pressure measurements for helium and methane. We also used our model to calculate gas production from a well-reservoir system and compared the results with previously developed models. Our model also predicts the onset and the contribution of sorption to gas production from a shale well.

Adsorption and desorption of arsenate in Louisiana rice soils

ABSTRACTAdsorption and desorption of arsenic (As) in the soil are dominant parameters that affect the mobility and bioavailability of arsenic. Batch arsenate adsorption and desorption experiments were conducted using soils collected from three Louisiana, USA, aquaculture ponds representing different crayfish farming and rice cultural practices. Arsenate adsorption behavior in the soils was investigated using Freundlich and Langmuir sorption equations. Results demonstrated that the Langmuir isotherm model was the best fit based on statistical correlation with soil properties governing adsorption, for the entire range of arsenate concentrations for all soils. Adsorption of As(V) was governed by soil physicochemical properties especially Fe and Al oxides, clay and organic matter. Desorption of As(V) was initially fast, but with increasing incubation times desorption occurred progressively slower. Chemical fractionation of arsenic in the soils showed that the most mobile fraction represented 4.74–5.18% of the total arsenic. A part of this mobile fraction could potentially be taken up by rice and enter the food chain, but would require additional research to quantify.

Simultaneous separation and purification of plutonium and americium from aqueous nitrate solutions using extractant impregnated macroporous polymeric beads

The removal of Pu(IV) and Am(III) ions from aqueous nitrate solutions was studied using indigenously synthesized Extractant Impregnated Macroporous Poly- meric Beads (EIMPBs). These beads exhibited almost quantitative sorption of Pu(IV) at acid strength of ( 2M HNO3 while that of Am(III) at pH 3. Langmuir sorption model was found suitable, with the sorption capacity of EIMPBs for Pu(IV) and Am(III) as 2.13 and 2.64 mg g -1 respectively. Its performance remained unchanged until seven cycles of extraction and stripping using 0.1 M oxalic acid. A flow sheet for Purification of Pu(IV)/Am(III) from its mixture is proposed.

Synthesis and structural characterization of magnetite/sepiolite composite and its sorptive properties for Co(II) and Cd(II)

In this work, the magnetite/sepiolite (M/SEP) composite was synthesized by chemical co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The characterization results showed that M/SEP was composed of magnetite and sepiolite and had a superparamagnetic property. Considering the good separation characteristic after use, M/SEP composite was used as a sorbent for the removal of Co(II) and Cd(II) from aqueous solutions. The pH and temperature on Co(II) and Cd(II) sorption to M/SEP composite were investigated. The results showed that the sorption of Co(II) and Cd(II) was strongly dependent on pH, and the Langmuir sorption capacities of M/SEP composite for Co(II) and Cd(II) were 18.85 and 14.15 mg/g at 20 ºC, respectively. The thermodynamic parameters indicated that the sorption processes of Co(II) and Cd(II) on M/SEP composite were endothermic and spontaneous processes. Herein, this finding suggests that M/SEP composite can be applied on the preconcentration of heavy metal ions in the field of water treatment.

Removal of thorium from water using modified magnetite nanoparticles capped with rosin amidoxime

The present study describes synthesis and characterization of diacrylamidoxime triaethylenetetralevopimaramide (DPAO) and its use in surface modification of Fe3O4 magnetic nanoparticles to obtain DPAO-based magnetic nanoparticles (DPAO-MNPs). The prepared composite was characterized by FTIR, 1HNMR, XRD, DLS, TEM, SEM and EDX. Vibrating sample magnetometer is used to determine the magnetic properties of DPAO-MNPs. Results of analyses indicate that the surface of Fe3O4 was successfully capped with DPAO. The adsorption features of the prepared composite towards thorium ions were investigated in a batch system. Kinetic study of Th(IV) adsorption on DPAO-MNPs indicate the adsorption equilibrium achieved within 150 min and is pH dependent. The adsorption results were described mathematically using Langmuir and Freundlich sorption models. The composite showed a maximum Th(IV) loading capacity of 666 mg/g at 25 °C and pH 4. The thermodynamic results indicated that the adsorption process was thermodynamically favorable, spontaneous and endothermic nature. The obtained results suggest that DPAO-MNPs composite may be considered as a potential fast, effective and simple adsorbent for sorption thorium(IV) from water.

Sludge-Derived Biochar for Arsenic(III) Immobilization: Effects of Solution Chemistry on Sorption Behavior.

Recycling sewage sludge by pyrolysis has attracted increasing attention for pollutant removal from wastewater and soils. This study scrutinized As(III) sorption behavior on sludge-derived biochar (SDBC) under different pyrolysis conditions and solution chemistry. The SDBC pyrolyzed at a higher temperature showed a lower As(III) sorption capacity and increasingly nonlinear isotherm due to loss of surface sites and deoxygenation-dehydrogenation. The Langmuir sorption capacity on SDBC (3.08-6.04 mg g) was comparable to other waste-derived sorbents, with the highest As(III) sorption on SDBC pyrolyzed at 400°C for 2 h. The As(III) sorption kinetics best fit with the pseudo-second-order equation, thus suggesting the significance of the availability of surface sites and initial concentration. Sorption of As(III) was faster than that of Cr(VI) but slower than that of Pb(II), which was attributed to their differences in molar volume (correlated to diffusion coefficients) and sorption mechanisms. The X-ray photoelectron spectra revealed an increase of oxide oxygen (O) with a decrease of sorbed water, indicative of ligand exchange with hydroxyl groups on SDBC surfaces. The As(III) sorption was not pH dependent in acidic-neutral range (pH < 8) due to the buffering capacity and surface characteristics of the SDBC; however, sorption was promoted by increasing pH in the alkaline range (pH > 8) because of As(III) speciation in solution. An increasing ionic strength (0.001-0.1 mol L) facilitated As(III) sorption, indicating the predominance of ligand exchange over electrostatic interactions, while high concentrations (0.1 mol L) of competing anions (fluoride, sulfate, carbonate, and phosphate) inhibited As(III) sorption. These results suggest that SDBC is applicable for As(III) immobilization in most environmentally relevant conditions.

Chemically modified biochar produced from conocarpus waste increases NO3 removal from aqueous solutions.

Biochar has emerged as a universal sorbent for the removal of contaminants from water and soil. However, its efficiency is lower than that of commercially available sorbents. Engineering biochar by chemical modification may improve its sorption efficiency. In this study, conocarpus green waste was chemically modified with magnesium and iron oxides and then subjected to thermal pyrolysis to produce biochar. These chemically modified biochars were tested for NO3 removal efficiency from aqueous solutions in batch sorption isothermal and kinetic experiments. The results revealed that MgO-biochar outperformed other biochars with a maximum NO3 sorption capacity of 45.36mmolkg(-1) predicted by the Langmuir sorption model. The kinetics data were well described by the Type 1 pseudo-second-order model, indicating chemisorption as the dominating mechanism of NO3 sorption onto biochars. Greater efficiency of MgO-biochar was related to its high specific surface area (391.8m(2)g(-1)) and formation of strong ionic complexes with NO3. At an initial pH of 2, more than 89% NO3 removal efficiency was observed for all of the biochars. We conclude that chemical modification can alter the surface chemistry of biochar, thereby leading to enhanced sorption capacity compared with simple biochar.

Preparation of new polysulfone capsules containing Cyanex 272 and their properties for Co(II) removal from aqueous solution

In this study, new polysulfone capsules containing Cyanex 272 (Cyanex 272@PSF capsules) were prepared by phase inversion technique for the sorption of Co(II) from aqueous solution. The characterization of the Cyanex 272@PSF capsules which were performed by using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and thermal gravimetric analysis (TGA) indicated that Cyanex 272 was successfully encapsulated by polysulfone. For the Cyanex 272@PSF capsules having the highest sorption efficiency, the encapsulation efficiency was determined as 7.2%. The batch sorption experiments showed that removal of Co(II) from aqueous solutions occurred through the cation-exchange and chelation mechanisms and maximum removal was achieved at an initial pH of 8.0 (final pH of 5.9). The Cyanex 272@PSF capsules produced with dispersed phase containing 2.0% of Cyanex 272 (by wt.) provided the highest Co(II) removal. The sorption equilibrium time was attained within 120min. By confirming the non-linear Chi-square (χ2) statistical test, Langmuir isotherm model was the best fit model. Langmuir sorption capacity (Qo) and sorption constant (b) were 2.014mg/g and 0.281L/mg, respectively. The regenerated capsules could be used three times with no change in their sorption capacities. Based on the experiments performed at initial pH of 8.0 for other metal ions, including Ni(II), Pb(II) and Cd(II), sorption ability of Cyanex 272@PSF capsules was in the order: Co(II)≈Ni(II)>Cd(II)>Pb(II). Consequently, Cyanex 272@PSF capsules have potential for removing Co(II) from aqueous solutions.

Investigations on the methane sorption capacity of marine shales from Sichuan Basin, China

High-pressure methane sorption isotherms measured at 30, 50 and 80°C and pressure up to 20MPa were measured on Lower Silurian marine shales from Sichuan Basin of China. The effect of total organic carbon content, temperature, thermal maturity, mineral composition, and pore structure on methane sorption capacity has been investigated. A linear combination approach has been developed to predict the Langmuir sorption capacity of shales based on the mass fractions of their organic and inorganic components. This information can be used to estimate the in situ sorption capacity of shale layers as a function of burial depth (formation pressure and temperature), and composition.Methane sorption capacity of the dry shales shows a positive relationship with TOC and specific surface area. The Langmuir pressure decreases with increasing maturity, but the TOC-normalized Langmuir sorption capacity of over-mature shales also decreases with increasing thermal maturity. This may be related to the carbonization of highly over-mature organic matter. For the samples investigated, approximately 16.3%–46.7% (average 28.6%) of the methane sorption can be attributed to clay minerals and 46.5%–81.5% to (average 67.6%) organic matter in these shales, respectively. Using the linear combination approach, the calculated Langmuir sorption capacity function matches the measured values reasonably. Methane sorption capacity computed as a function of depth (for a mean hydrostatic pressure gradient of 0.01MPa/m and a geothermal gradient of 0.03°C /m) shows a rapid increase and reaches a maximum between 900 and 1800m followed by a slow decrease with increasing depth. At shallow burial depths (<900–1800m), the sorption capacity is controlled by the combination of hydrostatic pressure and geothermal gradients. At deeper burial (>900–1800m) sorption capacity is controlled by the geothermal gradient. Higher geothermal gradients result in a steeper decline of sorption capacity.

Phosphorus sorption, supply potential and availability in soils with contrasting parent material and soil chemical properties

SummarySoil phosphorus (P) management requires a more targeted and soil‐specific approach than is currently applied for agronomic recommendations and environmental evaluation. Phosphorus buffering capacities control the supply of P in the soil solution and were measured across Irish soils with contrasting parent material and chemical properties. Langmuir sorption buffer capacities (MBCs) and binding energies (b) were strongly correlated with soil pH and extractable aluminium (Al). A broken‐line regression fitted to the relationship between MBC and Al derived a change‐point value for Al above which MBC increased linearly. Soils above the change point were predominantly acidic to neutral with non‐calcareous parent material, with larger buffering capacities and binding energies than calcareous soils. Ratios of Mehlich3‐Al and P (Al:P) were used to relate buffering capacity to supply potential in non‐calcareous soils. Large ratios of Al:P were associated with poor P availability, characteristic of strongly P‐fixing soils. Threshold values of iron‐oxide paper strip P (FeO‐P) and Morgan's P revealed Al:P ratios where soils began to supply P in available form. The change‐point for Morgan's P fell within the current target index for P availability; however, the confidence interval was more compatible with previous agronomic P indices used in Ireland. Relationships between Morgan's P and measures of extractable P, M3‐P and Olsen P, deviated in calcareous soils at large soil P contents, indicative of P precipitation processes dominating in these soils. Identifying differences in soil P buffering capacity at the laboratory scale would improve agronomic and environmental assessment at field and catchment scales.

Sorption of sulfisoxazole onto soil--an insight into different influencing factors.

Although sulfonamides (SAs) are among the most commonly used veterinary drugs and their presence in the environment is well documented, knowledge of their fate and behavior in the soil environment is still limited, especially for sulfisoxazole (SSX) which is characterized by the lowest (among other SAs) pK a value associated with acid-base equilibrium of sulfonamide group. Thus, this work was focused on determining the sorption potential of SSX onto natural soils differing in physicochemical properties. All the results were modeled using linear, Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin sorption isotherms. The established sorption coefficients (K(d)) for SSX were quite low (from 0.27 to 0.95 L kg(-1)), which indicated that this substance is highly mobile and has the potential to run off into surface waters and/or infiltrate ground water. The sorption data of SSX is well fitted to the Freundlich isotherm model (R(2) > 0.968). Moreover, we assessed the sorption mechanism of these compounds in the edaphic environment with respect to organic matter (OM) content, pH, and ionic strength. To clarify the current state of knowledge, these factors were examined much more thoroughly than in previous investigations concerning other SAs. The wide range of ionic strength examined showed positive correlation of this factor and sorption of SAs. The results also yielded new insight into dependency of sorption of SAs on organic matter content in soil.