Effects of temperature and surfactants on naphthalene and phenanthrene sorption by soil

Adsorption experiments were carried out to investigate the sorption behaviors of naphthalene and phenanthrene in six different soils and to determine the effects of temperature, linear alkylbenzene sulfonate （LAS） and cetylrimethyl ammonium bromide （CTAB） on sorption. The results show that for a given sorbent phenanthrene exhibited greater nonlinear and stronger sorption than naphthalene. There was a strong negative correlation for the Koc values with organic carbon content （foc）. The increase of temperature was not favorable to sorption. Sorption decreased along with the increasing aqueous LAS concentration from 0 to 1000 mg/L. At low CTAB concentration （〈 100 mg/L）, the adsorption increased as CTAB hemimicelles formed on the soil surface. At high concentration, CTAB decreased the adsorption by occupying active hydrophobic adsorption sites and solubilization of naphthalene and phenanthrene.

The Structure of Montmorillonites Modified with Zwitterionic Surfactants and Their Sorption Ability

In the past four decades, there is a growing use of surfactant modified clay complexes in wide range of applications. The mostly used surfactants to modify the swelling clay minerals are cationic surfactants, such as quaternary ammonium, which consists of two distinct moieties, a hydrophilic head, where the positive charge is concentrated, and a hydrophobic hydrocarbon chain tail. During the surface modification, this kind of surfactant molecules attach on the inner and outer surface of clay minerals, the hydrophilic surface of raw clay minerals may changed into hydrophobic surface. The changes of organophilicity and hydrophobicity of clay minerals enable them used in more wide fields, such as adsorbents for organic contaminant, geotechnical barriers, filling of nanocomposite, etc.

Adsorption Behavior and Mechanisms of Surfactants by Farmland Soils in Northeast China

The adsorption of two nonionic surfactants polyethylene glycol tert-octylphenyl ether Triton X-100 (TX-100), polyoxyethylene lauryl ether(Brij35) and an anionic surfactant sodium dodecyl benzene sulfonate(SDBS) by two soils(S1, S2) of different natures and their respective organic-matter-extracted samples(S3, S4) were investigated. These adsorption isotherms show different adsorption stages of different types of surfactants by soils. The data fitted Langmuir equation very well. The adsorption maximum capacity(Q0) indicates that TX-100 and SDBS were in the sequence of S3S4S1S2 in adsorption, however, Brij35 was in the sequence of S4S3S1S2 in adsorption. And the adsorption amounts of the different surfactants by soils followed the order of TX-100Brij35SDBS. Meanwhile, the adsorption of the nonionic surfactants TX-100 and Brij35 decreased with the increase of their ethylene oxide(EO) numbers. The results indicate that both soil organic matter and mineral played important roles in the adsorption of surfactants, and the adsorption of the surfactants by soils was affected by the physicochemical properties and structures of the soils and surfactants, especially the mineral type and content of soil.

Phosphorus Changes and Sorption Characteristics in a Calcareous Soil Under Long-Term Fertilization

Knowledge of phosphorus （P） behavior in long-term fertilized soils is essential for programming fertilization practices and for sustaining environmental quality. The long-term （1984-1997） effects of various fertilization treatments on P changes and sorption isotherms as well as the relationship of soil properties to P sorption and P forms were evaluated in an Ustic Isohumisol, a calcareous soil, on the Loess Plateau, China. Compared to 1984, after 13 years of crop production, total soil P in the no-P treatments （control and N treatment） decreased by 5%-7%, but in the phosphorus fertilizer alone （P）, nitrogen and phosphorus fertilizers in combination （NP）, manure alone （M）, and nitrogen and phosphorus fertilizers and manure in combination （NPM） treatments, it increased by 22%, 19%, 28%, and 58%, respectively. Residual fertilizer P was found mainly in NH4Ac-soluble P （Cas-P）, followed by NaHCO3-soluble P （NaHCO3-P）, and NH4F-soluble P （Al-P）. Phosphorus sorption in the soils with different fertilization practices fit the Langmuir equations. Phosphorus sorption capacity in the no-P treatments increased, whereas it decreased in the P-included treatments （P, NP, and NPM treatments）. Phosphorus sorption maximum （Qm） was significantly and negatively correlated to inorganic P including NaHCO3-P, Cas-P, NaOH-Na2CO3-soluble P （Fe-P）, and Al-P （P ≤ 0.01）. Moreover, long-term fertilization increased soil organic carbon in the NP, M, and NPM treatments and decreased pH in the NP and NPM treatments. Thus, the ability of the soil to release sorbed P to the environment increased under long-term P fertilization.

Soil Components Affecting Phosphate Sorption Parameters of Acid Paddy Soils in Guangdong Province

Soil components affecting phosphate sorption parameters were studied using acid paddy soils derived from basalt, granite, sand-shale and the Pearl River Delta sediments, respectively, in Guangdong Province. For each soil, seven 2.50 g subsamples were equilibrated with 50 mL 0.02 mol L-1 (pH=7.0) of KCI containing 0, 5, 10, 15, 25, 50 and 100 mg P kg-1, respectively, in order to derive P sorption parameters (P sorption maximum, P sorption intensity factor and maximum buffer capacity) by Langmuir isotherm equation. It was shown that the main soil components influencing phosphate sorption maximum (Xm) included soil clay, PH, amorphous iron oxide (Feo) and amorphous aluminum oxide (Alo), with their effects in the order of Alo > Feo > pH > clay. Among these components, pH had a negative effect, and the others had a positive effect. Organic matter (OM) was the only soil component influencing P sorption intensity factor (K). The main components influencing maximum phosphate buffer capacity (MBC) consisted of soil clay, OM,pH, Feo and Alo, with their effects in the order of Alo > OM > pH > Feo > clay. Path analysis indicated that among the components with positive effects on maximum phosphate buffer capacity (MBC), the effect was in the order of Alo > Feo > Clay, while among the components with negative effects, OM > pH. OM played an important role in mobilizing phosphate in acid paddy soils mainly through decreasing the sorption immensity of phosphate by soil particles.

Effect of Selected Organic Acids on Cadmium Sorption by Variable- and Permanent-Charge Soils

Batch equilibrium experiments were conducted to investigate cadmium （Cd） sorption by two permanent-charge soils, a yellow-cinnamon soil and a yellow-brown soil, and two variable-charge soils, a red soil and a latosol, with addition of selected organic acids （acetate, tartrate, and citrate）. Results showed that with an increase in acetate concentrations from 0 to 3.0 mmol L^-1, Cd sorption percentage by the yellow-cinnamon soil, the yellow-brown soil, and the latosol decreased. The sorption percentage of Cd by the yellow-clnnamon soil and generally the yellow-brown soil （permanent-charge soils） decreased with an increase in tartrate concentration, but increased at low tartrate concentrations for the red soil and the latosol. Curves of percentage of Cd sorption for citrate were similar to those for tartrate. For the variable-charge soils with tartrate and citrate, there were obvious peaks in Cd sorption percentage. These peaks, where organic acids had maximum influence, changed with soil type, and were at a higher organic acid concentration for the variable-charge soils than for the permanent charge soils. Addition of cadmium after tartrate adsorption resulted in higher sorption increase for the varlable-charge soils than permanent-charge soils. When tartrate and Cd solution were added together, sorption of Cd decreased with tartrate concentration for the yellow-brown soil, but increased at low tartrate concentrations and then decreased with tartrate concentration for the red soil and the latosol.

Impacts of soil organic matter, pH and exogenous copper on sorption behavior of norfloxacin in three soils

Norfloxacin sorption and the factors （soil organic matter （SOM）, pH, and exogenous copper （Cu） influencing the sorption were investigated in a black soil （soil B）, a fluvo-aquic soil （soil F）, and a red soil （soil R）. With increasing norfloxacin concentrations, sorption amount of norfloxacin increased in both the bulk soils and their SOM-removed soils, but the sorption capacity of SOM-removed soils was higher than that of their corresponding bulk soils, indicating that the process of norfloxacin sorption in soil was influenced by the soil properties including SOM. The sorption data in all bulk soils and SOM-removed soils were fitted to Freundlich and Langmuir models. The correlation coefficients suggested that the experimental data fitted better to Freundlich equation than to Langmuir equation. Furthermore, the data from soil F and SOM-removed F could not be described by Langmuir equation. The norfloxacin sorption amount decreased in soil B and soil F, whereas it increased in soil R as solution pH increased. The maximum KD and Koc were achieved in soil R when the equilibrium solution pH was 6. The norfloxacin sorption was also influenced by the exogenous Cu^2＋, which depended on the soil types and Cu^2＋ concentrations. With increasing Cu^2＋ concentrations in solution, generally, sorption amount, KD and Koc for norfloxacin in soils increased and were up to a peak at 100 mg/L Cu^2＋, and then the sorption amount decreased regardless of norfloxacin levels.

Sorption of dissolved organic matter and its effects on the atrazine sorption on soils

The dissolved organic matter(DOM), water soluble organic matter derived from sewage sludge was separated into hydrophobic fraction(Ho) and hydrophilic fraction(Hi). The sorption of DOM and its fractions on soils and the effects of DOM sorption on a nonionic pesticide(atrazine(2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine)) distribution between soil and water were investigated using a batch equilibrium technique. The total DOM sorption on soils described by the Langmuir equation reached saturation as the DOM concentration increased. The sorption of Ho fit the Freundlich model. In contrast, a negative retention evidently occurred as adding Hi at higher level in tested soils. The sorption of Ho dominated the total DOM sorption and the release of soil organic matter(SOM). Effects of DOM on the atrazine sorption by soils were DOM-concentration dependent and dominated by the interaction of atrazine, DOM, and soil solids. Generally, the presence of DOM with lower concentration promoted atrazine sorption on soils, namely the apparent partitioning constant(K*_d) for atrazine sorption in the presence of DOM was larger than the distribution constant(K_d) without DOM; whereas the presence of DOM with higher concentration inhibited atrazine sorption(i.e., K*_d<K_d). The overall effects of DOM on atrazine sorption in soils might be related to the DOM sorption and the release of soil intrinsic organic matter into aqueous solution. The sorption of Ho on soils promoted the atrazine sorption on soil, while the release of SOM by Hi and the competitive sorption between Hi and atrazine on soil surface led to a decrease of atrazine sorption. Information provided in this work may contribute to a better understanding of the DOM sorption and its impacts on the contaminant soil-water distribution.

Chemical Behavior of Cadmium in Purple Soil as Affected by Surfactants and EDTA

A soil batch experiment was conducted to investigate both separate and compound effects of three types of surfactants: anionic dodecylbenzene sulfonic acid sodiumsalt (DBSS), cationic cetyltrimethylammonium bromide (CTAB), and non-ionic nonyl phenol polyethyleneoxy ether (TX-100), as well as ethylenediaminetetraacetic acid (EDTA) on cadmium solubility, sorption kinetics, and sorption-desorption behavior in purple soil. The results indicated that both individual application of the three types of surfactants and surfactants combined with EDTA could stimulate Cd extraction from the soil with a general effectiveness ranking of EDTA/TX-100 > EDTA/DBSS > EDTA/CTAB > EDTA > TX-100 > DBSS > CTAB. Further study showed that the compound application of surfactants and EDTA had stronger (P < 0.05) effects on Cd solubility than those added individually. The application of surfactants and EDTA to purple soil (P < 0.05) decreased the proportion of Cd sorbed, while their effectiveness ranking was similar to that of enhanced solubilization. The sorption kinetics of Cd in purple soil was best described by the double-constant equation, while the Freundlich equation gave an excellent fit to the sorption isotherm curves. Therefore, surfactant-enhanced remediation of Cd contaminated soil is feasible and further research should be conducted.

Effects of dissolved organic matter from sewage sludge on sorption of tetrabromobisphenol A by soils

Sorption of tetrabromobisphenol A (TBBPA) by soil influences its fate and transport in the environment. The presence of dissolved organic matter (DOM) may complicate the sorption process in soil. The effects of DOM from sewage sludge on TBBPA sorption by three soils were investigated using batch equilibration experiments in the study. DOM was observed to be sorbed on the soils and the isotherms could be fitted by the Langmuir model. The effects of DOM on TBBPA sorption were dependent on the characteristics ...

Freeze-thaw Effects on Sorption/Desorption of Dissolved Organic Carbon in Wetland Soils

The effects of freeze-thaw cycles on sorption/desorption of dissolved organic carbon （DOC） in two wetland soils and one reclaimed wetland soil were investigated. DOC concentrations added were 0-600 mg/L. Laboratory incubations of sorption/desorption of DOC had been carried out at -15℃ for 10 h, and then at ＋5℃ for 13 h. Soil samples were refrozen and thawed subsequently for 5 cycles. Initial Mass model was used to describe sorption behavior of DOC. The results indicate that freeze-thaw cycles can significantly increase the sorption capacity of DOC and reduce the desorption capacity of DOC in the three soils. The freeze-thaw effects on desorpfion of DOC in soils increase with the increasing freeze-thaw cycles. The conversion of natural wetlands to soybean farmland can decrease the sorption capacity and increase the desorption capacity of DOC in soils. Global warming and reclamation may increase DOC release, and subsequently increase the loss of carbon and the emission of greenhouse gas.

Numerical simulation of PAHs sorption/desorption on soil with the influence of Tween80

In this paper, the influences of inionic surfactant Tween80 on polycyclic aromatic hydrocarbons （PAHs） sorption/desorption on artificially contaminated soil were studied, and γ model was applied to simulate the influences. Results showed that, with the use of Tween 80, the sorption behaviors of PAHs on soil altered significantly. Adsorbed Tween 80 increased the sorption amount of PAHs while the dissolved Tween80 increased the apparent solubility of PAHs. These two processes exert influences on the sorption coefficient of PAHs in soil-water system, which can be depicted by apparent sorption coefficient. The partition coefficients （the soil/water partition coefficient of PAHs and surfactants obtained fxom sorption experiments） and statistical parameters used in the amended γ model were obtained in independent experiments. With these parameters, the γ model could provide a satisfactory independent prediction of PAHs release from soil to aqueous phase at two surfactant concentrations.

Effect of biosurfactant on the sorption of phenanthrene onto original and H_2O_2-treated soils

The objective of this study was to examine the effect of biosurfactant on the sorption of phenanthrene （PHE） onto the original or HzO2-treated black loamy soil （typic isohumisols） and red sandy soil （typic ferralisols）. The sorption isotherms were performed with the original and ＂soft＂ carbon-removed soils in the presence and absence of biosurfactant （200 mg/L）. The sorption and degradation of biosurfactant were investigated. The result showed that organic matter played an important role in PHE sorption onto the black loamy and red sandy soils, and the PHE sorption isotherms on the ＂soft＂ carbon-removed soils exhibited more nonlinearity than those on the original soils. The values of partition coefficient （Kd） on the original black loamy soil with or without 200 mg/L biosurfactant were 181.6 and 494.5 mL/g, respectively. Correspondingly, in the red sandy soil, Kd was 246.4 and 212.8 mL/g in the presence or absence of biosurfactant, respectively. The changes of Kd suggested that biosurfactant inhibited PHE sorption onto the black loamy soil, but facilitated PHE sorption onto the red sandy soil. The nonlinearity of PHE sorption isotherm was decreased in the presence of biosurfactant. Site specific sorption might occur during PHE sorption onto both the original and the ＂soft＂ carbon-removed soils in the presence of biosurfactant. It was noted that biosurfactant could also be sorbed onto soils. The maximal sorption capacity of the red sandy soil for biosurfactant was （76.9 ± 0.007） μg/g, which was 1.31 times that of black loamy soil. Biosurfactant was degraded quickly in the two selected soils, and 92% of biosurfactant were mineralized throughout the incubation experiment for 7 d. It implied that biosurfactant should be added frequently when the remediation of polycyclic aromatic hydrocarbon （PAH）-contaminated soils was conducted through PAH desorption approach facilitated by biosurfactant.

Effects of free iron oxyhydrates and soil organic matter on copper sorption-desorption behavior by size fractions of aggregates from two paddy soils

Effects of free iron oxyhydrates （Fed） and soil organic matter （SOM） on copper （Cu^2＋） sorption-desorption behavior by size fractions of aggregates from two typical paddy soils （Ferric-Accumulic Stagnic Anthrosol （Soil H） and Gleyic Stagnic Anthrosol （Soil W）） were investigated with and without treatments of dithionite-citrate-bicarbonate and of H2O2. The size fractions of aggregates were obtained from the undisturbed bulk topsoil using a low energy ultrasonic dispersion procedure. Experiments of equilibrium sorption and subsequent desorption were conducted at soil water ratio of 1：20, 25℃. For Soil H, Cu^2＋ sorption capacity of the DCB-treated size fractions was decreased by 5.9% for fine sand fraction, by 40.4% for coarse sand fraction, in comparison to 2.9% for the bnlk sample. However, Cu^2＋ sorption capacities of the H2O2-treated fractions were decreased by over 80% for the coarse sand fraction and by 15% for the clay-sized fraction in comparison to 88% for bulk soil. For Soil W, Cu^2＋ sorption capacity of the DCB-treated size fraction was decreased by 30% for the coarse sand fraction and by over 75% for silt sand fraction in comparison to 44.5% for the bulk sample. Cu^2＋ sorption capacities of the H2O2-treated fractions were decreased by only 2.0% for the coarse sand fraction and by 15% for the fine sand fraction in comparison to by 3.4% for bulk soil. However, Cu^2＋ desorption rates were increased much in H2O2-treated samples by over 80% except the clay-sized fraction （only 9.5%） for Soil H. While removal of SOM with H2O2 tendend to increase the desorption rate, DCB- and H2O2-treatments caused decrease in Cu^2＋ retention capacity of size fractions, Particularly, there hardly remained Cu^2＋ retention capacity by size fractions from Soil H after H2O2 treatment except for clay-sized fraction. These findings supported again the dominance of the coarse sand fraction in sorption of metals and the preference of absorbed metals bound to SOM in differently stabilized status among the size fractions. Thus, enrichment and turnover of SOM in paddy soils may have great effects on metal retention and chemical mobility in paddy soils.

pH Effect on kinetics of Heavy Metal Sorption in Soils

The pH effect on the sorption kinetics of heavy metals in soils was studied using a Constant flow leaching method. The soil samples were red soil collected from Yingtan, Jiangxi, and yellow-browp soil from Nabing,Jiangsu. The heavy metals tested were zinc and cadmium.Assuming that the experimental data fitted to the following kinetic rate equation: 1/c dx/dt=kx∞-kx,the rate constant k of sorption could be determined from the slope of the straight line by plotting of 1/c.dx/dt vs. x. The results showed that the pH effect on the rate constants of heavy mental sorption in soils was very significant. The values of k decreased with inpeasing pH. The sorptions were more sensitive to pH in red soil than in yellow-brown soil.

Kinetics of Sorption of Pendimethalin on Soil Samples Obtained from the Banks of Rivers Katsina-Ala and Benue, Central Nigeria

Kinetics of the sorption of the herbicide, pendimethalin (3,4-Dimethyl-2,6-dinitro-N-pentan-3-yl-aniline) on four soil samples obtained from the banks of Rivers Benue and Katsina-Ala, in Central Nigeria was studied by contacting 5.0 g soil samples with 100 mL 7 × 10-6 M herbicide solution. The sorption was monitored by following the herbicide concentration in the aqueous phase spectrophotometrically at one hour intervals for 5 hours (at 25°C, 35°C, 45°C, 55°C and 65°C, respectively). Pseudo-first order kinetics treatment of the data showed that sorption rates as well as the accompanying activation energies were low, indicating that physical adsorption is the operative mechanism for its retention in the soils and that the herbicide tended to reside more in the aqueous phase, which raised its potential to contaminate natural water systems, when applied on the field.

Utilizing surfactants to control the sorption,desorption, and biodegradation of phenanthrene in soil-water system

An integrative technology including the surfactant enhanced sorption and subsequentdesorption and biodegradation of phenanthrene in the soil-water system was introduced and tested. For slightly contaminated agricultural soils, cationic-nonionic mixed surfactant- enhanced sorption of organic contaminants onto soils could reduce their transfer to plants, therefore safe-guarding agricultural production. After planting, residual surfactants combined with added nonionic surfactant could also promote thedesorption and biodegradation of residual phenanthrene, thus providing a cost-effective pollution remediation technology.0ur results showed that the cationic-nonionic mixed surfactantsdodecylpyridinium bromide （DDPB） and Triton X-100 （TX100） significantly enhanced soil retention of phenanthrene. The maximum sorption coefficient Kd＊ of phenanthrene for contaminated soils treated by mixed surfactants was about24.5 times that of soils without surfactant （Kd ） and higher than the combined effects of DDPB and TX100 individually, which was about 16.7 and 1.5 times Kd , respectively.0n the other hand, TX100 could effectively remove phenanthrene from contaminated soils treated by mixed surfactants, improving the bioavailability of organic pollutants. Thedesorption rates of phenanthrene from these treated soils were greater than 85% with TX100 concentration above2000 mg/L and approached 100% with increasing TX100 concentration. The biodegradation rates of phenanthrene in the presence of surfactants reached over 95% in30days. The mixed surfactants promoted the biodegradation of phenanthrene to some extent in 10-22days, and had no obvious impact on phenanthrene biodegradation at the end of the experiment. Results obtained from this study provide some insight for the production of safe agricultural products and a remediation scheme for soils slightly contaminated with organic pollutants.

Use of two-surfactants mixtures to attain specific HLB values for assisted TPH-diesel biodegradation

In a surfactant assisted biodegradation process, the choice of surfactant(s) is of crucial importance. The question is: does the type of surfactant(i.e. chemical family) affect the biodegradation process at fixed hidrophillic-lypofillic balance(HLB) values? Microcosm assessments were developed using contaminated soil, with around of 5000 mg/kg of hydrocarbons as TPH-diesel. Mixtures of three nonionic surfactants were employed to get a wide range of specific HLB values. Tween20 and Span20 were mixed in the appropriate proportions to get HLB values between 8.6 and 16.7. Tween/Span60 mixtures reached HLB values between 4.7 and 14.9. Finally, Tween/Span80 combinations yielded HLB values between 4.3 and 15. TPH-diesel biodegradation was measured at the beginning, and after 8 weeks, as well as the FCU/gr soil, as a measure of microorganisms′ development during the biodegradation period. A second aim of this work was to assess the use of guar gum as a biodegradation enhancer instead of synthetic products. The conclusions of this work are that surfactant chemical family, and not only the HLB value clearly affects the assisted biodegradation rate. Surfactant's synergism was clearly observed. Regarding the use of guar gum, no biodegradation enhancement was observed for the three assessed concentrations, i.e., 2, 20, and 200 mg/kg, respectively. On the contrary, TPH-diesel removal was lower as the gum concentration increased. It is quite possible that guar gum was used as a microbial substrate.