Sorption Of Linear Alkylbenzene Sulfonates Research Articles

Competitive sorption of linear alkylbenzene sulfonate (LAS) surfactants and the antibiotics sulfamethoxazole and ciprofloxacin in wastewater-irrigated soils of the Mezquital Valley, Mexico

The increasing reuse of wastewater for irrigation introduces surfactants and antibiotics into the environment. How these two kinds of compounds interact with regard to their sorption processes in soil is not clear. We performed batch experiments to investigate the sorption of linear alkylbenzene sulfonates (LAS) and its effect on sorption of sulfamethoxazole and ciprofloxacin in irrigated and non-irrigated soils with different organic matter (OM) contents. LAS sorption was non-linear in the presence of the antibiotics, and as general trend, it increased with rising OM content of soils. Free LAS was also removed from solution by complexation with Ca2+. Dissolved organic compounds released from soils with OM contents ≥18.4 g kg−1 further reduced LAS sorption. Sorption of sulfamethoxazole was reduced by LAS sorption only in one soil with a small OM content of 9.5 g kg−1. The strong sorption of ciprofloxacin is not affected by LAS. Sulfamethoxazole sorption only competes with LAS sorption in organic matter-poor soils. Accumulation of organic matter in soils, for example due to long-term wastewater irrigation, provides extra sorption capacity for LAS and sulfamethoxazole so that competition for sorption sites is reduced.

Sorption of Linear Alkylbenzene Sulfonate (LAS) onto El-Mex Bay Sediments, Mediterranean Sea, Egypt

The objective of this work is to study the sorption behavior of Linear Alkylbenzene sulfonate (LAS) onto El-Mex Bay sediments. The Bay is a part of Alexandria coast on the Mediterranean Sea located in Northern Egypt. The study showed homogenous distributions of LAS homologues in El-Mex Bay sediments. The range of the LAS concentration in sediments was between 0.370 and 0.540 μgg-1 dry solids. High total LAS concentrations in the bay sediments coincide with small amounts of DO (0.5-1.9 mgl-1) and low Eh values. The LAS homologues were usually detected between 10 and 13 carbon atoms, with C11- and C12-LAS; they are the most adsorbed on the bay sediments. Sorption experiments on the Bay sediments were performed with different organic matter content (ranged from 0.9 to1.16%) and were applied at different pH values (3.8, 8.5 and 12). The sorption behavior of LAS on El-Mex Bay sediments is satisfactory described by the Freundlich and Stern-Graham isotherm equations. Based on the data presented in this work, the following conclusion was drawn: Sorption distribution coefficients were significantly increased with the increasing the organic matter content due to the hydrophobic interaction between the alkyl chain and organic carbon content of the sediment. LAS sorption on sediments was strongly affected by pH and decreased with increasing pH value for each sediment sample which can be attributed either to electrostatic interactions or to specific chemical interactions.

Fate of linear alkylbenzene sulfonate in agricultural soil columns during inflow of surfactant pulses

The transport and reaction processes of linear alkylbenzene sulfonate (LAS) were characterised in columns of agricultural soil with a constant inflow of irrigation water. A pulse input of commercial LAS was performed with different mixtures of soil and sea sand (0/100%, 25/75% and 50/50%) and a continuous water flow of approximately 0.5 mL/min. LAS homologue retention was favoured at a higher soil rate, due mainly to higher clay and organic matter contents. C 10LAS and C 11LAS were less retained in soil columns, and were eluted faster and in higher proportion through soil columns than other homologues. C 12LAS and C 13LAS showed stronger interactions with soil due to their higher sorption capacity, and a lower proportion was eluted than the lightest homologues. In general, sorption of LAS was reversible and significant fractions were desorbed when the LAS input ceased and they were transported to deeper layers in the soil column, especially for short-chain homologues. Longer LAS homologues were eluted from soil columns, but required an elution of >10 pore-volumes. When there was biodegradation in the soil column, >25% of LAS could be removed, reducing percolation to deeper layers.

Effect of sediment properties on the sorption of C 12-2-LAS in marine and estuarine sediments

Linear alkylbenzene sulfonates (LAS) are anionic high production volume surfactants used in the manufacture of cleaning products. Here, we have studied the effect of the characteristics of marine and estuarine sediments on the sorption of LAS. Sorption experiments were performed with single sediment materials (pure clays and sea sand), with sediments treated to reduce their organic carbon content, and with field marine and estuarine sediments. C 12-2-LAS was used as a model compound. Sorption to the clays montmorillonite and kaolinite resulted in non-linear isotherms very similar for both clays. When reducing the organic content, sorption coefficients decreased proportionally to the fraction removed in fine grain sediments but this was not the case for the sandy sediment. The correlation of the sediment characteristics with the sorption coefficients at different surfactant concentrations showed that at concentrations below 10 μg C 12-2-LAS/L, the clay content correlated better with sorption, while the organic fraction became more significant at higher concentrations.

Equilibrium partitioning theory to predict the sediment toxicity of the anionic surfactant C 12-2-LAS to Corophium volutator

The study of the effect of the sorption of linear alkylbenzene sulfonates (LAS) on the bioavailability to marine benthic organisms is essential to refine the environmental risk assessment of these compounds. According to the equilibrium partitioning theory (EqP), the effect concentration in water-only exposure will be similar to the effect concentration in the sediment pore water. In this work, sorption and desorption experiments with two marine sediments were carried out using the compound C 12-2-LAS. The effect of the sediment sorption on the toxicity of benthic organisms was studied in water-only and in sediment bioassays with the marine mud shrimp Corophium volutator. In addition, three common spiking methods were tested for its application in the toxicity tests, as well as the stability of the surfactant during the water-only and sediment–water test duration. LC50 values obtained from water-only exposure showed a good correspondence with the pore water concentrations calculated from the sorption and desorption isotherms in the spiked sediments.

Sorption of sodium dodecylbenzene sulfonate by montmorillonite

Sorption of linear alkylbenzene sulfonates by soils and sediments is an important process that may affect their fate, transport, toxicity and their application in remediation of contaminated soil and groundwater. In this study, batch experiments were conducted to elucidate the sorption of a widely used anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), by montmorillonite. It was observed that: (i) SDBS was sorbed significantly by montmorillonite saturated with Ca 2+, but little by Na-saturated montmorillonite; (ii) the amount of SDBS sorbed by Ca 2+–montmorillonite was enhanced by NaCl; and (iii) no significant intercalation of SDBS into Ca 2+–montmorillonite was observed by X-ray diffraction (XRD) analysis. These results indicate that the removal of SDBS by Ca 2+–montmorillonite was primarily attributed to the precipitation between DBS − and Ca 2+ in solution which was released from montmorillonite via cation exchange. These results will help us to understand the sorption behavior and environmental effects of anionic surfactants.

Inhibition of Biogas Production by Alkyl Benzene Sulfonates (LAS) in a Screening Test for Anaerobic Biodegradability

The effect of the inoculum source on the digestion of linear alkylbenzene sulfonates (LAS) under anaerobic conditions has been investigated. The potential for primary and ultimate LAS biodegradation of anaerobic sludge samples obtained from wastewater treatment plants (WWTPs) of different geographical locations was studied applying a batch test system. It was found that only 4-22% of the LAS added to the batch anaerobic digesters was primarily transformed suggesting a poor primary degradation of the LAS molecule in anaerobic discontinuous systems. Regarding ultimate biodegradation, the addition of LAS to the batch anaerobic digesters caused a reduction on the extent of biogas production. Significant differences in the inhibition extent of the biogas production were observed (4-26%) depending on the sludge used as inoculum. Effect of the surfactant on the anaerobic microorganisms was correlated with its concentration in the aqueous phase. Sorption of LAS on anaerobic sludge affects its toxicity by depletion of the available fraction of the surfactant. LAS content on sludge was related to the total amount of calcium and magnesium extractable ions. The presence of divalent cations promote the association of LAS with anaerobic sludge reducing its bioavailability and the extent of its inhibitory effect on the biogas production.

Sorption of linear alkylbenzene sulfonate to soil components and effects on microbial iron reduction

When sewage sludge is applied to arable land, linear alkylbenzene sulfonate (LAS) is released into the environment. In soils, LAS has been shown to impede microbial processes, such as bacterial iron reduction. The aim of the present study was to quantify LAS adsorption and desorption to agricultural soils and iron oxides and relate this to the inhibition of microbial iron reduction. Two agricultural soils were used, namely, Askov (coarse sandy loam soil) and Lundgaard (coarse sandy soil). In both soils, LAS inhibited microbial iron reduction even at low LAS concentrations with 10% effect concentrations of 6 to 7 and 26 to 32 mg LAS/kg dry-weight soil for Lundgaard and Askov soil, respectively. The sorption isotherms showed that sorption of LAS to iron oxides was 10 to 100 times stronger than sorption to the agricultural soils. Also, it appeared that at low LAS concentrations (< 10 mg/kg dry-wt soil), Lundgaard soil adsorbed approximately 10 times more LAS than Askov soil. Thus, the inhibitory effect of LAS on microbial iron reduction was highest in the Lundgaard soil, which exhibited both the strongest sorption and the lowest desorption of the two soils. A possible hypothesis to explain this correlation was that LAS toxicity toward bacterial iron reduction was, at least partly, caused by LAS adsorbed to iron oxides, which could interfere with transfer of electrons between the bacteria and their respiratory electron acceptor.

Structure-activity relationships for association of linear alkylbenzene sulfonates with activated sludge.

Sorption of linear alkylbenzene sulfonates (LAS) on sludge particles from wastewater treatment plants was studied. The effect of alkyl chain length and the water hardness were investigated. Sorption on sludge increases with increasing alkyl chain length in the LAS molecules. The results are interpreted in terms of a hydrophobic bonding mechanism being the critical micelle concentration a good index of the surfactant hydrophobicity. The increase in free energy of adsorption for the addition of successive methylene groups to the alkyl chain was estimated as 2.4 kJ/mol. Water hardness clearly enhances the sorption of LAS homologues on sludge and seems to promote cooperative sorption at high surfactant and calcium ion concentrations. An empirical equation was provided that allow to estimate the partition coefficient between aqueous and solid phases for LAS homologues as a function of the alkyl chain length and the water hardness.

Laboratory and Field Investigation of Surfactant Sorption Using Single‐Well, “Push‐Pull” Tests

AbstractSorption to aquifer sediments can limit the effectiveness of surfactants injected to solubilize residual nonaqueous phase liquid contaminants in the subsurface. The objective of this study was to evaluate the ability of the single‐well, push‐pull test to characterize sorption of linear alkylbenzene sulfonate (LAS) and hexadecyl diphenyl oxide disulfonate (DOWFAX) surfactants to natural aquifer sediment in situ. Batch sorption isotherms for both surfactants exhibited Langmuir‐type sorption behavior with larger apparent sorption maxima for LAS than for DOWFAX. However, numerical transport simulations based on batch sorption isotherms were unable to predict the retardation and chromatographic separation of LAS homologs and conservative transport of DOWFAX observed during laboratory and field push‐pull tests, indicating that the single‐well, push‐pull test method can more accurately describe in situ surfactant sorption and transport behavior than batch sorption isotherms.

Behavior and fate of linear alkylbenzene sulfonate in different soils

To investigate the behavior of surfactants in soil ecosystems, the sorption of linear alkylbenzenesulfonate on soils from three different areas of Northern Greece and with different organic matter content was studied. LAS sorption on these soils decreased with increasing pH and correlated positively with the organic matter content of the soils.

Sorption of linear alkylbenzenesulfonates (LAS) on marine sediment

The sorption of a commercial-grade linear alkylbenzenesulfonate (LAS) and of its constituent homologous compounds was characterized in marine sediments from the Bay of Cadiz (southwestern Spain). Experimental data were fitted to a Freundlich model. The sorption coefficient K ranged from 96 for the homologue C10-LAS to 1112 for the homologue C13-LAS, with sorption expressed as μgg−1 LAS of sediment and equilibrium LAS concentration as mgl−1. LAS sorption on marine sediment was found to be an irreversible process. K increased substantially with increasing salinity. The relation was linear for the homologue C11-LAS, with a threefold increase in the value of K as salinity increased from 0 to 75.

Chemical fate and transport in a domestic septic system: Sorption and transport of anionic and cationic surfactants

AbstractThe sorption and transport of linear alkylbenzene sulfonate (LAS) and dialkyl quaternary ammonium compounds [ditallow dimethyl ammonium chloride (DTDMAC) and distearyl dimethyl ammonium chloride (DSDMAC)] were determined within the upper soil horizons and in the aquifer below a septic tank tile field at a study site in Ontario. Sorption of LAS was greatest immediately below the tile field (Kd = 17 L/kg) within the upper unsaturated soil horizons and lowest in the aquifer (Kd = 1 L/kg). LAS sorption appeared to be controlled by a hydrophobic mechanism and was positively correlated with the organic carbon (r = 0.9) and the clay content (r = 0.9) in the subsurface environment. The sorption of DTDMAC/DSDMAC (Kd = 25‐62 L/kg) was an order of magnitude higher than LAS but showed no trend throughout the subsurface environment. The retention of DTDMAC/DSDMAC was believed to be by ion exchange within the clay interlayer basal spaces. Samples collected from the field showed concentrations of DTDMAC to range from approximately 60 mg/kg in the tile field gravel to &lt;2 mg/kg within 10 cm of soil below the tile field gravel. Concentrations of LAS were approximately 20 mg/kg in the tile field gravel and diminished to &lt; 1 mg/kg within 5 cm of soil below the tile field gravel. Soil solution and aquifer concentrations of LAS were always &lt;50 μg/L and usually below the detection limit of 10 μg/L in the aquifer. Concentrations of DTDMAC in the aquifer were below the limit of detection (4 μg/L). Mathematical calculations illustrated the importance of biodegradation and sorption as removal mechanisms of these materials in subsurface environments.