Influence of the presence of heavy metals and surface-active compounds on the sorption of bisphenol A to sediment

The effects of different heavy metals (Cd, Pb), cationic surfactants cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecylbenzenesulfonate (SDBS) and the chemistry of the solution (pH and ionic strength) on the sorption of bisphenol A (BPA) to sediment were studied. Results showed that the presence of Cd and Pb caused a significant increase on the sorption of BPA to sediment and the sorption isotherms were in good agreement with Freundlich equation. The effect of surfactants on the adsorption of BPA onto sediment was found to strongly depend on the type of the surfactants. The presence of CTAB promoted BPA sorption and the amount of BPA adsorbed onto sediment increased linearly with concentration of CTAB. In contrast, the presence of anionic surfactant (SDBS) caused a slight reduction on the sorption of BPA. It was also found that the sorption behavior of BPA was affected by solution pH and ionic strength. The larger amount of BPA was absorbed with higher ionic strength and lower pH. This study may provide important insights into the understanding of the transport and fate of BPA in the environment.     

Effect of cationic and anionic surfactants on the sorption and desorption of perfluorooctane sulfonate (PFOS) on natural sediments

Sorption and desorption of PFOS at water-sediment interfaces were investigated in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and an anionic surfactant, sodium dodecylbenzene sulfonate (SDBS). CTAB remarkably enhanced the sorption of PFOS on the sediment. In contrast, the influence of SDBS to the sorption of PFOS was concentration dependent. Two contrasting factors were responsible for the phenomenon. One was the sorption of the surfactant itself to the sediment, which enhanced the sorption of PFOS. The other was the increase in solubility of PFOS caused by the adding of surfactants, which decreased the sorption of PFOS. SDBS had a much lower sorption capacity, but rather strong ability to increase the solubility of PFOS. High levels of SDBS remarkably reduced the sorption of PFOS on the sediment. These results imply that cationic and anionic surfactants may have contrast impacts on the distribution and transport of PFOS in the environment.     

Joint influence of surfactants and humic matter on PAH solubility. Are mixed micelles formed?

Mobilization of polycyclic aromatic hydrocarbons (PAH) by surfactants, present at contaminated sites or deliberately introduced for remediation purposes, is inevitably associated with the influence of humic substances, which are ubiquitous in natural systems. Therefore, the solubilizing effects of anthropogenic and natural amphiphiles must be considered in their combined action since synergistic or antagonistic effects may be expected, for instance, as a consequence of mixed micellization.

In this paper, solubilization of ¹⁴C-labeled pyrene in single-component and mixed solutions of surfactants and humic acid (coal-derived) was investigated up to the micellar concentration range. At low concentrations, antagonistic effects were observed for systems with cationic as well as anionic surfactants. Solubility enhancements in the presence of humic acid were canceled on addition of a cationic surfactant (DTAB) since charge compensation at humic colloids entailed precipitation. Solubility was also found to be decreased in the presence of an anionic surfactant (SDS), which was attributed to a competitive effect in respect of pyrene–humic interaction. This explanation is based on octanol–water partitioning experiments with radiolabeled humic acid, yielding evidence of different interaction modes between humic colloids and cationic/anionic surfactants. At higher concentrations, the effects of humic acid and SDS were found to be additive. Thus, a formation of mixed micelles is very unlikely, which was confirmed by size exclusion chromatography of mixed systems. It can be concluded that remediation measures on the basis of micellar solubilization are not significantly affected by the presence of natural amphiphilic compounds.     

表面活性剂对黄土中石油污染物的解吸影响研究

研究了用表面活性剂去除黄土中柴油类污染物。选用阴离子表面活性剂十二烷基苯磺酸钠和十二烷基硫酸钠 (LAS和SDS)和阳离子表面活性剂十六烷基三甲基溴化铵 (CTAB)对污染的土壤进行解吸实验 ,表明阴离子表面活性剂浓度从 0 .1%增加到 1.0 %时 ,其柴油的去除率可达 2 0 % ,而阳离子表面活性剂去除作用不甚明显。利用摩尔增溶比MSR值求得LAS和SDS的logKm 值为 4.5 5 2和 3 .63 0 ,这和理论的计算值很接近     

Electrochemical destruction of p-chlorophenol and p-nitrophenol -- Influence of surfactants and anode materials

The electrochemical oxidative removal of p-chlorophenol and p-nitrophenol was studied by cyclic voltammetry (CV) and constant current electrolysis on commercially available graphite and titanium substrate insoluble anodes (TSIA). The effect of cationic cetyl trimethylammonium bromide (CTAB), anionic sodium dodecyl sulphate (SDS) and non-ionic polyoxyethylene(23)lauryl ether (Brij-35) surfactants, which prevent adherent film formation on the electrode surface were also studied. CV experiments indicate that p-chlorophenol exhibits a relatively higher tendency for film formation on graphite and that sodium chloride is a better medium for the destruction of phenols. The electrochemical oxidation of phenols under galvanostatic conditions in chloride medium with CTAB enhanced the detoxification process with significantly lower fouling effects on TSIA. The surfactants, however, did not improve phenol removal on graphite under identical experimental conditions. A charge of 2.5F per mol was found to be sufficient to achieve 44-48% removal of phenol on both the electrodes in the absence of the surfactants. A 55-65% removal was achieved in the presence of the cationic surfactant on the TSIA electrode. Phenol was removed as a low molecular weight polymer (MW approximately 4450).     

Phenanthrene partitioning in sediment–surfactant–fresh/saline water systems

The objective of this study was to investigate the influence of salinity on the effectiveness of surfactants in the remediation of sediments contaminated with phenanthrene (PHE). This is an example of a more general application of surfactants in removing hydrophobic organic compounds (HOCs) from contaminated soil/sediment in saline environments via in-situ enhanced sorption or ex-situ soil washing. Salinity effects on surfactant micelle formation and PHE partitioning into solution surfactant micelles and sorbed surfactant were investigated. The critical micelle concentration of surfactants decreased, and PHE partition between surfactant micelles and water increased with increasing salinity. Carbon-normalized partition coefficients (K_ss) of PHE onto the sorbed cationic surfactant increased significantly with increasing salinity, which illustrates a more pronounced immobilization of PHE by cationic surfactant in a saline system. Reduction of PHE sorption by anionic surfactant was more pronounced in the saline system, indicating that the anionic surfactant has a higher soil washing effectiveness in saline systems.     

Benzene removal from waste water using aqueous surfactant two-phase extraction with cationic and anionic surfactant mixtures

A novel separation technique known as an aqueous surfactant two-phase (ASTP) extraction is a promising method to remove organic contaminants from wastewater. When cationic and anionic surfactants are mixed at certain surfactant concentrations and compositions, the solution separates into two immiscible aqueous phases. One is the surfactant-rich and the other is the surfactant-dilute phase. The organic contaminants will solubilize into the surfactant aggregates and concentrate in the small volume surfactant-rich phase. The other phase contains only small amount of surfactants and contaminants as the treated water. Most ASTP studies have used nonionic surfactants above the cloud point. Mixtures of anionic and cationic surfactants can also exhibit aqueous-aqueous phase separation and can be used in the ASTP extraction process. The phase behavior and performance of ASTP extraction using cationic surfactant dodecyltrimethylammonium bromide (DTAB) and anionic surfactant alkyldiphenyloxide di-sulfonate (DPDS) to extract benzene from wastewater was investigated in batch experiments. It was found that phase separation only occurs over a narrow range of molar ratios of DTAB:DPDS from 1.6:1 to 2.4:1. In this study, a 2:1 molar ratio of DTAB:DPDS at which there is no net charge in the surfactant aggregates show the highest extraction efficiency and lowest critical micelle concentration value with greatest synergism (highest negative values of the micellar interaction parameter). At a total surfactant concentration of 50mM, the benzene partition ratio is 48 and 72% of the benzene is extracted into the surfactant-rich phase solution in a single stage extraction, which is superior performance compared to ASTP extraction using nonionic surfactants.     

Effect of surfactants at low concentrations on the sorption of atrazine by natural sediment.

A series of experiments were carried out to determine the effect of surfactants at low concentrations on the sorption of atrazine by natural sediments. With surfactant concentrations ranging from 0 to 20 mg/ L, anionic and cationic surfactants appreciably reduce the adsorption of atrazine, while nonionic surfactant decreases the adsorption of atrazine at concentrations equal to or less than 1 mg/L and increases adsorption at higher concentrations. Desorption of atrazine in the presence of different sodium dodecylbenzene sulfonate (SDBS) concentrations shows that a portion of the bound pesticide resists desorption in the SDBS free system. However, the addition of SDBS accelerates the desorption of atrazine. Furthermore, the nature of sediment and the contacting sequence of SDBS, at 10 mg/L, with the sediment, also influence the adsorption of atrazine. The conclusions in this study could be explained partially by the effect of the type and concentration of surfactants and the characteristics of sediments.     

Effect of surfactants on desorption of aldicarb from spiked soil

Surfactant enhanced desorption of aldicarb from spiked soil was investigated in this paper. Anionic (sodium dodecyl benzene sulphonate, SDBS), cationic (hexadecyl trimethyl ammonium bromide, HTAB) and nonionic (octyl polyethylene glycol phenyl ether, OP) surfactants were tested to determine their optimal desorption conditions including desorption time, mixing speed and surfactant concentrations. The results showed that the optimal operating conditions were obtained at 2 h, 150 rpm, and surfactants concentrations were 1000, 100, and 200 mg l(-1) for SDBS, OP, and HTAB, respectively. The paper also investigated the desorption efficiency of mixture of different kinds of surfactants for aldicarb-spiked soil, and found that anionic-nonionic surfactant mixtures gave the best desorption efficiency up to 77%, while anionic-cationic surfactant mixture gave a poor desorption efficiency similar to water, suggesting that mixture of anionic-nonionic surfactants were highly promising on remediation of aldicarb-contaminated soil.     

胶束强化超滤去除水中双酚A

采用截留分子量(MWCO)为5000 Dalton、1000 Dalton的聚砜超滤膜,MWCO为1 kDa的再生纤维素超滤膜;采用十二烷基苯磺酸钠(SDBS)、曲拉通100(TritonX-100)、吐温80(Tween-80)、烷基多苷(APG)为表面活性剂,用胶团强化超滤工艺去除水中双酚A。研究了不同材质和截留分子量的超滤膜、表面活性剂浓度、膜操作压力、溶液pH和溶液中电解质等因素对该工艺的影响。结果表明,SDBS对双酚A有较好的去除效果,去除率在80%以上。在H+和Na+存在的条件下,双酚A的截留率增加,透过液中SDBS浓度降低。SDBS与非离子表面活性剂的复配可以提高双酚A截留率,降低透过液中SDBS的浓度,复配效果优劣顺序为Tween-80TritonX-100APG。     

Application of the headspace CO2 method (ISO 14 593) to the assessment of the ultimate biodegradability of surfactants: results of a calibration exercise

In the recent review of the control of marketing surfactants used in detergents, the EU decided to increase the severity of the testing procedure by using the criterion of ultimate biodegradability (mineralization) rather than primary biodegradation (removal of the parent molecule) to ensure that possible harmful organic metabolites do not reach the environment. The relatively new ISO headspace CO2 test, considered to be an improvement on the OECD 301B (Sturm CO2) test was chosen. The method was subjected to a ring test by 11 laboratories using one of each of four classes of surfactants plus a poorly degradable reference surfactant; all laboratories satisfactorily applied the method. The necessary addition of silica gel to the medium containing the cationic surfactant, known as a class to be more inhibitory than other classes, was confirmed as a technique for avoiding inhibition of the inoculum. The biodegradability of the surfactants was in general agreement with results reported in the literature and the often reported variable values of % inorganic carbon (IC) produced of the theoretical was found. The anionic and cationic surfactants were readily biodegradable (%IC > 60), the non-ionic surfactant was well below the pass value, while the amphoteric was borderline. The IC production by the blank controls, one of the validity criteria, was about 0.3 mg C/100 ml test medium, equivalent to 3 mg C/l, as recommended in the ISO text. Mild conditions of pre-exposure of the inoculum to the test surfactant did not produce consistent worthwhile effects on either the percentage biodegradation or on its variability.     

Solvent and surfactant enhanced solubilization, stabilization, and degradation of amitraz

In an effort to help with the development of effective dip vat management and waste disposal strategies this study determined how solution properties such as pH, buffer composition, ionic strength, temperature, solubility in organic solvents and the addition of commonly used solubilizing agents influenced the hydrolysis of amitraz. Amitraz degrade by means of hydrolysis described by a pseudo-first order rate process and a type ABCD pH rate profile. Hydrolysis increased with temperature and was fastest at low pH, slowest at neutral to slightly alkaline pH, and slightly increased above pH 10. However, buffer concentration and ionic strength influenced the hydrolysis rate and had to be accounted for before constructing a pH rate profile. Hydrolysis seems to depend on the dielectric constant of solvent mixtures and was fastest in water, slower in propylene glycol and ethanol solutions, and slowest in DMSO mixtures. In surfactant solutions, anionic micelles enhanced and cationic micelles retarded the hydrolysis rate. The magnitude of micellar effects decreased with increasing concentrations of the surfactants. The increased solubility and faster hydrolysis of amitraz in the sodium lauryl sulfate solutions showed that anionic surfactants potentially could be used for cleaning up amitraz spills, because it both solubilized the drug and catalyzed hydrolysis.     

胶团强化超滤法(MEUF)去除废水中氯苯的研究

研究了3种单一表面活性剂十二烷基硫酸钠(SDS)、十六烷基三甲基溴化铵(CTMAB)、聚氧乙烯失水山梨脂肪酸酯醇醚(TW80)和混合表面活性剂TW80-SDS对氯苯(CB)的强化超滤,以期为有机废水胶团强化超滤技术提供参考。结果表明,进料液静置时间对去除率无显著影响,而振荡时间在1 h后对去除率影响不大。氯苯的去除率随进料液中表面活性剂浓度的增大而增大,单一的表面活性剂对氯苯的去除效果顺序为TW80CTMABSDS,且表面活性剂对氯苯的去除效果与表面活性剂的临界胶束浓度值(CMC)、亲水-亲油平衡值(HLB)呈负相关。阴-非混合表面活性剂TW80-SDS对氯苯的去除效果明显强于单一的SDS,且去除率随着非离子表面活性剂质量分数的增加而增加。渗透通量随着进料液中表面活性剂浓度的增加而下降,单一表面活性剂种类对渗透通量的影响顺序为SDSTW80CTMAB,混合表面活性剂中随着非离子表面活性剂质量分数的增加而渗透液的渗透通量越低。     

Sorption of anionic surfactants on a fixed bed of rubber granules

The performance of a fixed-bed adsorber (FBR) column for the removal of anionic surfactants from aquatic environments has been studied. Waste tyre rubber granules were used as the adsorbent material, and sodium dodecyl sulfate, an anionic surfactant, as the adsorbate. The FBR column design parameters were evaluated using the column breakthrough data at different bed depths. The Bohert and Adams model was used with the bed depth service time approach for the design of the column. The bed efficiency obtained was 90.97%.     

Effect of synthetic cationic surfactants on dewaterability and settleability of activated sludge

Dimeric cationic surfactants with different lengths of carbon chains were synthesised, and then these surfactants were added to the activated sludge samples to evaluate the dewaterability and settleability. The adsorbability of cationic surfactants on activated sludge was also studied. By comparing the dewatering performances of different cationic surfactants, the effect mechanisms of cationic surfactant are elucidated. The dimeric cationic surfactants can not significantly improve the filtration performance of activated sludge, however, they can apparently decrease the moisture content in filtration cake and bound water content.     

Removal of vaporous naphthalene using polyoxyethylenated nonionic surfactants

Previous research has demonstrated that an anionic surfactant can increase the solubility of the vapor phases of both naphthalene and sulfur dioxide in water. This study examines the feasibility of removing polycyclic aromatic hydrocarbons (PAHs) during gas absorption by adding the polyoxyethylenated nonionic surfactants tetraethylene glycol monodecyl ether (C10E4), octaethylene glycol monodecyl ether (C10E8), and octaethylene glycol monotetradecyl ether (C14E8), to water. The apparent solubility and absorption rates of naphthalene in surfactant solution were slightly higher than in pure water at a concentration lower than the critical micelle concentration (CMC). However, the apparent equilibrium naphthalene solubility increased linearly in proportion to the concentrations of nonionic surfactants because of the solubilization effect of micelles at concentrations above the CMC. The solubilization effect exceeded that of the reduced mass transfer coefficient, increasing the rate of absorption of vaporous naphthalene. For the four surfactants, the capacity to solubilize naphthalene was in the order C10E4 > C14E8 > C10E8 > sodium dodecyl sulfate (SDS) and was related to the hydrophile-lipophile balance values of the surfactants. The enrichment factors, which can express the degree of naphthalene solubility in solution, were 6.09-14.2 at a surfactant concentration of 0.01 M for the three polyoxyethylenated nonionic surfactants. Empirical findings confirm that adding nonionic surfactants increases the absorption efficiency of hydrophobic organic compounds (HOCs) using spray or packed tower.     

Partitioning of naphthalene to gemini surfactant-treated alumina

Partitioning of naphthalene to anionic surfactants adsorbed on alumina in the aqueous phase was studied for immobilization of the contaminant in the subsurface. Three anionic surfactants with different molecular structures were used: a conventional (sodium dodecylbenzene sulfonate, SDDBS), a gemini (dialkylated disulfonated diphenyl oxide with alkyl chain length of 12, DADS-C12), and a dianionic (monoalkylated disulfonated diphenyl oxide with alkyl chain length of 12, MADS-C12). Sorption of the surfactants onto alumina was studied in a series of batch experiments and the effectiveness of the adsorbed surfactants onto aluminum oxide as a sorptive phase for naphthalene was compared.     

Binding of dialkylated disulfonated diphenyl oxide surfactant onto alumina in the aqueous phase

Adsorption of a gemini surfactant that has two monomers and a spacer in a molecule (dialkylated disulfonated diphenyl oxide with alkyl chain lengths of twelve, DADS-C12) onto positively-charged aluminum oxide in water was studied and compared with a single-monomer anionic surfactant (sodium dodecylbenzene sulfonate, SDDBS). More mass of the gemini surfactant was adsorbed than the conventional single-monomer SDDBS. Fewer moles of the first were bound to the substrate than the second indicating that larger molecular structure of the gemini surfactant does not hinder the sorption. Both surfactants followed similar sorption mechanisms, however, stronger hydrophobic interactions were shown in the bilayer formation of the adsorbed gemini surfactant.     

Influence of anionic, cationic and nonionic surfactants on adsorption and desorption of oxytetracycline by ultrasonically treated and non-treated multiwalled carbon nanotubes

High adsorption capacity of carbon nanotubes (CNTs) may greatly determine the bioavailability and mobility of organic contaminants. The fate of contaminants adsorbed by CNTs may be substantially influenced by surfactants used both in the synthesis and dispersion of CNTs. The aim of this research was to determine the influence of surfactants (nonionic - TX100, cationic - CTAB and anionic - SDBS) on adsorption and desorption of oxytetracycline (OTC) by multiwalled carbon nanotubes (MWCNTs). The surfactants used had a substantial influence on both adsorption and desorption of OTC. The direction of changes depended clearly on the type of surfactant. In case of anionic SDBS, increased adsorption of OTC by MWCNTs was observed. The presence of TX100 and CTAB decreased the adsorption of OTC by MWCNTs significantly. The increase of OTC adsorption after ultrasonic treatment was observed in case of MWCNTs alone and MWCNTs with SDBS and TX100. However, ultrasonic treatment caused OTC adsorption decrease in the presence of CTAB. The change of pH had also an important effect on OTC adsorption in the presence of surfactants. Depending on the surfactant and pH, an increase or decrease of OTC adsorption was observed. The presence of surfactants increased OTC desorption from MWCNTs significantly as follows: SDBS = CTAB < TX100. The results obtained suggest new potential threats and constitute a basis for further research considering the bioavailability and toxicity of antibiotics in the presence of MWCNTs and surfactants.