Presence Of Sodium Dodecyl Benzene Sulfonate Research Articles

Surfactant-assisted preparation of all-gel-state flexible supercapacitor with remarkable electrochemical performance based on polyaniline-polyacrylamide/sodium alginate hydrogels

The electrochemical performance of polyaniline-based all-gel-state supercapacitor (AGSSC) is significantly depended on the dispersity and mass loaded of polyaniline (PANI). In this manuscript, inspired by the properties of surfactant, sodium dodecylbenzene sulfonate (SDBS) was introduced to prepare various PANI-polyacrylamide/sodium alginate/SDBS (PANIy-PSSx) AGSSCs. With presence of SDBS, the electrochemical performance of PANIy-PSSx AGSSCs was greatly improved, displaying a trend of initial rise and then decrease with increasing concentration of SDBS from 0 to 0.75 wt%. As the content of SDBS was 0.5 wt%, the resulting PANI1.0-PSS0.5 AGSSC displayed the optimum electrochemical properties with area capacitance and energy density of 913.79 mF/cm2 and 81.23 μWh/cm2, respectively. The capacitance rate of PANI1.0-PSS0.5 AGSSC was still more than 93 % after 2000 cycles of sequential CV scans at the scan rate of 200 mV/s. These data were greatly higher than many reported PANI-based AGSSCs. Moreover, the resultant PANI1.0-PSS0.5 AGSSC could maintain high electrochemical performance even after various operations, such as compression, puncture, fluctuating temperature, bending situations and various voltage windows and series-parallel connections. The resultant PANI1.0-PSS0.5 AGSSC had the wide potentials to satisfy the real application requirements. This study offered a facile strategy for design and preparation of flexible supercapacitor with excellent electrochemical performance.

Fluorescent and visual sensing of sodium dodecylbenzene sulfonate with an aminosilane self-condensation promoting and electrostatic attraction effect-based ratiometric probe

BackgroundIncreasing attention has been paid to sodium dodecylbenzene sulfonate (SDBS) detection because it could cause damage to human body and environmental water. For example, SDBS must not be detected on tableware surface according to national standard of China (GB 14934-2016). However, there is no report heretofore addressing SDBS sensing on surfaces. More importantly, the interferents often affect the sensing performance of analytical approaches. Hence, there is an urgent need to establish a method with good anti-interference ability for SDBS detection both on tableware surfaces and in water. ResultsInspired by a finding that SDBS could cause the generation of white turbidity in (3-aminopropyl)trimethoxysilane (APTMS, an aminosilane) aqueous solution, APTMS modified Mn doped ZnS quantum dots (QDs) and fluorescent (FL) whitening agent (FWA) were constructed as a ratiometric probe for FL and visual sensing of SDBS. The modified QDs aggregated and settled in presence of SDBS, which was likely to be connected to the stimulatory effect of SDBS on the APTMS self-condensation and the electrostatic attraction. The FL emission from the QDs at 605 nm then decreased dramatically, whereas that at 425 nm was virtually constant owing to FWA. SDBS sensing could be achieved by calculating the ratio change of their FL intensities. The detection limits of FL and visual methods were found to be 0.011 and 10 μg/L, respectively, making it one of the most sensitive approaches in literature. Finally, it was successfully utilized for SDBS detection on tableware surfaces and in water. SignificanceHerein, the specific interaction between SDBS and APTMS was reported and the reaction mechanisms were explored for the first time. The proposed probe based on the effect described above provided a promising potential for SDBS analysis owing to high sensitivity, selectivity, anti-interference ability, and stability (in 20 days).

Transport of polystyrene nanoplastics in porous media: Combined effects of two co-existing substances

Both surfactants and natural organic matters (NOMs) are substances commonly found in aqueous environments, and their effects on the transport of nanoplastics that is gradually gaining widespread attention in porous media are currently in their infancy, while their combined effects are absent. We investigated innovatively the combined effect of surfactants and NOMs on the transport of polystyrene nanoplastics (PS-NPs) in saturated porous media. Adsorption tests of surfactants and NOMs onto PS-NPs, adsorption tests of PS-NPs onto quartz sand, and transport tests of PS-NPs in saturated quartz sand were conducted. Hydrophobicity and Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy were measured and calculated. A mathematical model was employed to fit the transport of PS-NPs in porous media. It was found that the effects and action mechanisms of cationic cetyl trimethylammonium bromide (CTAB) and anionic sodium dodecylbenzene sulfonate (SDBS) on the transport of PS-NPs in porous media were distinct. In the presence of CTAB, 1 mg/L humic acid (HA) and 10 mg/L sodium alginate (SA) could promote aggregation of PS-NPs by decreasing the absolute zeta potential of PS-NPs, and reducing the energy barrier between PS-NPs and porous media and increasing the blocking and straining, thus inhibiting the transport of PS-NPs. In the presence of SDBS, SA and HA could improve the adsorption of SDBS onto PS-NPs by bridging and increasing adsorption sites, thus increasing the hydrophilicity of PS-NPs and improving the transport of PS-NPs. Whether or not NOMs were present, the transport of PS-NPs in porous media was mainly governed by the DLVO interaction energy in the presence of cationic surfactants and by hydrophobicity in the presence of anionic surfactants. This innovative observation has led to an understanding on the environmental behaviour of nanoplastics in porous media under complex environments.

Nanofoaming by surfactant tunes morphology and performance of polyamide nanofiltration membrane

Fabricating nanofiltration (NF) membrane with a crumpled structure is promising for improving water permeance without compromising selectivity. Nanobubbles, which are in-situ produced during the interfacial polymerization (IP) of m-phenylenediamine (MPD)/trimesoyl chloride (TMC) system, enabled templating the “ridge-and-valley” structure of thin-film composite (TFC) reverse osmosis (RO) polyamide (PA) membranes. However, the templating effect of nanobubbles in NF PA membrane fabrication is rarely aware in the literature. Herein, we used a surfactant [sodium dodecylbenzene sulfonate (SDBS)] for reducing the interfacial tension and foaming, which enabled introducing additional nanobubbles into the piperazine (PIP)/TMC system. This would ensure that there are adequate amounts of nanobubbles to shape the PA structure, facilitating the encapsulation of nanobubbles between the PA layer and the substrate to form a bubble-like crumpled structure. The bubble-like crumpled structure increased the specific surface area and nanovoids of PA layer, beneficial for the improvement of membrane water permeance. In the presence of SDBS, the elimination of nanobubbles could change the crumpled structure to a smooth surface, while the enhancement of nanobubbles enabled more intensified crumpled structures. Our study provided a new dimension to manipulate the nanoscale structure of the PA layer of TFC NF membranes.

Cubic CsPbI3 Nanoarchitectonics with High and Stable Photoluminescence toward White Light-Emitting Diodes

The poor stability of cesium lead iodide (CsPbI3) perovskite nanocrystals (NCs) under light and humidity conditions limits their practical application. The dynamic binding of ligands is easy to desorb during the purification process, which results in a deterioration of their optical performance and stability. In this paper, sodium dodecyl benzene sulfonate (SDBS) was used to modify the surface of CsPbI3 NCs. By utilizing the strong combined effect of benzenesulfonic acid and Pb ions, the poor stability caused by the loss of weakly interacting amine ligands was effectively improved; meanwhile, the I ion vacancies can be filled to inhibit the occurrence of nonradiative recombination, so that the optical performance of the CsPbI3 NCs is improved. The radiative and nonradiative recombination process during photoluminescence is deeply discussed. After modification, the photoluminescence quantum yields of CsPbI3 NCs reached 90.7%, the superior photoluminescence intensity still retained 83% of the initial intensity after being stored for 60 days under environmental conditions, and the stability in water was remarkably improved. Additional SDBS was used after purification, suggesting that the presence of SDBS can effectively improve photostability. This method offers a new idea for preparing high-performance perovskite-based devices.

A novel Ni–Fe3O4@s-rGO/GCE electrode for electrochemical detection of H2O2

In this work, we report the synthesis of a novel non-enzymatic H2O2 electrochemical sensor based on reduced graphene oxide functionalized with sodium dodecylbenzenesulfonate (SDBS) and Fe3O4 and modified with Ni. The Ni–Fe3O4@s-rGO catalyst was synthesized via chemical reduction synthesis of graphene in the presence of SDBS following two solvothermal processes. To expose the sensor performance of Ni–Fe3O4@s-rGO, s-rGO, Ni@s-rGO, Fe3O4@s-rGO were also synthesized. Fabricated electrodes were characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), mapping, X-ray Powder Diffraction (XRD), Raman and Uv–vis Spectroscopy. After characterization analyses, thanks to SDBS contribution, the graphene layer has a larger surface area, and Ni and Fe3O4 deposited on the graphene layer with nano sizes (approximately 20 nm) and homogenously. Tauc plot result showed that Ni decreased the band gap of Fe3O4 from 2.6 eV to 1.83 eV so enhanced the charge mobility. This result is also supported by electrochemical impedance spectroscopy (EIS). The fabricated catalyst performance for H2O2 detection was investigated via cyclic voltammetry (CV), and amperometric measurement. Under the optimal conditions, the Ni–Fe3O4@s-rGO catalyst exhibited a low detection limit of 0.2 μM (S/N = 3) with a wide linear range from 1 μM to 1000 μM, with a sensitivity of 6012 mA M−1 and showed good selectivity towards H2O2.

A resonance Rayleigh scattering method for sensitive detection of chitosan based on supramolecular complex and mechanism study

A convenient and sensitive resonance Rayleigh scattering (RRS) method for the detection of chitosan (CTS) has been developed via forming Cu-Zn supramolecular complex by complexation reaction, hydrophobic force and electrostatic attraction. The microstructure of the complex was characterized by FT-IR, zeta potential, scanning electron microscope (SEM), UV–vis and RRS. Furthermore, the interaction mechanism among Cu(II), Zn(II), CTS and sodium dodecyl benzene sulfonate (SDBS) was studied. The results revealed that CTS and Cu(II) or Zn(II) formed a supramolecular complex with RRS enhancement in weak acid condition. In the presence of SDBS, the RRS intensity of CTS-Cu(II)-SDBS or CTS-Zn(II)-SDBS was significantly higher than that of the binary system without SDBS at the same CTS concentration. The RRS intensity of CTS-Cu(II)-Zn(II)-SDBS was higher than that of CTS-Cu(II)-SDBS and CTS-Zn(II)-SDBS. The RRS intensity increased linearly with the increase of CTS concentration made it possible to determine CTS quantitatively. In the range extending from 0.10 to 5.00 μg/mL, the equation of linear regression was ΔI=1848.8c-138.3 with a correlation coefficient 0.9996, and the detection limit was estimated to be 37.96 ng/mL. The study was successfully applied for the determination of CTS in health food samples, suggesting its great potential toward CTS analysis.

Surfactant assisted synthesis of pH responsive polyaniline-cellulose biocomposite for sensor applications

ABSTRACT In the present communication, an anionic surfactant, sodium dodecylbenzenesulfonate (SDBS) and a cationic surfactant tetradecyltrimethylammonium bromide (TTAB) were employed as soft templates for the preparation of biocomposites of polyaniline and cellulose, PAni/Cell, via oxidation polymerization. These biocomposites were characterized by UV/Vis, Fourier Transform Infra red (FTIR), and X-ray diffraction (XRD) methods. Wire-like and porous structures are observed for PAni/Cell prepared in the presence of SDBS whereas, presence of TTAB shows clusters-like structures. Electrochemical properties displayed by cyclic voltammograms (CV) of PAni/Cell/surfactant electrode, the effect of scan rate, and pH on the current response indicate its compatibility in sensor applications.

Display of hidden properties of flexible aerogel based on bacterial cellulose/polyaniline nanocomposites with helping of multiscale modeling

Tuning the synthesis conditions of polyaniline (PANI) such as aniline monomer’s protonation states and adding surfactants into polymerization mixture or even the existence of bacterial cellulose (BC) had a substantial influence on the final properties. To explore the relationship between components presented in the polymerization mixture, simulation tools (molecular dynamics (MD)/Monte Carlo (MC)/Density functional theory (DFT)) can be used. Herein, nanocomposite aerogels of BC/PANI were fabricated in the presence of anionic surfactants; sodium dodecyl benzene sulfonate (SDBS) or sodium dodecyl sulfonate (SDS) at two different concentrations (0.05 M and 1 M) of HCl solution. Two types of aniline monomers were considered in the polymerization mixture based on HCl solution’s concentrations including neutral and protonated aniline in 0.05 and 1 M, respectively. Various morphologies from nanobelts (with a width of 100–500 nm) and polyhedrons (with a thickness of 100–700 nm) in 0.05 M of acid solution in the presence of SDBS or SDS, respectively, were detected. Based on DFT computations it was found that electrostatic interactions and the formation of hydrogen bonds play a vital role in the interfacial interaction mechanism between both surfactants (SDBS and SDS) and different protonation forms of aniline monomers. Nevertheless, in the case of SDBS and aniline monomers (in both 0.05 and 1 M of HCl solutions), an excess interaction mechanism, namely π-π stacking, was observed, which enhanced the interaction between them and confirmed by experimental results. Therefore, the highest conductivity of 0.8 S/cm was obtained for the BC/PANI prepared with SDBS in 1 M of HCl solution. Besides, the smallest energy gap of 2.74 eV was predicted from DFT calculations for this sample that further confirmed its high electrical properties and smaller band gap at 3 nm, which was also confirmed by MD and MC.

Role of sodium dodecyl benzene sulfonate in enhancing coal dewatering: Experiments and theoretical calculations

The surface of low-rank coal has many oxygen functionalities, which leads to poor coal slime dehydration. To improve the effect of coal slime dewatering, sodium dodecyl benzene sulfonate (SDBS) was used as accelerator in the coal slime dehydration process. In addition, the mechanism of acceleration was studied using X-ray photoelectron spectroscopy (XPS) and molecular dynamics (MD) simulations. The results of dehydration experiments showed that adding a certain amount of SDBS into the slurry water was conducive to promoting the removal of water. When the concentration of the SDBS solution was 0.06 g/L, the water content of the filter cake decreased from an initial value of 59.98% to 54.55%. XPS measurements and MD simulations show that the polar groups (sulfonic acid) of SDBS are adsorbed on the oxygen-containing functional groups on the coal surface, thus, exposing the nonpolar groups (alkyl chains) of the molecule to the solution. The calculation of the self-diffusion coefficient (D) of water molecules in the simulated system indicate that the presence of SDBS improves the mobility of water at the coal surface, which is helpful in improving the loss of water from the coal surface, thus, improving its hydrophobicity. Crucially, the results of the MD simulations are consistent with those from experiment. Highlights Addition of a certain amount of SDBS helps to remove moisture from the coal slime. Oxygen-containing functional groups on the coal surface are effectively covered by SDBS. The interaction mechanism of SDBS at coal/water interface was studied by combining experiments and theoretical calculations.

Bacterial cellulose/polyaniline nanocomposite aerogels as novel bioadsorbents for removal of hexavalent chromium: Experimental and simulation study

In most countries, rapid industrialization poses a threat to the environment upon discharging the wastewater streams containing heavy metals, especially hexavalent chromium (Cr(VI)), into the environment. In this work, sustainable and biodegradable bacterial cellulose (BC)/polyaniline (PANI) nanocomposite aerogels with different morphology were fabricated in the presence of sodium dodecylbenzene-sulfonate (SDBS) and sodium dodecyl sulfate (SDS). The fabricated BC/PANI in the existence of SDBS and SDS showed thistle like and a cluster of grapes, respectively. The Cr(VI) removal was performed at a neutral pH condition. The highest adsorption capacity of 189 mg/g was determined at pH 7 for BC/PANI/SDBS (BPDB) compared with 151 mg/g for BC/PANI/SDS (BPDS) after 24 h. After five cycles, re-adsorption efficiency was reached to 68% for BPDB and 59% for BPDS. Simulation results showed that the effect of surface diffusion was prevailing compared with the pore volume diffusion (nearly 90% after 1 h). BPDB showed a faster adsorption rate than BPDS. Predicted concentration decay curves had good agreement with experimental data.

A study on optimum surfactant to multiwalled carbon nanotube ratio in alcoholic stable suspensions via UV–Vis absorption spectroscopy and zeta potential analysis

Common ultrasonication and centrifugation techniques could be utilized for dispersion of carbon nanotubes in solvents. However, there are few studies investigating the effect of concentration of species on stability of surfactant modified suspensions focusing on specific dispersants. Therefore, in this study, UV–Vis absorption spectroscopy, sedimentations tests, zeta (ζ) potential and dynamic light scattering analyses (DLS) were used as tools to estimate the optimal surfactant to multi walled carbon nanotubes (MWCNTs) weight ratio in stable centrifuged suspensions. MWCNTs colloids were prepared via addition of sodium dodecylbenzene sulfonate (SDBS) with ultrasonication and centrifugation in isopropyl alcohol (IPA). Coupling information gathered from overlapped absorption spectra and weighed dried sediments enabled estimation of MWCNTs concentrations in centrifuged suspensions (supernatant). By utilizing sediments weight and zeta potential observations, optimum SDBS/MWCNTs weight ratios were calculated. The results have shown that the SDBS/MWCNTs ratio should be 9 or higher in supernatants in order to obtain stable suspensions. It was also observed that increasing SDBS/MWCNTs concentrations over 9 in supernatants gradually decreased the zeta potentials of studied suspensions. Higher SDBS/MWCNTs ratios, also decreased settling velocities that were attributed to increased viscosity of supernatants. In addition to overlapping spectra technique, which relies on utilization of spectra related to centrifuged and uncentrifuged suspensions only for quantitative analysis, differential UV–Vis spectra were also utilized for the assessment of SDBS/MWCNTs ratios in supernatants. Presence of SDBS in supernatants (prepared by removing contribution of MWCNTs by using COOH modified MWCNTs’ UV–Vis absorption spectrum) exhibited an unexpected hyperchromic shift in maximum wavelength in spectra leading to misleading estimations of surfactant concentrations.

NIR-triggered doxorubicin photorelease using CuS@Albumin composites and in-vitro effect over HeLa cells

Drug photodelivery systems are emerging as useful tools for the development of new cancer chemotherapies with reduced side effects. In this context the development of nanodevices that utilize biodegradable components are especially appealing to reduce the accumulation of exogenous materials in important organs. Here we present the development of a nanocomposite comprising copper sulfide nanoparticles (CuSNPs) covered with human serum albumin (HSA) for transporting and photorelease doxorubicin (DOX) using near-infrared light. In a first step, 11 nm CuSNPs were synthesized by a hydrothermal method in the presence of sodium dodecylbenzene sulfonate (SDBS) as stabilizing intermediary ligand. In a second step, SDBS was exchanged with dopamine (DOP) to produce CuS@DOP that associates human serum albumin (HSA) through multivalent electrostatic interactions. The as-obtained CuS@HSA nanocomposite was observed capable to load DOX at the large extension of 27.8% (w/w) and deliver it to HeLa cells upon irradiation with an 808 nm laser (0.2 w/cm2), producing a therapeutic effect. This work proves the potential of the biodegradable CuS@HSA bioconjugate in biomedical applications that require the spatiotemporal administration of drugs.

CeO2 Encapsulated by Iron, Sulfur, and Nitrogen‐Doped Carbons for Enhanced Oxygen Reduction Reaction Catalytic Activity

AbstractThe design and synthesis of highly stable, low‐cost electrocatalysts for the oxygen reduction reaction to supersede noble‐metal catalysts is critical for their application in the field of fuel cells. Herein, we report a facile approach for the synthesis of CeO2 encapsulated by iron, sulfur, and nitrogen‐doped carbon nanoparticles (CeO2@Fe,S,N−C NPs) by pyrolyzing CeO2@polypyrrole, which is obtained in the presence of sodium dodecylbenzene sulfonate as a surfactant and FeCl3 as an oxidant during the polymerization of pyrrole on the CeO2 surface. As Fe and S are effectively doped into the N‐doped carbon derived from polypyrrole, a large number of active sites are created, which greatly enhances the catalytic activity of the sample. The achieved sample displays excellent catalytic activity with an onset and halfwave potential of 0.924 V and 0.835 V, respectively, and a limiting current density of 5.45 mA cm−2 at the potential of 0.4 V vs. RHE. Moreover, it illustrates a high durability and strong methanol tolerance, endowing it with the prospect of applications in energy conversion.

Highly sensitive detection of sulfasalazine based on the fluorescence quenching of a terbium complex probe

In the current study, a method for the determination of sulfasalazine (SSZ) based on the fluorescence quenching of Tb-2,6-pyridinedicarboxylic acid (Tb-DPA) complex probe in the presence of sodium dodecylbenzene sulfonate (SDBS) was established. Moreover, the mechanism of fluorescence quenching was studied and it was concluded that the process is static quenching and involved the formation of the SSZ-Tb-DPA ternary complex. Under the optimum conditions, the linear range of the method was 8.0 × 10−8–1.00 × 10−6 M and 1.00 × 10−6–1.00 × 10−4 M with the detection limit of 60 nM. The approach was successfully applied for the detection of SSZ in pharmaceutical preparations, urine, and human serum samples with recoveries between 98% and 106%.

Studying the removal of Hg(ІІ) from aqueous solution by using polyaniline and its nanocomposites

ABSTRACT Polyaniline/antimony oxide (PAn/Sb2O3) nanocomposite was prepared in aqueous media by the chemical polymerisation of aniline using ammonium peroxydisulfate (APS) as an oxidant in the presence of sodium dodecylbenzenesulfonate (DBSNa) and poly(vinyl pyrrolidone) (PVP) as surfactants. The application of PAn nanocomposite for the removal of Hg(II) from aqueous solutions was investigated. The chemical structure and morphology were studied by fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that the Sb2O3 and type of surfactant influence the properties of products. Adsorption studies were directed in a batch system as a function of solution pH, contact time and initial Hg(II) concentration. The optimum conditions of sorption were found to be: pH 6 and contact time of 40 min. The equilibrium adsorption capacity was obtained by using Langmuir and Freundlich isotherm models. The data were better fitted by using the Freundlich model. The results indicate that polyaniline/antimony oxide nanocomposite can be used as an effective adsorbent for the removal of Hg(II) from aqueous solution.

Effect of sodium dodecyl benzene sulfonate (SDBS) on the performance of anaerobic co-digestion with sewage sludge, food waste, and green waste

The anionic detergent sodium dodecyl benzene sulfonate (SDBS) inhibits anaerobic solid waste fermentation process in mesophilic anaerobic digesters. In this study, the effect SDBS on the performance of anaerobic digestion (AD) of mixture of sewage sludge, food waste, and green waste serving as substrate was investigated. The batch experiments were conducted with five SDBS concentrations namely 0, 0.01, 0.02, 0.05, 0.1, and 0.2 g/g (SDBS/dry sludge) under mesophilic condition (37 ± 1 °C) and lasted for 63 days. The results showed that the presence of SDBS remarkably increased the release of protein and carbohydrate, and resulting in the serious accumulation of volatile fatty acids (VFAs), especially for propionate accumulation. Likewise, the observed variations in enzyme activities associated with different stage of AD revealed that methanogenesis was quite sensitive to SDBS and inhibited by the increase of SDBS addition. Meanwhile, the presence of SDBS decreased the pH value and the concentration of free ammonia, but increased the concentration of NH4+-N. Furthermore, the production of biogas was reduced by SDBS. In conclusion, SDBS addition has a negative impact on anaerobic co-digestion. On the one hand, methanogens were severely inhibited and biogas yield decreased remarkably, on the other hand, the accumulation of VFAs was excessive. Thus, the presence of surfactant (SDBS) in the municipal organic waste should be concerned during the waste disposal via anaerobic digestion process.

Static sorption of heavy metal ions on ion exchanger in the presence of sodium dodecylbenzenesulfonate

The effect of sodium dodecylbenzenesulfonate (anionic surfactant) on removal of selected heavy metal ions such as copper(II), cobalt(II), zinc(II) and nickel(II) using Lewatit MonoPlus TP 220 were studied. The critical micellization of concentration in the system containing both heavy metal ions and the anionic surfactant was obtained (surface properties). The percentage removal of heavy metal ions in the system without the anionic surfactant was compared with that of heavy metal ions in the presence of the anionic surfactant of the concentration below (↓CMC) and above (↑CMC) (HCl—heavy metal ions—anionic surfactant systems). Moreover, Lewatit MonoPlus TP 220 was applied for the heavy metal ions removal from real wastewaters (used a pickling bath) originating from leaching of the heat-resistant nickel and cobalt alloys. The critical micellization of concentration values depends on the composition of solution, presence of hydrochloric acid and heavy metal ions. The presence of the surfactant improves slightly the removal efficiency of cobalt(II) and nickel(II) ions and deteriorates the zinc(II) removal efficiency. Lewatit MonoPlus TP 220 shows high affinity for copper(II) in the model and real wastewater solutions in the case of the systems without and with the anionic surfactant.

Different conformational states of hen egg white lysozyme formed by exposure to the surfactant of sodium dodecyl benzenesulfonate.

The aim of this study was to investigate the effects of sodium dodecyl benzenesulfonate (SDBS) on hen egg white lysozyme (HEWL) fibrillogenesis at pH 7.4. HEWL fibrillogenesis in the presence of SDBS was characterized using several spectroscopic techniques (turbidity, light scattering, intrinsic fluorescence, ThT binding assay, ThT kinetics, far-UV CD, and transmission electron mmicroscopy). The turbidity and light scattering data revealed that SDBS induces aggregation in HEWL in dose-dependent manner. HEWL aggregation was seen at low SDBS concentrations (0.03 to 0.5 mM) but it was not observed at concentrations of SDBS at >0.6 mM. The ThT and TEM data clearly showed that the aggregates formed in the presence of SDBS had an amyloid-like morphology. From the CD analysis it was clear that low SDBS concentrations decreases the α-helical content while the β-sheet content increased. As the SDBS concentration further increased, the α-helical content increased again. The ThT kinetics analysis revealed that the HEWL monomer directly converted into the amyloid fibril without lag phase. All the spectroscopic and microscopic results support the finding that low concentrations of SDBS stimulate fibrillogenesis in HEWL, and that no fibrillogenesis occurs at higher SDBS concentrations.

Effects of surfactants on the combined toxicity of TiO2 nanoparticles and cadmium to Escherichia coli

The combined ecological toxicity of TiO2 nanoparticles (nano-TiO2) and heavy metals has been paid more attention. As the common pollutants in water environment, surfactants could affect the properties of nanoparticles and heavy metals, and thus further influence the combined toxicity of nano-TiO2 and heavy metals. In this study, the effects of sodium dodecyl benzene sulfonate (SDBS) and Tween 80 on the single and combined toxicities of Cd2+ and nano-TiO2 to Escherichia coli (E. coli) were examined, and the underlying influence mechanism was further discussed. The results showed both SDBS and Tween 80 enhanced the toxicity of Cd2+ to E. coli in varying degrees. The reaction of SDBS and Cd2+ could increase the outer membrane permeability and the bioavailability of Cd, while Tween 80 itself could enhance the outer membrane permeability. The combined toxicity of nano-TiO2 and Cd2+ to E. coli in absence of surfactant was antagonistic because of the adsorption of Cd2+ to nano-TiO2 particles. However, in the presence of SDBS, both SDBS and nano-TiO2 influenced the toxicity of Cd2+, and also SDBS could adsorb to nano-TiO2 by binding to Cd2+. The combined toxicity was reduced at Cd2+ lower than 4mg/L and enhanced at Cd2+ higher than 4mg/L under multiple interactions. Tween 80 enhanced the combined toxicity of nano-TiO2 and Cd2+ by increasing the outer membrane permeability. Our study firstly elucidated the effects of surfactants on the combined toxicity of nano-TiO2 and Cd2+ to bacteria, and the underlying influencing mechanism was proposed.