Initial Surfactant Research Articles

Periodic reversals in Paenibacillus dendritiformis swarming.

Bacterial swarming is a type of motility characterized by a rapid and collective migration of bacteria on surfaces. Most swarming species form densely packed dynamic clusters in the form of whirls and jets, in which hundreds of rod-shaped rigid cells move in circular and straight patterns, respectively. Recent studies have suggested that short-range steric interactions may dominate hydrodynamic interactions and that geometrical factors, such as a cell's aspect ratio, play an important role in bacterial swarming. Typically, the aspect ratio for most swarming species is only up to 5, and a detailed understanding of the role of much larger aspect ratios remains an open challenge. Here we study the dynamics of Paenibacillus dendritiformis C morphotype, a very long, hyperflagellated, straight (rigid), rod-shaped bacterium with an aspect ratio of ~20. We find that instead of swarming in whirls and jets as observed in most species, including the shorter T morphotype of P. dendritiformis, the C morphotype moves in densely packed straight but thin long lines. Within these lines, all bacteria show periodic reversals, with a typical reversal time of 20 s, which is independent of their neighbors, the initial nutrient level, agar rigidity, surfactant addition, humidity level, temperature, nutrient chemotaxis, oxygen level, illumination intensity or gradient, and cell length. The evolutionary advantage of this unique back-and-forth surface translocation remains unclear.

Biosorption of malachite green from aqueous solutions by pine sawdust: equilibrium, kinetics and the effect of process parameters

abstract The study offers the use of Scots Pine (Pinus silvestris) sawdust as a biosorbent for the removal of cationic dye, malachite green, from aqueous solutions. The effects of process parameters, such as contact time, sorbent concentration, initial dye concentration, pH, temperature, salinity and surfactant addition, on the biosorption process were determined. The experimental biosorption kinetics and equilibrium results were described by a range of mathematical models. The equilibrium data were best described by the Langmuir-Freundlich model, while the kinetics was best described by the pseudo-second-order model. The maximum sorption capacity of sawdust was 71.67 mg/g. An increase in pH values results in the rise of biosorption degree, mostly below pH 5. Addition of inorganic salts results in a drop in sorption capacity, but for concentrations higher than 0.5% w/w, the uptake increases along with an increase in salt concentration. The presence of an ionic surfactant (sodium dodecyl benzene sulphonate...

Anionic Surfactant Adsorption through Porous Media in Carbonate Cores: An Experimental Study

The phenomenon of surfactant adsorption at solid/liquid interface is of major importance in the process of enhanced oil recovery. The basic objective of this study is to calculate adsorption density and also to model the kinetics of adsorption processes on carbonate rocks. The kinetics adsorption was calculated by examining adsorption behavior in a system of a solid phase (carbonate rock) and an aqueous phase of surfactant with 5,000 ppm synthetic/field brine. The surfactant adsorption on reservoir carbonate rocks was measured to determine the amount of excess surfactant that must be added into the injection stream in the surfactant alternating CO2 injection tests. The adsorption densities were measured by using circulation tests through core samples. The range of initial surfactant concentrations were 500, 1,000, 2,000, and 5,000 ppm in a circulating system. The applied commercial surfactant is sodium lauryl sulphate, which is an anionic surfactant. Finally, the Langmuir adsorption isotherm was used to characterize the equilibria between the amount of adsorbate that accumulates on the adsorbent and the concentration of the dissolved adsorbate. The adsorption process showed that the rate of adsorption is dependent on availability of surfactant in the system. It was found that the adsorption of surfactant increased with increasing surfactant concentration. Also, for the flow-through tests, the necessary equilibrium time was approximately 4 days.

Numerical Investigation of Thin Film Spreading Driven by Surfactant Using Upwind Schemes

Numerical solutions of a coupled system of nonlinear partial differential equations modelling the effects of surfactant on the spreading of a thin film on a horizontal substrate are investigated. A CFL condition is obtained from a von Neumann stability analysis of a linearised system of equations. Numerical solutions obtained from a Roe upwind scheme with a third-order TVD Runge-Kutta approximation to the time derivative are compared to solutions obtained with a Roe-Sweby scheme coupled to a minmod limiter and a TVD approximation to the time derivative. Results from both of these schemes are compared to a Roe upwind scheme and a BDF approximation to the time derivative. In all three cases high-order approximations to the spatial derivatives are employed on the interior points of the spatial domain. The Roe-BDF scheme is shown to be an efficient numerical scheme for capturing sharp changes in gradient in the free surface profile and surfactant concentration. Numerical simulations of an initial exponential free surface profile coupled with initial surfactant concentrations for both exogenous and endogenous surfactants are considered.

Removal of Methylene Blue from Aqueous Solution by Activated Carbon Prepared from Pea Shells (Pisum sativum)

An activated carbon was prepared from pea shells and used for the removal of methylene blue (MB) from aqueous solutions. The influence of various factors such as adsorbent concentration, initial dye concentration, temperature, contact time, pH, and surfactant was studied. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. The adsorption isotherm was found to follow the Langmuir model. The monolayer sorption capacity of activated carbon prepared from pea shell for MB was found to be 246.91 mg g−1 at 25 ∘C. Two simplified kinetic models including pseudo‐first‐order and pseudo‐second‐order equation were selected to follow the adsorption processes. Kinetic studies showed that the adsorption followed pseudo‐second‐order kinetic model. Various thermodynamic parameters such as ΔH∘, ΔS∘, and ΔG∘ were evaluated. The results in this study indicated that activated carbon prepared from pea shell could be employed as an adsorbent for the removal of MB from aqueous solutions.

A multi-headed surfactant as an efficient tool in solubilization of dimyristoylphosphatidycholine (DMPC) vesicles

In this study, the solubilization of DMPC (dimyristoylphosphatidycholine) vesicles by a novel multi-headed surfactant, C18N3, is reported. The headgroup of the surfactant contains two types of amine groups, which are protonated at different pH values. The protonation of the headgroup has significant effect on the solubilization process. The penetration of the surfactant into a DMPC monolayer was measured at different initial surface pressures and at different pH values. A linear relationship was found between the initial surfactant pressure (π) and the increase of the surfactant pressure (Δπ). Furthermore, turbidity titration shows that at low pH, the phase behavior with increasing surfactant concentration in the DMPC solution is similar to conventional ionic surfactants. This can be explained by the three-stage model. TEM images at different C18N3 concentrations confirmed the process of solubilization of DMPC vesicles, and small aggregates were observed at 1mmol/L C18N3. However, at higher pH, where the headgroup is deprotonated, the surfactant was not able to solubilize the DMPC vesicles. TEM images shows a coexistence of vesicles and a lamellar phase. The surfactant/lipid ratio of the multi-headed surfactant at pH 4 and 7 was compared to conventional nonionic surfactants with the same cross-sectional area of the headgroup, and a much lower ratio was observed for the new surfactant.

Wettability Alteration and Foam Mobility Control in a Layered, 2D Heterogeneous Sandpack

Summary In a layered, 2D heterogeneous sandpack with a 19:1 permeability contrast that was preferentially oil-wet, the recovery by waterflood was only 49.1% of original oil in place (OOIP) because of injected water flowing through the high-permeability zone, leaving the low-permeability zone unswept. To enhance oil recovery, an anionic surfactant blend (NI) was injected that altered the wettability and lowered the interfacial tension (IFT). Once IFT was reduced to ultralow values, the adverse effect of capillarity retaining oil was eliminated. Gravity-driven vertical countercurrent flow then exchanged fluids between high- and low-permeability zones during a 42-day system shut-in. Cumulative recovery after a subsequent foam flood was 94.6% OOIP, even though foam strength was weak. Recovery with chemical flood (incremental recovered oil/waterflood remaining oil) was 89.4%. An alternative method is to apply foam mobility control as a robust viscous-force-dominant process with no initial surfactant injection and shut-in. The light crude oil studied in this paper was extremely detrimental to foam generation. However, the addition of lauryl betaine to NI (NIB) at a weight ratio of 1:2 (NI:lauryl betaine) made the new blend a good foaming agent with and without the presence of the crude oil. NIB by itself as an IFT-reducing and foaming agent is shown to be effective in various secondary and tertiary alkaline/surfactant/foam (ASF) processes in water-wet 1D homogeneous sandpacks and in an oil-wet heterogeneous layered system with a 34:1 permeability ratio.

Removal of anionic surfactant sodium dodecyl sulphate from aqueous solution by adsorption onto pine cone biomass of Pinus Radiate: equilibrium, thermodynamic, kinetics, mechanism and process design

Abstract This study was undertaken to evaluate the adsorption potential of a natural, low-cost agricultural by-product adsorbent, Pine cone (Pinus Radiate), to remove sodium dodecylsulfate (SDS) from aqueous solution. It was found that the extent of SDS adsorption by pine cone biomass increased with initial surfactant concentration and contact time but decreased with increasing solution pH, amount of adsorbent, and temperature of the system. These studies also suggested that the electrostatic forces and surfactant self-assembly are dominant mechanisms governing this pH dependent adsorption process. Overall, kinetic studies showed that the surfactant adsorption process followed pseudo-second-order kinetics based on pseudo-first-order and intraparticle diffusion models. The different kinetic parameters including rate constant, half adsorption time, and diffusion coefficient were determined at different physicochemical conditions. Equilibrium data were fitted by both the Langmuir isotherm and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine cone biomass was 95.75 mg g−1 at 20°C. The value of separation factor, R L from Langmuir equation and “n” from Freundlich also indicated favourable adsorption. Thermodynamic parameters such as ΔG 0, ΔH 0, and ΔS 0 were calculated. A single-stage batch absorber design for the SDS adsorption onto pine cone biomass also presented based on the Freundlich isotherm model equation.

Sorption of Chromate and Arsenate by Surfactant Modified Erionite (E-SMZ)

In recent years, growth of various industry has led to the introduction of pollutants in nature, especially heavy metal ions such as Cr(III) and As(V), which are usually present in wastewater. Heavy metals containing waste are generated from metallurgical, mining, chemical, leather, distilleries, sugar, battery, electroplating, and pigment industries, to name a few. Chromium is found in natural water in oxidation states, Cr(III) and Cr(VI). The former is an essential element for mammals whereas the latter is reported to be toxic. Similarly, arsenic is an ubiquitous contaminant that can be found in high concentrations in natural waters and wastewaters. Arsenic containing waste streams are generated mainly by the microelectronic industry and by pesticide and pharmaceutical facilities. It occurs in two oxidation states that form oxyanions, arsenate As(V), and arsenite As(III); arsenite is more mobile and toxic than . As arsenic is a major hazardous contaminant for human health, its removal is an issue of increasing concern. Zeolites are crystalline, hydrated aluminosilicates containing exchangeable alkaline and alkaline earth cations in their structural frameworks. Since zeolites have a permanent negative charge on their surfaces, they have no affinity for anions. However, recent studies have shown that modification of zeolite with certain surfactants or metal cations yield sorbents with a strong affinity for many anions. Zeolite has high internal and external surface areas and high internal and external cation exchange capacities suitable for the surface modification by cationic surfactant (HDTMA). When the initial surfactant concentration is less than the critical micellar concentration (CMC), the sorted surfactant molecules primarily form a monolayer; limited chromate and arsenate sorption indicates that the patchy bilayer may also be formed. When the surfactant concentration is greater than the CMC and enough surfactant exists in the system, the sorbed surfactant molecules form a bilayer, producing maximum chromate and arsenate sorption. Quantitative sorption of chromate and arsenate and desorption of bromide ions indicate that the sorption of oxoanions is primarily due to surface anion exchange.

Degradation of anionic and cationic surfactants in a monolithic swirl-flow photoreactor

The photocatalytic oxidations of anionic, dodecylbenzene sulfonate (DBS), and cationic, cetylpyridinium chloride (CPC) surfactants were studied in a swirl-flow monolithic reactor. The degradation kinetics in aqueous TiO2 suspensions was investigated as a function of catalyst loading, light intensity, initial surfactant concentration, dissolved oxygen concentration, and pH. A systematic analysis of rates at various loadings of TiO2 was carried out to distinguish “kinetic” and “transport” limited regimes for the photocatalytic degradation of DBS and CPC in TiO2 suspensions. The optimal catalyst loading of DBS and CPC in TiO2 suspensions were determined to be 0.75 and 1.5gL−1, respectively, at a neutral pH. A small increase in oxidation rates was observed with an increase in initial concentration of the surfactant and partial pressure of the oxygen in the system. The rates as a function of initial surfactant concentration and partial pressures of oxygen were determined using a Langmuir–Hinshelwood model. The photocatalytic oxidation of DBS and CPC showed an opposite pH dependence. Removal of DBS was efficient in acidic condition while CPC showed efficacy at basic pH. The adsorption of surfactants onto TiO2 surfaces as a function of pH was studied to explain the influence of pH on the oxidation rates. The subsequent decreases in TOC levels of surfactant during oxidation were found to be more efficient at a neutral pH than acidic or basic pH.

Photocatalytic degradation of anionic surfactant using zinc oxide nanoparticles

In this paper the photocatalytic degradation of anionic surfactant LABS was studied by a batch process using ZnO nanoparticles with diameter size of 20 nm catalyst on irradiation with UV light and their behavior comparatively examined with respect to ZnO commercial powder. The effect of parameters such as initial surfactant concentration, initial solution pH has been studied. Also degradation at LABS in the presence of an electron acceptor like potassium peroxydisulfate and effect of anion presence on surfactant degradation has been systematically investigated. The obtained result demonstrated a high photocatalytic activity of nanosize semiconducting particles.

Removal of Cationic Dyes from Aqueous Solutions using Microspherical Particles of Fly Ash

Batch sorption experiments were carried out for the removal of cationic dyes (methylene blue and malachite green) from their aqueous solutions using sorbent made from fly ash-a waste material. Effects of various experimental parameters: initial dye concentration, contact time, pH, adsorbent dosage, solution temperature, surfactant addition and ionic strength on the fly ash sorption of dyes were evaluated. The isothermal data for sorption followed the Langmuir model. The maximum sorption capacity obtained for methylene blue and malachite green was 36.05 mg/g and 40.65 mg/g, respectively. Kinetic studies indicate that sorption on fly ash follows the pseudo-second order kinetics. Present research suggests that fly ash could be an appropriate adsorbent for the removal of basic dyes from aqueous solutions.

Production of xylanase under solid-state fermentation by Aspergillus tubingensis JP-1 and its application

The production of extracellular xylanase by a locally isolated strain of Aspergillus tubingensis JP-1 was studied under solid-state fermentation. Among the various agro residues used wheat straw was found to be the best for high yield of xylanase with poor cellulase production. The influence of various parameters such as initial pH, moisture, moistening agents, nitrogen sources, additives, surfactants and pretreatment of substrates were investigated. The production of the xylanase reached a peak in 8 days using untreated wheat straw with modified MS medium, pH 6.0 at 1:5 moisture level at 30 °C. Under optimized conditions yield as high as 6,887 ± 16 U/g of untreated wheat straw was achieved. Crude xylanase was used for enzymatic saccharification of agro-residues like wheat straw, rice bran, wheat bran, sugarcane bagasse and industrial paper pulp. Dilute alkali (1 N NaOH) and acid (1 N H(2)SO(4)) pretreatment were found to be beneficial for the efficient enzymatic hydrolysis of wheat straw. Dilute alkali and acid-pretreated wheat straw yielded 688 and 543 mg/g reducing sugar, respectively. Yield of 726 mg/g reducing sugar was obtained from paper pulp after 48 h of incubation.

TiO2 photocatalytic degradation of 4-chlorobiphenyl as affected by solvents and surfactants

TiO2 photocatalytic degradation of 4-chlorobiphenyl (PCB3) in aqueous solution under UV irradiation was investigated as affected by different environmental factors, including initial PCB3 concentration, TiO2 content, UV intensity, H2O2 concentration, cosolvents, and surfactants. The solution of PCB3 with TiO2 was irradiated by medium mercury lamp. The concentration of PCB3 and intermediates was analyzed by GC-μECD and GC–MS. The values of point charge and bond length were also calculated with ChemOffice 2004 (Mopac unit). Photocatalysis was very effective for PCB3 removal, and the degradation kinetics were fitted with a pseudo-first order reaction model. PCB3 was efficiently degraded in the presence of acetone and acetonitrile, but was completely inhibited with other examined cosolvents. HPCD and Tween80 also inhibited the degradation rate of PCB3, while Brij35 slightly decreased the degradation rate of PCB3 at first, and then increased. The reaction mechanism occurred principally by hydroxyl radicals involving the participation of holes and superoxide anion oxidation. A possible photocatalytic degradation pathway of PCB3 was proposed based on the identified reaction intermediates as well as computer simulation. The photocatalytic approach could be successfully applied to degrade PCB3, and cosolvents and surfactants significantly influenced its degradation kinetics.

Uptake of permanganate from aqueous environment by surfactant modified montmorillonite batch and fixed bed studies

Organo-clay was prepared by incorporating different amounts (in terms of CEC, ranging from 134–840 mg of quaternary ammonium cation (QACs) such as hexadecytrimethylammonium bromide ([C19H42N]Br) into the montmorillonite clay. Prepared organo-clays are characterized by CHN analyser and XRD to measure the amount of elemental content and interlayer spacing of surfactant modified clay. The batch experiments of sorption of permanganate from aqueous media by organo-clays was studied at different acidic strengths (pH 1–7). The experimental results show that the rate and amount of adsorption of permanganate was higher at lower pH compared to raw montmorillonite. Laboratory fixed bed experiments were conducted to evaluate the breakthrough time and nature of breakthrough curves. The shape of the breakthrough curves shows that the initial cationic surfactant loadings at 1·0 CEC of the clay is enough to enter the permanganate ions in to the interlamellar region of the surfactant modified smectile clays. These fixed bed studies were also applied to quantify the effect of bed-depth and breakthrough time during the uptake of permanganate. Calculation of thermodynamic parameters shows that the sorption of permanganate is spontaneous and follows the first order kinetics.

Long-chain anionic surfactants in aqueous solution. Removal by Moringa oleifera coagulant

Moringa oleifera seed extract was confirmed as a feasible coagulant in removing surfactants from aqueous effluents. Amongst them, long-chain anionic detergents such as Polyoxyethylene (3.5) sodium lauryl ether sulfate (SLES) was selected as a model compound for evaluating the coagulation response. The system coagulant–detergent was stable with different temperatures and pH, and the efficiency was very promising. M. oleifera was an effective coagulant since it was capable to reach up to 0.245 mg mg −1 coagulation capacity according to Gu–Zhu model. Design of experiments presented an optimum combination of coagulant dosage and initial surfactant concentration of 234 mg L −1 and 76 mg L −1, respectively.

Environmental Impact of Ether Carboxylic Derivative Surfactants

AbstractThe ultimate aerobic biodegradability and toxicity of three ether carboxylic derivative surfactants having different alkyl chains and degrees of ethoxylation were investigated. Ultimate aerobic biodegradability was screened by means of dissolved organic carbon determinations at different initial surfactant concentrations. For comparison, the characteristic parameters of the biodegradation process, such as half‐life, mean biodegradation rate, and residual surfactant concentration, were determined. Increased surfactant concentrations decreased mineralization and lengthened the estimated half‐life. The results demonstrate that the ultimate aerobic biodegradability is higher for the surfactants with the shortest alkyl chain and highest degree of ethoxylation. Toxicity values of the surfactants, and their binary mixtures, were determined using three test organisms, the freshwater crustacea Daphnia magna, the luminescent bacterium Vibrio fischeri and the microalgae Selenastrum capricornutum. The toxicity is lower for the surfactants with the shortest alkyl chain and highest degree of ethoxylation. The toxicity of binary mixtures of the three ether carboxylate surfactants at a 1:1 weight ratio was also measured. The least toxic mixture is formed by the surfactants having lower individual toxicity.

Modeling partial oxidation of a commercial textile surfactant formulation with the H2O2/UV-C process

In the present study, the reaction conditions required for the partial oxidation of a commercial nonionic textile surfactant, an alkyl polyethoxylate, with the H(2)O(2)/UV-C treatment process were optimized using central composite design and response surface methodology (CCD-RSM). CCD-RSM allowed for the development of empirical quadratic equations that satisfactorily predicted COD and TOC removal efficiencies under all studied experimental conditions. Analysis of variance revealed that the variables "H(2)O(2) concentration" and "initial surfactant COD" were found to be the process independent parameters most positively and negatively affecting the treatment performance, respectively, whereas the process variable "treatment time" had a smaller influence on COD and TOC removal efficiencies. According to the established polynomial regression models, for the degradation of the nonionic surfactant at an initial COD of 450 mg L(-1) and pH of 10.5, the optimized treatment conditions were 15 mM H(2)O(2) and a reaction time of 80 min. In order to achieve the treatment targets (complete surfactant removal accompanied by 60% COD and TOC elimination to meet the national discharge consents into receiving water bodies) either H(2)O(2) concentration or photochemical treatment time had to be increased. Activated sludge inhibition experiments conducted with nonionic surfactant solution being subjected to photochemical oxidation under optimized reaction conditions indicated that the inhibitory effect of the nonionic surfactant could be completely eliminated during H(2)O(2)/UV-C treatment and the partial degradation intermediates were more biodegradable than the original textile surfactant.

Application of micellar enhanced ultrafiltration and activated carbon fiber hybrid processes for lead removal from an aqueous solution

Micellar enhanced ultrafiltration (MEUF) and activated carbon fiber (ACF) hybrid processes were used to investigate the removal condition of lead ions and surfactant sodium dodecyl sulfate (SDS) from an aqueous solution. Lead removal efficiency increased with the increase of initial surfactant concentration. Molar ratio of lead to SDS up to 1: 5 has shown over 90% removal efficiency of lead, and the optimum molar ratio of lead to SDS was found to be 1: 5. Lead removal efficiency increased with the increase of pH, while it was maintained below 30% without surfactant. Lead removal was mainly due to the adsorption mechanism and no secondary layer was formed to reduce the flux. Lower molecular weight cut-off (MWCO) membrane has shown higher removal efficiency than higher MWCO one. Permeate flux decreased with the increase of molar ratio of lead to SDS. Flux decline was mainly due to the accumulation of micelles on the membrane surface. The presence of copper as a co-existing heavy metal highly affected the lead removal while nickel did not. Two sets of ACF unit in series were able to remove SDS surfactant effectively from the effluents of MEUF process.

On surfactant-enhanced spreading and superspreading of liquid drops on solid surfaces

The mechanisms driving the surfactant-enhanced spreading of droplets on the surface of solid substrates, and particularly those underlying the superspreading behaviour sometimes observed, are investigated theoretically. Lubrication theory for the droplet motion, together with advection–diffusion equations and chemical kinetic fluxes for the surfactant transport, leads to coupled evolution equations for the drop thickness, interfacial concentrations of surfactant monomers and bulk concentrations of monomers and micellar, or other, aggregates. The surfactant can be adsorbed on the substrate either directly from the bulk monomer concentrations or from the liquid–air interface through the contact line. An important feature of the spreading model developed here is the surfactant behaviour at the contact line; this is modelled using a constitutive relation, which is dependent on the local surfactant concentration. The evolution equations are solved numerically, using the finite-element method, and we present a thorough parametric analysis for cases of both insoluble and soluble surfactants with concentrations that can, in the latter case, exceed the critical micelle, or aggregate, concentration. The results show that basal adsorption of the surfactant plays a crucial role in the spreading process; the continuous removal of the surfactant that lies upon the liquid–air interface, due to the adsorption at the solid surface, is capable of inducing high Marangoni stresses, close to the droplet edge, driving very fast spreading. The droplet radius grows at a rate proportional to ta with a = 1 or even higher, which is close to the reported experimental values for superspreading. The spreading rates follow a non-monotonic variation with the initial surfactant concentration also in accordance with experimental observations. An accompanying feature is the formation of a rim at the leading edge of the droplet. In some cases, the drop spreads to form a ‘pancake’ or creates a ‘secondary’ front separated from the main droplet.