Surface-active Additives Research Articles

Enzymatic Remediation of Bisphenol A from Wastewaters: Effects of Biosurfactant, Anionic, Cationic, Nonionic, and Polymeric Additives

One of the limitations compromising the utilization of enzymes for the remediation of phenolic wastewaters is enzyme activity loss during the treatment. Some surface active additives have the potential to protect enzymes and, thus, improve their performance. In this study, the removal of bisphenol A from synthetic wastewater samples by laccase has been studied in the presence of rhamnolipid biosurfactant (RL), polyethylene glycol (PEG), Triton X-100, cetyltrimethylammonium bromide (CTAB), and sodium dodecylbenzenesulfonate (SDBS). The results demonstrated that the addition of 1 ppm RL provides the highest removal rate and removal extent of BPA. In the case of PEG and Triton X-100, the results showed that both additives have almost similar positive effects on the enzymatic remediation of BPA. However, unlike RL, the positive effects of PEG and Triton X-100 were appreciable only at higher concentration (i.e., 25 ppm). On the other hand, the addition of the two ionic surfactants (SDBS and CTAB) resulted in a negative effect on the enzyme activity and, thus, the remediation of BPA, demonstrating the undesirable interactions of these ionic surfactants with laccase. The negative effect of the charged additives was more pronounced for the case of the positively charged additive (i.e., CTAB).

Boost Effect of Water-Soluble Polymers on Enzymatic Hydrolysis of Lignocellulosic Biomass

Supplementation of surface-active additives during enzymatic saccharification of biomass helps to increase the activity of cellulase and thus reduces the enzyme dosage in the bioconversion processes. To evaluate the boost effect of additives on enzymatic hydrolysis, five different water-soluble polymers were studied in this work including: polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), cationic polyacrylamide (C-PAM), and polyethyleneimine (PEI). Lignin-containing substrates and lignin-free substrates were used in enzymatic hydrolysis tests. It was found that an addition of 10 mg polymer/g-substrate leads to up to a 25.4% increase in glucan hydrolysis and a 13.2% increase in xylan hydrolysis depending on the types of the substrate and polymer. Glucan digestibility achieved from low enzyme loading of 5 FPU/g-glucan with polymer is comparable to that from 15 FPU/g-glucan enzyme loading. Reducing the amount of enzyme required could make biomass conversion more cost-effective...

Surfactants and amino acids in the control of nanotubular morphology of polypyrrole and their effect on the conductivity

Polypyrrole nanotubes were prepared by the oxidation of pyrrole in aqueous solutions of methyl orange and in the presence of 1–5 wt% of surface-active additives, surfactants, or amino acids. Three types of additives – anionic, non-ionic, and cationic – have been tested in the control of polypyrrole morphology and conductivity. The morphology of nanotubes was little dependent on surfactant type but the changes in size and aspect ratios were more pronounced with amino acids. Except for anionic surfactant, bis(2-ethylhexyl) sulfosuccinate, which behaved indifferently, all additives reduced the conductivity of polypyrrole, some even by four orders of magnitude. Based on FTIR spectroscopy, it is proposed that the hydrophobic interactions and/or hydrogen bonding between the additives and growing polypyrrole chains play the important role in reducing chain ordering, while the ionic interactions have limited effect.

Effect of Surface Cleaning on Performance of Organic Friction Modifiers

The performance of surface-active additives, such as friction modifiers, depends on their interactions with surfaces. Their effectiveness thus hinges upon the surface conditions. In this work, the effect of cleaning methods of test substrates on the friction reduction capabilities of different organic friction modifier (OFM) additives was investigated. 52100 steel discs and balls were the test specimens. They were cleaned in five different ways. The cleaned surfaces were characterized by using ellipsometry and atomic force microscopy. The tribological performance of stearic acid (STA), octadecylamine (ODA), and octadecanol (ODO), on these surfaces was then tested.As-received steel surfaces were covered with contaminants that may impede the formation of an OFM surface layer. Cleaning these surfaces with solvents cannot completely remove these contaminants. Cleaning with oxygen or argon plasma results in cleaner surfaces compared to those cleaned by solvents only. The impact of the choice of cleaning method on friction depends on the strength of the interaction between the OFM and the steel surface, which determines the ability of an OFM to displace surface contaminations. Cleaner surfaces result in lower initial friction for STA and ODA. Steady-state friction is also affected but to a lesser extent. This may be because most contaminants that remained in the wear track were mechanically removed during rubbing.

Вплив хімічного складу розчинників на ступінь очищення поверхні перед напиленням йонно-плазмових покриттів

Наведено результати досліджень впливу різних класів розчинників на олієвмісні забруднення на поверхні деталей із вуглецевої сталі перед нанесенням йонно-плазмових покриттів. Як розчинники використано С6Н14, С8Н18, С6Н6, СНСl3, CCl4, С2Н4Сl2, С2Н5ОН, С4Н9ОН, С2Н5ОСОСН3, NaOH, HCl. Забруднювачами поверхні були солідол і мастильно-охолоджувальна рідина (МОР) Укрінол-4. Для зразків, оброблених солідолом, найкращий результат зафіксовано в неполярного розчинника октану С8Н18 і слабкополярного розчинника етилетаноату С2Н5ОСОСН3, для яких втрата маси перевищила 1 %. Втрату маси більше ніж 0,5 % виявлено в неполярних розчинників і хлорозаміщених вуглеводнів. У неполярних розчинників ступінь очищення покращувався зі зростанням молярної маси розчинника та насичення Гідрогеном, а для хлорозаміщених вуглеводнів – із зростанням вмісту Хлору. Найкращі результати очищення зі спиртів виявлено в ізобутанолу С4Н9ОН. Зразки, оброблені МОР Укрінол-4, відмивали розчинниками CCl4, С2Н5ОН, С6Н14, С2Н4Сl2, що свідчить про вагомий внесок поверхнево-активних речовин (ПАР) і присадок, що присутні у складі МОР. Здатність до очищення зростає у такій послідовності: лужні та кислі водні розчини спирти хлорозаміщені вуглеводні неполярні та слабкополярні розчинники. Досліджено фізико-хімічні властивості та визначено вміст сторонніх продуктів в оливах класу HLP для гідросистем і для напрямних верстатів. Проведено порівняння ІЧ-спектрів свіжої та вживаної олив. Встановлено, що в процесі роботи олива окиснюється. Найбільше процес експлуатації вплинув на зростання кислотного числа (в три рази) та вмісту води (в дев'ять разів).

NEW DIRECTION IN LIQUID QUENCHING MEDIA DEVELOPMENT

It is shown that in contrast to well known surface active additives (SAA), affecting physical properties of a liquid, the elimination of film boiling during quenching is achieved by creation of the thin polymeric layer on the surface of hardened metal. It is performed by using special polymers of optimal concentration in water. The obtained insulating polymeric layer decreases initial heat flux density below its critical value and by this way eliminates completely the film boiling without affecting clearly the physical properties of a liquid. Based on this fact and on the principle of decreasing distortion, quench crack formation, and increasing strength of material during intensive quenching, it is proposed to use low concentration of special polymers instead of their high concentration in water. All of this results in significant strengthening of metal, saves costly materials, and increases service life of hardened products. 

Impacts of cellulase deactivation at the moving air\u2013liquid interface on cellulose conversions at low enzyme loadings

BackgroundWe recently confirmed that the deactivation of T. reesei cellulases at the air–liquid interface reduces microcrystalline cellulose conversion at low enzyme loadings in shaken flasks. It is one of the main causes for lowering of cellulose conversions at low enzyme loadings. However, supplementing cellulases with small quantities of surface-active additives in shaken flasks can increase cellulose conversions at low enzyme loadings. It was also shown that cellulose conversions at low enzyme loadings can be increased in unshaken flasks if the reactions are carried for a longer time. This study further explores these recent findings to better understand the impact of air–liquid interfacial phenomena on enzymatic hydrolysis of cellulose contained in Avicel, Sigmacell, α-cellulose, cotton linters, and filter paper. The impacts of solids and enzyme loadings, supplementation with nonionic surfactant Tween 20 and xylanases, and application of different types of mixing and reactor designs on cellulose hydrolysis were also evaluated.ResultsAvicel cellulose conversions at high solid loading were more than doubled by minimizing loss of cellulases to the air–liquid interface. Maximum cellulose conversions were high for surface-active supplemented shaken flasks or unshaken flasks because of low cellulase deactivation at the air–liquid interface. The nonionic surfactant Tween 20 was unable to completely prevent cellulase deactivation in shaken flasks and only reduced cellulose conversions at unreasonably high concentrations.ConclusionsHigh dynamic interfacial areas created through baffles in reactor vessels, low volumes in high-capacity vessels, or high shaking speeds severely limited cellulose conversions at low enzyme loadings. Precipitation of cellulases due to aggregation at the air–liquid interface caused their continuous deactivation in shaken flasks and severely limited solubilization of cellulose.

Effects of Surface Active Additives on the Enzymatic Treatment of Phenol and Its Derivatives: a Mini Review

Phenolic wastewaters represent a serious health and environmental problem. The remediation of phenolic wastewaters using oxidoreductase enzymes has emerged as an attractive environmentally friendly treatment method. However, the loss of enzyme activity during the treatment remains a key limitation. Thus, the aim of this article is to review and assess the recent progress in utilizing surface active additives (i.e., polymers, biopolymers, surfactants, and biosurfactants) for the reduction of enzyme inhibition and, thus, the enhancement of enzymatic remediation of phenolic wastewaters. The reported effect of polymeric and surfactant additives on the enzymatic remediation of phenolic pollutants is mixed. Some studies reported significant enhancements while others demonstrated minimal or no gains. More seriously, it has been reported that these fossil-based additives might lead to a higher toxicity of the treated wastewaters. Bio-based (biopolymers and biosurfactants) additives might address this toxicity issue; however, the bio-based additives are not always as effective as the fossil-based ones. Despite the beneficial effect, with some exceptions, of additives, the enhancement level varies widely, probably due to the variations in the reaction environment. Thus, to draw meaningful and reliable conclusions on which additive(s) is more promising, thorough studies under unified conditions are needed. Additionally, generation of secondary pollutions associated with the fossil-based additives urges the replacement of such additives with bio-based ones. However, the effectiveness of the bio-based additives is still not sufficiently documented, stressing the need for more in-depth studies.

Study of oil sludge, waste oil and other auxiliary substances influence on the methane hydrate dissociation

In this paper, classes of oil medium that ensure the methane hydrate self-preservation were identified. The following compounds and substances were studied: asphaltenes, resins, asphaltene-resin-paraffin deposits (ARPD), multiwall carbon nanotubes, meloxicam (C14H13N3O4S2), kinetic hydrate inhibitors (KHI) Luvicap 55W (copolymer of N-vinylcaprolactam and N-vinylpyrrolidone) and Luvicap EG (poly(N-vinylcaprolactam)), refined petroleum products (initial and waste) and 2,6-Di-tert-butyl-4-methylphenol (antioxidant fuel additive AO-29). Isolated oil components had practically no effect on the decomposition process of methane hydrate. It was observed, that the presence of surface-active additives in refined petroleum products leads to suppression of the investigated effect (self-preservation). It seems to be that in the case of used engine oils, the degree of manifestation of methane hydrate self-preservation effect depends on the duration of its operation (mileage). The obtained results can be the basis of recycling of ARPD and hazardous waste petroleum products in technologies for storage/transportation of natural gas.

Investigation of the Properties of New Surface-Active Additives for Concretes

The results of the investigation of new surfactant additives for concrete are given in the article. Their values of density and surface tension are determined at temperatures of 10-50 oC in steps of 10 degrees. Dependences of the surface tension on temperature, the dependence of density on temperature, the dependence of the surface tension on the density for six types of additives for concrete are obtained.

Porous materials from oppositely charged nanoparticle gel emulsions

Sol–gel processing is an important colloidal processing route for the synthesis of macroporous materials of tunable microstructure. More recently, methods that use particle stabilized foams or emulsions have been developed. However, such methods generally involve the use of an external surface active additives that bind the particles together during processing. In this work, we present a simple and scalable additive-free method for the fabrication of porous materials that are both macroporous and microporous in nature. In particular, we show that silica-alumina porous materials can be fabricated by processing oppositely charged nanoparticle gel emulsions which are a dispersion of oil droplets in a space spanning network of colloidal particles. The nanoparticle gel emulsions obtained are initially characterized by optical microscopy and oscillatory rheology. The water and oil in these emulsion gels are removed by drying and it is finally sintered at 1000 °C to obtain porous material. The pore size and their distribution in the three-dimensional porous material is characterized using scanning electron microscopy (SEM) and X-ray tomography. Microscopy observations revealed a homogeneous distribution of macro-pores of 20–40 μm in diameter along the width, breadth and thickness of the porous material with an average porosity of 40% measured from 2D X-ray computed tomography images. One of the important features of the porous materials thus fabricated is the presence of nanosized pores due to the inherent porosity of the nanoparticle gel as well as micron sized pores due to the oil droplets.

COMPLEX MODIFICATION OF GRAY CAST IRON

The influence of the complex modifier by chemical – active and surface-active additives of gray cast iron on the size of chill and on the width of molted iron zone was researched. The width of a chill zone and molted iron zones were measured at chank ends of various diameter cores. The cores were casted on a massive steel plate and also in standard chill tests. It was established that additional adding of surface-active bismuth in structure of various graphitizing modifiers promoted to reduce the width a chill zone and molted iron zones. It was established that the complex modifiers consisting of chemical – active and surfaceactive components are effective in fight with chill in cast iron castings and can be recommended for application in foundry shops of the entities of a machine-building profile for production of high-quality castings.

Properties of tire rubber with zinc-containing technological additives

In this paper, we studied the influence of zinc-containing technological additives on partial replacement of zinc oxide and stearic acid on deformation-strength and performance properties of tire elastomeric compositions based on polyisoprene rubber and combination of oil-filled butadiene-styrene and polybutadiene rubbers. It was revealed that partial replacement of zinc oxide and stearic acid with zinc-containing technological additives does not significantly affect the basic physico-mechanical properties of rubbers based on synthetic rubbers of general use. It was determined that the introduction of zinc-containing technological additives SCC2 in combination with zinc oxide in all the studied ratios and SCC3 in combination with zinc oxide in 4: 1 and 3: 1 ratios leads to increase (up to 10.4%) of the resistance of these rubbers under the action of temperature-force fields, which is probably due to a more even distribution of polar components of curing system in non-polar elastomeric matrix, as well as the type of cross-links formed during vulcanization under the action of surface-active additives. It has been found that the introduction of zinc-containing additives into the elastomeric compositions based on SRMS-30 ARKM-15 + SRD in combination with zinc oxide leads to increase to 6.3% of wear resistance of rubbers, which may be due to a lower defectiveness of vulcanization structure of these rubbers, concentration of stress centers in the material. For rubbers based on SRI-3, preservation of bond strength of rubber with a textile cord at a sufficiently high level is shown.

Monitoring of Running-in of an EHL Contact Using Contact Impedance

Running-in is an important process for elasto-hydrodynamic lubricated contacts, which affect both service life and operating performance. However, the possibilities of monitoring running-in are still poor. Therefore, the properties of electrical contact impedance as a monitoring tool were studied by using an in-house made ball on disc apparatus. The contact impedance was monitored during run-in experiments with different initial surface roughness of the discs, different slide-to-roll ratios and with pure or additive containing paraffinic oil. The relationship between surface roughness parameters, contact resistance and contact capacitance was investigated. While the contact resistance seems to be affected by the parameter Rz, the contact capacitance seems more dependent on Rq. In addition, the experiments showed that surface active additives do not necessarily need to influence the contact impedance.

Chemically Triggered Formation of Two-Dimensional Epitaxial Quantum Dot Superlattices

Two dimensional superlattices of epitaxially connected quantum dots enable size-quantization effects to be combined with high charge carrier mobilities, an essential prerequisite for highly performing QD devices based on charge transport. Here, we demonstrate that surface active additives known to restore nanocrystal stoichiometry can trigger the formation of epitaxial superlattices of PbSe and PbS quantum dots. More specifically, we show that both chalcogen-adding (sodium sulfide) and lead oleate displacing (amines) additives induce small area epitaxial superlattices of PbSe quantum dots. In the latter case, the amine basicity is a sensitive handle to tune the superlattice symmetry, with strong and weak bases yielding pseudohexagonal or quasi-square lattices, respectively. Through density functional theory calculations and in situ titrations monitored by nuclear magnetic resonance spectroscopy, we link this observation to the concomitantly different coordination enthalpy and ligand displacement potency of the amine. Next to that, an initial ∼10% reduction of the initial ligand density prior to monolayer formation and addition of a mild, lead oleate displacing chemical trigger such as aniline proved key to induce square superlattices with long-range, square micrometer order; an effect that is the more pronounced the larger the quantum dots. Because the approach applies to PbS quantum dots as well, we conclude that it offers a reproducible and rational method for the formation of highly ordered epitaxial quantum dot superlattices.

Synthesis of bottlebrush copolymers based on poly(dimethylsiloxane) for surface active additives

Abstract Bottlebrush polymers have been used as surface-active additives for chemically-identical linear polymers because they spontaneously accumulate at surfaces through an entropy-mediated process. In this work, we design functional bottlebrush polymer additives with mixed side-chain chemistries that can deliver unique surface properties. Bottlebrush polymers with poly(dimethylsiloxane) (PDMS) side-chains and bottlebrush copolymers with PDMS and poly(lactic acid) (PLA) side-chains are synthesized using ring opening metathesis polymerization. Contact angle goniometry, X-ray photoelectron spectroscopy (XPS), and microscopy demonstrate a spontaneous accumulation of these additives at the film surface without lateral phase segregation. Bottlebrush polymers were found to enrich the film surface more strongly than linear block copolymers of PDMS-b-PLA, and the surface contact angle was tunable by varying the composition and quantity of added bottlebrush copolymer. Significantly, bottlebrush additives segregate rapidly, during film casting. This work demonstrates that low-surface energy bottlebrush copolymer additives can be used to introduce new surface properties in polymer films.

Synthesis of non-spherical patchy particles at fluid-fluid interfaces via differential deformation and their self-assembly.

Non-spherical patchy particles are potential candidates as building blocks for the design of target colloidal structures via spontaneous self-organization. We report a facile scheme to synthesize non-spherical particles with patchy electrostatic interactions. In this method, charged spherical latex particles such as polystyrene (PS) are deformed unequally at an oil-water interface due to heating and partial swelling. The spherical particles then evolve into non-spherical shapes such as 'acorn-like' and 'idly-like'. We explain the mechanism of differential deformation by comparing the heat of viscous dissipation and the interfacial energies. Furthermore, if oppositely charged additives such as the cetyltrimethylammonium bromide (CTAB) surfactant or silica nanoparticles are present in water (subphase), electrostatic attraction leads to adsorption of these species on the PS surface exposed to water. As a result, one side of the particles is selectively functionalized, while the other side remains unaltered. As the latex particles are negatively charged initially, this method yields particles that are non-spherical in shape and with negative charges on one side and positive charges on the other side. The degree of shape deformation and patch coverage can be varied by choosing different surface active additives. We extend this approach to curved interfaces and demonstrate a high throughput emulsion based approach for the synthesis of such particles. Self-assembly of these particles shows interesting structures such as linear, branched polymeric or worm-like chains and micelle-like spherical aggregates. These shape anisotropic particles with orientation specific interactions that mimic bio-macromolecular systems can be further explored for self-assembly into hierarchical mesoscale structures.

Copolymer films containing amphiphilic side chains of well-defined fluoroalkyl-segment length with biofouling-release potential

Novel methacrylate copolymers containing polysiloxane (SiMA) and mixed poly(ethyleneglycol)-perfluorohexyl side chains (MEF) were synthesised and dispersed as surface-active additives in crosslinked PDMS films.

Use of Electron Paramagnetic Resonance for Investigating Glasses and Raw Materials (Review)

It is shown that electron paramagnetic resonance can be used to study the fine structure of glasses and glass enamel materials as well as to find and identify defects in glass. The spectra of paramagnetic ions (Cu2+, V4+, Ti3+, Mo5+ Mn2+, Fe3+ ) are discussed. Specific examples of the detection of these ions in sitals, in which they are introduced as surface-active additives or are present as impurities entering the crystallized glass via the raw materials, are examined. It is determined that the most informative ions for studying the structure and phase separation of glass are Cu2+ and V4+.

Enhanced Surface Finishing of Tungsten Carbide By Using Organic Additives

The mechanical machining and finishing of cemented carbides is associated with high abrasive wear of cutting tools. Electrochemical Machining (ECM) is the technical application of high rate metal dissolution and well established for steels and several non –ferrous metals. ECM is a priory free of mechanical tool wear. Recently the authors investigated the high rate dissolution of cemented carbides in ammonia containing alkaline electrolytes [1]. The electrolyte system is suitable for ECM of tungsten carbide as well as cobalt. A homogenous dissolution of the compound material was achieved. In industrial practice, Electrochemical Machining is used to realize high surface quality of work pieces. The existence of anodic films during the machining step is important in controlling the texture of the machined surface obtained [2]. If the dissolution process is controlled by material transport through a film of compact dissolution intermediate, precipitated products [3] or viscous product layer [4] the surface will occurs bright and shiny. The formation of viscous surface layers can be enhanced by surface active organic additives of the electrolyte [5]. In the present work the authors investigated the effect of different solvents on the surface roughness during ECM of tungsten carbide. The electrochemical experiments were carried out in a channel flow cell. Firstly, an aqueous solution containing 2M ammonia and 1.5M sodium nitrate was used as reference electrolyte. In a second step ethanol and glycol, respectively, were added. Both additives change the conductivity as well as the viscosity of the electrolyte. All samples were investigated by SEM after the ECM experiments. A decreasing surface roughness in the order of water, water/ethanol and water/glycol was achieved. A quantitative evaluation will be given by using laser scanning microscopy.