Adsorption Of Sodium Dodecyl Sulfate Research Articles

Effect of the medium composition on the extraction of chromium, aluminium and iron hydroxides from wastewater by electroflotation

The process of electroflotation is used for treatment of wastewaters carrying heavy and non-ferrous metals in the form of poorly soluble compounds if the concentrations of contaminants are too high to be handled by adsorption process. The problem of raising the efficiency of electroflotation process is currently of relevance. This paper examines how the composition of the medium, i.e. the nature of the electrolyte, surfactants and hardness salts, can influence the extraction of iron, aluminum and chromium hydroxides from aqueous solutions by electroflotation. It was found that the electrolyte (NaCl, Na2SO4) nature has no significant effect on the process. The hydroxide extraction performance can be impacted by the presence of calcium ions regardless of the electrolyte nature. It happens due to the adsorption of Ca2+ on the hydroxide surface, which makes it more hydrophilic. The degree of dispersed phase extraction can be increased due to the introduction of surfactants: didecyldimethylammonium chloride, sodium dodecyl sulfate and a mixture of primary oxyethylated synthetic alcohols. Sodium dodecyl sulfate, which is an anionic surfactant, proved to deliver the best result. The high process efficiency in terms of dispersed phase extraction is due to the hydrophobization of the particle surface by adsorbed sodium dodecyl sulfate and the stabilization of gas bubbles. The particle sizes of iron and chromium hydroxides vary in the range of 0.04 to 4 microns. At the same time, most of the aluminum hydroxide particles are bigger than 10 microns, which can be attributed to the high polymerization ability of aluminum ions and subsequent particle coagulation. The efficiency of electroflotation extraction of chromium, aluminum and iron hydroxides in the presence of calcium ions using anionic surfactant is at least 90%. Additional filtration is recommended to ensure the treated wastewater is in compliance with applicable standard.

Sodium Dodecyl Sulfate Adsorption on Sulfuric Acid-Crosslinked Chitosan/Pectin Polyelectrolyte Complex Film

Sulfuric acid cross-linked chitosan/pectin polyelectrolyte complex (CPS) film was prepared as sodium dodecyl sulfate (SDS) adsorbent. CPS films were prepared in various compositions of chitosan/pectin and cross-linked by immersion in 0.1 M H2SO4 solution. CPS films were characterized using FTIR and SEM. CPS film was used for SDS adsorption with parameters of film composition, contact time, pH, initial SDS concentration. FTIR spectra showed characteristic peaks for chitosan, pectin and their interaction with sulfuric acid. The surface of the CPS film changed to become smoother after being used for SDS adsorption. CPS film composition 70:30 showed the highest percent swelling and was stable at the overall pH. The optimum conditions for SDS adsorption by sulfuric acid cross-linked chitosan/pectin CPS film occurred at a contact time of 120 minutes, pH 5, initial concentration of SDS 100 mg L–1 with a film composition of 70:30. Adsorption followed the pseudo-second-order kinetic and Freundlich isotherm models with KF and n of 0.0297 and 0.377, respectively. The highest SDS desorption of 97.6% was achieved using 0.1 M NaClO4 solution.

Effect of cations on surfactant induced membrane wetting during membrane distillation

Membrane wetting is regarded as challenges to the saline surfactant wastewater membrane distillation process, and the reason for wetting discrepancies under the assist of salt remains ambiguous. Herein, a comparative investigation was performed to reveal the mechanism of salt on sodium dodecyl sulfate (SDS) induced membrane wetting via the direct contact membrane distillation (DCMD) process. The results showed that different cations exhibited contrasting influences on membrane wetting. Compared to Na+, Mg2+ and Al3+, Ca2+ and K+ triggered significant flux increase. However, Ca2+ alleviated membrane wetting once feed temperature decreased. Feed solution characteristics indicated that Ca2+ and K+ significantly enhanced the Krafft point and hydrophobicity of micelles. Molecular dynamics simulation revealed the microcosmic interaction of Ca2+ and SDS, and verified that Ca2+ compressed the headgroup volume of SDS. By combining the critical packing parameter (CPP) of surfactants, dehydration of cations and micelle filtration experiments, it was concluded that the cations with weak hydration function in compressing the hydration layer of headgroups and facilitating the formation of more compact micelles that carry more SDS monomers, thus creating the transient adsorption of SDS in membrane pores and rapid membrane wetting. This study provides a new understanding of surfactant induced membrane wetting.

Surfactant Adsorption to Gypsum Surfaces and the Effects on Solubility in Aqueous Solutions.

Vibrational sum frequency generation (VSFG) spectroscopy, conductometric titration measurements, and EDX elemental mapping were used to examine surfactant adsorption to the gypsum (010) surface and assess the effects of surfactant adsorption on gypsum solubility in aqueous solutions. Sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium chloride (DTAC) were used as anionic and cationic surfactants, respectively. Gypsum/SDS interactions result in an ordered precipitate layer on the gypsum surface after water evaporation; gypsum/DTAC interaction did not show a similar effect, despite exposure of gypsum to equivalent amounts of surfactant. VSFG spectra showed that SDS molecules adsorb with their chains parallel to the gypsum surface; spectra from gypsum surfaces treated with DTAC, however, showed no measurable response, implying that these surfactants form disorganized aggregates with no polar ordering. Vibrational data were supported by independent EDX measurements that show a uniform distribution of SDS across the gypsum surface. In contrast, element-specific EDX images showed that DTAC clustered in tightly localized patches that left most of the gypsum surface exposed. The uniform adsorption of SDS on the gypsum surface suppresses long-term dissolution up to 40% when compared to samples exposed to DTAC. Gypsum samples in DTAC-containing solutions lose approximately the same amount of material to dissolution as samples immersed in pure water.

New Design of a Sample Cell for Neutron Reflectometry in Liquid–Liquid Systems and Its Application for Studying Structures at Air–Liquid and Liquid–Liquid Interfaces

Knowledge of interfacial structures in liquid–liquid systems is imperative, especially for improving two-phase biological and chemical reactions. Therefore, we developed a new sample cell for neutron reflectometry (NR), which enables us to observe the layer structure around the interface, and investigated the adsorption behavior of a typical surfactant, sodium dodecyl sulfate (SDS), on the toluene-d8-D2O interface under the new experimental conditions. The new cell was characterized by placing the PTFE frame at the bottom to produce a smooth interface and downsized compared to the conventional cell. The obtained NR profiles were readily analyzable and we determined a slight difference in the SDS adsorption layer structure at the interface between the toluene-d8-D2O and air-D2O systems. This could be owing to the difference in the adsorption behavior of the SDS molecules depending on the interfacial conditions.

Adjustable surface activity and wetting ability of anionic hydrocarbon and nonionic short-chain fluorocarbon surfactant mixtures: Effects of Li+ and Mg2+

Achieving wide variation ranges and various adjusting modes of the performances for surfactant mixtures is still a significant challenge which limits the extensive application of surfactant mixtures. Herein, we reported the physicochemical properties and performances of hydrocarbon/fluorocarbon surfactant mixtures constituted with an anionic hydrocarbon surfactant, sodium dodecyl sulfate (SDS), and a tri-block nonionic short-chain fluorocarbon surfactant (F9EG13F9). Meanwhile, the effects of Li+ and Mg2+ on them were investigated. The surface tension and contact angle measurements were adopted to reflect the surface activity and wetting ability of SDS/F9EG13F9 mixtures. The data showed that the surface tensions at the critical micelle concentrations and the contact angles on polytetrafluoroethylene film of these surfactant mixtures are 33.5–21.4 mN/m and 118.0–58.7°, respectively, which indicates that their surface activity and wetting ability possess wide variation ranges. Furthermore, the micellization, adsorption and thermodynamics behaviors of mixed surfactants were also analyzed using a series of theoretical parameters based on the regular solution theory, Clint’s model, Maeda’s model, etc. The results approved that Li+ and Mg2+ immensely reduce the electrostatic repulsion effect of SDS and increase the adsorption of SDS at phase interfaces to enhance mixed monolayer packing, in which the effect of Mg2+ is stronger than that of Li+. Thus, precisely adjustable surface activity and wetting ability can be realized by changing the molar ratio and adding the different cations, which enables SDS/F9EG13F9 mixtures to possess tunable performances to meet various practical application requirements.

Effect of sodium dodecyl sulphate on Cu electrodeposition: interaction with hydrophobic substrate and Cu ions

ABSTRACT In this study, the effect of sodium dodecyl sulphate (SDS) on Cu electrodeposition was evaluated using cyclic voltammetry. With the weak adsorption of SDS on Cu and Au surfaces, SDS slightly altered the cyclic voltammogram for Cu electrodeposition on these surfaces. However, the cyclic voltammogram on glassy carbon (GC) and pyrolytic graphite significantly changed with the addition of SDS, indicating that the hydrophobic interactions are critical for SDS adsorption. SDS adsorbed on the GC surface exhibiting an increase in current response, an indication of the enhancement of Cu nucleation, confirmed by the increase in the nuclei density on the GC surface. Moreover, the addition of SDS splits the voltammetric wave on GC, indicating that SDS might stabilise Cu+ intermediates that are probably associated with SDS micelles. In addition, the micellar association might lower the diffusion coefficient of Cu2+ leading to a depression in the reduction peaks in the cyclic voltammograms.

Study on Adsorption Characteristics of Sulfonate Gemini Surfactant on Lignite Surface

In order to explore the adsorption characteristics of sulfonate gemini surfactants on the surface of lignite, the molecular dynamics simulation method was used, and A kind of sulfonic acid bis sodium salt (S2) and the sodium dodecyl sulfate (SDS) were selected. A binary model of surfactant/lignite adsorption system and a ternary model of water/surfactant/lignite system were constructed, and a series of properties such as adsorption configuration, interaction energy, order parameters, relative concentration distribution, number of hydrogen bonds, etc., were analyzed. The results showed that the adsorption strength of S2 on the surface of lignite was higher than that of SDS. The results indicated that the large-angle molecular chain in S2 tended to become smaller, the small-angle molecular chain tended to become larger, and the angle between the molecular chains and the Z axis tended to be concentrated, making the formed network structure denser during the adsorption process. The number of hydrogen bonds in the water-coal system was 42, and the number of hydrogen bonds in the system after S2 adsorption was 15, which was much lower than the 23 hydrogen bonds in the system after SDS adsorption, and S2 could better adsorb and wrap the oxygen-containing groups on the surface of the lignite. The comparative study of the adsorption characteristics of the two surfactants on the surface of lignite can help us better understand the influence of the surfactant structure on the adsorption strength. The research results have important theoretical and practical significance for developing new surfactants, and enriching and developing the basic theory of coal wettability.

ZIF-8/carbon fiber for continuous adsorption of sodium dodecyl sulfate (SDS) from aqueous solutions: Kinetics and equilibrium studies

In this research, sodium dodecyl sulfate (SDS) separation from aqueous solutions using hierarchical porous zeolitic imidazolate framework-8/carbon fiber (ZIF-8/carbon fiber) nanosorbent was assessed by batch and column process. The characterization of the ZIF-8/carbon fiber nanocomposite was conducted by X-ray diffractometer (XRD) and field emission-scanning electron microscopy (FE-SEM). In addition, the influence of pH on the adsorption batch studies was investigated. The quantity and quality of SDS uptake by ZIF-8/carbon fiber were studied based on ultraviolet–visible spectroscopy measurements and Fourier transform infrared spectroscopy (FTIR) spectra. Aside from that, a practical process involving column of the ZIF-8/carbon fiber adsorbent to remove SDS was performed, dynamically. It was found that the loading of ZIF-8 nanoparticles on carbon fiber struts increased the hydrophobicity of carbon fiber, and its contact angle with water increased from 90° to 150°. Besides, the results of FTIR confirmed successful adsorption of SDS onto ZIF-8/carbon fiber surfaces, which is believed to be governed by both electrostatic attraction and hydrophobic interactions. In addition, the results of batch experiments illustrated that adsorption of SDS onto ZIF-8/carbon fiber adsorbent is rapid with an equilibrium time of 30 min and follows a first-order kinetic model (R2 = 0.9944). Furthermore, the Langmuir isotherm model was best fitted adsorption equilibrium (R2 = 0.9899), at different pH values. The results revealed the removal quantity after five cycles was decreased by 20% for SDS removal. Moreover, the maximum adsorption capacity of SDS on the ZIF-8/carbon fiber was obtained 377 ± 7 mg/g at the optimal conditions. The column adsorption experiments showed that inline SDS removal is possible.

Experimental studies on the influence of sodium lauryl sulfate on seepage and wetting of water infusion of coalbeds

Coal seam water injection is a disaster prevention technology that is commonly used in the mining of underground coal resources. Surfactants are widely used in the coal industry in China to enhance the effect of coal seam water injection. Surfactants may have a potential impact on the seepage stage while enhancing wetting. In order to study the characteristics of surfactants on coal seam water injection, we adopted sodium dodecyl sulfate (SDS) as a surfactant in this study. Based on the research background of the Houwenjialiang Coal Mine in Ordos City, Inner Mongolia Autonomous Region, China, we examined the effect of the surfactant SDS on the seepage stage of coal seam water injection using a laboratory triaxial seepage system. The influence of the surfactant SDS on the coal seam water injection wetting stage was investigated with a laboratory bottom-up imbibition experiment method. The main conclusions are as follows. The addition of surface activity can enhance the wetting effect but impede the seepage stage of coal seam water injection, which deteriorates the permeability coefficient. After the addition of surfactant, the permeability coefficient shows a rapid decrease first and then gradually stabilizes. The reason for the compromise to the permeability coefficient is mainly due to the small cracks or pores caused by the adsorption of SDS, which slows down the flow of the liquid. The addition of surfactants can effectively reduce the surface tension of the liquid, minimize the contact angle, and enhance the coal seam water injection wetting stage. The research results provide valuable information for evaluating coal seam water injection effect and the development of water injection technology.

The role of temperature and porous media morphology on the performance of anionic and cationic surfactants for enhanced heavy oil recovery

In spite of the numerous studies conducted on enhanced oil recovery using micromodels, the effect of temperature on the performance of surfactants has been grossly missing in the existing literature. Hence, this research scrutinized the variation in the performances of sodium dodecyl sulfate (SDS) as an anionic surfactant and dodecyl trimethylammonium bromide (C12TAB) as a cationic surfactant with temperature (25–98 °C) on microscopic and macroscopic scales. Viscosity, interfacial tension (IFT), and contact angle were measured using capillary tube, pendant drop and Wilhelmy Plate methods, respectively, to analyze the mechanisms of displacement and also the interaction between fluids in media with four different morphologies. The performances of brine and surfactants were found to be exceedingly temperature-dependent where this dependency was highly affected by the pores and throats structures. The measured values of the contact angle indicated a direct relationship between the temperature and the adsorption of surfactants on the glass surface. Additionally, SDS adsorption was more influenced by temperature change in comparison with C12TAB. The surfactants decreased the heterogeneity effects so that the recoveries of homogeneous and heterogeneous media were approximately equal. Nevertheless, the ultimate oil recovery of water flooding in heterogeneous micromodel was observed to be averagely 15% higher than homogeneous micromodel.

Double Phase Inversion of Pickering Emulsion Induced by Magnesium Hydroxide Nanosheets Adsorbed with Sodium Dodecyl Sulfate.

Surfactants are often used as a cooperation stabilizer with solid particles for increasing the efficiency of Pickering emulsion. Accordingly, the effects of interaction between surfactants and solid particles on stabilizing Pickering emulsions have been attracting great attention. In this study, magnesium hydroxide (MH) nanosheets adsorbed with different amounts of sodium dodecyl sulfate (SDS) surfactants were designed and used to stabilize paraffin-water emulsions. Using SDS-adsorbed MH nanosheets as a stabilizer, the phenomenon of double phase inversion was found for Pickering emulsion. Pickering emulsion was inverted initially from O/W to W/O at about 0.022 mmol/g of the adsorption amount of SDS on the MH nanosheets, and subsequently back to O/W at about 2.312 mmol/g. The first phase inversion was because of the increased hydrophobicity of modified MH nanosheets, where SDS molecules were monolayer-adsorbed on the MH nanosheets surface. The second phase inversion occurred due to the bilayer adsorption of SDS on MH nanosheets, which converted the modified MH nanosheets hydrophilic again. These results are of great importance to understanding the double phase inversion of Pickering emulsions with the addition of surfactants and finding prospective applications in fields such as reversible drilling fluids and oil extraction.

Visible light facilitated degradation of alternate dye solutions by highly reusable Mn-ZnO nano-photocatalyst

Keeping the industrial viability in view, manganese incorporated zinc oxide nanocomposites (Mn-ZnO NCs) was synthesized as a reusable photocatalyst. The photocatalytic efficiency of Mn-ZnO NCs was compared with ZnO nanoparticles. Morphology and size of the samples were modulated using sodium dodecyl sulphate (SDS) as the cappant. The crystallite size and crystalline parameters were estimated through X-ray diffraction spectra, while the adsorption of SDS on the samples was assessed through Fourier transform infrared spectra. Since the efficiency of any photocatalyst fundamentally depends upon its photo-physical and surface properties, UV-Visible, Photoluminescence, and Electron paramagnetic resonance spectroscopic techniques were used to access the optical properties while Field emission scanning electron microscopy was employed to deduce the morphology of the samples. Energy dispersive X-ray spectra and X-ray photoelectron spectra confirmed the elemental composition of the samples. The photocatalytic degradation of dye solutions was monitored initially through UV-Vis spectra. In order to confirm that the final products of photocatalytic degradation were non-toxic, Mass spectrometry was employed to estimate the types of intermediates and final products formed during and after the course of photocatalytic reaction. The results of visible light assisted photocatalytic degradation studies indicated that Mn-ZnO NCs were highly reusable for degrading alternate solutions of dyes (rhodamine B and methylene blue) as well as their mixture within a span of only 20 min. The difference in the morphology of Mn-ZnO NCs before and after performing the photocatalytic activity was also assessed.

Adsorptive Removal of Rhodamine B Using Novel Adsorbent-Based Surfactant-Modified Alpha Alumina Nanoparticles.

The objective of the present study is to investigate removal of cationic dye, rhodamine B (RhB), in water environment using a high-performance absorbent based on metal oxide nanomaterials toward green chemistry. The adsorption of sodium dodecyl sulfate (SDS) onto synthesized alpha alumina (α-Al2O3) material (M0) at different ionic strengths under low pH was studied to fabricate a new adsorbent as SDS-modified α-Al2O3 material (M1). The RhB removal using M1 was much higher than M0 under the same experimental conditions. The optimal conditions for RhB removal using M1 were found to be contact time 30 min, pH 4, and adsorbent dosage 5 mg/mL. The maximum RhB removal using M1 achieved 100%, and adsorption amount reached 52.0 mg/g. Adsorption isotherms of RhB onto M1 were well fitted by the two-step adsorption model. The electrostatic attraction between positive RhB molecules and negatively charged M1 surface controlled the adsorption that was evaluated by the surface charge change with zeta potential and adsorption isotherms. Very high RhB removal of greater than 98% after four regenerations of M1 and the maximum removal for all actual textile wastewater samples demonstrate that SDS-modified nano α-Al2O3 is a high-performance and reusable material for RhB removal from wastewater.

Mechanistic pathways of cationic and anionic surfactants sorption by kaolinite in water.

Surfactants are widely used in many chemical industries and as primary components of cleaning detergents due to their specific characteristics, which in turn results in high pollution of domestic and industrial wastewaters by such substances. In this study, the mechanistic pathways of the adsorption of cationic benzyl-dimethyl-dodecyl ammonium bromide (BDDAB) and anionic sodium dodecyl sulfate (SDS) surfactants on kaolinite clay in water were investigated. The results showed that the adsorption of anionic surfactant (SDS) on kaolinite is better compared with cationic surfactant (BDDAB), wherein the ♦maximum adsorption capacity was found 161.4μmolg-1 and 234μmolg-1 for BDDAB and SDS, respectively. Adsorption kinetics were the best suited to pseudo-second-order model for both BDDAB and SDS with an adsorption rate constant of 0.028gμmol-1min-1 and 0.023gμmol-1min-1, respectively. Meanwhile, the adsorption of BDDAB by kaolinite showed that the isotherm adsorption tended to follow the Langmuir-Freundlich and Freundlich isotherm models. However, the SDS adsorption isotherm obeyed only the Langmuir-Freundlich model.

Wet Spinning of Chitosan Fibers: Effect of Sodium Dodecyl Sulfate Adsorption and Enhanced Dope Temperature

Production of fibers from nonthermoplastic polymers, such as chitosan, usually requires dissolution with subsequent fiber formation, for instance, via coagulation. Good fiber-forming properties enable simultaneous spinning of multiple fibers into a yarn, which is one of the prerequisites for process scalability. Here, we report a multifilament wet-spinning process that eliminates the use of such volatile organic compounds as methanol and acetone, enhances fiber formation, and allows producing continuous well-separated chitosan fibers after drying. This is achieved by (i) solidification of the extruded solution by alkali and sodium acetate in the coagulation bath and (ii) further stabilization of the fibers by adsorbing the anionic surfactant, sodium dodecyl sulfate. The obtained fibers have a circular cross section and smooth surface. We demonstrate that it is possible to increase fiber breaking tenacity and Young’s modulus by applying stretching (draw ratios up to 1.77) or by incorporating cellulose nanofibrils (CNFs, up to 4 wt % based on chitosan) in the spinning solutions. However, the limitation of increased viscosity when adding CNF is needed to be overcome for possible higher reinforcement effects. We demonstrate that fiber breaking tenacity, Young’s modulus, and elongation at break can be enhanced even further by increasing the spin dope temperature from 22 to 60 °C, with simultaneously increasing the spin dope solid content to keep the same dope viscosity. The fibers with a maximum breaking tenacity of ca. 10 cN/tex at an elongation at break of ca. 7.5% were obtained.

A flow velocity dependence of dynamic surface tension in Plateau borders of foam

HypothesisLiquid drainage through foams is a multiscale process, that primarily occurs through channels known as Plateau borders (PBs). Recent experimental studies of isolated PBs have observed variations in channel surface tension, γ, with liquid flow rate, Q, for systems containing soluble low molecular weight surfactant (LMWS). The current study proposes that the dynamic surface tension (DST) could be responsible for this effect, where the residence time of surfactant molecules in the PB is similar to the time required for their adsorption to the channel interface. ExperimentsProfile geometries of isolated ‘ideal’ PB’s were created in a bespoke experimental setup at controlled forced liquid flow rates. Average surfactant residence times, τRes, were calculated for solutions of Sodium dodecylsulfate (SDS), Tween 20 (T20) and Tween 80 (T80), and used to calculate corresponding average DST values in discrete regions of measured PB profiles. DST values were combined with microscale drainage theory to assess the potential physical implications on liquid flow. FindingsSignificant variations in the magnitude of γ were calculated based on surfactant characteristics, where only the rapid adsorption of SDS was sufficient to produce DST values approaching equilibrium. These findings seriously question assumptions of near equilibrium surface tension in LMWS foam systems above their critical micelle concentration (CMC). Furthermore, the presence of surface tension gradients identified using this discrete approach, highlights the need to further refine the current theory to a continuous approach incorporating Marangoni effects.

Exploration the inhibition mechanism of sodium dodecyl sulfate on Mg alloy

The inhibition mechanism of sodium dodecyl sulfate (SDS) on Mg alloy in 3.5 wt. % NaCl solution was thoroughly investigated by means of SEM, EPMA, XPS, TEM and electrochemical corrosion tests. The active Mg surface is covered by a hydrophobic outer corrosion layer and a passive inner oxide layer in the presence of SDS, which suppress the cathodic hydrogen evolution and anodic dissolution of the substrate. The electrochemical reaction kinetics is inhibited due to adsorption of SDS in the corrosion products, while the oxidation reaction of the substrate is facilitated by the hydrophobic outer corrosion layer.

Adsorption characteristics of anionic surfactant onto laterite soil with differently charged surfaces and application for cationic dye removal

In this paper, we report the adsorption characteristics of the anionic surfactant, sodium dodecyl sulfate (SDS) onto laterite soil with positively and negatively charged surfaces. The laterite soil was characterized using X-ray fluorescence (XRF), scanning electron microscopy (SEM), as well as total organic carbon (TOC), Brunauer-Emmett-Teller (BET) and zeta potential measurements. The adsorption of SDS onto a positively charged laterite surface at pH 4 decreased with an increase in ionic strength, indicating that the electrostatic attraction was the main driving force for controlling the adsorption. On the other hand, the adsorption of SDS onto a negatively charged laterite surface at pH 10 was induced by both electrostatic and hydrophobic interactions as the adsorption increased with increasing NaCl concentrations. The adsorption isotherms of SDS onto laterite at different pH values and NaCl concentrations were fitted well by the two-step adsorption model. The adsorption mechanism of SDS onto laterite soil with differently charged surfaces was discussed in detail based on the changes in functional surface groups determined by Fourier transform infrared spectroscopy (FT-IR), variation in the change in surface charge as evaluated by zeta potential measurements, and adsorption isotherms. The application of SDS adsorption to the modification of the laterite surface for the removal of the cationic dye, rhodamine B (RhB) was also investigated. Optimum conditions for RhB removal were found to be pH 4, adsorption time 60 min, and adsorbent mass 0.25 g. The removal efficiency of RhB was >94% after five recycles. Our results indicate that the surface modification of laterite soil with SDS is valuable for the removal of cationic dyes from aqueous solutions.

The use of Al2O3 - pillared clay in cleaning of aqueous solutions from surfactants

The paper describes the Al2O3-pillared clays synthesized by modifying the natural montmorillonite clay with aluminum polyhydroxy complexes and subsequent heat treatment of the modified samples at temperatures of 400 °C and 500 °C. The textural characteristics of natural and Al2O3-pillared clays were determined by the method of low-temperature nitrogen adsorption. The results showed that the obtained materials had a specific surface area, which was 1.7 times larger than the surface of the original clay, and the total pore volume, which was 1.2 more, than the pore volume of the original clay. Anionic surfactants (sodium dodecyl sulfate C12H25OSO3Na and sulfonol C12H25C6H4SO3Na) adsorption results have shown that the clay modifying by polyhydroxocomplexes of aluminum leads to a significant increase in their aniono-exchange capacity. Al2O3-pillared clay exceeds the adsorption capacity of natural clay more than 2 times in the adsorption of sodium dodecylsulfate and sulfonol. It is established that the adsorption isotherms of sodium dodecylsulfate and sulfonol on Al2O3-pillared clays well obey the Freundlich adsorption isotherm equation, which describes multilayer adsorption on a heterogeneous surface of sorbents. Al2O3-pillared clays may be of interest for use in wastewater treatment from anionic surfactants.