Cetyltrimethylammonium Bromide Concentration Research Articles

Influence of isopropanol on the rheological behavior of wormlike micelles

Abstract The influence of replacing water with isopropanol (IP) on the rheological properties of aqueous solutions containing wormlike micelles (WLMs) prepared by mixing cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) at 25 °C was investigated. Viscosity of CTAB aqueous solutions exhibits two maxima and one minimum with increasing amounts of NaSal, consisting of entangled WLMs. When water is replaced by increasing amount of IP, the viscosity maxima and the minimum changes drastically. The elastic plateau modulus G° of these solutions remains almost the same with increasing IP contents (up to ∼5 wt%), whereas their relaxation time changes drastically. Critical micelle concentration (CMC) of CTAB has increased with further IP addition, indicating an increase in the micellar hydrophilicity. For WLMs at minimum viscosity, increasing addition of IP (>5.0 %) to WLMs at maximum and minimum viscosities, leads to a drastic decrease in the elastic modulus G°, indicating the formation of smaller micellar aggregates. The influence of IP as a co-solvent on the WLMs rheological properties is also compared to that of glycerol and 1,3 butanediol (1,3 BD) for the same NaSal/CTAB viscoelastic system.

Size optimization of mesoporous β-Cyclodextrin Metal-Organic frameworks as Bio-MOFs

In this study synthesis and size optimization of the β-cyclodextrin-metal–organic framework (β-CD-MOF) with potassium as the metal node through the vapor diffusion method was carried out. The effect of different solvents (methanol, ethanol, acetone, and acetonitrile), temperature (40, 50, and 60 °C), time (6, 12, and 24 h), the molar ratio of β-CD to KOH (1:4, 1:8 and 1:16) and different amount of CTAB (0, 56 and 112 mg) was investigated. One factor at a time approach was implemented and the optimum condition obtained from each parameter was used to synthesize a final crystal structure. Increasing time, temperature, and CTAB concentration reduced the size of the crystals. Methanol produced uniform morphology and smaller crystal size, and the optimum molar ratio of β-CD to KOH was obtained to be 1:8. The optimized particle had an average size of 301 ± 13 nm and surface area of 1123 m2/g, with mean pore diameter 2.2 nm.

The Effect of Concentration, Temperature, and pH on the Formation of Hyaluronic Acid-Surfactant Nanohydrogels.

The assembly of colloidal hyaluronic acid (HyA, as a polysaccharide) based hydrogel particles in an aqueous medium is characterized in the present paper, with an emphasis on the particular case of nanohydrogels formed by surfactant-neutralized polysaccharide networks. The structural changes and particle formation process of polysaccharide- and cationic-surfactant-containing systems were induced by the charge neutralization ability and the hydrophobic interactions of cetyltrimethylammonium bromide (CTAB) under different conditions. Based on the rheological, light scattering, ζ-potential, turbidity, and charge titration measurements, it can be concluded that the preparation of the HyA-CTAB particles can be greatly controlled. The results indicate that more available negative charges can be detected on the polymer chain at smaller initial amounts of HyA (cHyA < 0.10 mg/mL), where a molecular solution can be formed. The change in the pH has a negligible effect on the formation process (particle aggregation appears at nCTAB/nHyA,monomer~1.0 in every case), while the temperature dependence of the critical micelle concentration (c.m.c.) of CTAB determines the complete neutralization of the forming nanohydrogels. The results of our measurements confirm that after the appearance of stable colloidal particles, a structural change and aggregation of the polymer particles take place, and finally the complete charge neutralization of the system occurs.

Performance evaluation of different types of surfactants to inhibit clay swelling during chemical enhanced oil recovery

AbstractIn most cases, sandstone reservoirs contain clay particles. When a fluid with low salt content is injected into the reservoir, clay particles swell, and the rock's permeability decreases. Since surfactant flooding with water that has lower salinity than formation water is used to improve oil recovery, this study examines the swelling inhibitive strength of various surfactants. The study investigates the effect of surfactants on clay swelling inhibition through linear swelling and sedimentation experiments which showed that cetyl trimethyl ammonium bromide (CTAB) inhibits clay swelling. The optimum CTAB concentration was found to be 1 wt.%. However, sodium dodecyl sulphate (SDS) and Triton X‐100 (TX‐100) did not inhibit clay swelling. Sandpack experiments confirmed that CTAB prevented clay swelling and sandpack permeability reduction, while SDS and TX‐100 did not. The injection pressure results for the different surfactants were as follows: CTAB—39 psi, SDS—203 psi, TX‐100—223 psi, deionized water (DW)—324 psi, and KCl—78 psi. The mechanism of surfactant performance in affecting clay swelling was investigated based on thermal gravimetric analysis (TGA), zeta potential, and scanning electron microscope (SEM) images. The results showed that CTAB compensates for the surface charge of clays through a cation exchange mechanism. The amount of absorbed water for clays modified with CTAB was lower than that for other surfactants. The SEM images confirmed that the CTAB‐modified clays were larger and did not disintegrate during dispersion; however, in other cases, the particle size was smaller.

Gel tracking dye “Bromophenol blue” promote amorphous aggregation in insulin

Protein aggregation is implicated in different human diseases. It also makes the protein less desirable candidate for industry as they exhibit reduced biological activity. Proteins tend to aggregate under different conditions which generally depends on the physico-chemical property of environment. We have examined the effects of bromophenol blue dye (BPB) on the aggregation propensity of insulin protein at pH 2.0 and 7.4. The results showed that the BPB dye is inducing amorphous aggregation in insulin protein at pH 2.0 and aggregation was not recorded at pH 7.4. To characterize the aggregation caused by BPB dye, we used various spectroscopic techniques (turbidity, light scattering, and circular dichroism (CD) techniques. Turbidity and light scattering data indicated that the insulin form aggregates in the presence of 0.05–0.5 mM BPB dye concentrations at pH 2.0. The kinetics data reveled that the BPB dye induced aggregation kinetics is very fast and aggregation reaction completed within 150 s. The kinetics data also suggest that the aggregation is dose-dependent and varies with BPB dye concentrations. The nature of BPB dye-induced insulin aggregates was characterized by far-UV CD measurements and found that the aggregated samples have lost the CD signals without the change in spectrum position which confirm that the aggregates are amorphous in nature. The transmission electron microscopy (TEM) imaging measurements were suggesting that the aggregates formed in the presence of BPB dye is amorphous in nature. The salts are not interfering in BPB dye-induced aggregates process. However, surfactants i.e., CTAB and SDS is solubilizing the BPB dye-induced amorphous aggregates and CTAB is very effective compared to SDS. Very low concentrations of CTAB solubilized dye-induced insulin aggregation.

Facile synthesis of silver-rhenium nanoparticles with plasmonic and mesoporous properties

Cetyltrimethylammonium bromide (CTAB) capped rhenium (Re0@CTA(aq)) NPs were prepared by using chemical reduction method at room temperature in aqueous solution. The resulting Re0@CTA(aq) sol was utilized as sacrificial template and silver ions (Ag+) for the synthesis of silver-rhenium bimetallic NPs (Ag0-Re0@CTA(aq)) under metal displacement galvanic cell reaction in aqueous solution with CTAB. Surface Plasmon resonance (SPR) band intensity and wavelength maxima of Plasmon band of Ag0-Re0@CTA(aq) depends on the concentration of CTAB. The Plasmon band was blue shifted from 434, 439, 519, 535, 465, and 445 nm, respectively, for 0.0, 0.75, 1.0, 1.25, 1.5, and 2.0 mM of CTAB. Oxidation states, crystalline nature, elemental composition, surface morphology, shape, size, and textural properties of as-prepared silver-rhenium were determined with X-ray photoelectron spectrometry (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and nitrogen adsorption-desorption isotherm (BET). Fourier transform infrared spectrometry (FTIR), 1H NMR, 13C NMR, and gas chromatography-mass spectrometry (GC-EIMS) analysis were used to establish the capping properties of CTAB. Application of FTIR, 1H NMR, 13C NMR and GC-EIMS analysis shows that the CTAB consistently remains adsorbed on Ag0-Os0 NPs. Optical properties of plasmonic nanomaterials can be tuned by using a suitable concentration of CTAB surfactant.

Stability, Rheological Behavior, and pH Responsiveness of CTAB/HCl Acidic Emulsion: Experimental Investigation.

Cetyltrimethylammonium bromide (CTAB) surfactant was proven to be a reliable emulsifier for creating stable emulsions used for drilling, well stimulation, and EOR. The presence of acids like HCl during such operations may lead to the formation of acidic emulsions. No previous comprehensive investigations have been done to study the performance of CTAB-based acidic emulsions. This paper, therefore, presents experimental investigations of the stability, rheological behavior, and pH responsiveness of a CTAB/HCl-based acidic emulsion. The effects of temperature, pH, and CTAB concentration on the emulsion stability and rheology have been investigated using a bottle test and a TA Instrument DHR1 rheometer. Viscosity and flow sweep were analyzed for the steady state at a shear range of 2.5-250 s-1. For the dynamic tests, the storage modulus (G') and loss modulus (G″) were observed by applying the oscillation test at the range of shear frequency from 0.1 to 100 rad/s. The results revealed that the emulsion exhibits steady rheological behaviors ranging from Newtonian to shear-dependent (psedosteady), depending on the temperature and CTAB concentration. The tendency of the emulsion to exhibit a solid-like behavior is also dependent on CTAB concentration, temperature, and pH. However, the pH responsiveness of the emulsion is more significantly observed within the acidic range of the pH.

CTAB-assisted synthesis of porous cuboid NiCo2O4 powders for high-performance supercapacitor

NiCo2O4 powders with columnar-, rod-, porous cuboid-, and octahedral-like morphologies were prepared by hydrothermally treatment of oxalate precipitates in the presence of various amounts of cetyltrimethylammonium bromide (CTAB) surfactant. The structural, microstructural, and electrochemical properties of NiCo2O4 powders were characterized by X-ray diffractometry, scanning electron microscopy, cyclic voltammetry, and galvanostatic charge/discharge techniques. Because of agglomeration of NiCo2O4 nanoparticles, the specific surface areas decreased from 36.3 to 14 m2 g−1 with CTAB content. The porous cuboid-like NiCo2O4 powders showed the highest specific capacitance of 1353 F g−1 at 1 A g−1, decreasing to 1021 F g−1 at 10 A g−1. The analyzed contribution of various storage mechanisms showed that a mixture of capacitive and diffusion-controlled processes was necessary for obtaining the highest specific capacitance. The porous cuboid-like NiCo2O4 powders//activated carbon hybrid capacitor showed the comparable performance of electrochemical energy storage, including energy density of 23.3 Wh kg−1 at power density of 1398 W kg−1.

Insight of molecular interactions between short‐chain tetraalkylammonium bromides and cetyltrimethylammonium bromide: A spectroscopic and thermodynamic approach

AbstractThe influence of tetraalkylammonium salts, viz., tetraethylammonium, tetrapropylammonium, and tetrabutylammonium bromides (0.005, 0.010, 0.015 mol kg−1) on the micellar behavior of aqueous solutions of the cationic surfactant cetyltrimethylammonium bromide (CTAB, 0.2–2 mmol kg−1) over the 298.15–313.15 K temperature range has been studied by conductometric method. From conductivity versus surfactant concentration plots, the critical micelle concentration (CMC) of CTAB has been determined, which shows that the tetraalkylammonium bromides promote the formation of CTAB aggregates. Further, from the temperature dependence of CMC values, the degree of ionization, the counterion binding constant along with some thermodynamic parameters of micellization, such as standard free energy change (), standard enthalpy change (), standard entropy change () have been calculated. From the values of , and , it has been concluded that our ternary system is both enthalpy as well as entropy controlled. Similar CMC values were obtained from UV–Visible spectrometry measurements, using pyrene as a probe at ambient temperature. Also 1H‐NMR and FTIR methods give a greater understanding of the molecular scale interactions between the tetraalkylammonium bromides and the cationic surfactant.

Combined effects of nanoparticle size, and nanoparticle and surfactant concentrations on the evaporative kinetics, dried morphologies, and plasmonic property of gold colloidal dispersion droplets

Understanding the combined influence of various parameters on the formation and morphologies of distinct solute deposit patterns obtained after droplet drying is essential for developing numerous real-time applications. In this work, gold nanoparticle (Au-NP) dispersion droplets are dried on a hydrophilic substrate and the coupled effects of nanoparticle size, and nanoparticle and surfactant (CTAB) concentrations on the evaporative kinetics and evaporation-induced nanoparticle assemblies in dried deposit patterns are studied using optical and scanning electron microscopy. The distinct stages of drying of a cetyltrimethylammonium bromide (CTAB) stabilized Au-NP dispersion droplet, such as the evolutions of pinning, depinning, and a depletion region, change drastically for a combined increase of CTAB concentration and nanoparticle size for different nanoparticle concentrations. Accordingly, the dried pattern is composed of distinct regions of closely bound ordered Au-NP assemblies coexisting with loosely bound disordered packings of Au-NPs that form inside and outside the coffee stain pattern. The multilayers of densely packed and hexagonally arranged Au-NPs at the outer coffee stain edge are tested for surface-enhanced Raman scattering activity against a standard probe molecule (Rhodamine B—RhB). The least detection limit of RhB at the outer coffee stain edge improves by three orders of magnitude with increasing nanoparticle concentrations and nanoparticle sizes. The present study demonstrates that the drying kinetics, distinct dried deposit morphologies, and the limit of plasmonic activity of the deposited Au-NPs can be fine-tuned via a combined variation of CTAB concentration, nanoparticle size, and nanoparticle concentration in the Au-NP dispersion droplet.

Effect of ionic surfactants on the settling behavior of silt

Ionic surfactants are easily adsorbed by silt and clay particles, thus affecting the flocculation characteristics and settling behavior. The settling velocity, typical size, Zeta potential and surface tension of silt flocs were measured in the presence of two different kinds of ionic surfactants. The results indicated that the cetyltrimethylammonium bromide (CTAB, a typical cationic surfactant) can dramatically accelerate the settling of slit particles, while the linear alkylbenzene sulfonate (LAS, a typical anionic surfactant) slightly retarded silt sedimentation to some extent. In still water, the representative settling velocity dramatically increased from 0.36 cm s−1 to 0.43 cm s−1 with the increase of CTAB concentration, which increased by more than 20%. Oppositely, the sedimentation rate decreased from 0.36 cm s−1 to 0.33 cm s−1 with the increase of LAS concentration. In flowing water, as the flow rate increased from 0 to 20 cm s−1 and the ionic surfactant concentration increased from 0 to 10 mg L−1, the sedimentation rate decreased to 57% and 89% in the presence of CTAB and LAS respectively, which was due to an enhanced dispersion of silt particles and a breaking of flocs. The SEM image test shows that the floc particle size increased 1.5 times of the primary particle size under the high CTAB concentration. The flocculation induced by ionic surfactants greatly influences the sediment size as well as the law of settling velocity. The intrinsic influence mechanism was also discussed based on the variations of silt particle properties. This systematic study can be used for further development of flocculation models and particle size distribution of fine-grained soil.

Experimental investigation on the static and dynamic stability of water-based graphene nanofluids prepared by one-step liquid phase shear exfoliation of graphite

Graphene nanofluids show prospects in various applications due to their outstanding optical, thermal, and mechanical properties. However, achieving the long-duration stability of graphene nanofluids prepared by the traditional two-step method is still challenging. Herein, one-step liquid phase shear exfoliation was applied to fabricate stable graphene nanofluids in water from graphite with cetyl trimethyl ammonium bromide (CTAB) as the surfactant. Results indicated that high-quality graphene with multi-layer was fabricated. The graphene production rate depends on CTAB concentration up to 0.25 mg/ml, but beyond that, the graphene concentration almost remains constant (∼18 ppm). Extending the exfoliation time could improve the production rate of graphene nanosheets without sacrificing their quality. The zeta potential of nanofluids prepared at CTAB concentrations of 1 mg/ml and 4 mg/ml is 45–60 mV, demonstrating that the nanofluids exhibit high static stability. Besides, the nanofluids' relative concentration (RC) values are over 0.95 at 20 °C and 40 °C in the flow rate range of 0–1.5 l/min. The nanofluids subjected to static heating at 60 °C are stable; however, their dynamic stability deteriorates gradually with the increasing flow rate because the physically absorbed cationic surfactant more easily falls off from graphene nanosheets, and collision frequency among graphene nanosheets intensifies at high temperatures under the flow condition. Furthermore, high-low temperature cycling could effectively relieve the deterioration of the nanofluids' stability, suggesting that once the electrostatic stabilization effect could be guaranteed by timely cooling, the graphene nanofluids would keep stable.

Robust Optimization and Characterization of MCM‐41 Nanoparticle Synthesis using Modified Sol‐Gel Method

AbstractMesoporous silica nanoparticles (MSN) for drug delivery application requires great expertise to synthesize small sized monodisperse particles. We aimed at synthesizing and optimizing MCM‐41 particles with the modified Stober's method by adjusting factors such as concentrations of cetyltrimethylammonium bromide (CTAB), sodium hydroxide (NaOH) and water (H2O) with respect to tetraethyl orthosilicate (TEOS), and a process parameter (stirring). We comprehended that the reactants determined the shape and size of both the particles and pores. Upon extensive characterization we report the synthesis of spherical particles of ∼70 nm size in a monodisperse population; the structures had hexagonal ordered pores of diameter 3.071 nm and volume 3.124 cm3/g; the total surface area of 3410.648 m2/g of the particles was covered with silanol groups that aid in functionalization; the particles exhibited great thermal stability. Thus, the extensive optimization fabricated robust MCM‐41 particles fit for drug delivery application.

Fabrication, characterization, and emulsifying properties of hexadecyltrimethylammonium bromide (CTAB) complexed alginate microgel

In the current study, complexes (CAMs) of alginate microgels (AMs) and hexadecyltrimethylammonium bromide (CTAB) were prepared, and further used to stabilize O/W emulsions. Physical properties and emulsifying capacity of CAMs with different CTAB concentration were investigated, which indicated emulsifying capacity of AMs could be extensively improved by CTAB. Improved stability against centrifugation (3000 rpm), pH value (2.0–8.0), and NaCl concentration (0–200 mM) was also reported in CAMs stabilized emulsions. Interfacial adsorption and morphology observation suggested that the interfacial activities of CAMs were benefited from CTAB complexing, and an interfacial layer could be observed on the surface of the CAMs stabilized oil droplets. In this work, even a slight amount of surfactant (0.4 mM, or 0.01456 wt% CTAB) could make remarkable improvement on the emulsifying performance of alginate microgels. However, excessive CTAB would result in over aggregation of AMs, which was not conducive to the emulsifying performance of CAMs. This study proposed that the surfactant complexing was a feasible strategy to improve the emulsifying performance of polysaccharide microgels.

Synthesis and efficient electrocatalytic performance of Bi2O3/Dy2O3 nanoflakes

Abstract Bi2O3/Dy2O3 nanoflakes with triclinic Bi2O3 and cubic Dy2O3 phases were synthesized by a hexadecyl trimethyl ammonium bromide (CTAB)-assisted hydrothermal route. The Bi2O3/Dy2O3 nanoflakes were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, electron microscopy and electrochemical impedance spectroscopy. The size of the Bi2O3/Dy2O3 nanoflakes with curled surface is about 2 μm and thickness is about 25 nm. X-ray photoelectron spectroscopy confirms the chemical composition of the Bi2O3/Dy2O3 nanoflakes. The formation process of the Bi2O3/Dy2O3 nanoflakes was investigated by controlling the CTAB concentration, reaction temperature and reaction time. The formation of the Bi2O3/Dy2O3 nanoflakes depends on CTAB. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy demonstrate good electro-catalytic activity of the Bi2O3/Dy2O3 nanoflakes towards L-cysteine with a pair of quasi-reversible CV peaks at +0.01 V and –0.68 V, respectively. Bi2O3/Dy2O3 nanoflakes modified electrode detects L-cysteine linearly over a concentration ranging from 0.001 to 2 mM with a detection limit of 0.32 μM. The proposed nanocomposites modified electrode possesses good reproducibility and stability which can be used as a promising candidate for L-cysteine detection.

Slow development of induced-charge electro-osmosis in cetyltrimethylammonium bromide solutions

Induced-charge electro-osmosis (ICEO) is an important phenomenon in microfluidics and has been widely studied. Existing studies, both theoretical and experimental, have shown that ICEO is fully developed in milliseconds after an electric field is applied. In this study, we experimentally found that ICEO of cetyltrimethylammonium bromide (CTAB) solutions takes several seconds to be fully developed after the electric field is applied, which is significantly different from the existing literature. To reveal the underlying mechanism of this slow development, we propose a phenomenological model for ICEO of CTAB solutions by incorporating a dynamic viscosity formula. The ICEO model successfully explains the slow development and attributes it to the thixotropy of CTAB solutions. In addition, we also found that ICEO velocity varies irregularly as CTAB concentration increases, which is due to the variations of viscosity and electrical conductivity of CTAB solutions. The ICEO velocity of CTAB solutions reduces as the electric field frequency increases, which is different from the existing literature. The findings may enrich the understanding of ICEO and promote the application in complex fluids such as biological fluids.

In-situ design of hierarchical durable silica-based coatings on polypropylene films with superhydrophilic, superhydrophobic and self-cleaning properties

Superhydrophobic surfaces are receiving increasing attention due to their real-world applications. However, these surfaces suffer from a lack of durability and complicated synthetic processes. This research uses a combination of a simple in-situ coating process between oxygen-activated polypropylene films and unreacted silane monomers. The in-situ process uses a modified Stöber method with the addition of the surfactant cetyltrimethylammonium bromide (CTAB) which aggregates silica (SiO 2) particles in a basic aqueous solution. This resulted in a layer of covalently bonded hierarchical coating of individual and aggregated SiO 2 “flakes” and particles. These coatings were found to have at least double the surface roughness than samples prepared without CTAB with superhydrophilic properties due to their high surface roughness and hydrophilic surface chemical groups. A second layer of fluorocarbon silane monomers was reacted with the hydroxyl groups on the hierarchical SiO 2 coating resulting in films with excellent superhydrophobic and self-cleaning properties. The sample containing aggregated SiO 2 particle structures exhibited higher chemical and physical durability against external irritations including adhesion, different pH levels, detergent, abrasion and UV radiation by retaining high contact angles and low rolling angles. Samples coated with flake structures were negatively affected by mechanical irritations. This simple in-situ SiO 2 coating process in combination with different concentrations of CTAB has not been investigated and has promising potential for many practical applications such as superhydrophilic, superhydrophobic and self-cleaning surfaces.

Controlling Water Delivery to an Electrochemical Interface with Surfactants.

Most electrochemical reactions require delivery of protons, often from water, to surface-adsorbed species. However, water also acts as a competitor to many such processes by directly reacting with the electrode, which necessitates using water in small amounts. Controlling the water content and structure near the surface is an important frontier in directing the reactivity and selectivity of electrochemical reactions. Surfactants accumulate near surfaces, and therefore, they can be used as agents to control interfacial water. Using mid-IR spectro-electrochemistry, we show that a modest concentration (1 mM) of the cationic surfactant CTAB in mixtures of 10 M water in an organic solvent (dDMSO) has a large effect on the interfacial water concentration, changing it by up to ∼35% in the presence of an applied potential. The major cause of water content change is displacement due to the accumulation or depletion of surfactants driven by potential. Two forces drive the surfactants to the electrode: the applied potential and the hydrophobic interactions with the water in the bulk. We have quantified their competition by varying the water content in the bulk. To our knowledge, for the first time, we have identified the electrochemical equivalent of the hydrophobic drive. For our system, a change in applied potential of 1 V has the same effect as adding a 0.55 mole fraction of water to the bulk. This work illustrates the significance of surfactants in the partitioning of water between the bulk and the surface and paves the way toward engineering interfacial water structures for controlling electrochemical reactions.

Molecular mechanism of insulin aggregation in the presence of a cationic surfactant

Protein aggregation and amyloid fibrillation are connected with neurodegenerative disorders. Insulin, a small molecular weight protein related to type II diabetes, has been shown to self-assemble to form protein aggregates. In this work, we investigated the effects of cetyltrimethylammonium bromide (CTAB) of insulin on the in vitro aggregation process at pH 7.4 and 2.0. The aggregation tendency of insulin was measured using a variety of biophysical approaches, including turbidity measurements, light scattering, far UV-CD, ThT dye binding, and transmission electron microscopy. The turbidity results demonstrated that at pH 7.4, a low concentration of CTAB (30–180 μM) causes insulin aggregation but at higer concentration (>180 μM) aggregation was not seen. However, at pH 2.0, both low as well as high concentrations of CTAB were unable to promote insulin aggregation. The ThT dye binding and far-UV CD data suggest that aggregation induced by CTAB is not having an ordered structure. Insulin treated with higher concentrations (>180 μM) of CTAB, the insulin gained a secondary structure. The possible cause of inducing aggregation in insulin is electrostatic and hydrophobic interaction because insulin contains a net negative charge at pH 7.4 and no aggregation at pH 2.0 due to electrostatic repulsion.

Surface Modification of Bamboo-based Activated Carbon for Methylene Blue Removal

The feasibility of biomass-based activated carbon has received tremendous attention owing to its excellent properties, such as insensitivity, good adsorption performance, and potential to reduce the strong dependence on non-reproducible precursors. In this study, bamboo-based activated carbon (BAC) was used as the raw material for methylene blue (MB) removal. Cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and sodium dodecylbenzene sulfonate (SDBS) were used as BAC surface modifiers. The morphologies and structures of the samples were characterized. In addition, the effects of the surfactant type and concentration on the adsorption-based removal of MB from aqueous solutions by the modified BAC were systematically investigated. For the 0.2 g/L MB solution, the MB removal rate reached 99.7% when the concentration of CTAB was 0.25 g/L. Moreover, the kinetic model curve of 0.25 g/L CTAB-modified BAC (CAC) was consistent with the Freundlich isotherm model. This research work enriches the technical pathway of modification and application of activated carbon, which is not only beneficial for realizing the high-value utilization of biomass bamboo resources but also can play an active role in guiding the treatment of MB-containing wastewater.