Tetradecyl Trimethyl Ammonium Research Articles

Simultaneous determination of 10 quaternary ammonium salt bactericides in oral care products by high performance liquid chromatography-evaporative light-scattering detection

Quaternary ammonium salt bactericides are broad-spectrum bactericides often used in oral care products because of their high antibacterial efficacy, strong penetration, and low toxicity. However, the excessive use of quaternary ammonium salt bactericides may cause contact dermatitis, scalding poisoning, and even death. Existing methods to determine quaternary ammonium salt bactericides are unable to meet current requirements owing to the lack of determination components. Therefore, establishing a simple and accurate method for the simultaneous detection of more quaternary ammonium salt bactericides is necessary. In this study, a method that couples sample pretreatment with high performance liquid chromatography-evaporative light-scattering detection (HPLC-ELSD) was developed for the simultaneous determination of quaternary ammonium salt bactericides in oral care products, including dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, benzethonium chloride, tetradecyl trimethyl ammonium chloride, tetradecyldimethylbenzylammonium chloride, N-hexadecyltrimethylammonium chloride, benzyldimethylhexadecylammonium chloride, trimethylstearylammonium chloride, stearyldimethylbenzylammonium chloride, and docosyltrimethylammonium chloride. Some of these bactericides do not absorb ultraviolet light, so a universal evaporative light-scattering detector was used owing to testing cost and stability concerns. The paste samples contained thickening agents, which are highly soluble in water but insoluble in organic solvents; these agents can seriously affect the results of sample pretreatment and damage the chromatographic column. Hence, sample dehydration was necessary. In this study, four dehydration methods were compared. Anhydrous sodium sulfate (Na2SO4) was selected, and the amount of Na2SO4 was optimized. Based on the solubility of the 10 target compounds and extraction efficiency, three extraction solvents were compared, and ethanol was selected. Ultrasonic extraction was the primary extraction process used in this study. The effects of different ultrasonication times, temperatures, and powers on the extraction recoveries were also investigated. Ultimately, the optimized conditions were as follows: extraction of the dehydrated paste and powder samples using ethanol at room temperature (25 ℃) for 20 min under 100 W ultrasound power, and dilution of the liquid sample with ethanol. After extraction, the samples were separated on an Acclaim Surfactant column (150 mm×4.6 mm, 5 μm) with 50 mmol/L ammonium acetate aqueous solution (pH=5.5) (A) and acetonitrile (B) as mobile phases. The gradient elution program were as follows: 0-5.0 min, 75%A-35%A, 5.0-15.0 min, 35%A-20%A, 15.0-20.0 min, 20%A, 20.0-21.0 min, 20%A-75%A, 21.0-25.0 min, 75%A. An external standard method was used for quantitative determination. The 10 compounds were analyzed within 25 min. Linear equations, correlation coefficients, and linear ranges were obtained by analyzing a series of mixed standard working solutions. The limits of detection (LODs, S/N=3) and quantification (LOQs, S/N=10) of the 10 components were determined. Stearyldimethylbenzylammonium chloride and docosyltrimethylammonium chloride showed good linear relationships in the range of 10-200 mg/L, while the other compounds demonstrated good linear relationships in the range of 5-100 mg/L. In all cases, correlation coefficients (R2) of no less than 0.9992 were obtained. The LODs and LOQs were in the range of 1.42-3.31 mg/L and 4.25-9.94 mg/L, respectively. Ten analytes were spiked in blank matrices, such as toothpaste (paste), mouthwash (liquid), and dentifrice powder (powder) at three levels, and the recoveries and precisions were calculated. The average recoveries were 87.9%-103.1%, and the corresponding relative standard deviations (RSDs) did not exceed 5.5% (n=6). The developed method was used to detect 109 oral care products. Benzyldimethylhexadecylammonium chloride and stearyldimethylbenzylammonium chloride revealed high detection rates. Moreover, the amount of stearyldimethylbenzylammonium chloride in one toothpaste sample exceeded regulatory requirements. Given its advantages of good precision and accuracy, the developed method is suitable for the quantitative analysis of the 10 aforementioned compounds in typical oral care products. The study findings can serve as a reference for the quality and safety monitoring of oral care products.

Synergistic corrosion inhibition effect of N-benzyl pyridinium chloride and three cationic surfactants in the H2S/CO2/NaCl solution

The investigation into the synergistic corrosion inhibition effects of N-benzyl pyridinium chloride (BPC) and three cationic surfactants (i.e., dodecyl trimethyl ammonium bromide, tetradecyltrimethyl ammonium bromide and cetyltrimethyl ammonium bromide) in H2S/CO2/NaCl solution was conducted using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, surface tension and X-ray photoelectron spectroscopy. Corrosion inhibition efficiencies of these surfactants correlated to their surface activity levels. Notably, the addition of BPC significantly improved the protective effectiveness of surfactants, demonstrating a strong synergistic inhibitory impact. The enhancement is attributed to the co-adsorption of the surfactants with BPC, which effectively covers the flaws in BPC adsorbed layer. This increases the overall coverage of inhibitive film, thereby offering high inhibition efficiencies for carbon steel in the tested environment.

Micellization of a cationic and an anionic surfactant in the presence of diphenylcarbazide in aqueous media and the effect of micelle surface charge on the complexation of the solubilised ligand with metal ions

ABSTRACT In the present study, we carried out conductometric and surface tension analyses to report the critical micelle concentration (CMC) of tetradecyltrimethyl ammonium bromide (TTAB) and sodium dodecyl sulphate (SDS) as a function of the concentration of a diphenylcarbazide (DPC). It is found that the micellization of TTAB becomes unfavourable while that of SDS becomes favourable in the presence of DPC. This indicates a substantial difference in the mutual interaction of the sparingly soluble ligand with the cationic and the anionic surfactants. The complexation ability of the solubilised DPC with hydrated Zn(II) and Cd(II) ions at varying concentrations of the cationic and anionic surfactants was studied by UV–Vis spectral analyses. With increasing the concentration of both surfactants up to their respective CMC values, the absorbance of the metal–DPC complex increases. However, the absorbance of the complex in TTAB micelles sharply decreases, showing almost zero values beyond the CMC, but that in SDS remains almost steady with increasing the concentration of the surfactant, as evidenced from the visible spectra.

Analysis of Two Single and Three Double Long-Chain Quaternary Ammonium Compounds via Non-Aqueous Capillary Electrophoresis with Indirect Ultraviolet Detection

A novel method utilizing non-aqueous capillary electrophoresis (NACE) with indirect ultraviolet detection (IUD) has been developed for the analysis of five quaternary ammonium compounds (QACs). The QACs analyzed in this study include dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, dioctyl dimethyl ammonium chloride, octyldecyl dimethyl ammonium chloride and didecyl dimethy ammonium bromide. The separation process was carried out on an uncoated fused quartz capillary with a total length of 50.2 cm (effective length 40.0 cm) and a diameter of 50 μm. The separation buffer consisted of a mixture of MeOH/ACN (90:10, v/v) containing 2 mmol/L sodium acetate, 2 mmol/L trifluoroacetic acid (TFA) and 16 mmol/L dodecyl dimethyl benzyl ammonium chloride. The sample buffer utilized a mixture of MeOH/ACN (20:80, v/v) containing 2 mmol/L TFA. During analysis, a separation voltage of 7 kV was applied, resulting in a current of approximately 2.3 μA. The detection wavelength was set at 214 nm to ensure optimal sensitivity. Under optimal conditions, the method exhibited excellent performance characteristics, with a limit of detection of 0.5 mg/L and a limit of quantitation of 5.0 mg/L for the five QACs. Linear calibration curves were obtained in a concentration range of 5.0 to 100.0 mg/L, with correlation coefficients exceeding 0.999 for all compounds. The recoveries of the five QACs ranged from 92.3% to 114.7%, with relative standard deviations below 7.4%. To assess the applicability of the NACE-IUD method, 17 commercially available samples were successfully analyzed. The results confirmed the suitability of the method for accurate determination of the five QACs in disinfectant products. Notably, this method offers an environmentally friendly approach for the analysis of these QACs.

Isolation, Molecular Characterization and Mycochemical Analysis of Aspergillus quadrilineatus

Secondary metabolites of microbial origin, either as pure compounds or crude extracts, provide opportunities for new drug development because of their chemical diversity. The aim of the present study is to isolate Molecular characterization and extract the bioactive compounds from the fungus of A. quadrilineatus (OL979151) in the rhizospheric soil of sunflower and mustard crop fields in Davanagere region. Dilution plate technique was used to isolate the rhizosphere fungi. The total genomic DNA was extracted from isolate of Aspergillus quadrilineatus based on Cetrimide Tetradecyl Trimethyl Ammonium Bromide (CTAB). Mass production of the fungal mat of A. quadrilineatus was established on potato dextrose broth medium. The dried methanol extract of fungus was subjected to HR-LCMS analysis; Methanol extract of A. quadrilineatus fungus shows that the compounds Amobarbital, Pirbuterol, Bambuterol, Cilazaprilat, Oxotremorine, Aminopyrine and Oryzanol as the major constituents. The compounds exhibit analgesic, anti-inflammatory, and antipyretic properties and various therapeutic uses.

Enhanced Mn2+ solidification and NH4+-N removal from electrolytic manganese metal residue via surfactants

Electrolytic manganese metal residue (EMMR) harmless treatment has always lacked a low-cost and quick processing technology. In this study, surfactants, namely tetradecyl trimethylammonium chloride (TTC), sodium dodecyl benzene sulfonate (SDBS), sodium lignin sulfonate (SLS), and octadecyl trimethylammonium chloride (OTC), were used in the solidification of Mn 2+ and removal of NH 4 + -N from EMMR. The Mn 2+ and NH 4 + -N concentrations under different reaction conditions, Mn 2+ solidification and NH 4 + -N removal mechanisms, and leaching behavior were studied. The results revealed that the surfactants could enhance the Mn 2+ solidification and NH 4 + -N removal from EMMR, and the order of enhancement was as follows: TTC ＞ SDBS ＞ OTC ＞ SLS. The NH 4 + -N and Mn 2+ concentrations were 12.3 and 0.05 mg·L -1 with the use of 60.0 mg·kg -1 TTC under optimum conditions (solid–liquid ratio of 1.5:1, EMMR to BRM mass ratio of 100:8, temperature of 20 °C, and reaction duration of 12 h), which met the integrated wastewater discharge standard (GB8978-1996). Mn 2+ was mainly solidified as Mn(OH) 2 , MnOOH and MnSiO 3 , and NH 4 + -N in EMMR was mostly removed in the form of ammonia. The results of this study could provide a new idea for cost-effective EMMR harmless treatment.

Robust Superhydrophobic Brass Mesh with Electrodeposited Hydroxyapatite Coating for Versatile Applications.

A robust superhydrophobic brass mesh was fabricated based on a low-energy surface and a roughness on the nano/micro-meter scale. It was carried out by the forming of hydroxyapatite (HP) coatings on its surface through a constant current electro-deposition process, followed by immersion in fluoroalkylsilane solution. Surface morphology, composition and wetting behavior were investigated by field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high speed camera, and contact angle goniometer. Under optimal conditions, the resulting brass mesh exhibited superhydrophobicity, excellent anti-corrosion (η = 91.2%), and anti-scaling properties. While the surfactant liquid droplets of tetradecyl trimethyl ammonium bromide (TTAB) with different concentration were dropped on the superhydrophobic surface, maximum droplet rebounding heights and different contact angles (CAs) were observed and measured from side-view imaging. The plots of surfactant-concentration−maximum bounding height/CA were constructed to determine its critical-micelle-concentration (CMC) value. Close CMC results of 1.91 and 2.32 mM based on the determination of maximum rebounding height and CAs were obtained. Compared with its theoretical value of 2.1 mM, the relative errors are 9% and 10%, respectively. This indicated that the novel application based on the maximum rebounding height could be an alternative approach for the CMC determination of other surfactants.

A cost-effective method for enhancing manganese leaching from rhodochrosite caused by surfactant-regulated crystal growth of CaSO4·2H2O

The cost-effective leaching of manganese (Mn2+) from rhodochrosite is critical for achieving energy saving, curtailing pollutants, and cleaner production of electrolytic metallic manganese (EMM). In this work, different surfactants were used to enhance Mn2+ leaching from rhodochrosite. The effects of the surfactants: trisodium citrate (TC), sodium oleate (SOL), ethylenediaminetetraacetic acid (EDTA), sodium dodecyl sulfate (SDS), and tetradecyltrimethyl ammonium bromide (TTAB) on the Mn2+ leaching efficiency were evaluated. The enhanced mechanism of Mn2+ leaching is discussed, and an economic evaluation is presented. The leaching efficiency of Mn2+ reached 91.8% in the presence of 5 mg/L TC, which is 13.8% higher than that in the absence of TC using a temperature of 50 °C, a solid-liquid ratio of 1:5, an acid-to-ore ratio of 0.58:1, and reaction time of 3.5 h. In the leaching mechanism, TC inhibited the growth of the 020, 040, and 041 crystal planes of CaSO4·2H2O; thus, CaSO4·2H2O crystals with a shortened columnar morphology and smaller sheet shapes were obtained. The grain refinement of CaSO4·2H2O did not readily wrap on the surface of rhodochrosite, consequently increasing the probability for rhodochrosite to react with H+, and improving the leaching efficiency of Mn2+. Moreover, TC did not remain in the leachate to impact the subsequent electrolytic deposition. This study provides a cost-effective method for leaching Mn2+ from rhodochrosite.

Enhanced Corrosion Resistance of Layered Double Hydroxide Films on Mg Alloy: The Key Role of Cationic Surfactant.

In this study, dense anticorrosion magnesium–aluminum layered double hydroxide (MgAl-LDH) films were prepared for the first time by introducing a cationic surfactant tetradecyltrimethyl ammonium bromide (TTAB) in the process of in situ hydrothermal synthesis of Mg-Al LDH films on an AZ31 magnesium alloy. Results of XRD, FTIR, and SEM confirmed that TTAB forms the MgAl-LDH-TTAB, although TTAB cannot enter into LDH layers, and MgAl-LDH-TTAB powders are much smaller and more homogenous than MgAl-CO32−-LDH powders. Results of SEM, EDS, mapping, and XPS confirmed that TTAB forms the MgAl-LDH-TTAB films and endows LDH films with denser structure, which provides films with better shielding efficiency. Results of potentiodynamic polarization curves (PDP) and electrochemical impedance spectroscopy (EIS) confirmed that MgAl-LDH-TTABx g films have better corrosion resistance than an MgAl-CO32−-LDH film. The corrosion current density (icorr) of the MgAl-LDH-TTAB0.35 g film in 3.5 wt.% NaCl solution was reduced to 1.09 × 10−8 A.cm−2 and the |Z|f = 0.05 Hz value was increased to 4.48 × 105 Ω·cm2. Moreover, the increasing concentration of TTAB in MgAl-LDH-TTABx g (x = 0.025, 0.05, 0.1, 0.2 and 0.35) provided denser outer layer LDH films and thereby increased the corrosion resistance of the AZ31 Mg alloy. Additionally, the |Z|f = 0.05 Hz values of the MgAl-LDH-TTAB0.35 g film still remained at 105 Ω·cm2 after being immersed in 3.5 wt.% NaCl solution for 168 h, implying the good long-term corrosion resistance of MgAl-LDH-TTABx g films. Therefore, introducing cationic surfactant in the process of in situ hydrothermal synthesis can be seen as a novel approach to creating efficient anticorrosion LDH films for Mg alloys.

Removal of Cr(VI) in aqueous solution using cationic gemini surfactant-modified rectorite

The adsorption of hexavalent chromium (Cr(VI)) on rectorite (REC) modified by gemini surfactant (butane-1,4-bis (dodecyl dimethyl ammonium bromide)) (gBDDA) was investigated in this research. The results of a series of characterization methods such as X-ray diffraction (XRD), infrared spectroscopy, and thermogravimetric analysis proved that gBDDA was successfully embedded into the interlayer of REC. The effect of the amount of gBDDA on the adsorption of Cr(VI) by gBDDA-modified REC was studied (gBDDA: cation exchange capacity = 1:2 or 1:4). The adsorption capacity of Cr(VI) by gemini surfactant-modified REC reached 38 mg/g, which was higher than that of tetradecyl trimethyl ammonium bromide-modified REC. In addition, ultrasound-assisted synthesis was found to have an effect on the adsorption capacity of REC modified with a high ratio of gemini surfactant. The structures of gBDDA before and after adsorption were analyzed to clarify the adsorption mechanism. The electrostatic interaction between Cr(VI) and two positively charged groups in the gBDDA was found to be crucial during the adsorption process. The foundings of this study demonstrate that REC modified by gBDDA can be used as an adsorbent for the removal of Cr(VI) in water.

Real-time monitoring the staged interactions between cationic surfactants and a phospholipid bilayer membrane.

The cationic surfactant-lipid interaction directs the development of novel types of nanodrugs or nanocarriers. The membrane action of cationic surfactants also has a wide range of applications. In this work, combining a photo-voltage transient method with the traditional dynamic giant unilamellar vesicle (GUV) leakage assay and molecular dynamics (MD) simulations, we monitored the molecular actions of a representative cationic surfactant, tetradecyl trimethyl ammonium bromide (TTAB), in a wide concentration range (i.e., 0.5 μM-10 mM), on a phospholipid bilayer membrane in real time. With low concentrations (e.g., ≤10 μM), TTAB performed a three-stage acting process, including the structural-disturbance-dominated, adsorption-dominated, and dynamic equilibrium stages. At higher concentrations (e.g., ≥100 μM), this process was accelerated to two stages. Furthermore, TTAB induced deformation and even rupture of the membrane, due to the asymmetric disturbance of surfactant molecules on the two leaflets of a bilayer. All these disturbances induced membrane permeabilization, and the times at which these transitions occurred are given. This work provides information on time and molecular mechanism during the membrane actions of cationic surfactants, and provides a simple and real-time method in studying the dynamic processes at the membrane interface.

Organobeidellites for Removal of Anti-Inflammatory Drugs from Aqueous Solutions.

Diclofenac (DC) and ibuprofen (IBU) are widely prescribed non-steroidal anti-inflammatory drugs, the consumption of which has rapidly increased in recent years. The biodegradability of pharmaceuticals is negligible and their removal efficiency by wastewater treatment is very low. Therefore, the beidelitte (BEI) as unique nanomaterial was modified by the following different surfactants: cetylpyridinium (CP), benzalkonium (BA) and tetradecyltrimethylammonium (TD) bromides. Organobeidellites were tested as potential nanosorbents for analgesics. The organobeidellites were characterized using X-ray powder diffraction (XRD), Infrared spectroscopy (IR), Thermogravimetry and differential thermal analysis (TG/DTA) and scanning microscopy (SEM). The equilibrium concentrations of analgesics in solution were determined using UV-VIS spectroscopy. The intercalation of surfactants into BEI structure was confirmed both using XRD analysis due to an increase in basal spacing from 1.53 to 2.01 nm for BEI_BA and IR by decreasing in the intensities of bands related to the adsorbed water. SEM proved successful in the uploading of surfactants by a rougher and eroded organobeidellite surface. TG/DTA evaluated the decrease in dehydration/dehydroxylation temperatures due to higher hydrophobicity. The Sorption experiments demonstrated a sufficient sorption ability for IBU (55–86%) and an excellent ability for DC (over 90%). The maximum adsorption capacity was found for BEI_BA-DC (49.02 mg·g−1). The adsorption according to surfactant type follows the order BEI_BA > BEI_TD > BEI_CP.

Physical properties of deep eutectic solvents based on p-toluene sulfonic acid and employment as catalyst

This work studied the physical properties of three deep eutectic solvents (DESs) and their catalytic activity in the esterification of palmitic acid and ethanol. Three types of deep eutectic solvents (DESs) were successfully prepared using p-toluene sulfonic acid monohydrate (PTSA) as hydrogen bond donor (HBD) with dodecyl trimethyl ammonium chloride (DTAC), tetradecyl trimethyl ammonium chloride (TTAC) and octadecyl trimethyl ammonium chloride (OTAC) as hydrogen bond acceptor (HBA). The freezing points of DESs were measured in the range of 50%–80% HBD mole percentage, and the composition of DTAC-PTSA, TTAC-PTSA and OTAC-PTSA at the eutectic point (the lowest freezing points) was determined respectively (DES1, DES2 and DES3). The physical properties (density, refractive index, dynamic viscosity, conductivity and pH value) of DES1∼DES3 were studied respectively in the temperature range of 298.15 K to 343.15 K. The results showed that dynamic viscosity, conductivity, density and refractive index all change approximately regularly with the increase of temperature, while pH value remains almost constant when the temperature exceeds 325 K. The catalytic ability of the three DESs in the esterification reaction of palmitic acid and ethanol was investigated, and DES2 was selected as the catalyst for subsequent experiments. The effects of temperature, acid-ethanol molar ratio, catalyst dosage and reaction time on esterification reaction were further studied, and DES’ recyclability was also tested. The results obtained showed the great potential of DES in catalytic applications.

Effects of surfactants on aqueous foams properties: a step towards mineral foams

This study focus on foaming properties of three surfactants: α-olefin sulphonate sodium salt (Hostapur OSB), Trimethyl tetradecyl ammonium bromide (Cetrimide) and Hexadecyl trimethyl ammonium bromide (CTAB) usable for mineral foaming. The ability of these surfactants to reduce surface tension is evaluated. Foamability and foam stability of aqueous foams made up with these surfactants are assessed at different concentrations, using the Dynamic Foam Analyzer providing parameters which describe the foaming and decay phases. They considerably depend on the type of surfactant and its concentration. By analysing the bubble size distribution, the relationship between the stability and the foam structure can be observed. The Hostapur OSB appears to be the most efficient surfactant in terms of stability and foamability, representing the thinnest foam structure and the highest characteristic times (deviation, transition and half-life) at CMC (critical micelle concentration).

Multistep Micellization of Standard Surfactants Evidenced by Second Harmonic Scattering.

Processes involving in solution a reduced number of molecules are difficult to identify and characterize. Here, we show that micellization of standard surfactants, namely sodium dodecyl sulfate and trimethyl tetradecyl ammonium bromide, two nonefficient compounds for quadratic nonlinear optics, can be investigated by second harmonic scattering (SHS). In particular, the formation of aggregates at concentrations smaller than the critical micellar concentration is evidenced through a nonmonotonic behavior of the SHS intensity as a function of the surfactant concentration. A simple model based on chemical equilibria between monomers and micelles is proposed to account for the experimental observations. Signature of long-range molecular orientation correlation is revealed by polarization resolved experiments and is discussed regarding micellization and charge-induced effects.

Optimization of the demulsification of crude oil-in-water emulsions using response surface methodology

Emulsions are undesirable in the petroleum industry, as these often lead to numerous problems such as the corrosion of equipment, high-pressure drop in the pipeline, high pumping cost, and poisoning of the catalyst in upstream facilities, thus, add to the overall production cost. These emulsions are mostly encountered during enhanced oil recovery (EOR) because of the chemicals used in the process. Petroleum emulsions are commonly treated using surface-active agents known as demulsifiers. Demulsifiers can disrupt the interface between the water and the oil and separate them into individual phases. This study aims at optimizing some existing parameter conditions to obtain maximum demulsification efficiency of oil-in-water emulsions using two cationic demulsifiers namely, Cetyl-trimethylammonium bromide (CTAB), and Trimethyl-tetradecyl ammonium chloride (TTAC). The bottle test technique was used to investigate the effect of demulsifier concentration, settling time, and oil to water ratio on the demulsification efficiency. Experiments were designed using the Central Composite Design (CCD). The analysis of variance (ANOVA) was used to evaluate the significance of the experimental factors, and the factors were then optimized using response surface methodology (RSM). The results showed that all the factors studied significantly impacted the response (demulsification efficiency) and presented a p-values < 0.0001. The maximum demulsification efficiency of 82.6% and 80% were achieved at the optimum conditions of 850 ppm demulsifiers concentration within 10 h of settling time for both CTAB and TTAC emulsifiers.

A simple and sensitive colorimetric sensor for cadmium (II) detection based on self-assembled trimethyl tetradecyl ammonium bromide and murexide on colloidal silica

A sensitive and selective colorimetric sensor based on self-assembled trimethyl tetradecyl ammonium bromide (TTAB) and murexide on colloidal silica surface was developed for the detection of cadmium ion (Cd2+). Cd2+ was formed complex with murexide on the colorimetric probe (TTAB/Murexide/Silica sol) which the solution was changed immediately from light purple to orange color and was detected by spectrophotometry at 485 nm. Under the optimum conditions, the linearity was in the range of 0.01–0.12 mM with the determination coefficient of 0.9933, the limit of detection was 0.21 µM. Good precision was obtained with %RSD less than 1.28 and 4.17 for the intra-day and inter-day, respectively. The proposed colorimetric method, TTAB/Murexide/Silica sol, was successfully applied for determination of Cd2+ in rice samples and the obtained results were comparable to those from AAS method. In addition, smartphone combined with Image J program was also employed for the determination of Cd2+. The superiority of this colorimetric sensor is simple, rapid and low cost.

Removal of Trichloroethylene by Clay Modified with Cationic Surfactant in Aqueous Solutions: Equilibrium, Kinetic, and Thermodynamic Study

AbstractTrichloroethylene (TCE) is commonly found in ground water, and it may serve as a major source of many types of cancers such as kidney, liver, lymphatic glands, and spinal cord. In the present research, TCE uptake from aqueous media by montmorillonite (Mt) modified by tetradecyl trimethyl ammonium bromide (TTAB) surfactant was explored. Firstly, the characteristics of raw and modified montmorillonite (raw‐Mt and TTAB‐Mt) were analyzed by SEM, FTIR, XRD, and XRF instruments. Then, the sorption process was evaluated as a function of different factors such as surfactant loading rate, pH, ionic strength, contact time, sorbent dosage, TCE concentration, temperature, and regeneration agent. The maximum TCE sorption by the modified clay was obtained at surfactant loading rate of 120% cation exchange capacity of the clay. The maximum removal efficiency of TCE by the modified clay was 99.6% at pH 5 and 30 min contact time. The findings also exhibited that the isotherm and kinetic sorption followed the Freundlich and pseudo‐second‐order models, respectively. It can be concluded that TTAB‐Mt, as a cheap, abundant, non‐toxic, and environmental friendly adsorbent can be considered to remove TCE in aqueous phase.

Effect of Temperature on the Dynamic Properties of Mixed Surfactant Adsorbed Layers at the Water/Hexane Interface under Low-Gravity Conditions

An increase in temperature typically leads to a decrease in the interfacial tension of a water/oil interface. The addition of surfactants to the system can complicate the situation significantly, i.e., the interfacial tension can increase or decrease with an increasing temperature. For most concentrations of the two studied surfactants, the cationic tetradecyl trimethyl ammonium bromide (TTAB) and the nonionic tridecyl dimethyl phosphine oxide (C13DMPO), the measured interfacial tension of the aqueous mixed surfactant solutions against hexane increases when the temperature decreases between 30 °C and 20 °C. However, with a further temperature decrease between 20 °C and 15 °C, the reverse effect has also been observed at some concentrations, i.e., a decrease of interfacial tension. Additionally, the corresponding dilational interfacial visco-elasticity shows some discrepant temperature effects, depending on the bulk concentration and oscillation frequency. The experiments have been performed with a capillary pressure tensiometer under the conditions of micro-gravity. The reason for the positive and negative interfacial tension and visco-elasticity gradients, respectively, within certain ranges of the temperature, concentration and mixing ratios, are discussed on the basis of all available parameters, such as the solubility and partitioning of the surfactants in the two liquid phases and the oscillation frequency.

Hydrogen storage performances for mesoporous silica synthesized with mixed tetraethoxysilane and methyltriethoxysilane precursors in acidic condition

H2 adsorption properties of ordered mesoporous silica prepared with different ratios of functionalized precursors have been studied. Silica particles were synthesized by sol-gel method, with tetradecyltrimethyl ammonium bromide (C14) or dodecyl trimethyl ammonium bromide (C12) as structure directing agents, and tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES), by varying the molar ratio of the two precursors. The porosity and microstructure of the materials in function of the MTES/TEOS ratio were evaluated by using nitrogen adsorption and X-ray diffraction and showed that the samples contained amorphous and ordered porous domains. Stable porous structure able to hold H2 molecule and give them back when required has been obtained. The higher hydrogen adsorption capacities measured at 77 K were obtained for the samples synthesized with reduced amount of MTES, followed by the samples with no MTES, with both C12 and C14 directing agents. Increased amount of MTES precursor led to lowering of the adsorption capacity. The increase of the adsorption capacity already below 20 bar, observed for all samples, could be an advantage for practical application since a lower pressure is preferable. The study revealed the influence of the synthesis parameters to the hydrogen sorption performance and serves as guidance for applications as hydrogen adsorptive materials.