Dodecyl Dimethyl Ammonium Research Articles

Preparation of novel chitosan derivatives and applications in functional finishing of textiles

A novel chitosan derivative, O-acrylamidomethyl-N-[(2-hydroxy-3- dimethyldodecylammonium) propyl] chitosan chloride (NMA-HDCC), was synthesized by reacting chitosan (CTS) with epoxypropyl dodecyl dimethyl quaternary ammonium salt and N-methylolacryl amide (NMA). The chemical structure of the quaternized chitosan was analyzed by FTIR and NMR. The water soluble derivative can form covalent bonding with cellulosic fibers and bring quaternary salt groups onto the fibers. Anti-bacterial as well as salt-free reactive dyeing properties of the treated cotton samples were analyzed. The NMA-HDCC treated cotton fabrics showed durable antimicrobial functions even after 30 consecutive home launderings. The cotton treated with the chitosan and different chitosan derivatives showed improved uptakes, fixation rates, K/S values and fastness of reactive dyes without using auxiliary salt.

Removal of ethyl, isobutyl, and isoamyl xanthates using cationic gemini surfactant-modified montmorillonites

Xanthate is a widely used collector in the flotation of sulfide minerals and discharge of xanthate-bearing solution could cause detrimental effects on ecological balance. In this study, the cationic gemini surfactant, butane-1,4-bis(dodecyl dimethyl ammonium bromide) (gBDDA), was applied to modify montmorillonite (Mt) for removal of ethyl, isobutyl, and isoamyl xanthates from aqueous solution. Different amounts of gBDDA that were stoichiometrically equivalent to 0.5 and 1.0 times the cation exchange capacity of Mt were used to investigate the effects of gBDDA dosage on xanthates removal by the obtained products (gOMt). Characterization results of gOMt by X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis showed the successful intercalation of gBDDA into the interlayer space and the higher content of gBDDA on the external surface of gOMt-1.0. Ion exchange and hydrophobic interaction accounted for the similar adsorption capacities of gOMt-1.0 for three xanthates (ca., 0.6 mmol/g), regardless of the molecular structure of xanthates. The rapid adsorption rate and high selectivity of gOMt to xanthates were obtained as supported by the complete removal within 60 min and the stable uptake in the sulfate-coexisting system, respectively, suggesting that gOMt could be a promising adsorbent for removal of xanthates from aqueous solution.

A Superhydrophobic and Antibacterial Surface Coated on Cotton Fabrics by Polydopamine

In this paper, superhydrophobic and antibacterial fabric is fabricated via the sequential deposition of polydopamine (PDA), quaternized nanosilica particles and hexadecyltrimethoxy silane (HDTMS). The epoxypropyl dodecyl dimethyl ammonium chloride (EPDDAC)-modified silica particles simultaneously contributed to the antibacterial activity and generated a rough surface on the textiles. According to the results, the obtained fabric showed excellent superhydrophobicity, good washability, and high antibacterial activity against Escherichia coli and Staphylococcus aureus.

Study on the Complex System of Sodium Lauryl Diphenyl Ether Disulfonate and Dodecyl Dimethyl Hydroxyethyl Ammonium Chloride

AbstractSurface chemical properties of the mixed system of sodium lauryl diphenyl ether disulfonate (C12-MADS, an anionic surfactant with double hydrophilic groups) and dodecyl dimethyl hydroxyethyl ammonium chloride (K3, a cationic quaternary ammonium surfactant) along with different proportion have been studied at 298 K and 318 K. Synergistic parameters of the mixture in the mixed micelles and the mixed adsorption layer were also calculated by using the regular solution theory. The composition of the mixed micelles and of the mixed adsorption layer was obtained. The results show that the surface chemical properties of C12-MADS/K3 mixture are better than either of single system, and when the solution ratio (α1 = [n (K3)/n (C12-MADS + K3)]) is 0.7 and 0.9, the surface tension curve has a double inflection point which indicates a synergistic effect between the surfactant molecules. The complex system showed a strong synergistic effect in the mixed adsorption layer and the mixed micelles. The mixed system of C12-MADS/K3 has synergism in surface tension reduction effectiveness, surface tension reduction efficiency and mixed micelle formation. When α1 is 0.67, the synergistic effect is the strongest.

One-pot synthesis of alkylammonium-functionalized mesoporous silica hollow spheres in water and films at the air\u2013water interface

This paper reports a one-pot sol–gel approach for the synthesis of the alkylammonium-functionalized mesoporous silica particles with hollow structures and mesoporous silica films via hydrothermal reaction through the self-assembly of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) and tetraethoxysilane (TEOS) as a silica source, dodecyldimethyl(3-sulfopropyl)ammonium hydroxide (DDAPS) and fluorocarbon anion (ammonium perfluorooctanoate (APFO)) as the structure-directing agent. The alkylammonium-functionalized hollow mesoporous silica particles exhibited a different morphology, mesoporosity, and hollow structure with a layered mesostructure in the shell according to the DDAPS/APFO surfactant molar ratios (DDAPS/APFO = 3/1~1/9 or APFO in the range of 10~80 mM), reaction times (6~48 h), and reaction temperatures (45~95 °C). Alkylammonium-functionalized hollow mesoporous silica particles with spherical morphologies were produced from precipitation in the bottom of the reaction bottle after the hydrothermal reaction. At a DDAPS/APFO surfactant ratio of 1/3, reaction temperature of 60 °C, and reaction times of 24 h and 48 h, the alkylammonium-functionalized hollow mesoporous silica spheres displayed a multilayered mesostructure in the shell. The sphere size could be controlled from ca. 76 nm to ca. 350 nm with a shell thickness of ca. 35 nm. In addition, alkylammonium-functionalized mesoporous silica films were produced at the air–water interface, whereas hollow mesoporous silica spheres were produced with precipitation in the bottom of the reaction bottle. The film thickness was controlled from ca. 210 nm to ca. 400 nm.

Preparation of surface-modified monodisperse polystyrene microspheres with cationic functional comonomer

A two-stage synthesis of surface-functionalized monodisperse polystyrene (PS) microspheres in ethanol/water medium by introducing methacryloyloxyethyl dodecyl dimethyl ammonium bromide (QDMDB) to dispersion polymerization of styrene is reported. Polyvinylpyrrolidone (PVP) and fatty alcohol polyoxyethylene ether (AEO-9) are used as dispersion stabilizers. The novel microspheres are characterized by FT-IR, SEM, GPC, TGA, water contact angle (WCA), etc. The dispersion polymerization goes through successfully with the solid content up to 58.75%, in which the water content in the medium is 20%. The water content in the medium has a certain effect on the particle size and molecular weight of microspheres. Under the experimental conditions, the average diameters of the obtained microspheres are approximately 550–1200 nm with the number average molecular weight of up to 5.8 × 105. The introduction of QDMDB improves the wettability and thermal stability of the poly(St-co-QDMDB) microspheres. A mechanism of dispersion copolymerization based on XPS and 1H NMR is proposed.

Rheo-SANS study on relationship between micellar structures and rheological behavior of cationic gemini surfactants in solution

HypothesisGemini surfactant 12–2–12 (dimethylene-1,2-bis(dodecyl dimethylammonium bromide)) solutions are known to show shear thickening and thinning under salt-free conditions. Because the rheological behavior of the wormlike micelles formed by 12–2–12 in solution is related to their structure, we expected that changes to the precursor structure would affect their rheological behaviors. It is also important to understand the effect of the introduction of a spacer group in the 12–2–12 molecules on the rheological behavior and structure of the wormlike micelles under shear flow. ExperimentsSimultaneous small-angle neutron scattering and rheological measurements (Rheo-SANS) of the 12–2–12 solutions were performed. We exhaustively studied the structural changes in the wormlike micelles upon increasing shear rate. FindingsWe found that the wormlike micelles were oriented in the direction of the flow due to elongation and that changes to the precursor of the wormlike micelles did not affect the shear thickening. As a precursor structural change of shear thinning, the wormlike micelles elongated while maintaining their orientation. We found that an increase in the molecular curvature of the 12–2–12 due to the introduction of a spacer-group contributed to the unusual rheological behaviors of the wormlike micelles in a solution under shear flow.

Microwave/ultrasound-assisted modification of montmorillonite by conventional and gemini alkyl quaternary ammonium salts for adsorption of chromate and phenol: Structure-function relationship

Butane-1,4-bis(dodecyl dimethyl ammonium bromide) (gBDDA) and dodecyl trimethyl ammonium bromide (DTMA) in same stoichiometric amounts were applied to modify montmorillonite (Mt) under microwave and ultrasound conditions. The composition and structure of products were obtained through multiple characterizations including XRD, FTIR, TG/DTG, SEM, TEM, and N2 adsorption/desorption measurements, and the adsorption performance of chromate and phenol on these products were also investigated. Intercalations of gBDDA and DTMA into interlayer space of Mt were observed, but the amount of anchored modifier on the external surface was larger for gBDDA compared with DTMA when the stoichiometric amount of modifier larger than 1.0 times cation exchange capacity of Mt was added. Although there was no significant difference in morphology among products, the interlayer space distance, specific surface area, and pore size distribution were closely associated with the species and amount of applied modifier. Adsorption of phenol on products through partition mechanism relied on not only organic content, but also the configuration of modifier. Meanwhile, adsorption of chromate mainly depended on the presence of counter ion (bromide), which accounted for the high adsorption capacity and initial adsorption rate on gOMt-0.75. The fitting parameters of adsorption results using pseudo-second order model and Freundlich model suggested that gBDDA-modified Mt could sequester phenol or chromate in the faster manner with higher affinity. Compared with the conventional surfactant such as DTMA, the study revealed that, using gemini surfactant such as gBDDA to modify Mt would significantly reduce or even has the potential to eradicate the secondary pollution by modifier release during adsorption process. This study provides a new direction for Mt modification intended to be used as adsorbents to treat polluted water with high standards such as drinking water.

Effect of [Zr(α-PW11O39)2]10− Polyoxometalate on the Self-Assembly of Surfactant Molecules in Water Studied by Fluorescence and DOSY NMR Spectroscopy

The catalytic fragmentation of hydrophobic proteins by polyoxometalates (POMs) requires the presence of surfactants in order to increase the solubility of the protein. Depending on the nature of the surfactant, different effects on the kinetics of protein hydrolysis are observed. As the molecular interactions between the POMs and surfactants in solutions have been scarcely explored, in this study, the interaction between the catalytically active Keggin polyoxometalate [Zr(α-PW11O39)2]10− and four different surfactants—sodium dodecyl sulfate (SDS), dodecyldimethyl(3-sulfopropyl)ammonium (Zw3-12), dodecyldimethyl(3-sulfopropyl) ammonium (CHAPS), and polyethylene glycol tert-octylphenyl ether (TX-100)—have been studied in aqueous media. The effect of polyoxometalate on the self-assembly of surfactant molecules into micelles and on the critical micellar concentration (CMC) has been examined by fluorescence spectroscopy and diffusion ordered NMR spectroscopy (DOSY).

Thermodynamic and Interfacial Properties of Cationic Gemini Surfactant in the Presence of Alcohols

Abstract The micellar properties of the cationic Gemini surfactant ethanediyl-1,2-bis(dimethyldodecyl ammonium bromide), C12H25 · (CH3)2N+–(CH2)2–N+(CH3)2C12H25 · 2Br− (12-2-12), with short chain alcohols have been studied by conductivity and surface tension measurements within the temperature range 293.15 K–313.15 K and alcohol percentage. The critical micelle concentration (CMC) of 12-2-12 solution, degree of ionization (α) and standard Gibbs free energy of micellization (ΔG°m), standard enthalpy of micellization (ΔH°m) were calculated from conductivity and surface tension data. The experimental data show that the CMC values of cationic Gemini surfactants increased with addition of methanol, ethanol and n-propanol. The thermodynamic parameters (ΔG°m), (ΔH°m) and (ΔS°m) of micellization of 12-2-12 in alcohol were also calculated from the temperature dependence of the CMC values. CMC, (α), (ΔH°m) and (ΔS°m) increased linearly with increasing temperature. In the mixture of dimeric cationic surfactant (12-2-12) and alcohol solutions, the CMC values showed a slight increase with increasing alcohol concentration. CMC, maximum surface excess concentration at the solution/air interface, Γmax, minimum area per surfactant molecule, Amin, and the surface pressure at CMC, ¶CMC, values calculated from the surface tension measurements and thermodynamic parameters have been evaluated at same temperatures.

Short-Chain n-Alcohol-Induced Changes in Phase Behaviors of Aqueous Mixed Cationic/Anionic Surfactant System.

The short-chain n-alcohol-induced changes in phase behaviors of aqueous mixed 1,3-propanediyl bis(dodecyl dimethylammonium bromide) (12-3-12) and sodium dodecyl sulfonate (AS) system have been investigated. For the 12-3-12/AS/H2O mixed system, there are two kinds of aqueous two-phase systems with excess cationic surfactant (ATPS-C). The molar ratio of 12-3-12 to AS (MR12-3-12/AS) and the total surfactant concentration ( mT) in the top phase are smaller than those in the bottom phase of ATPS-C. It is worth noting that the addition of ethanol or n-propanol leads to different influences on the ATPS-C. Molecular dynamics (MD) simulation results illustrate that the different influences ascribe to the difference in the cosurfactant effect of ethanol and n-propanol. When ethanol is used as additive, the difference in mT leads to the difference in interactions between surfactants and ethanol for the two coexisting phases of ATPS-C, determining the difference in their combination ability with the mixed solvent. It is the main reason for the ethanol-induced phase inversion of the first kind of ATPS-C. When n-propanol is added, in addition to mT, MR12-3-12/AS is also a key factor influencing the interactions between 12-3-12 and AS and between surfactants and n-propanol due to the stronger cosurfactant effect of n-propanol. MD simulations indicate that vesicles with smaller MR12-3-12/AS are easier and faster to form. These vesicles spontaneously accumulate at the top phase accompanied by certain amount of mixed solvent transferred from the bottom phase of ATPS-C. Meanwhile, the competition for the mixed solvent arising from the surfactant-rich bottom phase prevents the transferring. The two factors work together to cause the increase of mT in the top phase of ATPS-C with the addition of n-propanol, leading to n-propanol-induced phase concentration inversion rather than phase inversion of ATPS-C. On the basis of the experimental results and MD simulations, ethanol-induced phase inversion mechanism or n-propanol-induced phase concentration inversion mechanism of ATPS-C has been proposed.

Study on a Ternary Surfactant System of Disodium Hexadecyl Diphenyl Ether Disulfonate, Dodecyldimethyl Hydroxyethyl Ammonium Chloride and Fatty Alcohol Polyoxyethylene Ether

AbstractThis study was focused on a ternary complex system composed of hexadecyl diphenyl ether disulfonate (C16-MADS), dodecyl dimethyl hydroxyethyl ammonium chloride (K3) and fatty alcohol polyoxyethylene ether (AEO9). The binary mixture C-K consisting of C16-MADS and K3 was investigated and the maximum synergism was obtained when the mole ratio was 0.33:0.67. Subsequently, AEO9 was added to the binary C-K complex system to investigate whether the behavior of the new complex system, in which C-K is thought to be a surfactant, can be explained by the theory of regular solution. The maximum synergism was achieved when the molar ratio of C-K and AEO9 was 7:3. The regular solution theory could well explain the synergism in mixed micelle formation and the synergism in surface tension reduction efficiency, but the synergism in surface tension reduction effectiveness did not match with the experimental data. So, there still exist some deficiencies in the application of the regular solution theory to a complex system of three surfactants.

Adsorption Properties of Gemini and Monomeric Cationic Surfactants on Sandstone and Silica Nanoparticles

The surface modification of pore throat by adsorption of surfactants is thought to have a positive effect on water flooding in low and ultralow permeability reservoirs. In this paper, Gemini cationic surfactants, containing 12 and 16 carbon alkyl chains(ethanediyl-1,2-bis(dimethyl dodecyl ammonium bromide) and ethanediyl-1,2-bis(dimethyl cetyl ammonium bromide), referred to as GC12 and GC16) and hexadecyl trimethyl ammonium bromide (CTAB) were used as modifying agents to investigate the effects of the surfactant concentration, adsorption time and temperature on static adsorption onto the surface of sandstone and silica nano particles (NPS). The results show that the equilibrium adsorption amount of GC16 on sandstone and NPS is higher than that of GC12 on sandstone and NPS with the same initial concentration of 0.225 mmol/L in solution at 45°C. It is found that the adsorption amounts of GC12 and GC16 decrease as the raise of temperature. The adsorption rate of surfactant on sandstone surface is slower than that of NPS. The equilibrium adsorption time of these surfactants on sandstone is 20 h, while the time of NPS is only 2 h. At 55°C, the static saturation absorption amount of GC12 is 210.56 μmol/g on NPS and 117.67 μmol/g on sandstone, while the amounts of CTAB on sandstone and NPS under static conditions are 1.18 times and 1.46 times of GC12, respectively. Considering the number of tail chain in a molecule of surfactant, the packing densities of Gemini surfactants on solid surface are higher than that of the single-tail surfactant (CTAB). Therefore, the adsorption rate and amount of surfactant are affected by the specific surface of solid particles, charged density, tail chain number and length of the cationic group.

Uptake and phytotoxic effect of benzalkonium chlorides in Lepidium sativum and Lactuca sativa

Cationic surfactants such as benzalkonium chlorides (BACs) are used extensively as biocides in hospitals, food processing industries, and personal care products. BACs have the potential to reach the rooting zone of crop plants and BACs might thereby enter the food chain. The two most commonly used BACs, benzyl dimethyl dodecyl ammonium chloride (BDDA) and benzyl dimethyl tetradecyl ammonium chloride (BDTA), were tested in a hydroponic system to assess the uptake by and phytotoxicity to lettuce (Lactuca sativa L.) and garden cress (Lepidium sativum L.). Individually and in mixture, BACs at concentrations up to 100 mg L−1 did not affect germination; however, emergent seedlings were sensitive at 1 mg L−1 for lettuce and 5 mg L−1 for garden cress. After 12 d exposure to 0.25 mg L−1 BACs, plant dry weight was reduced by 68% for lettuce and 75% for garden cress, and symptoms of toxicity (necrosis, chlorosis, wilting, etc.) were visible. High performance liquid chromatography-mass spectroscopy analysis showed the presence of BACs in the roots and shoots of both plant species. Although no conclusive relationship was established between the concentrations of six macro- or six micro-nutrients, growth inhibition or BAC uptake, N and Mg concentrations in BAC-treated lettuce were 50% lower than that of control, indicating that BACs might induce nutrient deficiency. Although bioavailability of a compound in hydroponics is significantly higher than that in soil, these results confirm the potential of BACs to harm vascular plants.

Removal Efficiency of Different Gemini Surfactants and Related Modified Clay to Chattonella marina.

To obtain new modified clays with excellent algae removal efficiency, three gemini surfactants including ethylene bis (dodecyl dimethyl ammonium chloride), ethylene bis (octadecyl dimethyl ammonium chloride) and ethylene bis (dodecyl dimethyl ammonium bromide) (EDAB), and a poly quaternary ammonium salt, poly dimethyl diallyl ammonium chloride, were screened with Chattonella marina. The four chemicals all exhibited high removal efficiencies against C. marina, with EDAB achieving the highest. A series of organ-clays with different ratios of EDAB were prepared, and the associated removal efficiencies were evaluated. The removal efficiencies of the organ-clays were improved by the EDAB intercalation and the organ-clay with 15% EDAB had the highest removal efficiency. The LC50 of EDAB intercalated clay for zebrafish and shrimp was much higher than the values of intercalated clay required to obtain a desirable removal efficiency of algae. Taken together, EDAB intercalated clay might be a potential alternative to control harmful algal blooms (HABs).

Entrapment of amino acids in gas phase surfactant assemblies: The case of tryptophan confined in positively charged (1R,2S)-dodecyl (2-hydroxy-1-methyl-2-phenylethyl) dimethylammonium bromide aggregates.

The ability of positively charged aggregates of the surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) to incorporate D-tryptophan or L-tryptophan in the gas phase has been investigated by electrospray ion mobility mass spectrometry (ESI-IM-MS). Strongly impacted by the pH of the electrosprayed solutions, both protonated (T+ ) and deprotonated (T- ) tryptophan are effectively included into the aggregates, whereas, tryptophan in zwitterionic (T0 ) form is practically absent in singly charged DMEB aggregates but can be found in multiply charged ones. The ability to incorporate tryptophan increases with the aggregation number and charge state of aggregates. More than 1 tryptophan species can be entrapped (aggregates including up to 5 tryptophan are observed). Collision induced dissociation experiments performed on the positively singly charged DMEB hexamer containing 1 T- show that at low collision energies the loss of a DMEB molecule is preferred with respect to the loss of the DMEB cation plus T- species which, in turn, is preferred with respect to the loss of mere tryptophan, suggesting that the deprotonated amino acid is preferentially located in proximity of a DMEB head group and with the ionic moiety pointing towards the core of the aggregate. The analysis of the collision cross sections (CCS) of bare and tryptophan containing aggregates allowed evaluating the contributions of tryptophan and bromide ions to the total aggregate CCS. No significant discrimination between D-tryptophan and L-tryptophan by the chiral DMEB aggregates has been evidenced by mass spectra data, CID experiments, and CCS values.

Metabolomic imaging of a quaternary ammonium salt within a marine bacterial biofilm on carbon steel

A novel method to investigate penetration, distribution and metabolic effects of biocides in microbial biofilms is described. LASCA (laser ablation solvent capture by air flow) mass spectrometry imaging (MSI) allowed for the visualization of distributions of specific ion masses, including the signature of a quaternary ammonium salt biocide, benzyl dimethyl dodecyl ammonium chloride (BDDAC), throughout the biofilm. The biocide penetrated the upper layers of a Marinobacter sp. biofilm on a carbon steel coupon in seawater after 30 min. The concentration initially decreased with depth; however, it again increased close to the metal surface. Penetration of the biocide primarily occurred close to the center of the circular coupon, where ions with negative mass defects were preferentially detected, indicating that this is the anodic region of the corroding coupon. Future work using high performance liquid chromatography/mass spectrometry (HPLC/MS) will allow the identification within the biofilm of bacterial metabolites directly affected by biocide action.

Preparation of Poly(ethylene‐co‐acrylic acid) Grafted with Aliphatic Quaternary Ammonium Salts as Antibacterial Polymers

To improve the antibacterial performance of poly(ethylene‐co‐acrylic acid) (PEAA) copolymer, aliphatic quaternary ammonium salts (QASs) was grafted into PEAA copolymers via a Steglich esterification reaction using N,N′‐dicyclohexylcarbodiimide (DCC) as a dehydrating agent. The polymers were synthesized using dodecyl dimethyl hydroxyethyl ammonium chloride (DDHAC), which was prepared by quaternization of dimethylethanolamine (DMEA) with 1‐chlorododecane. These polymers effectively inhibited the growth of microorganisms due to their hydrophobic chains, which were bound to PEAA copolymers. The obtained PEAA‐g‐DDHAC (PGD) was investigated by attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), proton nuclear magnetic resonance (1H NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and antibacterial tests. The results showed that the antibacterial effects of PGDs were significantly improved by alkyl grafting, and this improvement depended on reaction temperature. The highest antibacterial activity was observed for polymers synthesized at 135°C against Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli. Their decomposition rate was accelerated as the temperature increased above 165°C because of the thermal decomposition of DDHAC.

Micelles of the chiral biocompatible surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB): molecular dynamics and fragmentation patterns in the gas phase.

The study of self-assembly processes of surfactant molecules in the gas phase is of great interest for several theoretical and technological reasons related to their possible exploitation as drug carriers, protein shields and cleaning agents in the gas phase. The stability and fragmentation patterns of singly and multiply charged (either positively or negatively) aggregates of the surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethyl ammonium bromide (DMEB) in the gas phase have been studied by ion mobility mass spectrometry and tandem mass spectrometry. Molecular dynamics (MD) simulations of positively and negatively singly and multiply charged DMEB aggregates have been performed to obtain structural and energetics information. Finally, in order to ascertain some clues on the DMEB growth mechanism, quantum mechanics calculations were carried out. It has been evidenced that positively and negatively singly charged aggregates at low collision energy decompose preferentially by loss of only one DMEB molecule. Increasing the collision energy, the loss of neutrals becomes increasingly abundant. Multiply charged DMEB aggregates are unstable and decompose forming singly charged monomers or dimers. MD simulations show reverse micelle-like structures with polar heads somewhat segregated into the aggregate interior. Finally, a good correlation between experimental and calculated collisional cross sections (CCS) was found. The fragmentation pathways of DMEB charged species evidenced for singly charged aggregates exhibit features similar to that of other detergent aggregates, but multiply charged aggregates showed a system-specific behavior. QM calculations on the optimized structures (21+ , 31+ , 11- and 21- ) indicate that the most determinant interactions are due to an OH---Br hydrogen bonding that is also involved in the link between monomeric DMEB units. The MD models gave CCS values in good agreement with experimental ones, evidenced by a less strict reverse micelle-like structure and a reasonably spread bromine anion distribution Copyright © 2017 John Wiley & Sons, Ltd.

Toxicity reduction and improved biodegradability of benzalkonium chlorides by ozone/hydrogen peroxide advanced oxidation process

Abstract Advanced oxidation of a mixture of two benzalkonium chlorides (BACs), benzyl dimethyl dodecyl ammonium chloride (BDDA) and benzyl dimethyl tetradecyl ammonium chloride (BDTA), using O3 and H2O2 at elevated pH was performed in Milli-Q water and in a municipal wastewater influent. The potential for O3/H2O2 advanced oxidation process (AOP) to reduce the toxicity of BACs was evaluated. Experimental conditions were optimized using a central composite design (CCD). About 1.28 g h−1 O3 and 200 mg L−1 of H2O2 at pH 11 degraded 90% of the initial BACs (BDDA:BDTA at 50:25 mg L−1) within 30 min. Formation of 25 intermediates and six degradation pathways for the hydrophilic (benzyl and ammonium moiety) and hydrophobic (alkyl chain) constituents of BACs were proposed. Despite the formation of various intermediates, toxicity of BACs in the treated water, assessed using two fresh water algae species (Chlorella vulgaris and Chlamydomonas reinhardtii), was completely removed by O3/H2O2 oxidation. Based on the ratio of the 5-day biological oxygen demand (BOD5) to chemical oxygen demand (COD), AOP improved the biodegradability of BACs.