Ammonium-functionalized Silica Research Articles

Highly CO2-Selective Membranes Composed of Quaternary Ammonium Functionalized Silica Nanoparticles

Highly CO₂-Selective Membranes Composed of Quaternary Ammonium Functionalized Silica Nanoparticles

Preparation of superhydrophobic, antibacterial and photocatalytic cotton by the synergistic effect of dual nanoparticles of rGO-TiO2/QAS-SiO2

In this study, the cotton fabric was endowed with superhydrophobic, antibacterial, and photocatalytic properties by a simple and easily-operated coating method. The optimal dual-particle coating, firmly adhered to the textile surface using polydimethylsiloxane (PDMS) as a binder, was obtained with the mixture of reduced graphene oxide-added titanium dioxide (rGO-TiO 2 ) and quaternary ammonium-functionalized silica (QAS-SiO 2 ), under the most appropriate mass ratio. The experimental results reveal that the water contact angles (CAs) of the optimal-treated cotton fabric can reach up to154°, and the bactericidal effect against Escherichia coli and Staphylococcus aureus is over 99 %, with the degradation rate for methylene blue solution as high as 98 %. On top of the excellent self-cleaning and bacterial shielding capabilities of the coating, its enhanced performance mentioned above can be maintained well against repeated washing, continuously abrasion, strong acids/bases and UV rays. Meanwhile, the finding suggests that the coating does not affect the strength of the fabric, and can retain the original deformability of the fabric. Most notably, the application of the coating method can cover a wide range of materials, including a variety of textiles as well as nontextiles such as paper, stainless steel etc. In short, this novel coating method is eco-friendly and strongly feasible, which paves the solid way for great potential in a wide range of application. • Cotton was functionalized with nano-silica and nano-titanium dioxide particles. • The processed cotton fabric was endowed with super-hydrophobicity and excellent photocatalytic activity. • The bactericidal effect of cotton against Escherichia coli and Staphylococcus aureus is over 99 %. • The degradation rate of MB solution finally reached the maximum 98 %. • The functional finishing will not visibly affect other properties of cotton fabrics.

Efficient and Economic Heparin Recovery from Porcine Intestinal Mucosa Using Quaternary Ammonium-Functionalized Silica Gel

Heparin, usually isolated from porcine intestinal mucosa, is an active pharmaceutical ingredient of great material value. Traditionally, diverse types of commercial resins were employed as an adsorbent for heparin retrieval from biological samples. However, more recent years have encouraged the advent of new cost-effective adsorbents to achieve enhanced heparin retrieval. Inexpensive cationic ammonium-functionalized silica gels, monodispersed with larger surface area, porosity, and higher thermal stability, were chosen to evaluate the heparin recovery yield from porcine intestinal mucosa. We demonstrated that higher positively charged and less bulky quaternary modified silica gel (e.g., QDASi) could adsorb ~28% (14.7 mg g-1) heparin from the real samples. In addition, we also determined suitable surface conditions for the heparin molecule adsorption by mechanistic studies and optimized different variables, such as pH, temperature, etc., to improve the heparin adsorption. This is going to be the first reported study on the usage of quaternary amine-functionalized silica gel for HEP uptake.

Synthesis of quaternary ammonium-functionalized silica gel through grafting of dimethyl dodecyl [3-(trimethoxysilyl)propyl]ammonium chloride for nitrate removal in batch and column studies

Abstract In this study, quaternary ammonium functionalized-silica gel was synthesized for nitrate removal using dimethyl dodecyl[3-(trimethoxysilyl)propyl] ammonium chloride (DMDAC) as a quaternary ammonium silane coupling agent, which was grafted to silica gel to obtain the DMDAC-silica gel. Batch experiments showed that the DMDAC-silica gel could effectively remove nitrate in the pH range of 4 to 10. Kinetic and equilibrium experiments showed that nitrate removal by the DMDAC-silica gel reached equilibrium in 60 min with a maximum nitrate removal capacity of 56.4 mg/g. Fixed-bed column experiments (bed depth = 10–30 cm; inner diameter of column = 2.5 cm; flow rate = 0.06–0.18 L/h) in nitrate solution demonstrated the dynamic behaviors of nitrate removal by the DMDAC-silica gel under various experimental conditions of flow rate, bed depth, and influent nitrate concentration. The DMDAC-silica gels could be successfully used for nitrate removal and regenerated and reused with 10% NaCl solution in the column. In groundwater (nitrate = 140 mg/L, chloride = 63 mg/L, sulfate = 440 mg/L, and bicarbonate = 20–300 mg/L), the nitrate BTCs appeared behind the sulfate BTCs with α S N values of 5.7–11.3, indicating that the DMDAC-silica gel could selectively remove nitrate over sulfate in dynamic flow conditions.

Quaternary ammonium-functionalized silica sorbents for the solid-phase extraction of aromatic amines under normal phase conditions

Quaternary ammonium-functionalized silica materials were synthesized and applied for solid-phase extraction (SPE) of aromatic amines, which are classified as priority pollutants by US Environmental Protection Agency. Hexamethylenetetramine used for silica surface modification for the first time was employed as SPE sorbent under normal phase conditions. Hexaminium-functionalized silica demonstrated excellent extraction efficiencies for o-toluidine, 4-ethylaniline and quinoline (recoveries 101–107%), while for N,N-dimethylaniline and N-isopropylaniline recoveries were from low to moderate (14–46%). In addition, the suitability of 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica as SPE sorbent was tested under normal phase conditions. The recoveries achieved for the five aromatic amines ranged from 89 to 99%. The stability of the sorbent was evaluated during and after 150 extractions. Coefficients of variation between 4.5 and 10.2% proved a high stability of the synthesized sorbent.Elution was carried out using acetonitrile in the case of hexaminium-functionalized silica and water for 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent. After the extraction the analytes were separated and detected by liquid chromatography ultraviolet detection (LC-UV). The retention mechanism of the materials was primarily based on polar hydrogen bonding and π–π interactions. Comparison made with activated silica proved the quaternary ammonium-functionalized materials to offer different selectivity and better extraction efficiencies for aromatic amines. Finally, 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent was successfully tested for the extraction of wastewater and soil samples.

Preparation and characterization of ammonium-functionalized silica nanoparticle as a new adsorbent to remove methyl orange from aqueous solution

Quaternary ammonium polyethylenimine (PEI) was successfully modified to silica nanoparticle (QPEI/SiO2) as a new adsorbent to remove methyl orange from aqueous solution. The isotherm and kinetics of dye adsorption were studied, which showed that Langmuir isotherm fit the experimental results well. The maximum adsorption capacity of QPEI/SiO2 for methyl orange is 105.4mg/g. The equilibrium time for methyl orange adsorption onto QPEI/SiO2 was as short as 10min, indicating that the adsorbent has a strong affinity for methyl orange. The adsorption capacities of the methyl orange are slightly influenced by the pH in the range of 3.2–9.6. The QPEI/SiO2 adsorbent can be used in the wide pH range, which is different from other adsorbent. This may attribute to the quaternary ammonium carrying positive charges in acidic and basic solution.

Dual Action Antimicrobials: Nitric Oxide Release from Quaternary Ammonium-Functionalized Silica Nanoparticles

The synthesis of quaternary ammonium (QA)-functionalized silica nanoparticles with and without nitric oxide (NO) release capabilities is described. Glycidyltrialkylammonium chlorides of varied alkyl chain lengths (i.e., methyl, butyl, octyl, and dodecyl) were tethered to the surface of amine-containing silica nanoparticles via a ring-opening reaction. Secondary amines throughout the particle were then functionalized with N-diazeniumdiolate NO donors to yield dual functional nanomaterials with surface QAs and total NO payloads of 0.3 μmol/mg. The bactericidal activities of singly (i.e., only NO-releasing or only QA-functionalized) and dual (i.e., NO-releasing and QA-functionalized) functional nanoparticles were tested against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa . Particles with only NO release capabilities alone were found to be more effective against P. aeruginosa , while particles with only QA-functionalities exhibited greater toxicity toward S. aureus . The minimum bactericidal concentrations (MBC) of QA-functionalized particles decreased with increasing alkyl chain length against both microbes tested. Combining NO release and QA-functionalities on the same particle resulted in an increase in bactericidal efficacy against S. aureus ; however, no change in activity against P. aeruginosa was observed compared to NO-releasing particles alone.

Dual Action Antimicrobials: Nitric Oxide Release from Quaternary Ammonium-Functionalized Silica Nanoparticles

Dual Action Antimicrobials: Nitric Oxide Release from Quaternary Ammonium-Functionalized Silica Nanoparticles

Ion exchange and ion exchange voltammetry with functionalized mesoporous silica materials

Ordered mesoporous silicas prepared by the surfactant template route can be readily used as effective ion exchangers when they are functionalized with organic groups bearing either positive or negative charges. This is illustrated here on the basis of sulfonic acid- and/or quaternary ammonium-functionalized silica spheres obtained by the sol–gel process in the presence of cetyltrimethylammonium as a template. Various materials have been synthesized at several functionalization levels and their physico-chemical characteristics (especially their porosity) have been discussed with respect to the amount of functional groups in the porous solids. Their ion exchange behavior was then studied from batch experiments (determination of cation and anion exchange capacities) and by electrochemistry at carbon paste electrodes (CPE) modified with these solids (ion exchange voltammetry). The preconcentration efficiency was discussed on the basis of the organic group content in the materials as well as their structure and porosity. The series of materials containing both sulfonic acid and quaternary ammonium moieties displayed zwitterionic surfaces and thus both cation and anion exchange properties.

Ion-Exchange Properties and Electrochemical Characterization of Quaternary Ammonium-Functionalized Silica Microspheres Obtained by the Surfactant Template Route

Porous silica spheres functionalized with quaternary ammonium groups have been prepared by co-condensation of N-((trimethoxysilyl)propyl)-N,N,N-trimethylammonium chloride (TMTMAC) and tetraethoxysilane (TEOS) in the presence of cetyltrimethylammonium as a template and ammonia as a catalyst. The physicochemical characteristics of the resulting ion exchangers have been analyzed by various techniques and discussed with respect to the amount of organofunctional groups in the materials. For comparison purposes, both an ordered MCM-41 type mesoporous silica and two silica gels of different pore size have been grafted with TMTMAC. The ion-exchange capabilities were first evaluated from batch experiments (determination of anion-exchange capacities) and then by ion-exchange voltammetry at carbon paste electrodes modified with these hybrid materials. Effective concentration of Fe(CN)(6)(3)(-) species in the anion exchangers was pointed out, while no significant accumulation of Ru(NH(3))(6)(3+) was observed. The preconcentration efficiency was discussed on the basis of the organic group content in the materials as well as their structure and porosity. A second series of materials displaying zwitterionic surfaces was finally prepared and characterized with respect to their physicochemical properties and ion-exchange voltammetric behavior. They consisted of sulfonic acid-functionalized mesoporous silica samples resulting from the oxidation of thiol-functionalized silica spheres obtained by co-condensation of mercaptopropyl-trimethoxysilane (MPTMS) and TEOS, which were then grafted with TMTMAC at various functionalization levels. Possible interactions between the ammonium and sulfonate moieties in the confined medium were pointed out from X-ray photoelectron spectroscopy. The competitive accumulation-rejection of Fe(CN)(6)(3)(-) and Ru(NH(3))(6)(3+) redox probes was finally studied by cyclic voltammetry.