Hexamethylenediamine Research Articles

Estradiol Removal by Adsorptive Coating of a Microfiltration Membrane.

This work demonstrates the enhancement of the adsorption properties of polyethersulfone (PES) microfiltration membranes for 17β-estradiol (E2) from water. This compound represents a highly potent endocrine-disrupting chemical (EDC). The PES membranes were modified with a hydrophilic coating functionalized by amide groups. The modification was performed by the interfacial reaction between hexamethylenediamine (HMD) or piperazine (PIP) as the amine monomer and trimesoyl chloride (TMC) or adipoyl chloride (ADC) as the acid monomer on the surface of the membrane using electron beam irradiation. The modified membranes and the untreated PES membrane were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), water permeance measurements, water contact angle measurements, and adsorption experiments. Furthermore, the effects of simultaneous changes in four modification parameters: amine monomer types (HMD or PIP), acid monomer types (TMC or ADC), irradiation dosage (150 or 200 kGy), and the addition of toluene as a swelling agent, on the E2 adsorption capacity were investigated. The results showed that the adsorption capacities of modified PES membranes toward E2 are >60%, while the unmodified PES membrane had an adsorption capacity up to 30% for E2 under similar experimental conditions, i.e., an enhancement of a factor of 2. Next to the superior adsorption properties, the modified PES membranes maintain high water permeability and no pore blockage was observed. The highlighted results pave the way to develop efficient low-cost, stable, and high-performance adsorber membranes.

Development of novel nanocomposite polyurethane ultrafiltration membranes based on multiwalled carbon nanotubes functionalized with PAMAM dendrimer

ABSTRACT Novel biodegradable nanocomposite membranes were prepared using a chemo-enzymatic route. Polyester-urethane-urea matrix was obtained from poly(ε-caprolactone) diol, isophorone diisocyanate (IPDI), and hexamethylene diamine (HMDA) as a chain extender. Nanocomposites (0.5% wt/wt) were synthesized by in situ polymerization using reinforced multi-walled carbon nanotubes (MWNTs) grafted with two distinct-generation dendritic poly(amidoamine) (PAMAM). Membranes were prepared by the so-called inversion phase method, using N,N dimethylformamide as solvent and water as non-solvent. The effect of the amine group content into filler in the mechanical and filtration properties of membranes was evaluated. It was observed that the content of amine groups in the dendrimer-modified MWNTs provides sites for hydrogen bonding interactions in the matrix, which influence mechanical properties such as toughness and extensibility, and the porous morphology of the membrane. Additionally, it was observed that PAMAM grafted MWNTs may interact with soft segments of PU, modifying the filtering properties of membranes.

Engineering of amine-based binding chemistry on functionalized graphene oxide/alginate hybrids for simultaneous and efficient removal of trace heavy metals: Towards drinking water

Engineering of versatile binding chemistry on graphene oxide surface using nucleophilic substitution/amidation reactions for highly efficient adsorption of Cd (II), Cu (II) and Pb (II) is herein proposed. Graphene oxide (GO) was used as a precursor for covalent bonding of hexamethylenediamine (HMDA) molecules via the nucleophilic substitution/amidation reactions on epoxy (COC) and carboxyl (COOH) groups to yield hexamethylenediamine functionalized graphene oxide (GO-HMDA) with multiple binding chemistries such as oxygen and nitrogen. Afterwards, GO-HMDA was encapsulated in alginate hydrogel beads with different loadings 5, 10, 15 and 20 wt% to produce Alg/GO-HMDA hybrid adsorbents for the removal of trace heavy metal ions from aqueous solution. Batch adsorption studies showed remarkable adsorption rates reaching 100% for Pb (II), 98.18% for Cu (II) and 95.19 for Cd (II) (~1 mg L−1) with only 15 wt% of GO-HMDA incorporated into the alginate beads. Moreover, Alg/GO-HMDA showed high removal efficiencies of heavy metals from tap water with a removal order of (Pb > Cu > Cd) similar to that observed in single aqueous solution. In Addition, the Alg/GO-HMDA adsorbents displayed excellent regeneration ability for six consecutive adsorption–desorption cycles confirming the high performance and potential of these adsorbents, for real heavy metals remediation in environment and in drinking waters in both single and multiple systems. Finally, the adsorption mechanism of traces heavy metals resulted from several phenomena including the electrostatic interactions occurring between the COOH groups of Alginate and the GO-HMDA surface groups as well as, through chelation interactions occurring between the metal cations and amino-functionalized groups of Alg/GO-HMDA 15 hybrid adsorbent.

Measurement of vapour-liquid equilibrium and e-NRTL model development of CO2 absorption in aqueous dipropylenetriamine.

Vapour-liquid equilibrium (VLE) of CO2 in aqueous dipropylenetriamine (DPTA) is investigated experimentally using a stirred equilibrium cell setup. Equilibrium solubility of CO2 is measured in the temperature and pressure range of (313-333) K and (1-100) kPa respectively. Composition of aqueous DPTA solvent used for the absorption study is in the range of (5-15) mass%. Experimental data shows higher CO2 loading capacity of this solvent compared to conventional solvents like monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and N-methyldiethanolamine (MDEA) as well as recently developed polyamine solvents like aminoethylethanolamine (AEEA), piperazine (PZ), and hexamethylenediamine (HMDA). Experimental VLE data is then correlated using the electrolyte non-random two-liquid (e-NRTL) theory which is an activity coefficient-based model for the electrolyte system. Data regression system (DRS) in Aspen Plus® (V8.8) is employed to fit the e-NRTL model equation with the experimental data by regressing the model parameters. Model-predicted data is found to be in good agreement with the experimental VLE data with an average absolute deviation of 22.3%. Performance of aqueous DPTA solvent is also analysed by predicting solvent capacity, equilibrium liquid-phase speciation, and heat of CO2 absorption using the newly developed e-NRTL model for the investigated system.

Efficiency of application of the microbiological method of waste water treatment to remove hexamethylendiamine

Wastewater contaminated with hexamethylenediamine (HMD), which is discharged into natural reservoirs, causes damage and loss of hydrobionts, worsens the quality of water which becomes unsuitable for use. For wastewater treatment from HMD, the possibility of applying bacterial cultures-destructors which use the HMD as a nutrition source is considered.

Soy Protein Isolate Non-Isocyanates Polyurethanes (NIPU) Wood Adhesives

Soy-protein isolate (SPI) was used to prepare non-isocyanate polyurethane (NIPU) thermosetting adhesives for wood panels by reacting it with dimethyl carbonate (DMC) and hexamethylene diamine. Both linear as well as branched oligomers were obtained and identified, indicating how such oligomer structures could further cross-link to form a hardened network. Unusual structures were observed, namely carbamic acid-derived urethane linkages coupled with lactam structures. The curing of the adhesive was followed by thermomechanical analysis (TMA). It appeared to follow a two stages process: First, at a lower temperature (maximum 130°C), the growth of linear oligomers occurred, finally forming a physically entangled network. This appeared to collapse and disentangle, causing a decrease of MOE, as the temperature increases. This appears to be due to the ever more marked Brownian movements of the linear oligomer chains with the increase of the temperature. Second, chemical cross-linking of the chains appeared to ensue, forming a hardened network. This was shown by the thermomechanical analysis (TMA) showing two distinct MOE maxima peaks, one around 130°C and the other around 220°C, with a very marked MOE decrease between the two. Plywood panels were prepared and bonded with the SPI-NIPU wood adhesive and the results obtained are presented. The adhesive appeared to pass comfortably the requirements for dry strength of relevant standards, showing to be suitable for interior grade plywood panels. It did not pass the requirements for wet tests. However, addition of 15% of glycerol diglycidyl ether improved the wet tests results but still not enough to satisfy the standards requirements.

Organosolv Lignin for Non-Isocyanate Based Polyurethanes (NIPU) as Wood Adhesive

A non-isocyanate-based polyurethane (NIPU) wood adhesive was produced from organosolv lignin, which is a bio-sourced raw material, available in large quantities and produced as a by-product of the paper industry. The formulation of this new lignin-based NIPU adhesive, which is presented, was chemically characterised by Matrix-Assisted Laser Desorption Ionization Time of Flight (MALDI ToF) mass spectrometry and by Fourier Transform Infra-Red (FTIR) spectrometry analyses. The oligomers formed were determined and showed that the three species involved in the NIPU adhesive preparation were formed by the co-reaction of the three reagents used: lignin, dimethyl carbonate, and hexamethylene diamine. Linear and branched structures were both identified. Mechanical properties of the adhesive were determined using the Automated Bonding Evaluation System (ABES) and internal bond (IB) strength test of the laboratory particleboard bonded with it. The adhesive has shown satisfactory mechanical properties after hot pressing at 230°C. Such a temperature is used industrially in the most modern particleboard factories, but since it is hardly feasible for more conventional wood bonding equipment, the reactivity of the NIPU adhesive was successfully increased with the addition of a small percentage of a silane coupling agent. With the addition of the silane, the proposed NIPU adhesive could also be used at a hot-pressing temperature lower than 200°C.

Novel magnetic polymer/bentonite composite: Characterization and application for Re(VII) and W(VI) adsorption

A novel magnetic polymer/bentonite composite was prepared by suspension copolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate in the presence of magnetic bentonite (MB-PGME) and functionalized with ethylene diamine and hexamethylene diamine (MB-PGME-ED and MB-PGME-HD). The obtained samples were characterized in terms of structure as well as thermal, magnetic and morphological properties. The sorption of rhenium (Re) and tungsten (W) from aqueous solution onto MB-PGME-ED and MB-PGME-HD was investigated considering their contact time and different initial ion concentration, giving possibility for usage of these composites as commercial sorbents. The sorption system follows the pseudo-second order and intraparticle diffusion kinetic models. The results indicated a better fit with the Freundlich isotherm model.

Economically-feasible production of a nylon monomer using RANEY® catalysts

This research was aimed at developing an economically-feasible process to produce a value-added chemical used to synthesize nylon, hexamethylenediamine (HMDA), by hydrogenating adiponitrile (ADN) using an inexpensive catalyst such as RANEY® Ni or RANEY® Co.

Non-Isocyanate polyurethane from the extracted tannin of sumac leaves: Synthesis, characterization, and optimization of the reaction parameters

The extracted tannin from Sumac leaves (Rhus coriaria L.) as a bioresource was utilized for Non-isocyanate Polyurethanes (NIPUs) synthesis. The extracted tannin pre-reacted with dimethyl carbonate. Subsequently, NIPUs were synthesized via the reaction of carbonated tannin with hexamethylene diamine. The condition of the reaction was optimized for different parameters including tannin/DMC weight ratio, reaction time, and reaction temperature by response surface methodology (RSM). The results indicate the influence of the mentioned variables on the polyurethane synthesis yield was negative, positive, and ineffective, respectively.The structural, thermal, and mechanical properties of the synthesized materials were investigated by FTIR, MALDI-TOF, GPC, DSC, DMTA, TGA analyses, and tensile testing. The successful synthesis of NIPUs was confirmed by MALDI-TOF and FTIR spectroscopies. Tannin as a polyphenolic material contains many aromatic benzene rings. During thermal degradation due to benzene rings fusion, these rings convert to thermally stable materials and increase the char yield (36 wt% at 800 °C). Also, the synthesized NIPU demonstrated a high value of Tg (DSC: 75 °C, DMTA: 79 °C) which can be attributed to the existence of intermolecular hydrogen bonding, high crosslinked density, as well as restriction of the molecular segments mobility due to benzene rings rigidity. Finally, the Higher mechanical properties of the optimum sample confirm the efficiency of the optimization process. The results exhibited that the extracted tannin from the biobased resource can be a good alternative material for the NIPUs synthesis.

Thin film composite hollow fibre membrane for pharmaceutical concentration and solvent recovery

A 100-piece hollow fibre thin-film composite membrane module was successfully developed for pharmaceutical concentration and solvent recovery. To increase its packing density, thinner P84 polyimide hollow fibre substrates were spun using a smaller spinneret. The substrates were subsequently cross-linked with hexamethylene diamine to achieve organic solvent resistance. An MPD-based thin-film composite was synthesized through interfacial polymerisation to increase selectivity for solutes of less than 300 Da. The thin-film composite was then solvent-activated using N,N-dimethylformamide to increase its solvent permeability. The resulting membrane exhibited excellent performance with 24.2 l m−2 h−1 bar−1 acetone permeability and 90.1% methyl red (269 Da) rejection. In addition, the solvent-activated membrane maintained its performance for prolonged period, demonstrating the scalability of the thin-film composite fabrication process and stability of solvent-activated membranes. The membrane was also able to concentrate levofloxacin (361 Da) from 500 ppm to 20,000 ppm in acetone using a batch process, showing promising results for pharmaceutical applications.

New epoxy composite polymers as a potential anticorrosive coatings for carbon steel in 3.5% NaCl solution: Experimental and computational approaches

Abstract Herein, diglycidyl bis disulfide carbon ether of bisphenol A sulfur epoxy resin (SER) crosslinked through hexamethylene diamine (HMDA) and methylene diamine (MDA) were investigated as a potential anticorrosive coatings for elevating carbon steel protection in sodium chloride (3.5% NaCl) solution using electrochemical and theoretical analysis. Potentiodynamic polarization data showed that the epoxy composite coatings investigated in 3.5% NaCl solution lateness the anticorrosive coatings and present the maximum protective efficiency obtained 97.9% in the presence of the sulfur epoxy resin crosslinked by MDA (SER/MDA) composite coating. Electrochemical impedance spectroscopy results indicate that the composite coatings employed retard the corrosion inhibition and have a higher protective efficiency compared with controlled (3.5% NaCl). Scanning electron microscope result displayed that the both SER/HMDA and SER/MDA composite polymers could be significantly retard chloride ions attack. Density functional theory calculations, Monte Carlo and molecular dynamics computational approaches support our experimental data.

Hexanediamine Monolayer Electrografted at Glassy Carbon Electrodes Enhances Oxygen Reduction Reaction in Aqueous Neutral Media

This study presents for the first time the electrocatalytic behaviour of hexanediamine (HDA) monolayer electrografted at glassy carbon (GC) electrodes that enhanced oxygen reduction reaction (ORR) in aqueous neutral media. HDA modified GC electrodes gave a higher current density than platinum bare electrodes based on the cyclic voltammograms (CV), although a ∼0.21 V vs. Ag/AgCl higher onset potential was observed at −0.1 mA cm-2. Electrochemical impedance spectra (EIS) showed that the electrocatalytic reaction on HDA monolayer film towards dissolved oxygen molecules is controlled by diffusion and charge transfer processes. From the scan rate studies and the Laviron equation, it was found that the ORR on this modified electrode proceeded via a fast four-electrons transfer.

Synthesis and characterization of amine-functionalized sugarcane bagasse fiber magnetic nanoparticle biocomposites

Sugarcane bagasse is one of the by-products in the sugar industry which contains 60% of cellulose. Cellulose can be used as a matrix for biocomposite. The purpose of this research was to produce amine-functionalized sugarcane bagasse fiber magnetic nanoparticle biocomposites (SBB). The SBB was produced from sugarcane bagasse (SB) by solvothermal reaction. The SB was dried and blended into small size (±60 mesh), then lignin was removed with 1% NaOH (w/v) through the delignification. The biocomposites was made by adding delignified SB (SB-D) into a mixture of ethylene glycol, FeCl3.6H2O, and hexamethylenediamine (HMDA) in solution, and then heated for 6 h at 200 °C. HMDA as an amine source was applied different concentrations (5, 7, and 9 mL). The surface morphology of biocomposites was covered by the magnetic nanoparticles along SB-D which contained amine of about 17.78 mmol/g. The Fe content of SBB was 98.34% which had specific peaks for magnetite at 36°, 43°, and 57° which were measured by X-Ray Diffraction (XRD). The Fourier Transformed Infrared (FT-IR) identified N–H bending vibration on SBB at 1640 cm−1. The iron content and amine group on the surface may affect high adsorption capacity for a wide range of biological pollutants.

Evaluation of the prepared amino styrene derivatives for the uranium recovery from sulphate media

ABSTRACT Low-cost polymer styrene maleic anhydride copolymer has been modified by the reaction with ethylene diamine, hexamethylene diamine and dodecyl diamine in aqueous media. The prepared derivatives have been characterised by elemental analysis, spectral analysis and thermal analysis. The derivatives were used for the adsorption of uranyl ions from sulphate media. The adsorption was investigated at different pH, time, uranium concentration and temperature. The adsorption kinetics was found to follow a pseudo-second-order model. The adsorption isotherm was found to follow the Langmuir model better than the Freundlich one. The experimental studies confirmed that the prepared modified copolymers are good candidates for U(VI) ions adsorption from sulphate media. The adsorption data have shown that the styrene maleic anhydride dodecyl diamine has an adsorption efficiency reaching 97.75% with a capacity of 61.35 mg g−1.

Hydrogenation of Adiponitrile to Hexamethylenediamine over Raney Ni and Co Catalysts

Hexamethylenediamine (HMDA), a chemical for producing nylon, was produced on Raney Ni and Raney Co catalysts via the hydrogenation of adiponitrile (ADN). HMDA was hydrogenated from ADN via 6-aminohexanenitrile (AHN). For the two catalysts, the effects of five different reaction parameters (reaction temperature, H2 pressure, catalyst loading, and ADN/HMDA ratio in the reactant) on the hydrogenation of ADN were investigated. Similar general trends demonstrating the dependence of ADN hydrogenation on the reaction conditions for both catalysts were observed: higher temperature (60–80 °C) and H2 pressure, as well as lower ADN/catalyst and ADN/HMDA ratios, led to higher HMDA yields. A further increase in temperature from 80 to 100 °C increased the HMDA yield from 90.5 to 100% for the Raney Ni catalyst, but did not affect the HMDA yield (85~87%) for the Raney Co catalyst. A 100% HMDA yield (the highest yield reported to date) was also achieved via ADN hydrogenation over the Raney Ni catalyst, with a high HMDA content in the reactant (e.g., ADN/HMDA volumetric ratio of 0.06). No sign of metal leaching into the product solution was found, meaning that the Raney Ni and Raney Co catalysts were stable during ADN hydrogenation.

Nylon 6 and nylon 6,6 micro- and nanoplastics: A first example of their accurate quantification, along with polyester (PET), in wastewater treatment plant sludges

A novel procedure for nylon 6 and nylon 6,6 polyamide (PAs) microplastics (MPs) quantification is described for the first time. The overall procedure, including quantification of poly(ethylene terephthalate) (PET), was tested on wastewater treatment plant (WWTP) sludges. The three polymers account for the largest global share of synthetic textile microfibers, being possibly the most common MPs released upon laundering in urban wastewaters. Therefore, measuring their content in WWTP sludges may provide an accurate picture of the potential risks associated with both the inflow of these MPs in natural water bodies and the practice of using WWTP sludges as agricultural soil amendment. The novel procedure involves PAs depolymerization by acid hydrolysis followed by derivatization of the monomers 6-aminohexanoic acid (AHA) and hexamethylene diamine (HMDA) with a fluorophore. Reversed-phase HPLC analysis with fluorescence detection results in high sensitivities for both AHA (LOD = 8.85·10–4 mg/L, LOQ = 3.73·10–3 mg/L) and HMDA (LOD = 2.12·10–4, LOQ = 7.04·10–4 mg/L). PET quantification involves depolymerization, in this case by alkaline hydrolysis, followed by HPLC analysis of its comonomer terephthalic acid. Eight sludge samples from four WWTPs in Italy showed contamination in the 29.3–215.3 ppm and 10.6–134.6 ppm range for nylon 6 and nylon 6,6, respectively, and in the 520–1470 ppm range for PET.

Selective diammonium reagents hosted on nanofibers for recovery of iridium from rhodium: Theoretical and experimental studies

Quaternary diammonium-functionalized polyvinyl benzyl chloride nanofibers were done using different diamines such as ethylenediamine (EDA), tetramethylene diamine (TMDA), hexamethylenediamine (HMDA), octamethylenediamine (OMDA), 1,10-diaminodecane (DMDA) and 1,12-diaminododecane (DDMDA) with quaternization using methyl iodide, followed by conversion to a chloride form. These were called F-QUAT EDA, F-QUAT TMDA, F-QUAT HMDA, F-QUAT OMDA, F-QUAT DMDA and F-QUAT DDMDA, respectively. Materials characterization was supported using elemental analysis, FTIR, XPS, SEM-EDS, TG and BET analysis. Langmuir and Freundlich's models were applied to analyze the adsorption of [IrCl6]2− and [RhCl5(H2O)]2− onto the materials, and the Freundlich model was obeyed. The mass transfer kinetics were tested on the pseudo-first-order and pseudo-second-order equations, and the process obeyed the pseudo-second-order kinetics. Column studies for the sorption of [IrCl6]2− using the functional materials were carried out and the loading capacities were 5.98 mg/g, 7.95 mg/g, 15.23 mg/g, 21.71 mg/g, 32.94 mg/g and 9.70 mg/g for F-QUAT EDA, F-QUAT TMDA, F-QUAT HMDA, F-QUAT OMDA, F-QUAT DMDA and F-QUAT DDMDA, respectively. This was the order of an improvement in the methylene chain amongst the two ammonium groups up to ten carbons. Theoretically calculated electrostatic potential energies of the cations, dipole moments and solvation energies of the free cations and anions, energies for replacement of the chloride by [IrCl6]2−, and thermodynamic parameters for the formation of ion-pair complexes were used to explain this trend observed for the capacity of the functional reagents. The functional nanofibers displayed potential for use in selective recovery of iridium from rhodium.

Simultaneous phase-inversion and crosslinking in organic coagulation bath to prepare organic solvent forward osmosis membranes

Organic solvent forward osmosis (OSFO) is an emerging separation process, which can realize simultaneous concentration of pharmaceutical ingredients and solvent recovery. In this work, a time-saving preparation process for solvent-resistant support layers was proposed by a simultaneous phase-inversion and crosslinking (SIM) method. The SIM method combines the formation of porous polyimide (PI) support layer and crosslinking between the PI and hexanediamine (HDA) in the coagulating baths, thus avoiding an extra need of solvent-based synthesis step. Furthermore, isopropanol (IPA) was used as coagulation bath for solvent-resistant PI support layers preparation, which can more effectively retarding the phase-inversion process compared with the DI-water. In addition, the morphologies and properties of these support layers with different synthesis time were prepared and characterized. After interfacial polymerization reaction using the as-prepared solvent-resistant PI support layers, the resultant OSFO membranes exhibited reasonable ethanol fluxes, lower reverse salt fluxes, and excellent pharmaceutical (oxytetracycline, OTC) rejections in both forward and reverse osmosis modes. Moreover, the long-term tests of as-prepared OSFO membranes indicated an excellent stability in 10 h operation with ethanol. After 10 h activation using DMF, the ethanol fluxes of OSFO18h membranes with different thickness of solvent-resistant support layers were significantly improved without sacrificing OTC rejection, which furtherly demonstrated the timeliness of SIM method and potential application of OSFO process in both concentrate the pharmaceutical and solvent recovery.

Hexamethylene diamine-modified epoxidized natural rubber and its effect on cure characteristics and properties of natural rubber blends

Compatibility is a serious problem in silica-added natural rubber (NR) because of the difference in the polarities of silica and NR. Thus, a coupling agent, such as silane, or a compatibilizer must be incorporated. In this work, amine-functionalized NR was synthesized by an in situ epoxidation process using performic acid and later modified with hexamethylene diamine (HMDA) by a ring-opening reaction. The effects of amine-modified epoxidized NR (ENR-HMDA) content on the cure characteristics, physical and mechanical properties of various NR blends (NR/ENR-HMDA) without filler were studied. ENR-HMDA enhanced the vulcanization process. The maximum torque of compounds increased with the corporation of ENR-HMDA and scorch time and cure time decreased. The cure rate index of NR/ENR-HMDA increased by 98%. All vulcanized rubber blends showed the strain-induced crystallization at high extension. Mechanical properties and crosslink density of the blends were higher than those of NR and NR incorporated with unmodified ENR. Tensile strength was 61% and 43% higher than that for NR and NR/ENR, respectively. The NR/ENR-HMDA blends showed a single Tg that indicated the miscibility of both components. The developed ENR-HMDA compound can be used to improve the compatibility of NR and fillers which would enable the fabrication of a wide range of rubber products.