Grafting Amino Research Articles

Selectivity adsorption of sulfate by amino-modified activated carbon during capacitive deionization

ABSTRACT Capacitive deionization (CDI) is an environmentally friendly desalination technique with low energy consumption. However, unmodified carbon electrode materials have poor sulfate selectivity and adsorption capacity. In this work, to improve sulfate selectivity, we prepared activated carbon materials loaded with different amino contents by grafting amino groups via acid treatment for different times. In the competitive ion adsorption experiments, the sulfate selectivity of AC was only 0.64 and the amino-modified AC increased by 1.98-2.52 times due to the formation of stronger hydrogen bonds between the amino group and sulfate. AC-NH2-4 had the best selectivity and the sulfate selective coefficient was 2.25. The desorption of sulfate was 92.46% within one hour. In addition, the surface of the amino-modified activated carbon showed significantly improved electrochemical properties and better capacitance. The specific capacitance of amino-modified AC in different electrolyte solutions was consistent with the competitive adsorption results. The specific capacitance of amino-modified AC in Na2SO4 electrolyte solution was the highest. The modified electrode material also had the advantages of a higher adsorption capacity and excellent regeneration performance after continuous electric adsorption–desorption cycles. Therefore, it may have development potential to selectively adsorb sulfate in practical applications.

Development and tailoring of amino-functionalized activated carbon based Cucumerupsi manni Naudin seed shells for the removal of nitrate ions from aqueous solution

The removal of nitrate ions with ethylenediamine (EDA)-functionalized activated carbon (AC-NH2) was studied in this work. Activated carbon prepared from Cucumerupsi manni Naudin seed shells using ZnCl2 (ACZ) was functionalized with EDA via a nitric acid oxidation followed by acyl chlorination and amidation process. The effect of pH, contact time, initial concentration and co-existing ions on the adsorption of nitrate ions have been investigated. The FTIR and elemental analysis revealed that amino groups were successfully grafted onto the ACZ after functionalization. The surface area and average pore of ACZ were found to be 1008.99 m2/g and 2.02 nm respectively. However, it was noticed that, after functionalization (AC-NH2), its surface area decreases to 113.43 m2/g meanwhile, its pore diameter increases to 2.48 nm. The experimental results of adsorption showed that AC-NH2 exhibit excellent nitrate ions uptake performance compared to ACZ which is attributed to the presence of the grafted amino groups on the ACZ. Nitrate adsorption follows pseudo-first-order kinetic model while the equilibrium adsorption data was best fitted the Freundlich isotherm suggesting that the adsorption process was predominated by physisorption. This study demonstrates that the prepared AC-NH2 is a promising adsorbent for nitrate ions removal from aqueous media.

A Methodology to Identify the Releasing of the Amide-Containing β-Glucan from the Usnea Lichen: A Spectroscopic Study

Polymer fractions from a biological matrix have been well-characterized by vibrational spectroscopy, XPS, CP/MAS 13C NMR, MALDI-TOF mass spectrometry, thermal analysis, and SEM, and all the results had corroborated for the chemical extraction of β-glucan polymers grafted amino groups by peptide bonds (namely NH2-β-glucan) as well as a cyclic oligosaccharide. Our primary purpose was to explore the polysaccharide extraction parameters in the sample of Usnea lichen, mainly in terms of extraction time and concentration of the extractive alkaline solution, to investigate the chemical characterization of the polysaccharide fractions. The low-cost methodology adopted in this work was able to extract the materials of interest with the expected efficiency without the significant impact of chemicals on the environment. The chemical extraction of an NH2-bonded biopolymer can be a very interesting material for many applications since chemical functionalization is crucial to introducing specific properties for developing new materials. In this regard, the cyclic β-glucan described as a very porous material is highly desirable for various applications in the biomedical, biotechnological, and environmental areas.

Optimized microwave-assisted functionalization and quantification of superficial amino groups on porous silicon nanostructured microparticles.

This work presents an optimized microwave (MW)-assisted method for the chemical functionalization of porous silicon particles (PSip). 3-(Aminopropyl)triethoxysilane (APTES) was grafted on previously stabilized PSip. The functionalization efficiency was studied and optimized in terms of reaction time (Rt) and reaction temperature (RT) using a central composite design (CCD). The effect of MW irradiation on the surface coverage was found to strongly depend on the PSip surface chemistry, Rt, RT, and percentage of APTES. Quantification of grafted amino groups was performed by the ninhydrin method (NHIM); confirming the results by thermogravimetric analysis (TGA). Reacting with 5% APTES solution at 95 °C for 26 min was the best functionalization conditions. The efficiency of PSip-APTES prepared under the optimized conditions was compared to those functionalized by the traditional method; MW irradiation increases by 39% the number of functional groups grafted onto the PSip surfaces with the additional benefit of having a drastic reduction in Rt.

Monodisperse amino-modified nanosized zero-valent iron for selective and recyclable removal of TNT: Synthesis, characterization, and removal mechanism

Nitroaromatic explosives are major pollutants produced during wars that cause serious environmental and health problems. The removal of a typical nitroaromatic explosive, 2,4,6-trinitrotoluene (TNT), from aqueous solution, was conducted using a new recyclable magnetic nano-adsorbent (Fe@SiO2NH2). This adsorbent was prepared by grafting amino groups onto Fe@SiO2 particles with a well-defined core-shell structure and demonstrated monodispersity in solution. The removal performance of the nano-adsorbent towards TNT was found to be 2.57 and 4.92 times higher than that towards two analogous explosives, 2,4-dinitrotoluene (2,4-DNT) and 2-nitrotoluene (2-NT), respectively, under neutral conditions. The difference in the removal performance among the three compounds was further compared in terms of the effects of different conditions (pH value, ionic strength, humic acid concentration, adsorbent modification degree and dosage, etc.) and the electrostatic potential distributions of the three compounds. The most significant elevation is owing to modification of amino on Fe@SiO2 which made a 20.7% increase in adsorption efficiency of TNT. The experimental data were well fit by the pseudo-second-order kinetic model and the Freundlich adsorption isotherm model, indicating multilayer adsorption on a heterogeneous surface. The experimental results and theoretical considerations show that the interactions between Fe@SiO2NH2 NPs and TNT correspond to dipole-dipole and hydrophobic interactions. These interactions should be considered in the design of an adsorbent. Furthermore, the adaptability to aqueous environment and excellent regeneration capacity of Fe@SiO2NH2 NPs makes these remediation materials promising for applications.

Investigating Microcystin-LR adsorption mechanisms on mesoporous carbon, mesoporous silica, and their amino-functionalized form: Surface chemistry, pore structures, and molecular characteristics

Microcystin-LR (MC-LR) is the most common cyanotoxin released from algal-blooms. The study investigated the MC-LR adsorption mechanisms by comparing adsorption performance of protonated mesoporous carbon/silica (MC-H, MS-H) and their amino-functionalized forms (MC-NH2 and MS-NH2) considering surface chemistry and pore characteristics. The maximum MC-LR adsorption capacity (Langmuir model) of MC-H (37.87 mg/g) was the highest followed by MC-NH2 (29.25 mg/g) and MS-NH2 (23.03 mg/g), because pore structure is partly damaged during amino-functionalization. However, MC-NH2 (k2 = 0.042 g/mg/min) reacted faster with MC-LR than MC-H during early-stage adsorption due to enhancing electrostatic interactions. Intra-particle diffusion model fit indicated Kp,1 of MC-H (2.11 mg/g/min1/2) was greater than MC-NH2 due to its greater surface area and pore volume. Also, large mesopore diameters are favorable to MC-LR adsorption by pore diffusion. The effect of adsorbate molecular size on adsorption trend against MC-H, MC-NH2 and MS-NH2 was determined by kinetic experiments using two dyes, reactive blue and acid orange: MS-NH2 achieved the highest adsorption for both dyes due to the large number of amino groups on its surface (41.2 NH2/nm2). Overall, it was demonstrated that adsorption of MC-LR on mesoporous materials is governed by (meso-)pore diffusion and π – π (and hydrophobic) interactions induced by carbon materials; in addition, positively-charged grafted amino groups enhance initial MC-LR adsorption rate.

Grafting of amino groups onto carbon fibers by bromination followed by ammonolysis

Because of the low content of chelating groups onto carbon fibers (CFs), their adsorptive parameters are poor, and this has negative effects on their applications as lightweight sorbents. In this work, we established a modification method to incorporate amine groups into carbon fiber surfaces by bromination followed by ammonolysis to create an interfacial layer which can adsorb heavy metal ions from solutions. The changed chemical composition, surface morphology, and thermal stability were investigated. Thermoprogrammed desorption mass-spectrometry and thermal analysis showed thermal transformation and interplay between forms of the grafted bromine groups of 0.5 mmol/g and the resulting amino groups of 0.44–0.56 mmol/g. After grafting, the surface chemistry parameters were improved due to the covalent bonding and grafting of the amine groups as interface modifier. Scanning electron microscopy observation also confirmed that the surface morphology maintains the same, without impairment of fiber properties. This work is therefore a beneficial approach towards enhancing the adsorption parameters by controlling the interface layer of CFs.

Surface modification of polyetheretherketone by grafting amino groups to improve its hydrophilicity and cytocompatibility

Although special engineering plastics polyether ether ketone (PEEK) have many excellent properties, its hydrophobicity and biological inertia limit its application in the field of implant materials. In this study, amino modification of PEEK was conducted to endow it with good hydrophilicity and bioactivity. PEEK was sulfonated with concentrated sulfuric acid, and reacted with sulfoxide chloride to obtain aromatic sulfonyl chloride. Finally, amino (–NH2) was introduced onto the surface of PEEK by acylation reaction between acyl chloride group and ethylenediamine (EDA) to improve its hydrophilicity and cell compatibility. The PEEKs before and after modification were characterized by FTIR, XPS and WCA. The cell compatibility was evaluated by human umbilical vein endothelial cells (HUVEC). The results showed that –NH had been successfully introduced onto the surface of PEEK, and the hydrophilicity of the aminated PEEK was significantly improved. Compared with the PEEK before amino modification, the aminated PEEK significantly promoted adhesion and spread of cells, indicating good cell compatibility. This study breaks through the limitations of traditional wet chemical methods and provides a new way for further modification of PEEK.

Diaminomaleonitrile functionalized double-shelled hollow MIL-101 (Cr) for selective removal of uranium from simulated seawater

Hollow metal-organic frameworks (MOFs) have attracted wide interest because of their unique core-shell structure. As a novel uranium adsorbent, diaminomaleonitrile (DAMN) functionalized double-shelled hollow (DSHM) metal-organic framework of chromium(III) terephthalate was prepared by a post-synthetic method of grafting amino group onto coordinatively unsaturated sites (CUS). TEM, XRD, nitrogen sorption and FT-IR spectrometry were used to characterize the obtained DAMN functionalized hollow MOF. The maximum capacity of uranium adsorption is 601 mg g−1, which exceeds all known functionalized MIL-101 uranium adsorption materials. The optimal adsorption pH is 8 which is close to the pH of seawater. Furthermore, the high selectivity of uranium and high adsorption rate in simulated seawater provide a promising prospect to introduce DSHM-DAMN for the extraction of uranium from seawater. In this work, we first applied hollow MOF for uranium adsorption, which greatly improves the uranium adsorption performance of MOF materials; we also explored the practical application of hollow MOF materials.

Amino graphene oxide/dopamine modified aramid fibers: Preparation, epoxy nanocomposites and property analysis

Dopamine modified aramid fiber (AF) surface was grafted with amino functionalized graphene oxide to improve the interfacial adhesive performance. The self-polymerized polydopamine (PDA) coating and subsequent amino GO grafting on the AF surface attributed to the increase in its surface roughness and surface-active groups. The functional groups, chemical composition and surface topography of unmodified and modified AF was investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM). The interfacial properties were analyzed by measuring interfacial shear strength (IFSS) of unmodified and modified AF embedded epoxy matrix. Further, the properties were tuned by optimizing the reaction temperature and concentration of ethylenediamine. The IFSS of AF/epoxy composites was increased by 34% after grafting amino graphene oxide.

Simultaneous determination of pindolol, acebutolol and metoprolol in waters by differential-pulse voltammetry using an efficient sensor based on carbon paste electrode modified with amino-functionalized mesostructured silica

In this work, hexagonal mesoporous silica (HMS) and amino-functionalized HMS (HMS-NH2) were prepared and incorporated into carbon paste electrodes (CPEs) to obtain electrochemical sensors for pindolol (Pin), acebutolol (Ace) and metoprolol (Met) determination in waters by voltammetric techniques. The materials were characterized and they showed high specific surface area, large pore volume and a quasi-spherical morphology. Firstly, the electrochemical behaviour of the modified CPEs was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Then, the dependence of the current intensity with the electrolyte support (type and pH) and the accumulation time was investigated to optimize the experimental conditions for simultaneous β-blockers determination by DPV. Results showed that the sensor modified with functionalized silica (NH2-HMS-CPE) exhibited strong adsorption activity, showing three well-defined peaks in the differential pulse voltammograms, that appeared at about +0.85 V (Pin), +1.11 V (Ace) and +1.45 V (Met). This fact can be attributed to the high surface area of the material, with a 3 D wormhole-like channel structure that favoured excellent pore accessibility, and the synergistic effect produced by the grafted amino groups producing hydrogen bond interactions with the oxygen atoms of the target β-blockers. The prepared sensor exhibits good reproducibility, wide linear ranges and very low detection limits (0.1, 0.046 and 0.23 μmol L−1 for Pin, Ace and Met, respectively). Moreover, the NH2-HMS-CPE was successfully applied for the simultaneous determination of Pin, Ace and Met in tap, mineral, river and sewage effluent waters with simple sample treatment (recoveries 97–112%).

High-Gradient Magnetic Separator (HGMS) combined with adsorption for nitrate removal from aqueous solution

This paper investigates the adsorption of nitrate anions from aqueous solutions on ammonium-functionalized magnetic mesoporous silica. The adsorbent was prepared via two-step coating process of silica on magnetic core (Fe3O4). The resultant structure was modified by 3-aminopropyl triethoxysilane (APTES), and finally acidified in HCl solution to convert the grafted amino groups to ammonium ones. Field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibration sample magnetometer (VSM), Energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and N2 adsorption/desorption were used to characterize the obtained samples. Experimental results showed that several factors affected the uptake behavior such as pH, contact time, and initial concentration of nitrate. The amount of sorbent loading were examined and the adsorbent shows great adsorption capacity for NO3¯ (ca.51.28 mg g−1 at 25 °C). The nitrate loaded multifunctional microsphere can be easily regenerated with NaOH solution. The separation of multifunctional magnetic microspheres from solution by novel high gradient magnetic separation (HGMS), using the collection of rods, was also investigated in details. Contrast to other methods based on filter and batch conditions, large volumes of water can be easily handled by the new designed HGMS due to the decreasing pressure drop and retention times. The effect of a set of two different experimental variables, i.e. flowrate and magnetic field strength, were investigated to identify the best working conditions for the separation of adsorbent from treated water. The most efficient backwash system was offered to reuse the magnetic particles, too. The removal efficiency of NO3¯ from solution was around 86.24% by the constructed HGMS under the optimal experimental conditions of 7.5 mL s −1 flowrate and: 3.49 mT magnitude of the magnetic field.

MIL-101(Cr) metal–organic framework functionalized with tetraethylenepentamine for potential removal of Uranium (VI) from waste water

The metal–organic frameworks material functionalized by grafting amino group of tetraethylenepentamine on the coordinative unsaturated Cr (III) centers is described. The obtained tetraethylenepentamine-functionalized adsorbents with different mass ratios of tetraethylenepentamine have been characterized by scanning electron microscopy, Fourier-transform infrared, X-ray powder diffraction, and N2 adsorption and desorption isotherms. Significantly, MIL-101-tetraethylenepentamine 60% exhibited high adsorption capacity (350 mg/g) for removal of uranium (VI) from water at pH 4.5. At uranium concentration <20 mg/L, the isothermal plot was best represented by Freundlich model. At U(VI) concentration approximately >30 mg/L, the isotherm was best described by Langmuir model.

Preparation of Gap-Controlled Monodispersed Ag Nanoparticles by Amino Groups Grafted on Silica Microspheres as a SERS Substrate for the Detection of Low Concentrations of Organic Compounds

The synthesis of new surface-enhanced Raman scattering (SERS) substrates for the detection of trace poisonous organic pollutants is important for environmental monitoring. Herein, we designed and prepared monodispersed and uniform Ag NPs anchored on silica microspheres (Ag@ASMs) by the orientation of grafted amino groups and applied it as a SERS substrate for the detection of ultralow concentrations of poisonous organic pollutants (Rhodamine 6G (R6G), crystal violet (CV), and melamine) with high sensitivity and reproducibility in aqueous solution. A ratio of 2:1 Ag@ASMs exhibited optimum SERS performance, allowing the detection of 10–12 M of R6G with an enhancement factor of 6.36 × 107 (collect the normal Raman signal based on 10–4 M R6G) as well as 10–8 M of CV and melamine. The density functional theory calculation also provided evidence that modified 3-triethoxysilylpropylamine molecules are interspaced, and the optimum Ag dosage further tuned the gap between Ag NPs as well as the size of Ag NPs. This ...

Mechano-Chemical Modification of Waste Rubber Powder with 2-Mercatobenzothiozole and 3-Aminopropyltriethoxysilane

A mechano-chemical modification process for waste rubber powder (WRP) was investigated in this paper. 2-Mercatobenzothiozole (accelerator M) was introduced as a peptizer to improve plasticity of WRP, and 3-aminopropyltriethoxysilane (silane coupling agent KH550) was used as a surfactant to further modify the surface of plasticized rubber powder (PRP) to improve interfacial bonding with epoxidized natural rubber (ENR). Infrared spectrums showed that the WRP generated more oxygen-containing groups by mechanical forces in the presence of accelerator M and then grafted amino groups with KH550. The mechano-chemical process with accelerator M changed the structure of WRP obviously shown by sol fraction and microstructure of PRP, which increased the mechanical properties and crosslink density of full rubber powder vulcanizates. After further modified by KH550, the modified rubber powder (MRP) had a positive chemical interfacial bonding with ENR, changing the fracture surface and improving the mechanical properties of vulcanizates. The cure characteristics of the vulcanizates also illustrated that accelerator M and KH550 participated in the vulcanization process increasing the curing efficiency. The best mechanical properties of ENR/MRP vulcanizates were better than the neat ENR vulcanizates. It indicated that the mechano-chemical process with accelerator M and KH550 will be a potential method to reclaim WRP.

Surface modification of bamboo‐char and its reinforcement in PLA biocomposites

High‐temperature bamboo‐char is a potential polymer reinforcement due to its porous structure, high strength and modulus. To improve the surface structure and properties of bamboo‐char, different concentrations of HNO3 and NaOH solution modifications were conducted. The HNO3 treatment grafted amino groups on bamboo‐char and NaOH treatment modified carbonyl and carboxyl groups. The specific surface area and the total pore volume of bamboo‐char reduced with HNO3 treatment, whereas the two values firstly increased and then decreased in the case of NaOH treatment; the maximum values of 30.422 m2·g−1 and 0.066 cm3·g−1 were reached at 10 wt% NaOH concentration. The maximum tensile strength and modulus of PLA/bamboo‐char composites were achieved up to 65.36 and 1012.0 MPa at 15 wt% NaOH concentration. The maximum elongation at break was reached at 15.36% and impact strength of 25.69 KJ·m−2 were obtained at the HNO3 concentration of 39 and 54 wt%, respectively. These results will help to extend the application of bamboo‐char in polymer composites. POLYM. COMPOS., 39:E633–E639, 2018. © 2018 Society of Plastics Engineers

Modification with Amino Groups of Composite SiO2–TiO2 and Pure TiO2 Spheres Prepared via the Peroxo Route

A series of porous composite SiO 2 –TiO 2 and pure TiO 2 spherical particles were prepared via the peroxo route and subsequently used as the support for catalyst. Aminopropyltrimethoxysilane (APTMS) was grafted to the surface of support in the strictly unhydrous media leading to bonding of free amino groups to the support surface covalently. Procedure of APTMS grafting is easy to perform and may be spread for grafting other different functional groups to the inorganic surfaces of the catalyst support. The support samples were calcined at various temperatures in order to optimize the preparation conditions and boost the density of surface amino groups. It has been found that the quantity of grafted APTMS varies insignificantly for the different support samples. Grafted amino groups would be applied as active catalytic sites in different reactions of organic chemistry such as acylation of amines and alcohols, polymerization of lactones with hydroxyl groups, isomerization of unsaturated compounds, aldol condensation, Diels-Alder, Michael, Knoevenagel reactions. The mechanisms of reaction activation by amino groups are the transfer of electron density to a reacting molecule and formation of an intermediate complex. While widely applied catalysts are liquid amines, it is desirable to transform these substances into the heterogeneous form for better regeneration and purification of reaction products from the initial reagents. Prepared catalysts exhibit high amino groups load equal to 1 mmol/g, taking into account the localization of amino groups on the surface of the catalyst.

Adsorption-assisted decontamination of Hg(ii) from aqueous solution by multi-functionalized corncob-derived biochar.

Mercury (Hg) contamination of wastewater streams as a result of anthropogenic activities is a great threat to living organisms due to its acute toxicity. Therefore, current research is focused on the development of effective remediation technologies to protect human health and the environment. In this study, a novel chemical modification route was applied for the multi-functionalization of biochar in order to make it more efficient and selective for Hg(ii) removal from aqueous solution. The amino-grafted modified biochar (AMBC) having multifunctional groups on its surface was successfully synthesized through the activation of excessively available carboxylic groups (–COOH) on pre-oxidized biochar (BC–COOH). The maximum Hg(ii) adsorption capacity for the optimized amino-BC2 sample was 14.1 mg g−1, which was almost twice as that for pristine biochar (BC, 7.1 mg g−1). SEM, FTIR, and XPS techniques were applied for the confirmation of chemically grafted amino groups as well as the presence of residual –COOH groups on the biochar surface. Based on the batch adsorption data, adsorption kinetics and isotherms as well as XPS results, it was concluded that the Hg(ii) removal mechanism was purely driven by chemisorption such as electrostatic interaction, surface complexation, ion exchange with no precipitation and crystalline material being adsorbed on the adsorbent surface. These research findings not only provide a suitable adsorbent for decontamination of Hg(ii) from aqueous solution but also offer a new route for the multi-functionalization of biochar in order to make environment-friendly and inexpensive adsorbents.

Surface modification of polyisobutylene via grafting amino acid-based poly (acryloyl-6-aminocaproic acid) as multifunctional material

Amino acid-based P(acryloyl-6-aminocaproic acid) (PAACA) brushes were fabricated on polyisobutylene (PIB) surface combined with plasma pre-treatment and UV-induced grafting polymerization to construct an antifouling and functional material. The hydrophilicity and hemocompatibility of PIB were largely improved by surface modification of AACA, which were confirmed by water contact angle and platelet adhesion, respectively. PAACA brushes were precisely located onto the surface of PIB to create a patterned PIB-g-PAACA structure, and then the carboxyl groups on PAACA was activated to immobilize functional protein-Concanavalin A (Con A). The obtained Con A-coupled microdomains could further capture erythrocytes. This method developed a platform on commercial PIB surface via amino acid-based polymer brushes which had a promising application in drug delivery and disease diagnosis.

Kinetics of isoleucine chemisorption on the modified silica surface

Kinetics of isoleucine chemisorption on the modified silica surface involving an amide bond formation was studied. The grafted amino groups acting as chemisorption sites are uniformly distributed with respect to the activation energies. The reaction kinetics obeys the Roginsky–Zeldovich equation.