Ring-opening Reaction Of Epoxy Groups Research Articles

Effect of Condensed Water at an Alumina/Epoxy Resin Interface on Curing Reaction.

The adhesion of epoxy adhesives to aluminum materials is an important issue in assembling parts for lightweight mobility. Aluminum surfaces typically possess an oxide layer, which readily adsorbs water. In this study, the aggregation states of water and its effect on the curing reaction were examined by placing a water layer between an amorphous alumina surface and a mixture of epoxy and amine components. This study used molecular dynamics simulations and density functional theory calculations. Before the reaction, water molecules strongly adsorbed onto the alumina surface, aggregating excess water. Some water diffused into the epoxy/amine mixture, accelerating the diffusion of unreacted substances. This led to faster reaction kinetics, particularly in proximity to the alumina surface. The adsorption of water molecules onto the alumina surface and the aggregation of excess water were similarly observed even after the curing process. Subsequently, the interaction between the alumina surface and various functional groups of the epoxy/amine mixture was evaluated before and after the reaction. Epoxy monomers had little interaction with the alumina surface before the reaction, whereas hydroxy groups formed by the ring-opening reaction of epoxy groups exhibited notable interaction. Conversely, sulfonyl and amino groups in amine compounds formed hydrogen bonds with OH groups on the alumina surface before the reaction. However, after the reaction, amino groups weakened their interaction with the alumina OH groups as they transformed from primary to tertiary during the curing reaction. Both epoxy and amine monomers/fragments similarly interacted with water molecules, both before and after the reaction. The insights gained from this study are expected to contribute to a better understanding of the impact of moisture absorption on the application of epoxy resins.

A lysine and amide functionalized polymer-based polar stationary phase for hydrophilic interaction chromatography

A novel polymer-based polar stationary phase for hydrophilic interaction chromatography (HILIC) is described. It was obtained by grafting lysine and acrylamide onto poly (glycidyl methacrylate-divinylbenzene) (GMA-DVB) microspheres via ring-opening reaction of epoxy groups and free radical polymerization with pendant double bonds of the microspheres. Multiple types of polar groups including zwitterionic (carboxylate and amine), amide and diol onto the microspheres make them highly hydrophilic. It showed typical HILIC character and good separation performance towards model polar analytes. Negligible bleed level under gradient elution mode (up to 50% fraction of water) was observed. It also exhibited specific separation selectivity to ionic analytes and simultaneous separation of anions and cations could be achieved in ideal electrostatic selectivity elution order, e.g. I−< NO3− <Br− <Cl− or K+< Na+ < Li+.

Magnetic Poly(glycidyl methacrylate) Microspheres with Grafted Polypyrrole Chains for the High-Capacity Adsorption of Congo Red Dye from Aqueous Solutions

In this study, novel magnetic poly(glycidyl methacrylate) (PGMA) microspheres with grafted polypyrrole chains (magnetic PGMA-g-PPy) were developed for the high-capacity adsorption of Congo red (CR) from aqueous solutions. The magnetic PGMA-g-PPy was synthesized by the typical dispersion polymerization method and the ring-opening reaction of epoxy groups, producing abundant hydroxyls for the grafting polymerization of pyrrole in the presence of FeCl3 as an oxidizing agent on the surface of the microspheres. The characterization results showed that magnetic PGMA-g-PPy was successfully fabricated. The adsorption equilibrium data of the adsorbents could be well fitted by the Langmuir isotherm model, showing a high maximum adsorption capacity of 502.5 mg/g for CR. The adsorption followed pseudo-second-order kinetics with a fast speed. The adsorbents had no leaching of Fe in the solution at pH 1.0–11.0 for 24 h. The adsorption process was strongly pH-dependent and weakly ionic-strength-dependent. Furthermore, the magnetic microspheres could be easily regenerated, rapidly separated from the solution, and reused for wastewater treatment. The results suggest that magnetic PGMA-g-PPy microspheres are a promising efficient adsorbent for the removal of CR from wastewater.

Manufacturing of polystyrene panels with tunable colors

In this study, the synthesis of polyamine functional grafts that capable of reversible metal complexation with the transition metals has been achieved on the surface of commercial polystyrene (PS) panels. The brushes were generated via surface-initiated photo-iniferter polymerization (SI-PMP) on the active sites of PS panels. The active dithiocarbamate sites were created on the surface of the PS in four steps. First, the panels reacted with chlorosulfonic acid to obtain chlorosulfonic functionality on the surface without losing transparency. Diethanolamine was easily tethered to the surface of the PS panel from the chlorosulfonyl group. Then hydroxyl groups belonging to the diethanolamine were mesylated by methane sulfonylchloride, and resulting mesylated panels were reacted with pyridinium N,N′-diethyldithiocarbamate salt to get the dithiocarbomate functionality on the surface of the panel. After generation of the initiation sites on the panel, glycidyl methacrylate (GMA) was grafted via SI-PMP under UV light irradiation. The resulting PGMA brushes were converted to polyamine grafts via ring-opening reaction of epoxy groups with triethylenetetramine in a yield of 0.032 mmol amine per cm2. The functional surface grafts were employed for reversible metal complex formation with metal ions. The surface topologies and functionalities of modified panels were determined with SEM, AFM and FTIR.

Multifunctional Phosphorus-Containing Triazolyl Amine toward Self-Intumescent Flame-Retardant and Mechanically Strong Epoxy Resin with High Transparency

In this work, phosphorus-containing triazolyl amine (P-ATA) was incorporated into epoxy resin (EP) through the ring-opening reaction of epoxy groups, so as to obtain the intrinsically flame-retardant epoxy resin with excellent mechanical properties and high transparency. The modified EP with the addition of 7.5 wt % P-ATA obtained the limited oxygen index value of 33.1% with 32.5% increase compared to pure EP. Meanwhile, the self-intumescent flame-retardant action of EP/P-ATA was also evidenced by the remarkably reduced heat release and the expanded char of high yield, and the relevant flame-retardant mechanism of P-ATA was analyzed systematically. Moreover, EP containing 5.0 wt % P-ATA exhibited excellent mechanical properties with the enhancement of 16% of flexural strength, 17% of tensile strength, and 73% of charpy impact strength. Besides, EP-2.5% and EP-5.0% P-ATA maintained the transmittance more than 90% of neat EP, reserving its potential application in optical fields.

Radiation Synthesis of Pentaethylene Hexamine Functionalized Cotton Linter for Effective Removal of Phosphate: Batch and Dynamic Flow Mode Studies

A quaternized cotton linter fiber (QCLF) based adsorbent for removal of phosphate was prepared by grafting glycidyl methacrylate onto cotton linter and subsequent ring-opening reaction of epoxy groups and further quaternization. The adsorption behavior of the QCLF for phosphate was evaluated in a batch and column experiment. The batch experiment demonstrated that the adsorption process followed pseudo-second-order kinetics with an R2 value of 0.9967, and the Langmuir model with R2 value of 0.9952. The theoretical maximum adsorption capacity reached 152.44 mg/g. The experimental data of the fixed-bed column were well fitted with the Thomas and Yoon–Nelson models, and the adsorption capacity of phosphate at 100 mg/L and flow rate 1 mL/min reached 141.58 mg/g. The saturated QCLF could be regenerated by eluting with 1 M HCl.

Epinephrine-modified methacrylate monolithic column with fumed silica nanoparticle for pressurized capillary electrochromatography.

Via the ring-opening reaction of epoxy groups with epinephrine, a novel epinephrine functionalized polymethacrylate monolith with fumed silica nanoparticles has been fabricated for pressurized capillary electrochromatography. The preparation of epinephrine-modified monoliths has been optimized. In addition, morphology, electroosmotic flow, separation mechanism and column performance have been studied. The internal structure of the monolithic stationary phase was more uniform and the column efficiency increased after the incorporation of nanoparticles. With this column, satisfactory separation capability of aromatic compounds and alkaloids has been achieved and the column efficiency for naphthalene reached 138696plates/m. As for the real sample, 3 alkaloids were separated in Huanglian Shangqing capsules, a Chinese traditional medicine.

Interfacial polymerized reduced graphene oxide covalently grafted polyaniline nanocomposites for high-performance electromagnetic wave absorber

The high-performance electromagnetic wave (EMW) absorption materials have great potential in both civil and military fields. A novel approach to prepare the reduced graphene oxide covalently grafted polyaniline (rGO-g-PANI) nanocomposites with the strong absorption intensity and broad bandwidth was employed in this paper. Specifically, the aniline monomers were bonded with the graphene oxide (GO) nanosheets via the nucleophilic ring-opening reaction of epoxy groups of GO. Coupling with the role of the reducer, rGO modified with aniline (rGO-An) was prepared. Subsequently, the rGO-g-PANI nanocomposites were synthesized by the interfacial polymerization, in which the rGO-An nanosheets served as the reactivity point for the interfacial polymerization of aniline, and PANI nanorods grew vertically on the rGO nanosheets. The calculated results of electromagnetic parameters suggest that the minimum reflection loss of the rGO-g-PANI nanocomposites can reach up to − 60.3 dB at the frequency of 11.1 GHz with the thickness of 2.86 mm, and the effective absorption bandwidth less than − 10 dB (90% microwave absorption) is as wide as 4.7 GHz (from 9.3 to 14 GHz) when the content of rGO-g-PANI in the paraffin matrix is 30 wt%. Compared with the rGO/PANI nanocomposites prepared via non-covalent absorption, the microwave absorption performance of the rGO-g-PANI nanocomposites has been greatly enhanced. The results in turn demonstrate that the covalent bonds between rGO nanosheets and PANI nanorods can facilitate the formation of the highly conductive networks, further promoting the EMW absorption.

Integration of graft copolymerization and ring-opening reaction: A mild and effective preparation strategy for “clickable” cellulose fibers

A mild and effective strategy to prepare alkynyl-functionalized cellulose fibers (A-CFs) and azido-functionalized cellulose fibers (N3-CFs) was presented. Epoxy-cellulose fibers (Epoxy-CFs), graft copolymerization products of cellulose fibers (CFs) and glycidyl methacrylate (GMA), were prepared using cerium ammonium nitrate (CAN) as initiator. Epoxy groups content of Epoxy-CFs were as high as 2.5 mmol/g. Introduction of alkynyl/azido groups into Epoxy-CFs were achieved through ring-opening reactions of epoxy groups with propargylamine (PgAm) and sodium azide (NaN3), respectively. Under appropriate conditions, A-CFs with alkynyl groups of 0.57 mmol/g and N3-CFs with azido groups of 0.35 mmol/g were obtained. Click reactivities of A-CFs, N3-CFs and Epoxy-CFs were verified by Cu(I) catalyzed alkyne-azido cycloaddition (CuAAC) and thiol-epoxy click reactions. A-CFs, N3-CFs, Epoxy-CFs and their clicked products were characterized by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS).

Quinine-modified polymer monolithic column with reversed-phase /strong anion-exchange mixed-mode for pressurized capillary electrochromatography.

Via the facile ring-opening reaction of epoxy groups with quinine, a novel polymer monolith with quaternary ammonium for reversed-phase/strong anion-exchange mixed-mode has been fabricated for pressurized capillary electrochromatography (pCEC). Optimization on the preparation of quinine-modified monoliths has been investigated, and characteristics including morphology, permeability, mechanical stability, reproducibility, and column performance have been also studied. Active quaternary ammonium groups were conveniently produced to generate cationic action sites and stable anodic electroosmotic flow. Multiple interactions including reversed-phase, strong anion-exchange, electrostatic repulsion and π-π stacking interactions were obtained. Satisfactory separation capability of various analytes such as alkylbenzenes, polycyclic aromatic hydrocarbons, benzoic acid and its homologs, and β2 -receptor excitants has been achieved. Applied to the real sample, the good resolution of three alkaloids in Corydalis yanhusuo were achieved by pCEC with the quinine-modified monolith. The results light a potential access to facilely fabricating quaternary ammonium-functionalized polymer monolith with multiple interactions for efficient electrochromatography profiling of various compounds.

Morphology evolution of poly(glycidyl methacrylate) colloids in the 1,1-diphenylethene controlled soap-free emulsion polymerization

This work reports for the first time that milky poly(glycidyl methacrylate) (PGMA) colloids produced in the early stage of 1, 1-diphenylethene (DPE) controlled soap-free emulsion polymerization of GMA evolved into transparent polymer solution 90min after the polymerization was initiated. Qualitative and quantitative analysis confirmed that during the polymerization, large amount of hydrophilic hydroxyls and flexible aliphatic ethers were generated by the ring-opening reactions of epoxy groups catalyzed by H+ which is a byproduct of the decomposition of potassium persulfate. As a control agent, DPE could dramatically decrease the polymerization degree of PGMA, resulting in much shorter hydrophobic main chains comparing with PGMA produced in the absence of DPE. The hydrophilic hydroxyls by ring-opening reaction and the shorter hydrophobic main chains by DPE controlled polymerization would facilitate water swelling into the polymers. The swelled polymers along with the aliphatic ethers and shorter main chains endowed the particles with flexible and proteiform, forming structures similar to transparent polymer solution rather than milky colloidal suspensions.

High-efficiency and magnetically separable nanocatalyst: β-cyclodextrin modified core–shell hybrid magnetic nanoparticles

A novel hybrid magnetic nanoparticle, which was fabricated by Fe3O4 nanoparticle modified with β-cyclodextrin (Fe3O4@SiO2-GPTSCD), was prepared via a flexible method, including thermal decomposition, sol–gel process and ring-opening reaction of epoxy group. The structures had been characterized by fourier transform infrared spectra, transmission electron microscopy, and thermogravimetric analysis. The magnetic property of the resulting nanoparticles was kept, that they could be used for magnetic separation. Most excitingly, they showed high-efficiency catalytic activity with sodium hypochlorite and hydrogen peroxide as the oxidant in selective oxidation of benzyl alcohol, even higher than pure β-cyclodextrin (CD). It suggests that the hybrid nanoparticles are expected to be applied in more extensive fields, due to the combination of the activity of CD immobilized on the surface of nanoparticles and the characteristic of nanomaterials.

Study on the dual-curing mechanism of epoxy/allyl compound/sulfur system

Allyl-based epoxy resin/Sulfur (S) system is a facile and novel dual-curing system which conducts a unique curing mechanism. In this paper, Bisphenol-A diglycidyl ether (BADGE) and 2-Allylphenol (OAP) cured by S were comparatively investigated to clarify the dual-curing mechanism of Epoxy (EP)/Allyl Compound (AC)/S system. When the temperature was above 170 °C, DSC and FTIR data showed that S could cleave to form thiyl radicals, and FTIR, NIR, and 1H NMR measurements proved the disappearance of allyl groups and the generation of thiol groups by the thiyl radicals abstracting α-H atoms of allyl groups in the OAP/S reaction system. Real-time infrared spectroscopy (RT-FTIR) results showed that the reaction of the generation of thiol groups is the dominant reaction in the two possible pathways of the OAP/S system; allyl groups and epoxy groups disappeared sequentially in the OAP/S/BADGE system. DSC curve also revealed the one-stage reaction for OAP/S system and two-stage reaction for OAP/S/BADGE system. These data were used to develop a detailed, experimentally validated pathway for the dual-curing of EP/AC/S system, in which thiol groups are important intermediate, and the dual-curing process included the crosslinking of double bonds that initiated by thiyl radicals and the ring-opening reaction of epoxy groups with thiol groups. Besides, the dual-curing mechanism of EP/AC/S system shares a close resemblance to the classical rubber vulcanization mechanism and the recent thiol-ene radical addition mechanism.

N-substituted Carboxyl Polyaniline Covalent Grafting Reduced Graphene Oxide Nanocomposites and Its Application in Supercapacitor

A novel approach to covalent grafting N-substituted carboxyl polyaniline(NPAN) onto the graphene oxide (GO) is described in this study. In order to carry out this purpose, aniline is bonded to the graphene oxide via the nucleophilic ring-opening reaction of epoxy group of GO, where partial reduction of GO also concomitantly occurred. The reduced graphene oxide modified with aniline (aRGO) further serves as reactivity point for the in-situ polymerization of the N-phenylglycine(NAN) monomer. The covalent grafting aRGO-g-NPAN hybrid is confirmed and characterized by FT-IR, UV-vis, Raman, XRD, XPS and TEM. The analysis indicates that the NPAN is successfully grafted on the surface of aRGO, and exhibits nanorod structure with the diameter of 40–50nm and a length of tens to hundreds of nanometers. Electrochemical tests reveal that the specific capacitance of the aRGO-g-NPAN hybrids is 654.3Fg−1 at 1Ag−1, while the capacitance performances of 418.5Fg−1 for traditional physical mixture, indicating that the covalent grafting hybrids can reduce the interface resistance between aRGO and NPAN polymer to increase the charge transfer in the faradic transformation of NPAN process. Under the successive charge/discharge 1000 cycles, the specific capacitance of aRGO-g-NPAN based capacitor preserves 79.1% of its initial capacitance, while the traditional physical mixture shows 67.4% of its initial capacitance, suggesting the good cycling stability for the aRGO-g-NPAN hybrids.

Effect of carbon black on self-crosslinking network structure of polychloroprene rubber and epoxidized natural rubber blends

The goal of this research is to improve poor network structure of polychloroprene rubber (CR)/epoxidized natural rubber (ENR) self-crosslinking blends, which could substitute traditional vulcanizates in some application area. Carbon black (CB)–CR/ENR blends were prepared by reacting CR with ENR in the presence of CB. The structure of CR/ENR blends was characterized by attenuated total-reflectance Fourier transform infrared spectroscopy (FTIR-ATR). The effect of CB loading on curing characterization and mechanical properties of CR/ENR blends was investigated, and the interaction among CR, ENR, and CB was studied using differential scanning calorimetry. The effect of CB loading on the Payne effect of CR/ENR was investigated using rubber process analyzer. Scanning electron microscope was used to characterize the morphology of CB–CR/ENR blends. The results showed that CR/ENR blends were obtained by the ring-opening reaction of epoxy groups in ENR and chlorine groups in CR. Mechanical properties of CR/ENR blends increased with the increase of CB loading. The Payne effect of CR/ENR became more remarkable with increasing CB loading. Morphology study indicated that interfacial compatibility between CR and ENR increased with the increase of CB loading because CB could strengthen the self-crosslinking network structure of CR/ENR blends. The promoting effect of CB on self-crosslinking reaction was verified by the assessment of crosslink density. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Layer-by-layer assembly of graphene oxide on polypropylene macroporous membranes via click chemistry to improve antibacterial and antifouling performance

Polypropylene is an extensively used membrane material; yet, polypropylene membranes exhibit extremely poor resistance to protein fouling. To ameliorate this issue, graphene oxide (GO) nanosheets were used to modify macroporous polypropylene membrane (MPPM) via layer-by-layer assembly technique through click reaction. First, alkyne-terminated GO was prepared through esterification between carboxyl groups in GO and amide groups in propargylamine; azide-terminated GO was synthesized by the ring-opening reaction of epoxy groups in GO with sodium azide. Second, GO was introduced to the membrane by click chemistry. Characterizations of infrared spectra and X-ray photoelectron spectroscopy confirmed the modification. The sharply decreasing of static water contact angle indicated the improvement of the surface hydrophilicity for GO modified membrane.Introducing GO to the membrane results in a dramatic increase of water flux, improvements in the antifouling characteristics and antibacterial property for the membranes. The pure water flux through the 5-layered GO modified membrane is 1.82 times that through the unmodified one. The water flux restores to 43.0% for the unmodified membrane while to 79.8% for the modified membrane. The relative flux reduction decreases by 32.1% due to GO modification. The antibacterial property was also enhanced by two-thirds. These results demonstrate that the antifouling and antibacterial characteristics can be raised by tethering GO to the membrane surface.

Reinforcing styrene butadiene rubber with lignin-novolac epoxy resin networks

In this study, lignin-novolac epoxy resin networks were fabricated in the styrene butadiene rubber (SBR) matrix by combination of latex compounding and melt mixing. Firstly, SBR/lignin compounds were co-coagulated by SBR latex and lignin aqueous solution. Then the novolac epoxy resin (F51) was added in the SBR/lignin compounds by melt com- pounding method. F51 was directly cured by lignin via the ring-opening reaction of epoxy groups of F51 and OH groups (or COOH groups) of lignin during the curing process of rubber compounds, as was particularly evident from Fourier trans- form infrared spectroscopy (FTIR) studies and maximum torque of the curing analysis. The existence of lignin-F51 net- works were also detected by scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). The structure of the SBR/lignin/F51 was also characterized by rubber process analyzer (RPA), thermogravimetric analysis (TGA) and determination of crosslinking density. Due to rigid lignin-F51 networks achieved in SBR/lignin/F51 composites, it was found that the hardness, modulus, tear strength, crosslinking density, the temperature of 5 and 10% weight-loss were signif- icantly enhanced with the loading of F51.

Tailoring the morphology of emulsion-based (glycidylmethacrylate-divinylbenzene) monoliths

Poly(glycidylmethacrylate-divinylbenzene) monoliths [poly(GMA-DVB)] were prepared in the presence of a porogen using a high internal phase emulsion (HIPE) template. Tripolyglycerol monostearate was used as a surfactant to effectively inhibit Ostwald ripening and coalescence, and stable HIPE containing GMA was obtained. Epoxy groups of poly(GMA-DVB) were verified by FT-IR and solid-state 13C NMR spectroscopy. The effects of surfactant amount, cross-linking degree, water fraction, and porogen amount on the surface area, average void diameter, range of void diameter, average interconnection diameter, and average pore diameter of poly(GMA-DVB) were investigated. The morphology of poly(GMA-DVB) may be tailored by tuning each of the factors described above according to the requirements of specific applications. Finally, poly(GMA-DVB) were further functionalized by diethylamine via the ring-opening reaction of epoxy groups. The results showed that most epoxy groups of poly(GMA-DVB) could react with diethylamine.

β-Cyclodextrin polymer brushes decorated magnetic colloidal nanocrystal clusters for the release of hydrophobic drugs

β-Cyclodextrin (β-CD) polymer brushes decorated magnetic Fe3O4 colloidal nanocrystal clusters (Fe3O4@PG-CD) were fabricated by a combination of surface-initiated atom transfer radical polymerization on the surface of Br-anchored Fe3O4 colloidal nanocrystal clusters (Fe3O4–Br) and ring-opening reaction of epoxy groups. The resulted Fe3O4@PG-CD hybrid nanoparticles were characterized by several methods including Fourier transform infrared, transmission electron microscope, dynamic light scattering instrument, X-ray diffraction, thermogravimetric analysis, and vibrating sample magnetometer. Moreover, the potential of as-synthesized Fe3O4@PG-CD as a carrier of hydrophobic anticancer drug 5-fluorouracil (5-FU) was also investigated. The results showed that the prepared Fe3O4@PG-CD have core/shell structure and high saturated magnetism. 5-FU could be loaded into the Fe3O4@PG-CD via the formation of β-CD/5-FU inclusion complex. Furthermore, the Fe3O4@PG-CD displayed a high loading capacity and pH-dependent release behavior for 5-FU. The release behavior demonstrated a simple Fickian diffusion in the acidic environment (pH 2.0 and 4.0) but neither non-Fickian nor anomalous when neutral. The results reveal that this nanosystem seems to be a very promising vehicle for the hydrophobic drugs for pH-dependent controlled release.

Amino-functionalized magnetic cellulose nanocomposite as adsorbent for removal of Cr(VI): Synthesis and adsorption studies

A novel amino-functionalized magnetic cellulose composite was prepared by a process involving: (1) synthesis of magnetic silica nanoparticles using the co-precipitation method followed by the hydrolysis of sodium silicate, (2) coating with cellulose through the regeneration of cellulose dissolved in 7wt% NaOH/12wt% urea aqueous solvent, (3) grafting of glycidyl methacrylate using cerium initiated polymerization and (4) ring-opening reaction of epoxy groups with ethylenediamine to yield amino groups. Once generated, the resulting composite was tested for its ability to remove Cr(VI) from an aqueous solution in batch experiments. The results demonstrated that Cr(VI) adsorption was highly pH dependent. The optimized pH value was 2.0. The adsorption isotherms of the adsorbent fit the Langmuir model, with the maximum adsorption capacity of 171.5mg/g at 25°C. The adsorption rate was considerably fast, and the adsorption reached equilibrium within 10min. The obtained thermodynamic parameters showed that the adsorption of Cr(VI) onto the adsorbent was an exothermic and spontaneous process. In addition, the Cr(VI) ions could be effectively desorbed using a 0.1mol/L NaOH solution and the adsorbent exhibited a good reusability. The composite material should be a promising adsorbent for Cr(VI) removal, with the advantages of high adsorption capacity, rapid adsorption rate and convenient recovery under magnetic field.