Epichlorohydrin Cross-linking Research Articles

Self-cleaning and multi-active sites amphoteric composite sponges: Efficient removal, selective adsorption and photocatalyst substrates of dyes

To address the complex dyeing wastewater containing oil pollution and bacterial microorganisms in practical environments, in this work, amphoteric (CHI/ALG) C/A composite sponges with self-cleaning and multi-active sites were prepared by composite chitosan (CHI) and alginate (ALG) using urea/alkali composite solutions. The C/A composite sponges have good water wettability and demonstrated underwater anti-oil and anti-bacterial microbial adhesion. The adsorption process was spontaneous entropy-increasing and could be accurately described using the Pseudo-First-Order and Langmuir models. Notably, the adsorption capacity of C/A composite sponges for methylene blue and acid blue dye reached 656.33 mg/g and 502.49 mg/g, respectively. The amphoteric C/A composite sponges can selectively adsorb both anionic and cationic dyes. Additionally, epichlorohydrin (ECH) cross-linking and intermolecular self-assembly molding enabled the C/A composite sponges to form a three-dimensional network structure with nanofiber weaving and a specific surface area of 67.63 m2/g. Interestingly, this endowed the C/A composite sponges with the potential to serve as dyes photocatalyst substrates, and the photocatalytic degradation of dyes was successfully achieved by loading TiO2 on the C/A composite sponges. More importantly, the C/A composite sponge remained self-cleaning after loading TiO2. The amphoteric C/A composite sponges have great potential in complex dyeing wastewater treatment containing oil and bacterial microbes.

Aluminum soap nanoparticles-lignin powder form phase-selective gelator as an efficient sorbent for oils/water separation

Rapid and efficient recovery of oil spill is the key link for oil spill remediation, and also a great challenge. Here, the organogelator-polymerized porous matrix composed of adsorbents and organogelators can provide a new strategy for solving this problem. The gelling mechanism of aluminum 12-hydroxystearate (Al HSA) to form spherical nano micelles in solvents was investigated via UV–vis, FT-IR, and XRD. A creative method for aluminum soap-lignin gelator (OTS-AL/Al HSA) syntheses was put forward through the saponification of 12-hydroxystearic acid (HSA) and lignin via epichlorohydrin (ECH) crosslinking. By adjusting the ECH content, the growth of Al HSA nanoparticles (15–40 nm) on lignin can be realized, and the accordingly increased roughness endowed gelator with better hydrophobicity (WCA of 134.6°) before octadecyltrichlorosilane (OTS) modification. Thanks to the porous structures, the gelator powder exhibited a high sorption capacity in the range of 3.5–5.2 g g−1 for oils and organic solvents. Rheological studies demonstrated high mechanical strength of gels (>1.6 × 105 pa) and the gelator still retained 70% sorption capacity after 6 gelation-distillation cycles. The gelation characteristics of OTS-AL/Al HSA were attributed to the rapid sorption of oils by lignin and the self-assembly of Al HSA nano micelles on lignin to form an aggregated network structure trapping oils, thus realizing the synergistic effect of oil sorption-gelation.

Preparation of a novel high-performance lignin-based anionic adsorption resin for efficient removal of Cr(VI) in aqueous solutions

To remove Cr(VI) in water, a novel lignin-based anionic adsorption resin epichlorohydrin cross-linking lignin grafted by diethylenetriamine (E-DAL) was prepared by the direct cross-linking and curing of alkali lignin grafted by diethylenetriamine in aqueous solutions. Under the determined optimum synthesis conditions, E-DAL with higher nitrogen (7.46%) and lignin (32.78%) contents was obtained. Structural and physicochemical measurement results showed E-DAL was a macroporous resin, having a regular connected pore structure with porosity of 67.48% and pore size of 615.6 nm, also strong hydrophilicity, excellent acid-alkaline resistance and thermal stability. Adsorption experiment results indicated the adsorption isotherm of E-DAL to Cr(VI) was well-described by Langmuir model. E-DAL showed a higher adsorption capacity to Cr(VI), and the fitted maximum adsorption capacity reached up to 775.2 mg/g. Pseudo-second-order model could fit this adsorption process well, suggesting its chemisorption characteristics. The calculated thermodynamic parameters indicated a spontaneous and endothermic adsorption of E-DAL to Cr(VI). Dynamic column adsorption results showed E-DAL could completely remove Cr(VI) in wastewater. This whole preparation process only used a very small amount of cheaper amination agent and was relatively low-cost. This work provided efficient technical supports for the structural design of high-performance lignin-based anionic adsorption materials in water treatment field.

Carboxymethyl Cellulose-Based Composite Polymer Hydrogels Cross-Linked with Epichlorohydrin and Application for Cu(II) Removal

In this work, CMC-ECH/PAM hydrogels with perfect compressive strength were prepared by epichlorohydrin (ECH) cross-linking sodium carboxymethyl cellulose (CMC) grafted with polyacrylamide (PAM) to remove the copper ion (Cu2+) from water. The chemical and structural morphology of the product was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The compressive strength was measured by successive compression–decompression cycles and up to 70 kPa. Adsorption was studied at different pH values 1–5, adsorbent doses (0.2–8) g/L, and initial Cu2+ concentrations from (50 to 400) mg/L to obtain the optimum conditions for maximum removal of Cu2+. The experimental adsorption data were well fitted by the pseudo-second-order kinetics model, Langmuir isotherm model, and Freundlich isotherm model. The maximum adsorption capacity calculated by the Langmuir model was 75.930 mg/g at 338.15 K. In addition, the negative ΔG° and positive ΔH° also indicated that the adsorption of Cu2+ is a spontaneous, endothermic, and chemical process. The adsorption mechanism was further verified by X-ray photoelectron spectroscopy analysis. CMC-ECH/PAM hydrogels also exhibited excellent reusability after five adsorption–desorption cycles, maintaining about 80% Cu2+ removal efficiency.

Valorization of agro-waste biomass as composite adsorbents for sustainable wastewater treatment

Agro-waste biomass in form of torrefied wheat straw (S) and oat hulls (Oh) were combined with kaolinite (K) and chitosan (Ch) to obtain pelletized adsorbent materials. The agro-waste pellets were compared to a common food-waste material in form of spent coffee grounds (SCG) as a reference biomass system. The composites were prepared with variable biomass content via physical blending and compared against their epichlorohydrin (ECH) crosslinked counterparts. IR and 13C NMR spectroscopy were employed for structural characterization of the composites, along with complementary thermogravimetric analysis. Composites with 80% Oh content were unstable and required ECH crosslinking, whereas their SCG and S counterparts were stable without crosslinking. A cationic methylene blue (MB) dye probe was employed to evaluate the adsorption properties of the pelletized materials. The Sips model was used to estimate the adsorption capacity (Qm), which was correlated with increasing biomass content: Qm = 22 ̶ 34 mg/g for the Oh composites, Qm = 21 ̶ 86 mg/g for the S composites, and Qm = 18 ̶ 98 mg/g for the SCG composites. Crosslinking notably reduced the adsorption capacity for both Oh and S composites, whereas greater MB uptake occurred for the SCG composites (Qm ∼ 135 mg/g). A cost-benefit analysis showed that S composites are competitive adsorbents for MB per dollar material cost versus SCG composites. Composites that contain torrefied biomass have lower chemical input costs that afford the design of sustainable adsorbent technology in a pelletized form.

Synchronous reduction and removal of hexavalent chromium from wastewater by modified magnetic chitosan beads

As one of the highly toxic heavy metal contaminants, hexavalent chromium (Cr(VI)) poses a serious hazard to the environment and public health due to its excellent solubility in aqueous environment. To synchronously reduce and remove Cr(VI) from wastewater efficiently, a class of functionalized magnetic chitosan (CS) beads (MCB-ECH-SH/SO3H) was synthesized with CS as the substrate material and in situ assembling Fe3O4 nanoparticles as the incorporated magnetic material, followed by epichlorohydrin (ECH) cross-linking and l-cysteine grafting. Results showed that Cr(VI) in aqueous solution could be rapidly adsorbed onto MCB-ECH-SH/SO3H via electrostatic attraction, meanwhile -SH groups introduced by l-cysteine grafting could not only significantly facilitate the reduction of Cr(VI) to less toxic trivalent chromium (Cr(III)), but also promote the resultant Cr(III) chelating onto adsorbent due to the proton consumption caused by Cr(VI) reduction, resulting in the synergistic enhancement of Cr(VI) detoxification and total chromium (Cr(Total)) removal. The batch adsorption experiments revealed that the well designed MCB-ECH-SH/SO3H could be applied over a wide pH range (initial pH of 1.0–7.0), and showed much higher remove efficiency (99.6 ± 0.2 %) of Cr(VI) than MCB and MCB-ECH at initial pH 5.0 (60 °C) due to the improvement of stability and reducing capacity. The Cr(Total) sorption behaviors were well according with the pseudo-second-order kinetic and Langmuir models, indicating a single-layer, exothermal, and chemical sorption process, while the maximum Cr(Total) removal capacity of MCB-ECH-SH/SO3H was estimated to be 293.46 mg∙g−1, exceeding most of previously reported related adsorbents. Moreover, MCB-ECH-SH/SO3H could still maintained strong adsorption performance after five cycles and exhibited excellent ability to remove 95 % Cr(VI) within 1 h for low concentration Cr(VI)-containing wastewater. The combination of synchronous reduction and adsorption property, high removal capacity, convenient magnetic separation and good recycling performance makes MCB-ECH-SH/SO3H an ideal candidate for chromium-containing wastewater treatment.

Simple synthesis of cellulose hydrogels based on the direct dissolution of cellulose in tetrabutylphosphonium hydroxide followed by crosslinking

AbstractCellulose‐based hydrogels are valuable sustainable materials with significant potential applications in biomedical fields such as cell therapy, hemostasis, wound healing, tissue transplantation, regeneration technology, and drug delivery carrier to cells. In contrast to previous studies, the standard synthesis procedure needs high temperature, low cellulose concentration, and many additives. Here cellulose‐based hydrogels with a high cellulose concentration are produced at room temperature. The one‐pot preparation of chemical hydrogels involves the dissolution of cellulose in tetrabutylphosphonium hydroxide followed by epichlorohydrin crosslinking. The effects of the wide range of microcrystalline cellulose concentrations and the crosslinker ratio on swelling properties and crosslink density under different conditions are investigated. The hydrogels are characterized using Fourier transform infrared spectroscopy and X‐ray diffraction. The morphology of hydrogels is examined through scanning electron microscope. The transparency of hydrogel is determined by ultraviolet–visible (UV–vis) spectrophotometer.

Botryoidal nanolignin channel stabilized ultrasmall PdNP incorporating with filter membrane for enhanced removal of Cr(VI) via synergetic filtration and catalysis

Catalytic membrane technology, as a combination of membrane separation and catalysis, is a high-efficiency and feasible route for wastewater remediation. The controllable synthesis of ultrasmall metal nanoparticles on the membrane to maximize the size effect is a challenging task yet. Herein, the filter paper-based botryoidal nanolignin channel stabilized ultrasmall PdNP membrane (Pd@LNP/FP) was prepared by chemical crosslinking of epichlorohydrin (EPI), the nanolignin (LNP) serves as both reducing and capping agent for the in-situ synthesis of ultrasmall PdNP with enhanced active sites. The mean size of PdNP was effectively tuned from 1.76 to 2.09 nm by varying the LNP loading amount of composite membranes. The botryoidal LNP supported on FP also provides the nanoscale channel to keep reactants on active sites of ultrasmall PdNP to improve the catalytic performance of Pd@LNPE/FP. The complete removal of hazardous Cr(VI) required only 2.5 min using Pd@LNPE/FP membrane, the pseudo-first-order rate constant (k) is 1.2725 min−1, much higher than that of the Pd@LNPp/FP membrane prepared by physical composite (0.2885 min−1). Moreover, the rapid filtration-catalysis removal of Cr(VI) can be achieved by twice filtration, demonstrating the high efficiency and feasibility of Pd@LNPE/FP via synergetic filtration enrichment and catalysis reduction.

Modulation of physicochemical properties of magnetic agarose microspheres by hydrolysis-suppressive sequential crosslinking

Separation and purification of target proteins are essential for drug discovery and development. A magnetic separation has been exploited due to its high efficiency. Despite many studies on chemical crosslinking of a magnetic agarose microsphere (MAM), the study on a crosslinking reaction preventing MAM from hydrolytic degradation during the reaction and the effects of the crosslinks on the physicochemical and electrochemical properties of the crosslinked MAM (CL-MAM) has rarely been reported. In our study, CL-MAM was prepared using a sequential crosslinking by which MAM was crosslinked using epichlorohydrin (ECH) in DMSO after crosslinking the MAM by 1,3-dichloro-2-propanol (DCP) for a short time. Such a crosslinking prevented the hydrolytic degradation of DCP-crosslinked MAM ( D -CL-MAM) and DCP and ECH-crosslinked MAM (DE-CL-MAM). MAM had a mean diameter of 110 ± 57.42 µm and its morphology was not affected by the crosslinking. In FT-IR analysis, increase of peak intensity at 1037 cm −1 confirmed newly formed C-O-C bonds in the agarose of CL-MAM. Thermal stability of MAM increased by both DCP crosslinking and subsequent ECH crosslinking of the agarose. While T g of MAM was not shifted by the crosslinking, the onset temperatures of glass transition and thermal decomposition increased by DCP crosslinking and further increased by DCP and ECH-crosslinking. Stiffness (S) and elastic modulus (E) of MAM were enhanced by DCP crosslinking and subsequent ECH crosslinking, indicating a half of ECH formed crosslinks between agarose mainchains while the other half crosslinked adjacent pyranose rings in the agarose mainchain. Permittivity analysis revealed that α relaxation temperature of the agarose film corresponded to T g determined by DSC analysis and the relaxation intensity decreased with increasing crosslink density of the agarose. The higher swelling ratio of DE-CL-MAM compared to D -CL-MAM was attributed to greater S and E values of DE-CL-MAM. The hydrolysis-repressive sequential crosslinking of MAM using DCP and ECH can be a feasible approach to modulate physicochemical and electrochemical properties of MAM. • Hydrolysis-suppressive crosslinkings by DCP and ECH were effective to crosslink MAM. • DCP-crosslinked MAM had enough stability to be crosslinkable by ECH in DMSO. • The sequential crosslinkings did not induce morphological changes of the MAM. • The crosslinking improved thermal stability of MAM, not influencing T g . • Mechanical and swelling properties of crosslinked MAM depended on degree of crosslinks.

Polycyclodextrin as a linker for nanomedicine fabrication and synergistic anticancer application

Polycyclodextrin (denoted PCD) composed of cyclodextrin monomer units and 1,3-diethoxypropan-2-ol containing many hydroxyl groups with lone pairs of electrons, easily coordinated with transition metals with empty orbitals. The CD unit can also provide host-guest binding sites for functional molecules. This article utilizes this feature of PCD for the first time as a “linker” to combine transition metal nanomaterials with synergistic functional molecules. We synthesized PCD with 50% CD monomer by epichlorohydrin cross-linking method. Utilizing the coordination effect of the hydroxyl group in PCD and the iron ion in photothermal nanoparticles (PB-Yb), the PCD is coated on its surface; simultaneously, CD in PCD can form a host-guest complex with adamantane-modified zinc phthalocyanine (Pc) photosensitizer. Using PCD as a “linker”, PB-Yb and Pc (denoted PYPP) were combined to improve the solubility of PB-Yb, reduce the aggregation degree of Pc to increase their activity, and achieve photothermal and photodynamic synergistic tumor therapy.

Hydrogels Based on Cross-Linked Cationic Cellulose Derivatives

Cationization of wood and cotton celluloses using 3-chloro-2-hydroxypropyltrimethylammonium chloride in aqueous suspensions in the presence of various amounts of NaOH followed by cross-linking with epichlorohydrin was studied in detail. The compositions of the cationic cellulose ethers and the reaction efficiency depended strongly on the ratio of the alkylating mixture components. The physicochemical properties of the synthesized samples were studied using chemical analysis, IR spectroscopy, X-ray structure analysis, and centrifugation to determine water absorption. The content of cationic groups and concentration of cationic cellulose in the epichlorohydrin cross-linking stage had decisive effects on the degree of swelling in water and aqueous NaCl solution of the cross-linked cationic cotton and wood celluloses.

Perchlorate adsorption onto epichlorohydrin crosslinked chitosan hydrogel beads

Perchlorate (ClO4−) in water is an emerging contaminant that threatens human health by inhibiting the uptake of iodine in the thyroid gland. Biopolymer adsorbents including chitosan hydrogel beads (CSBs) have attracted increasing attentions in water treatment for their low costs, ease in preparation, and environmental friendliness. However, the adsorption capacity for ClO4− by several crosslinked CSBs has been shown to be low. To overcome this, epichlorohydrin (ECH) crosslinked CSBs (ECH-CSBs) that preserved -NH2 functional groups as potential sites for adsorption are synthesized and characterized, followed by batch adsorption experiments to evaluate adsorption and desorption reactions. The point of zero charge is determined to be 5.1 ± 0.1. Both XPS spectra and DFT calculations support that electrostatic interaction between ClO4− and protonated -NH3+ functional groups is responsible for adsorption that reaches a capacity of 63.4 to 76.3 mg/g between pH of 4.0–10.0 at 303.15 K that follows Langmuir isotherm. ECH crosslinking also enhances hydrophilicity of CSBs to allow for increased adsorption for ClO4−. Adsorption of ClO4− (10 and 100 mg/L) follows a pseudo-first order kinetics with equilibrium time of 2–6 h but is limited by intra-particle diffusion. Anions common in natural waters exhibit interference effects due to similar electrostatic attraction mechanism, thus HCO3− and SO42− with high abundance in natural waters need pre-treatment. Regeneration of the adsorbents to 100% of its adsorption capacity by rinsing with 0.1 M NaOH is demonstrated for 12 cycles due to complete desorption of ClO4− via electrostatic repulsion, assuring reusability.

Fabrication of Hydroxypropyl Chitosan/Soy Protein Isolate Hydrogel for Effective Hemorrhage Control.

Hemostatic materials are increasingly important in civilian and military clinics. In this work, a hydrogel was fabricated from hydroxypropyl chitosan (HPCS) and soy protein isolate (SPI) through the crosslinking of epichlorohydrin. Effects of SPI content on the structure, and physical and biological properties of the prepared hydrogels were characterized using Fourier-transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, water uptake testing, mechanical properties testing, MTT assay, hemolysis ratio testing, and routine blood coagulation test. The results indicated that the hydrogels showed high water uptake ability and compressive strength. The in vitro biocompatibility evaluation revealed that the hydrogel contains 30% SPI content (HCSH-30), could promote blood coagulation and cell proliferation. Furthermore, the hemostatic model of liver in New Zealand rabbit was applied to assess the hemostatic efficacy of the hydrogels. The results demonstrated that HCSH-30 stopped bleeding in 75 ± 1.63 s and improved hemostasis as compared with medical gauze. Thus, the HPCS/SPI hydrogel is expected to be a potential candidate for effective hemorrhage control. Impact statement Stoppage of bleeding is of paramount clinical significance in prophylactic, surgical, and emergency scenarios. This work describes a hydroxypropyl chitosan (HPCS)/soy protein isolate hydrogel, which could promote blood coagulation and cell proliferation, as well as stop bleeding in 75 ± 1.63 s on the liver of New Zealand rabbits. Thus, we provide a new candidate for hemostatic material and broaden the application of HPCS-based materials.

Dialdehyde Oxidation of Cross-Linked Waxy Corn Starch: Optimization, Property and Characterization

The functionalization of waxy corn starch (WCS) was better realized by combing the cross-linking of epichlorohydrin with oxidation of sodium periodate. The results indicated that the cross-linking had a greater influence on the retrogradation than the oxidation, and the oxidation worsened the freeze–thaw stability of WCS. Both cross-linking and oxidation could ameliorate the alkali and acid resistance of WCS, and enhanced its heat stability. Cross-linking weakened the absorption peak of the –OH groups according to FTIR and had a small influence on the crystalline configuration of WCS belonging to a typical A-type structure, whereas the oxidation almost entirely damaged the particle structure. After the cross-linking, the tiny pits with a diameter of around 1 μm only appeared on sides of WCS granules, and proving that the cross-linking was very unevenly completed on some of WCS particles. The pasting curve of WCS was obviously different from those of its derivatives. The combination of oxidation and cross-linking could effectively decrease the setback of WCS.

Multiple active sites cellulose-based adsorbent for the removal of low-level Cu(II), Pb(II) and Cr(VI) via multiple cooperative mechanisms

A novel multiple active sites cellulose-based adsorbent (MCC/TEPAA-BCTTC) with a high density of multiple active adsorption sites (N, O, S) was prepared by using epichlorohydrin cross-linking microcrystalline cellulose (MCC) with tetraethylenepentamine (TEPA), followed by grafting with bis(carboxymethyl) trithiocarbonate (BCTTC). It was shown that the removal rates of MCC/TEPAA-BCTTC for Pb(II) (1 mg/L), Cu(II) (3 mg/L) and Cr(VI) (1 mg/L) reached 100 %, 98 % and 99 %, respectively, and the remaining concentration after adsorption reached the United States Environmental Protection Agency (US EPA) standards for Pb(II) and Cu(II) and the China integrated wastewater discharge standard for Cr(VI). These results indicate that the high removal rate of MCC/TEPAA-BCTTC for removing anionic and cationic heavy metal ions in low-concentration mixed heavy metal ions environments was mainly due to the high density of multiple adsorption sites that act via multiple cooperative mechanisms.

Structural Design of a Cellulose-Based Solid Amine Adsorbent for the Complete Removal and Colorimetric Detection of Cr(VI).

A cellulose-based solid amine adsorbent (MCC/TEPAA) with high amino density for the detection and removal of Cr(VI) was designed and prepared through using epichlorohydrin cross-linking with MCC (microcrystalline cellulose) and tetraethylenepentamine (TEPA). The structure and amino density of the cellulose-based solid amine adsorbents could be tailored by adjusting the structure of the amines (triethylenetetramine or diethylenetriamine). The as-prepared cellulose-based solid amine adsorbents could detect and completely remove Cr(VI) from water, and the concentration of Cr(VI) solution after adsorption met the standard concentration of Cr(VI) solution for drinking water (0.05 mg/L). In particular, the MCC/TEPAA, supported by MCC with porosity as a framework, promoted the adsorption rate (adsorption equilibrium within only 10 min), removal rate (100%) of Cr(VI), and adsorption capacity (327.72 mg/g). In addition, the limit of colorimetric detection of Cr(VI) by MCC/TEPAA was 0.5 mg/L at 20 min when other interfering heavy metal ions exist. The adsorption and colorimetric detection mechanism of Cr(VI) on MCC/TEPAA was proposed to include electrostatic interactions, chelating reactions, and oxidation-reduction reactions, all of which contributed to the excellent adsorption and detection performance.

Overcoming drug-resistance in lung cancer cells by paclitaxel loaded galactoxyloglucan nanoparticles

Paclitaxel, an effective chemotherapeutic drug, is insoluble in aqueous solvents and is usually administered with excipients which have side effects. The use of this drug is also limited due to multi-drug resistance. In this study polysaccharide nanoparticles are used in the delivery of chemotherapeutic drug while minimizing side-effects, solubility issues and drug resistance. The use of biopolymers like galactoxyloglucan to synthesize nanoparticle makes it more biocompatible. This study involves the synthesis of PST-PTX nanoparticles using tamarind seed polysaccharide and Paclitaxel by epichlorohydrin crosslinking. The particles were further characterized by Dynamic Light Scattering (DLS), High-resolution transmission electron microscopy (HR-TEM) Fourier Transform Infrared Spectroscopy (FTIR) and UV–Visible spectroscopy. The cytotoxicity of PST-PTX nanoparticles in cancer cell lines and resistant cancer cell lines were determined by MTT assay. The quantitative analysis of cell death was determined by Annexin V dead cell assay, Caspase 3/7 assay and expression of pro-apoptotic protein Bax. The ability of the nanoparticle to overcome multi-drug resistance was evaluated by the expression of multidrug-resistant proteins P-glycoprotein (P-gp) and Breast cancer resistant protein (BCRP) in lung adenocarcinoma resistant cells (A549R). The present study provides evidence for the ability of PST-PTX nanoparticle to overcome multi-drug resistance and cause apoptotic cell death. The particle was found to be more effective than Paclitaxel in causing cell death in resistant cancer cells. Moreover, the particles were found to downregulate the expression of multi-drug resistant proteins P-gp and BCRP in resistant cell lines suggesting the ability of PST-PTX nanoparticles to overcome multi-drug resistance.

Robust cellulose nanocomposite films based on covalently cross-linked network with effective resistance to water permeability

Cellulose films are of poor water-vapor barrier performance. Herein, we put forward an effective way to suppress adsorption by crosslinking of hydroxyl groups via epichlorohydrin (ECH), meanwhile graphene oxide (GO) nanosheets are utilized to prolong the pathway of vapor penetration. The strategy confers a significant enhancement of vapor barrier performance as well as mechanical properties to cellulose-based films. Specifically, an outstanding reduction of 67.4% in water-vapor permeability coefficient is achieved in nanocomposite films compared to the uncrosslinked cellulose films. Furthermore, for the first time, two-dimensional correlation analysis reveals that crosslinking of ECH do not alter penetration direction, while GO can eminently act as shielding for the formation of bound water which change the sequential order of firstly-interacted vapor area from crystalline to amorphous area. Free volume is the penetration destination. The retarding effect introduced by the GO in amorphous area gives rise to the improvement of the vapor-barrier.

Lignin: Isolation and preparing the lignin based hydrogel

Efficient recovery of valuable materials from by-products of pulping has been a strong asset to the environmental concern. The objectives of this research were to recovery and utilization of lignin from kraft black liquor. Lignins of oil palm empty fruit bunch were isolated from kraft black liquor by acidic method. Results showed that the optimal condition of kraft lignin precipitation was at pH 3, which contributed the higher yield and purity of isolated lignin. The chemical and physical properties of isolated lignin was characterized as a mixture of lignin-agarose hydrogel by fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. Lignin and agarose hydrogel were synthesized by chemical crosslinking of epichlorohydrin (ECH). The lignin-agarose hydrogel obtained at 5%lignin, 5% agarose and ECH 10 mL provided the higher mechanical properties when compared to other conditions. Gel strength of lignin-agarose hydrogel has been comprehensively determined by texture personal analysis (TPA).

Comparison of Co2+ adsorption by chitosan and its triethylene-tetramine derivative: Performance and mechanism

A cross-linked chitosan derivative (CCTS) was synthesized via cross-linking of epichlorohydrin and grafting of triethylene-tetramine. The adsorption performance and capacity of the raw chitosan (CTS) and its derivative were also investigated for removal of Co2+ from aqueous solution. A maximum adsorbed amount of 30.45 and 59.51mg/g was obtained for CTS and CCTS, respectively under the optimized conditions. In addition, the adsorption kinetics for the adsorption of Co2+ by CTS and CCTS were better described by the pseudo second-order equation. The adsorption isotherm of CCTS was well fitted by the Langmuir equation, but the data of the adsorption of Co2+ onto CTS followed Freundlich and Sips isotherms better. Furthermore, the adsorbent still exhibited good adsorption performance after five regeneration cycles. Finally, Co2+ removal mechanisms, including physical, chemical, and electrostatic adsorption, were discussed based on microstructure analysis and adsorption kinetics and isotherms. Chemical adsorption was the main adsorption method among these mechanisms.