Cr (VI) adsorption from aqueous solutions on grafted chitosan

Chitosan was grafted on the surface of a cotton gauze (20, 50, and 100 mg chitosan g⁻¹ cotton) to improve its stability in aqueous solutions. The adsorption of hexavalent chromium ions from water on the grafted chitosan was evaluated to determine, by means of linear and nonlinear models, the kinetic and isotherm adsorption of the process. The kinetics of pseudo second-order, pseudo first-order, and adsorption isotherms type II were obtained, that is, a monolayer adsorption on nonporous adsorbents with physical adsorption was present. The most probable energy of adsorption corresponded to a physisorption with hydrogen bond interactions between chromium ions and ammonium groups. Moreover, three different cross-sectional areas of hexavalent chromium ions were calculated and used to estimate the specific surface area employed by active sites to adsorb metal ions in terms of chitosan or cotton mass. Finally, the percentage of the area occupied by chromium ions on the surface was estimated by dividing the resulting specific surface area in terms of cotton mass by the specific surface area of cotton reported in literature. As a result, it was determined that the occupied area is between 6% (for 20 mg chitosan g⁻¹ cotton)-24% (for 100 mg chitosan g⁻¹ cotton) from the total area of cotton.     

Hydroxyethyl cellulose hydrogel modified with tannic acid as methylene blue adsorbent

This work developed an effective way to improve the methylene blue (MB) adsorption performance of cellulose-based hydrogel by modified with tannic acid (TA). HEC-co-p(AA-AM)/TA hydrogel was synthesized by grafting of acrylic acid (AA) and acrylamide (AM) onto hydroxyethyl cellulose (HEC), followed by modified with TA. Fourier transform infrared spectroscopy manifested that AA and AM were successfully grafted onto the hydrogel, and TA was immobilized in the hydrogel. Field emission scanning electron microscope demonstrated that the hydrogel after TA modification had a homogeneous pore structure. Brunauer-Emmett-Teller (BET) surface areas, total pore volume, and average pore diameters of the hydrogel are 11.821 m² g⁻¹, 0.0641 cm³ g⁻¹, and 2.538 nm, respectively. The high swelling ratio (1179.2 g g⁻¹ in deionized water) was in favor of the MB adsorption. The results of the adsorption experiments illustrated that HEC-co-p(AA/AM) hydrogel had excellent MB adsorption performance. As the pH increases, the electrostatic attraction is enhanced, and the adsorption capacity is improved. The adsorption process was more fit with pseudo-second-order kinetics, and the maximum adsorption capacity (3438.27 mg g⁻¹) was determined by Langmuir model. Thermodynamic studies suggested that the adsorption process is spontaneous, exothermic, and entropy reduction. X-ray photoelectron spectroscopy analysis confirmed that MB molecules were reacted with the oxygen atoms in hydroxyl and carboxyl groups by ion-exchange. High reusability demonstrated that the hydrogel could be a potential candidate for removal cationic dye from industrial effluents.     

Affinity microspheres and their application to lysozyme adsorption: Cibacron Blue F3GA and Cu(II) with poly(HEMA-EGDMA)

Lysozyme adsorption onto Cibacron Blue F3GA attached and Cu(II) incorporated poly(2-hydroxyethyl methacrylate–ethylene glycol dimethacrylate) [poly(HEMA-EGDMA)] microspheres was investigated. The microspheres were prepared by suspension polymerization. Various amounts of Cibacron Blue F3GA were attached covalently onto the microspheres by changing the initial concentration of dye in the reaction medium. The microspheres with a swelling ratio of 65%, and carrying different amounts of dye (between 1.4 and 22.5 µmol/g⁻¹) were used in the lysozyme adsorption studies. Lysozyme adsorption on these microspheres from aqueous solutions containing different amounts of lysozyme at different pH values was investigated in batch reactors. The lysozyme adsorption capacity of the dye–metal chelated microspheres (238.2 mg g⁻¹) was greater than that of the dye-attached microspheres (175.1 mg g⁻¹). The maximum lyzozyme adsorption capacities (q_m) and the dissociation constant (k_d) values were found to be 204.9 mg g⁻¹ and 0.0715 mg ml⁻¹ with dye-attached and 270.7 mg g⁻¹ and 0.0583 mg ml⁻¹ with dye–metal chelated microspheres, respectively. More than 90% of the adsorbed lysozyme were desorbed in 60 min in the desorption medium containing 0.5 M KSCN at pH 8.0 or 25 mM EDTA at pH 4.9. © 1999 Society of Chemical Industry     

Structure and electrically conductive properties of porous PAN-based nanocomposites prepared by Pickering emulsion template method

A carbon nanohybrid Pickering stabilizer was synthesized by the hydrothermal reaction of 2-ethyl-4-methylimidazole (EMI), graphene oxide (GO), and carbon nanotubes (CNTs). A water-in-oil (w/o) type Pickering emulsion was achieved using the mixed carbon nanohybrids/Span 80 to form a porous and conductive polyacrylonitrile (PAN) nanocomposites after polymerization. Contact angle and X-ray photoelectron spectroscopy (XPS) results show that the carbon nanohybrid stabilizer is amphiphilic. The effects of the composition and concentration of stabilizers were investigated. When the concentration of the carbon nanohybrid stabilizer is 4 mg ml⁻¹, the conductivity of the resulting material is 2.31 × 10⁻⁹ S m⁻¹, which is six orders of magnitude higher than that of porous PAN composites without carbon nanohybrid stabilizer. At the mass ratio of 6GO:1CNTs, the conductivity of porous PAN-based composites reaches 2.47 × 10⁻⁸ S m⁻¹. The significantly increased conductivity is the evidence for the three dimensional conductive network constructed by carbon nanohybrid stabilizer at the oil/water interface.     

Graphene oxide–tripolyphosphate hybrid used as a potent sorbent for cationic dyes

Graphene oxide–tripolyphosphate material (GPM) was synthesized through an ethanolamine (EA) mediated graphene oxide (GO) self-assembly. The synthesis route to GPM is simple and benign. GPM was composed of GO nanosheets as building blocks and the tripolyphosphate as cross-linkers and chelators of cations in solutions. GPM showed higher potency for adsorption of cationic dyes than anionic dyes, and the adsorption process was through electrostatic and π–π interactions. Adsorption was spontaneous and exothermic, and the adsorption capacity of GPM for cationic dyes (>2540 mg g⁻¹) far exceeded those reported in literature for GO materials.     

Synthesis of monodisperse nonporous crosslinked poly(glycidyl methacrylate) particles with metal affinity ligands for protein adsorption

Monodisperse nonporous crosslinked poly(glycidyl methacrylate) (PGMA) particles with immobilized metal affinity ligands were prepared for selective recovery of proteins. The PGMA particles, with an average size of 2.2 µm, were prepared by a simple dispersion polymerization of glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA). The particles were characterized by scanning electron microscopy (SEM) and Fourier‐transform infrared spectroscopy (FTIR). The epoxy groups of the particles were modified with the metal chelating agent iminodiacetic acid (IDA), which forms metal–IDA chelates at the active sites. After charging with copper ions, the particles were used to recover a model protein, bovine hemoglobin (BHb), in a batchwise manner. The particles had the adsorption capacity of 218.7 mg g⁻¹ with little nonspecific adsorption. The adsorption behavior could be described with the Langmuir equation. The effect of pH on the adsorption was also studied. Regeneration of the metal‐chelated particles was easily performed with 50 mmol L⁻¹ ethylenediaminetetraacetic acid (EDTA), followed by washing with water and reloading with Cu²⁺. The particles could be very useful as an affinity separation adsorbent. Copyright © 2005 Society of Chemical Industry     

Highly selective adsorption of Pt(IV) from spent catalyst by polyethyleneimine functionalized polyethylene/polypropylene non-woven fabric

Aiming at efficient recovery of platinum (Pt) from aqueous solution, the aminated polyethylene/polypropylene non-woven fabric (PE/PP NWF) was synthesized via radiation grafting of glycidyl methacrylate (GMA), followed by ring-opening reaction with polyethyleneimine (PEI). The effects of different parameters, including pH, sorption time, initial Pt(IV) concentration, competing ions and adsorbent dosage on the Pt(IV) adsorption performance were investigated by batch adsorption tests. A high Pt(IV) adsorption capacity of 485.0 mg g⁻¹ (initial concentration: 263.5 mg L⁻¹) was achieved, and the adsorption kinetics and isotherm conformed to the pseudo-second-order model and the Langmuir isotherm model, respectively. Moreover, the PEI functionalized PE/PP NWF exhibited excellent adsorption performance over the wide pH range (1–6), and also good selectivity for Pt(IV) over multiple coexisting metal cations (Ni, Cu, Co, Pb, Mg, and Zn). The recovery ratio of Pt from spent proton exchange membrane fuel cell (PEMFC) catalysts reached 89.7% after three cycles of regeneration.     

Modified activated carbon for the removal of copper,zinc, chromium and cyanide from wastewater

Modified activated carbon are carbonaceous adsorbents which have tetrabutyl ammonium iodide (TBAI) and sodium diethyl dithiocarbamate (SDDC) immobilised at their surface. This study investigates the adsorption of toxic ions, copper, zinc, chromium and cyanide on these adsorbents that have undergone surface modification with tetrabutyl ammonium (TBA) and SDDC in wastewater applications. The modification technique enhance the removal capacity of carbon and therefore decreases cost-effective removal of Cu(II), Zn(II), Cr(VI) and CN⁻ from metal finishing (electroplating unit) wastewater. Two separate fixed bed modified activated carbon columns were used; TBA-carbon column for cyanide removal and SDDC-carbon column for multi-species metal ions (Cu, Zn, Cr) removal. Wastewater from electroplating unit containing 37 mg l⁻¹ Cu, 27 mg l⁻¹ Zn, 9.5 mg l⁻¹ Cr and 40 mg l⁻¹ CN⁻ was treated through the modified columns. A total CN⁻ removal was achieved when using the TBA-carbon column with a removal capacity of 29.2 mg g⁻¹ carbon. The TBA-carbon adsorbent was found to have an effective removal capacity of approximately five times that of plain carbon. Using SDDC-carbon column, Cu, Zn and Cr metal ions were eliminated with a removal capacity of 38, 9.9 and 6.84 mg g⁻¹, respectively. The SDDC-carbon column has an effective removal capacity for Cu (four times), Zn (four times) and Cr (two times) greater than plain carbon.     

Water‐resistant modification of poly(vinyl alcohol)/polyamidoxime chelating fibers prepared by emulsion spinning and their adsorption properties

The poly(vinyl alcohol)/polyacrylonitrile (PVA/PAN) precursor fiber prepared by emulsion spinning was separately crosslinked with dimethyloldihydroxyethyleneurea (DMDHEU), formaldehyde (FA), and both DMDHEU and FA for preparing PVA/polyamidoxime (PAO) chelating fibers with elevated water‐resistance. Effects of different crosslinking systems on the properties of the composite amidoxime chelating fibers have been investigated. Results show that FA treatment can effectively increase the water‐resistance of composite fiber, but would dramatically decrease the adsorption properties of composite fiber. Conversely, DMDHEU treatment has inferior effects on the water‐resistance of the composite fiber, but would impressively increase the adsorption properties of composite fiber. The composite fiber treated with both DMDHEU and FA could reach good overall performances (water contact angle: 94.83°; soft point in hot water: 116 °C; breaking strength in dry condition: 441.80 MPa; the maximum adsorption capacities of precious ions: 1207.66 and 653.59 mg Ag g^?1). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44965.     

Electrospun nanofiber polyacrylonitrile coated separators to suppress the shuttle effect for long-life lithium–sulfur battery

Polymeric coating on the separator with effective polysulfides diffusion inhibition can provide intimate contact between intermediate polysulfides and conductive layer of separator for high-energy lithium–sulfur (Li–S) batteries. Herein, polyacrylonitrile–poly(1,5-diaminoanthraquinone) (PAN/PDAAQ) and PAN-potassium functionalized graphene (PAN/K-FGF) nanofibers are synthesized via electrospinning method and act as effective separators for Li–S batteries to minimize polysulfides diffusion toward the anode. PAN/K-FGF coated separator shows capacity retention of 768 mAh g⁻¹ after 100 cycles at 1C. The capacity maintains at 419 mAh g⁻¹ after 500 cycles. PAN/PDAAQ nanofibers are coated on glass fiber separator functions as physical and chemical barrier for polysulfides diffusion. Therefore, the cell with PAN/PDAAQ coating on the separator demonstrates capacity retention of 881 mAh g⁻¹ after 100 cycles at 1C and small capacity decay rate of 0.11% per cycle resulted in 800 cycles at 1C. PAN/PDAAQ could define as an ideal separator material for Li–S batteries. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48606.     

Preparation of hydrazine‐modified polyacrylonitrile nanofibers for the extraction of metal ions from aqueous media

Polyacrylonitrile (PAN) nanofibers (prepared by an electrospinning technique) were chemically modified with hydrazine. The Fourier transform infrared spectrum of the hydrazine‐modified polyacrylonitrile (HM–PAN) showed that the intensity of the nitrile peak (2250 cm⁻¹) of the PAN nanofibers decreased significantly after treatment with hydrazine. New peaks at about 3400–3100 cm⁻¹ (N H stretching vibration) also appeared, which showed that the hydrazine was chemically attached to the PAN nanofibers. HM–PAN had a smooth surface (as confirmed by a scanning electron microscopy) and was a suitable material for the adsorption of metal ions from aqueous solutions. The adsorption capacity of HM–PAN increased as the adsorption time increased and became constant at 114 and 217 mg/g for Cu(II) and Pb(II) ions, respectively, after 24 h. In addition, more than 90% of the adsorbed Cu(II) and Pb(II) ions were recovered in a 1M HNO₃ solution after 1 h. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and adsorption mechanism of polyvinyl alcohol/graphene oxide-sodium alginate nanocomposite hydrogel with high Pb(II) adsorption capacity

A series of polyvinyl alcohol (PVA)/graphene oxide (GO)-sodium alginate (SA) nanocomposite hydrogel beads were prepared through in situ crosslinking for Pb²⁺ removal. It was found that PVA and SA molecules were intercalated into GO layers through hydrogen bonding interactions, leading to the destruction of orderly structure of GO, while GO uniformly distributed in PVA matrix. With increasing PVA solution concentration, the hydrogel beads became more regular, a large number of polygonal pores with thin walls and open pores formed, the average pore size decreased, and the dense network structure formed. Meanwhile, the permeability of the composite hydrogel decreased, leading to the decline of Pb²⁺ adsorption capacity of the composite hydrogel. With increasing GO content, the ballability of the hydrogel beads was weakened, the pore size increased, and relatively loose network structure formed, resulting in an increase in permeability and Pb²⁺ adsorption capacity of the hydrogel, reaching up to 279.43 mg g⁻¹. Moreover, the composite hydrogel presented relatively good reusability for Pb²⁺ removal. The adsorption mechanism was explored and showed that the adsorption system of the composite hydrogel belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model for Pb²⁺ removal, which might be mono-layer chemical adsorption. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47318.     

Removal of acid dyes from aqueous solutions using a new eco-friendly nanocomposite of CoFe2O4 modified with Tragacanth gum

A new composite of cobalt ferrite and Tragacanth gum (TG) was developed and applied to remove methyl orange (MO) and methyl red (MR) from wastewater samples simultaneously. The results showed that the presence of TG improved the capability of cobalt ferrite in removing the pollutants in considerably. The adsorption properties and surface morphology of the sorbent were compared with those of bare cobalt ferrite, TG, and TG grafted copolymer. The properties of the adsorbents were studied using Fourier transform infrared, scanning electron microscope, transmission electron microscope, X-ray diffraction, and vibrating sample magnetometer, and the effects of different factors such as the amount of the adsorbent, sample pH, contact time, and initial concentration were also evaluated and optimized through response surface methodology using central composite design. The optimal conditions for the adsorption of both dyes (100 mg L⁻¹ as the concentration) were pH of 4.0, adsorbent dose of 0.5 mg mL⁻¹, and contact time of 110 min. Under these conditions, the MO and MR adsorption processes were found to follow pseudo-second-order kinetic model. The equilibrium adsorption data followed the Langmuir isotherm and the highest adsorption capacity was determined to be 336 and 387 mg g⁻¹ for MO and MR, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48605.     

Thermodynamic and kinetic studies of crystal violet dye adsorption with poly(methyl methacrylate)–graphene oxide and poly(methyl methacrylate)–graphene oxide–zinc oxide nanocomposites

We successfully prepared poly(methyl methacrylate) (PMMA)–graphene oxide (GO) and PMMA–GO–zinc oxide (ZnO) nanocomposites and characterized them using different techniques. The adsorption performances of the as-prepared composites were investigated for crystal violet (CV) dye removal. The contact time as a main factor affecting the adsorption process by adsorbents was studied. Because the adsorption capacity value for CV was found to show no extensive changes after 35 min, 35 min was selected as the best contact time for our system. The adsorption results revealed that the best capacity of CV adsorption onto the PMMA–GO and PMMA–GO–ZnO nanocomposites occurred at pH 12 and 298 K. The respective entropies (−0.208 and −0.168 kJ mol⁻¹ K⁻¹) and enthalpies (−72.86 kJ/mol, and −55.54 kJ/mol) for PMMA–GO and PMMA–GO–ZnO and Gibbs energy revealed that the process of adsorption was exothermic. In addition, the Elovich, pseudo-first-order, intraparticle diffusion, and pseudo-second-order (four types) models were applied to our kinetic study. Our results indicate that CV adsorption onto PMMA–GO and PMMA–GO–ZnO was good with the pseudo-second-order (type 1) and pseudo-first-order models because of the low χ² value and the high correlation coefficient value. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47495.     

Larger pore volume tetraphenyladamantane-based hybrid porous polymers: Facile Friedel–Crafts preparation,CO2 capture,and Rhodamine B removal properties

Synthesis of covalently linked porous polymers with high surface area and larger pore volume for two or more task-specific functionalities is always a big challenge. In this article, the facile Friedel–Crafts reaction is employed to construct the hierarchical hybrid porous polymers (HPPs) from tetraphenyladamantane and octavinylsilsesquioxane. The resulting polymers, HPP-1 to HPP-3, possessed the surface areas from 1356 to 1511 m² g⁻¹, and the pore volumes from 2.05 to 2.67 cm³ g⁻¹. All these polymers feature micropores, mesopores, and macropores in nature. The resultant polymers exhibit high CO₂ adsorption capacity up to 2.0 mmol g⁻¹ (8.82 wt %), at 273 K, 1.0 bar, and the maximum Rhodamine B (RB) sorption capacity of 653.6 mg g⁻¹. To illustrate the adsorption process, the effects of factors, contact time, initial concentration, temperature, and pH value on the adsorption capacity of RB were studied. The adsorption equilibrium data displayed a better fitting to the Langmuir isotherm model than the Freundlich model and the adsorption kinetics fitted well with the pseudo-second-order kinetic model. The recycle experiments displayed that the capacity recovery was still higher than 95% after four cycles. Theses polymers are promising to be the adsorbents for capturing CO₂ and removing RB. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 136, 48572.     

Stability constants of amidoximated chitosan‐g‐poly(acrylonitrile) copolymer for heavy metal ions

Amidoximated chitosan‐g‐poly(acrylonitrile) (PAN) copolymer was prepared by a reaction between hydroxylamine and cyano group in chitosan‐g‐PAN copolymer prepared by grafting PAN onto crosslinked chitosan with epychlorohydrine. The adsorption and desorption capacities for heavy metal ions were measured under various conditions. The adsorption capacity of amidoximated chitosan‐g‐PAN copolymer increased with increasing pH values, and was increased for Cu²⁺ and Pb²⁺ but a little decreased for Zn²⁺ and Cd²⁺ with increasing PAN grafting percentage in amidoximated chitosan‐g‐PAN copolymer. In addition, desorption capacity for all metal ions was increased with increasing pH values in contrast to the adsorption results. Stability constants of amidoximated chitosan‐g‐PAN copolymer were higher for Cu²⁺ and Pb²⁺ but lower for Zn²⁺ and Cd²⁺ than those of crosslinked chitosan. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 469–476, 1999     

Efficient adsorptive extraction materials by surface protein-imprinted polymer over silica gel for selective recognition/separation of human serum albumin from urine

In this study, we report the development of adsorptive extraction materials by surface protein-imprinted polymers (MIPs) over silica gel for selective recognition/separation of human serum albumin (HSA) from urine. The HSA-imprinted polymers prepared on silica particle had at interface between the silica gel and different MIPs greatly produced enrichment for the binding of protein from the urine. The solid-phase extraction of the optimized polymer layer was prepared by copolymerization of methacrylic acid (MAA), acrylamide (AAm), and dimethylaminoethylmethacrylate (DMAEMA) and a crosslinker methylenebisacrylamide (MBA) at the mole ratio of 1:158:88 (T:M:C) and showed moderate affinity (<10⁴ order M⁻¹) toward target protein HSA and selectivity. Four analogues, egg white albumin (EWA), bovine serum albumin (BSA), lysozyme (Lyz), and creatinine (Cre) were selected to study the binding efficiency of MIPs in single and binary protein solutions. We studied the influence on recognition ability for HSA and found that prepolymer mixture and matrix flexibility of the optimized thin polymer layer (35 ± 10 nm) on the submicrosilica particles. The high-binding affinity (Q_MIP, 86.7 mg g⁻¹) and fast kinetics (180 min) were observed for this synthesized HSA-MIP when compared with other reported HSA-MIPs in surface imprinting (5.9 and 11.3 mg g⁻¹) and epitope surface imprinting (46.6 mg g⁻¹) methods. We demonstrated the application in real and synthetic urine samples that the approach allowed the efficient adsorption of HSA in real urine (129.48 mg g⁻¹) is almost double to the binding of HSA in synthetic urine (67.84 mg g⁻¹). Apart from this, only minor interference of Cre (2.74 mg g⁻¹) was observed, eventhough Cre is the final metabolite in urine. These adsorptive submicrosilica materials have potential in the pharmaceutical industry and clinical analysis applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46894.     

A chelating cellulose adsorbent for the removal of Cu(II) from aqueous solutions

Regenerated cellulose wood pulp was grafted with the vinyl monomer glycidyl methacrylate (GMA) using ceric ammonium nitrate as initiator and was further fuctionalised with imidazole to produce a novel adsorbent material, cellulose‐g‐GMA‐imidazole. All cellulose, grafted cellulose and functionalized cellulose grafts were physically and chemically characterized using a number of analytical techniques, including elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, and scanning electron microscopy. The cellulose‐g‐GMA material was found to contain 1.75 mmol g^?1 epoxy groups. These epoxy groups permitted introduction of metal binding functionality to produce the cellulose‐g‐GMA‐imidazole final product. Following characterization, a series of adsorption studies were carried out on the cellulose‐g‐GMA‐imidazole to assess its capacity in the removal of Cu²⁺ ions from solution. Cellulose‐g‐GMA‐imidazole sorbent showed an uptake of ～70 mg g^?1 of copper from aqueous solution. The adsorption process is best described by the Langmuir model of adsorption, and the thermodynamics of the process suggest that the binding process is mildly exothermic. The kinetics of the adsorption process indicated that copper uptake occurred within 30 min and that pseudo‐second‐order kinetics best describe the overall process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006     

Graft polymerization of acrylonitrile onto wheat straw

Acrylonitrile was graft polymerized onto ground, water-washed wheat straw using Fe²⁺-H₂O₂ as initiator. Reaction conditions were selected to minimize homopolymer formation and maximize the amount of polyacrylonitrile (PAN) grafted to straw. Polymerizations typically yielded straw-g-PAN containing 30–35% PAN. A two-step fractionation scheme was developed for determining the relative amounts of PAN grafted to cellulose, hemicellulose, and lignin. This scheme involved (1) delignification of straw-g-PAN with sodium chlorite followed by removal of lignin-grafted PAN by extraction with dimethylformamide (DMF), and (2) hydrolysis of the hemicellulose component with 1 N trifluoroacetic acid followed by DMF extraction of hemicellulose-grafted PAN. Product remaining after these two treatments was assumed to be cellulose-g-PAN. When relative amounts of PAN grafted to cellulose, hemicellulose, and lignin were compared with relative percentages of these components present in wheat straw, the percentage of total PAN grafted to lignin was less than its relative percentage in straw, whereas that grafted to hemicellulose was considerably more. Although the use of Ce⁴⁺ as initiator gave little or no polymer with whole, water-washed straw, grafted polymerization occurred when delignified straw was used as substrate. Relative amounts of PAN grafted to cellulose and hemicellulose were not greatly different from those observed with Fe²⁺-H₂O₂ initiation onto whole straw.     

Electrospun melamine-blended activated carbon nanofibers for enhanced control of indoor CO2

Electrospun carbon nanofibers were activated with melamine–polyacrylonitrile [melamine-blended carbon nanofibers (MACNFs)] for use as a fibrous adsorbent for indoor CO₂ removal. Although, melamine doping was intended solely to incorporate basic nitrogen functionalities on the nanofibers, it also shortened fabrication time, conserving time, and energy cost. The specific surface area and microporosity of the fibers were enhanced from 412 m² g⁻¹ and 0.1646 cm³ g⁻¹ to 547 m² g⁻¹ and 0.220 cm³ g⁻¹, respectively, upon final CO₂ activation of the nanofibers. With the chemical properties, we observed significant tethering of pyridine functionality. The sample, MACNF-7 (10 mL of polymer solution doped with 0.7 g of melamine), provided the optimum melamine doping condition to achieve the highest CO₂ adsorption capacity of 3.15 mmol g⁻¹. The adsorption performance was based on simultaneous improvement in microporosity (physical) and surface basicity (chemical) properties of the adsorbent. However, in a binary mixture with nitrogen, the selective adsorption of CO₂ showed the predominance of the improved surface basicity over microporosity. The highest CO₂ selective capture (1.22 mmol g⁻¹) was occurred for a CO₂:N₂ ratio of 0.15:0.85, with a selectivity of 58.19 at 273 K. In a regeneration test, stable and robust performance was achieved more than five cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47747.