Recyclability Research Articles

One-pot route to synthesize HNTs@PVDF membrane for rapid and effective separation of emulsion-oil and dyes from waste water.

Water-purification membranes with high water flux, excellent recycling ability, good anti-fouling property, wide range for different oil/water emulsions separation, and strong water-soluble dyes removal ability are highly desirable for water purification but still a challenge to be realized. In this work, we show a simple method to address this challenge, in which halloysite nanotubes (HNTs) have been decorated on the poly (vinylidene fluoride) (PVDF) membrane surface through one-pot method via the aid of KH550 and dopamine. The HNTs@PVDF composite membrane exhibits superhydrophilic and under-water superoleophobic performance. In addition, our membrane can separate wide oil/water emulsions (including surfactant-stabilized and surfactant-free emulsions) from wastewater with high efficiency (>99.65%), outstanding recycle ability with good flux recovery rate (FRR > 95%) and good anti-fouling performance (the underwater oil contact angle (OCA) is 155.8 ± 1.8° with low oil adhesion) and high water flux (7994 ± 150 L m-2 h-1). Interestingly, our membrane also removes different water-soluble dyes (e.g., Congo red, methylene blue, and rhodamine B) from waste water by simply filtering. Those outstanding properties make our membrane hold great potential applications in real-world water purification and environmental protection.

Crystal violet dye removal using crosslinked grafted xanthan gum

As water is the most important source for survival for all individuals around the world, water pollution via synthetic toxic dyes and microorganisms is considered as a serious worldwide environmental problem. The present work aimed to synthesize crosslinked grafted xanthan gum (XG) films with poly (N-vinyl imidazole), PVI, for both removing crystal violet (CV) dye and inhibiting Escherichia coli (E. coli) growth. XG-grafted-PVI was prepared using potassium persulfate as an initiator to give different percentage of graft yield and using N, N′-methylene bisacrylamide (MBA) as a crosslinking agent. The structure of grafted XG films was elucidated via various analysis tools including FTIR, XRD, FE-SEM and EDX. Results of CV adsorption studies showed that maximum CV removal was 99.7% (625 mgg−1) which was achieved at: 95% GY, 2.5% MBA, 40 mg of adsorbent into 50 mL of 500 mgL−1 CV dye solution, pH 7, temperature (30 °C) and adsorption time (7 h). Also, results fitted well with Langmuir isotherm model. Moreover, pseudo-first order and intraparticle diffusion model participated in the mechanism of CV adsorption on grafted XG surface, in addition to its efficient recycling ability. Furthermore, antibacterial activities results of crosslinked grafted XG revealed their high inhibiting effect for E.coli growth.

β-Cyclodextrin/Quaternary Ammonium Salt as an Efficient Catalyst System for Chemical Fixation of CO2

The environmental friendly biomaterial β-cyclodextrin (β-CD) was used for the synthesis of cyclic carbonates from CO₂ with epoxides in the presence of quaternary ammonium salts as co-catalyst. The factors affecting the activity of this binary catalyst system, such as reaction temperature, time, CO₂ pressure and the mole ratio of reactants, were investigated systematically. The excellent yield of cyclic carbonate (100%) was obtained at 130 °C, 3 MPa after 5 h with the catalyst system of β-CD/tetrabutylammonium bromine (TBABr). The catalyst system of β-CD/TBABr can also be applied to a wide substrates of epoxides with good to excellent yield and high selectivity (>99%). Recyclable ability of β-CD/TBABr can also be detected and there was no significant decline in activity after five recycles. Finally, reaction mechanism was proposed based on the reaction results and literatures.

Combination of La-TiO2 and activated carbon fiber for degradation of toxic organic pollutants under the visible light

La-TiO2 combined with activated carbon fiber (ACF) was prepared and used for removal of toxic organic pollutants including bisphenol A (BPA) and 2-chlorophenol (2-CP) from aqueous solution. Characterization results showed that La loaded on TiO2 has narrowed bandgap energy of TiO2 and extended adsorbing light in the range of 400–600 nm. The photocatalytic degradation of BPA and 2-CP by various influencing factors such as solution pH, initial concentration of pollutants, reaction time and recycle ability of material were investigated. The results meant that removal of BPA and 2-CP highly dependent on the initial concentration and solution pH. At pH 9.0, and 10 mg/L of initial concentration, the photocatalytic efficiency of La-TiO2/ACF for BPA and 2-CP was achieved 85.7 and 96.3% within 60 min under visible light irradiation, respectively. Afterwards, the photocatalytic properties of recycling and the generated intermediates products from the photocatalytic degradation of BPA and 2-CP were also evaluated.

Fabrication of Novel Ag/AgBr/Cs2Nb4O11 Ternary Composite for Visible-Light Driven Photocatalysis

In recent years, tuning the structural and photocatalytic properties of semiconductors with the introduction of Ag nanoparticles through their well-known surface plasmon resonance (SPR) effect has gained much interest in the field of environmental applications. Herein, a new plasmonic Ag/AgBr/Cs2Nb4O11 composite was successfully fabricated by applying a visible-light reduction method using the pre-prepared AgBr/Cs2Nb4O11 and Cs2Nb4O11 catalysts synthesized by sonication-assisted deposition precipitation and solid-state methods, respectively. The synthesized samples were characterized by FESEM/EDX/EDS elemental mapping, TEM/HRTEM, XRD, N2–sorption, UV–Vis DRS, PL and XPS techniques. Photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation was performed for the composite and well compared with the counter parts. In contrast to parent Cs2Nb4O11, the AgBr/Cs2Nb4O11 and Ag/AgBr/Cs2Nb4O11 composites exhibited extended absorption edges and improved photoabsorption in the visible region, which are discretely due to the intrinsic absorption of AgBr and SPR effect of metallic Ag nanoparticles. The PL results revealed that the ternary composite showed a better separation of photo-generated charge carriers. Amongst the samples, the Ag/AgBr/Cs2Nb4O11 composite exhibited the highest photoactivity, degrading 97% of RhB after 60 min of visible-light irradiation. The correlation between the structural properties and the origin of the enhanced photocatalytic activity of the Ag/AgBr/Cs2Nb4O11 composite is discussed in detail, and possible reaction mechanism is proposed. Moreover, the good recycling ability (up to 5 cycles) suggests that the Ag/AgBr/Cs2Nb4O11 composite can be exploited successfully in the wastewater treatment.

0D/2D Z-scheme heterojunctions of g-C3N4 quantum dots/ZnO nanosheets as a highly efficient visible-light photocatalyst

Constructing Z-scheme heterojunctions comprising of constituents with different dimensionality is an effective strategy to spatially separate electron and hole. To fully utilize the synergistic coupling effect of dimensionality, herein, we first immobilize g-C3N4 quantum dots (CNQDs) onto ZnO nanosheets with oxygen vacancies (OV-ZnO) to create a 0D/2D hybrid via a facile and cost-effective approach. The CNQDs/OV-ZnO heterojunctions display CNQDs content-dependent performance in visible-light photocatalytic activity. The optimal CNQDs/OV-ZnO heterojunction exhibits high photocatalytic activity for degradation of methyl blue and bisphenol A, where the kinetic constant is 11.4 and 32.5 fold of pure OV-ZnO, respectively. Photoluminescence, electrochemical impedance spectroscopy and photocurrent verify that the photogenerated electron-hole pairs in this 0D/2D Z-scheme heterojunction have been effectively separated. The enhanced photocatalytic activity could be attributed to the synergistic effect of efficient Z-scheme charge separation, highly dispersed 0D CNQDs, coordinating sites of 2D OV-ZnO nanosheets and the strong coupling between them. In addition, the 3D flower-like structure constructed by 2D nanosheets greatly inhibits the leaching and loss of the photocatalyst in the recycling process, and ensures the high recycling ability of CNQDs/OV-ZnO. This work paves the way toward designing novel visible-light 0D/2D photocatalysts in the application of solar energy.

New Nanocatalyst for Vocs Removal from Recycled Plastics

Graphene-based supports for catalysis are currently attracting great attention due to their unique and advantageous properties. However, their application in gas-phase thermal catalysis including catalytic oxidation of volatile organic compounds (VOCs) remains a theoretical research stage. Here, a new use of a graphene-based material as a catalyst support for 2-ethyl-1-hexanol (2-EH) oxidation was developed. The design of CuO/Ag catalyst incorporated into the porous structure of reduced graphene oxide aerogel (rGOA) exposes more active surface for catalysis. Therefore, this hybrid design enables great performance enhancements in 2-EH oxidation, displaying a ( 99% removal at a temperature of 350 °C. Highly stable performance and excellent recycling ability are observed over CuO/Ag-rGOA dual function adsorbent-catalyst material. The high activity and good stability of CuO/Ag-rGOA make it an excellent candidate for the development of 2-EH oxidation catalysis.

Performance Evaluation of Modified Black Clay as a Heterogeneous Fenton Catalyst on Decolorization of Azure B Dye: Kinetic Study and Cost Evaluation

Black clay (BC) was used as a catalyst for the decolorization of Azure B dye by Fenton process. BC was modified by acid, alkali, distilled water, and calcination to check their changes in characterization and efficiency on decolorization of Azure B. Among three modified catalysts, maximum decolorization was obtained by acid-modified BC (AMBC) catalyst due to the highest removal of impurities, comparatively. The characterization of AMBC was done by Fourier-transform infrared spectroscopy and X-ray diffraction spectroscopy which show the presence of metal ion. The BET surface area, pore volume, pore size, and density of AMBC were calculated to be 79.402 m2/g, 0.0608 m3/g, 0.00306 nm, and 16 g/cm3, respectively. The highest decolorization of 97.59% was achieved only in 10 min using AMBC at optimized calcination of 100 °C and 3 h of aging. AMBC was considered as the main catalyst for optimizing the different process parameters. Optimized conditions were obtained: pH 2, 0.2 mL of H2O2, catalyst dose 0.3 g, room temperature (30 °C), and stirring speed 400 r/min. The catalyst has showed excellent stability and reusability. It could remove more than 85% of color even after four cycles of run and less than negligible leaching of iron. AMBC has good recycling ability among other modified catalysts. To check the selectivity of catalyst, different dyes such as Congo red and mixed dye (mixture of Azure B and Congo red) decolorization were studied. In the present work, kinetic study was also carried out and a three-stage decolorization process was found.

Porous Aromatic Framework Modified Electrospun Fiber Membrane as a Highly Efficient and Reusable Adsorbent for Pharmaceuticals and Personal Care Products Removal.

Water contamination by emerging organic pollutants, such as pharmaceuticals and personal care products (PPCPs), is becoming more and more serious. Porous aromatic frameworks (PAFs) are considered as promising adsorbents to remove the PPCPs. To overcome the limitation of PAFs in their powder forms for large-scale applications, herein, we proposed a strategy to covalently anchor PAFs onto electrospun polymer fiber membranes. Polyaniline (PANI) played the role of aromatic seed layer, which was coated on the electrospun polyacrylonitrile (PAN) fiber membrane first. Then, PAF-45 modification was in situ synthesized in the presence of the PANI-coated electrospun PAN fiber membrane. This study could make the PAF-based materials be handled more easily and improve the surface area of electrospun fiber membrane. The obtained composite adsorbent (PAF-45-PP FM) was applied for the adsorption of three PPCPs: ibuprofen (IBPF), chloroxylenol (CLXN), and N, N-diethyl-meta-toluamide (DEET), which exhibited high adsorption capacity and good recycling ability. According to the Langmuir model, the maximum adsorption capacities of PAF-45-PP FM toward IBPF, CLXN and DEET were 613.50, 429.18, and 384.61 mg/g, respectively. In addition, after ten adsorption-desorption cycles, the adsorption capacities toward the three PPCPs decreased slightly. Through an adsorption comparison test, the adsorption capacity of PAF-45-PP FM almost attributed to the loading PAF-45. The adsorption mechanism analysis illustrated that there were pore capture, hydrophobic interaction and π-π interaction between PPCPs and PAF-45-PP FM. Therefore, the PAF-45-PP FM can be potential adsorbents to purify water contaminated with PPCPs.

Alcohol acylation by acetic acid over novel lanthanide-grafted catalytic systems

In the present study, novel heterogeneous analogues of lanthanide triflates [trifluoromethanesulfonates; Ln(SO3CF3)3 or Ln(OTf)3] were proposed as acidic catalysts for fine organic synthesis. A series of supported Ln3+ and Ln3+SFP systems (SFP—sulfonated fluoropolymer; Ln = La, Pr, Eu, Tm, Yb) were synthesized and tested in the acylation of alcohols with acetic acid. The synthesized systems were found to be stable under the reaction conditions and showed the ability for catalytic recycling. It was shown that high texture characteristics of the SFP/CNF samples have also a great impact on the efficiency of the catalytic process. For example, Ln3+SFP/CNF systems exhibit significantly higher catalytic activity if compare with the unsupported samples (Ln3+SFP) or the sample without sulfated fluoropolymer (CNF-SO3−Ln3+). It was found that Ln-composite contains blocks of SFP and thin SFP layer over the surface of CNF fibers. The lanthanide ions are evenly distributed within the polymer structure. Among the studied lanthanides, Yb-containing systems were found to be the most active one.

Porous Al2O3 plates prepared by combing foaming and gel-tape casting methods for efficient collection of oil from water

Absorbent materials are considered as the most effective way of dealing with oil spill accidents and the increasing industrial oily wastewater leakages. However, poor recycling ability and low efficiency limit their application. This paper presents a fabrication approach of porous Al2O3 plates (PAP), which combines foaming and gel-tape-casting methods. The plates, which had high bending strength (4.5 ± 0.2 MPa) and oil permeation (4.4 × 105 L·m−2·h−1·bar−1), absorbed various kinds of oils rapidly, with space utilization >98%, while the absorbed oil was readily collected by simply being poured out or gas blown. Furthermore, the plate markedly maintained its high separation efficiency, mechanical strength, and hydrophobic properties after 1000 absorption-blowing cycles, as well as after treatment in several harsh environments. The results suggest that this fast and simple ceramic plate preparation approach can be proposed for practical applications in technologies of collecting oils and organic solvents from water.

Urea Hydrolysis Over α-MnO2 Catalyst: Preparation, Characterizations and Influencing Factors

MnO2 was screened from various metal oxides and different crystal structures of MnO2 were prepared, which were used to hydrolyze urea process wastewater for energy conservation and environmental protection. The characterizations of XRD, SEM, Raman, FT-IR, XPS and H2-TPR were employed and the hydrolysis experiments were carried out, demonstrating that oxygen vacancy on the surface of MnO2 might be the catalytic activity source on urea hydrolysis. By optimizing reaction influencing factors, the residual urea concentration reduced to 1.61 mg/L over α-MnO2, far below the effluent standard. Meanwhile, the temperature of heterogeneous hydrolysis over α-MnO2 dropped drastically compared with that of thermal hydrolysis. Further, the kinetic parameters of hydrolysis were obtained over α-MnO2. And α-MnO2 also showed excellent recycling ability on the reused test.

Self-sintering of BOS Filter Cake for Improved Recyclability

Self-sintering of BOS Filter Cake for Improved Recyclability

Polymer anchored copper complex as an effective catalyst for photodegradation of organic dyes

Polymer anchored Cu(II) complex of 2-furylbenzimidazole was synthesized and characterized by elemental analysis, FT-IR, UV–vis/DRS, ESR spectroscopy techniques, magnetic moment measurements and thermogravimetric analysis. The photocatalytic activity of this complex was investigated towards photodegradation of organic dyes using H2O2 as an oxidant under UV irradiation. Influence of external factors such as pH, concentration of catalyst, dye and H2O2 and effect of dye structure on photodegradation efficiency of the catalyst have been examined. Its photodegradation activity is compared with the unsupported complex. The extent of mineralization of the dye has been evaluated by measuring the reduction in chemical oxygen demand (COD). Under the optimized reaction conditions, the catalyst displayed excellent recycling ability without any appreciable loss in its activity. Based on the results obtained, a tentative mechanism has been proposed.

Preparation of superhydrophobic and superoleophilic polylactic acid nonwoven filter for oil/Water separation

Superhydrophobic and superoleophilic surfaces exhibit a remarkable feature in separation of oil from oily wastewaters. In this work, a green superhydrophobic/ superoleophilic polylactic acid (PLA) nonwoven filter was prepared via a non-solvent assisted phase separation method. The results showed addition of non-solvent endowed the PLA nonwoven filter with typical micro/nano hierarchical structures and high porosity. Moreover, the resultant filter exhibited excellent oil/water separation efficiency more than 95% for various kinds of oils or solvents. In addition, the filter maintained favorable recycle ability even after 20 separation cycles. Therefore, the PLA nonwoven filter showed a high separation efficiency and an excellent recyclability, which is potential in rapid separation of oil/water mixture for ocean pollution cleanup.

Constructing magnetic and high-efficiency AgI/CuFe2O4 photocatalysts for inactivation of Escherichia coli and Staphylococcus aureus under visible light: Inactivation performance and mechanism analysis

Magnetic materials usually exhibit advanced performance in many areas for their easy separating and recycle ability. In this study, silver iodide/copper ferrite (AgI/CuFe2O4) catalysts with excellent magnetic property were successfully synthesized and characterized by a series of techniques. Two typical bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were applied to estimate the photocatalytic inactivation performance of obtained AgI/CuFe2O4 catalysts. Results revealed that the AgI/CuFe2O4 (12.5% AgI) composite could absolutely inactivate 3 × 109 CFU/mL E. coli and 2.7 × 108 CFU/mL S. aureus cells severally in 50 min and 40 min under visible light irradiation, which showed a much higher photo-disinfection activity than monomers. Transmission electron microscopy was used to study the biocidal action of this nanocatalyst, the results confirmed that the treated E. coli cells were damaged, the nanocatalyst permeated into cells and resulting in death of cells. Besides, it was found that the destruction of bacterial membrane together with substantial leaked potassium ion (K+) which caused by the photo-generated reactive species superoxide radical (O2−) and holes (h+) could be the direct disinfection principles. For a deep insight into practical applications, the influences of different catalyst concentrations and reaction pH were also taken into discussion in details. The overall results indicated the novel photocatalyst with strong redox capacity and outstanding reusability can be widely employed in bacteria elimination.

Baroplastics with Robust Mechanical Properties and Reserved Processability through Hydrogen-Bonded Interactions.

Conventional polymers are usually processed at a much higher temperature than room temperature, which inevitably leads to huge energy consumption and degradation of the polymers and thus a low recycling ability. Herein, we synthesized a poly( n-butyl acrylate)@polystyrene (PBA@PS) core-shell polymer to prepare a typical baroplastic (processible at room temperature). However, this type of baroplastics always has a low mechanical property. To solve this problem, in this work, we introduced hydrogen bonds into the matrix and successfully reinforced baroplastics for the first time. The hydrogen-bonded interaction was introduced by complexing PBA@PS with poly(acrylic acid) and poly(ethylene oxide). The results show that the reinforced baroplastics possessed notably enhanced mechanical properties and good processability. Their mechanical strength and modulus reached as high as 5.6 (by 73%) and 10 MPa (by 400%), respectively. Moreover, the baroplastics could be remolded many times at room temperature and, at the same time, still showed a higher tensile strength (10.5 MPa, 3.3 times that of the initial PBA@PS, which was never achieved in previous works), which resulted from the reversible hydrogen bonds and reserved orientation of molecular chains. Our work opened a new path to reinforce baroplastics and could widen their applications. Furthermore, not limited to the hydrogen bonds, more sacrificial bonds, such as ionic bonds, host-guest interactions, and metal-ligand coordination bonds, could be used to fabricate high-performance baroplastics.

Design of Nitrile Rubber with High Strength and Recycling Ability Based on Fe3+–Catechol Group Coordination

In this work, nitrile rubber (NBR) with high strength and recycling ability was designed based on the interaction between metal ions and ligands. Herein, we first epoxidized the nitrile rubber late...

Novel magnetic amine functionalized carbon nanotube/metal-organic framework nanocomposites: From green ultrasound-assisted synthesis to detailed selective pollutant removal modelling from binary systems.

Herein, magnetic amine functionalized carbon nanotube (NH2-CNT/Fe2O3)-zeolitic imidazolate framework-8 (ZIF-8) nanocomposites (NH2-CNT/Fe2O3/ZIF-8: NCFZ) with different amounts of NH2-CNT/Fe2O3 (5, 10, and 15 wt% denoted as NCFZ-5, NCFZ-10, and NCFZ-15) were synthesized. The synthesized nanomaterials including ZIF-8, Fe2O3, CNT/Fe2O3, NH2-CNT/Fe2O3, CNT/Fe2O3/ZIF-8, NCFZ-5, NCFZ-10, and NCFZ-15 were characterized using BET, TEM, XRD, SEM, FTIR, VSM and zeta potential. The synthesized nanomaterials were applied for selective removing cationic dyes (MG: Malachite Green and RhB: Rhodamine B) from a binary system. Response surface methodology (RSM) and artificial neural networks (ANN) were used for optimizing dye removal. The BET data showed that the surface area of nanocomposite (NH2-CNT/Fe2O3/ZIF-8: 1659 m2/g) was higher than that of pure ZIF-8 (1485 m2/g). Contaminant removal obeyed the Freundlich isotherm and pseudo-second order kinetic models. The optimum adsorption condition predicted by RSM was pH = 6, dye concentration = 25 mg/L, Dosage = 0.004 g and at time = 145 min. The outputs of ANN model well overlapped with the experimental data. The binary system dye removal data indicated the synthesized nanocomposite with recycling and regeneration ability could be used for treating wastewater.

Manufacturing and Flexural Characterization of Infusion-Reacted Thermoplastic Wind Turbine Blade Subcomponents

Reactive thermoplastics are advantageous for wind turbine blades because they are recyclable at end of life, have reduced manufacturing costs, and enable thermal joining and shaping. However, there are challenges with manufacturing wind components from these new materials. This work outlines the development of manufacturing processes for a thick glass fiber–reinforced acrylic thermoplastic resin wind turbine blade spar cap, with consideration given to effects of the exothermic curing reaction on thick composite parts. Comparative elastic properties of these infusible thermoplastic materials with epoxy thermoset materials, as well as thermoplastic coupon components, are also included. Based on the results of this study it is concluded that the thermoplastic resin system is a viable candidate for the manufacturing of wind turbine blades using vacuum-assisted resin transfer molding. Significant gains in energy savings are realized avoiding heated molds, ability for recycling, and providing an opportunity for utilizing thermal welding.