Recyclability Research Articles

Study on reversible hydrogen uptake and release of 1,2-dimethylindole as a new liquid organic hydrogen carrier

Indole derivatives have been considered as promising liquid organic hydrogen carriers (LOHCs) for onboard hydrogen storage applications. Here a new member of indole family, 1,2-dimethylindole (1,2-DMID), was reported as a potential liquid organic hydrogen carrier with a hydrogen storage content of 5.23 wt%, a meting point of 55 °C and a boiling point of 260 °C. Full hydrogenation and dehydrogenation of 1,2-DMID can be achieved with fast kinetics under mild conditions. The hydrogenation of 1,2-DMID followed the first order kinetics with an apparent activation energy of 85.1 kJ/mol. Dehydrogenation of fully hydrogenated product, octahydro-1,2-DMID was conducted over 5 wt% Pd/Al2O3 at 170–200 °C. The stored hydrogen can be completely released at 180 °C in 3 h and at 200 °C in 1 h. The energy barrier of dehydrogenation of octahydro-1,2-DMID was calculated to be 111.9 kJ/mol 3 times cycles of hydrogenation and dehydrogenation were employed to test the recycle ability of 1,2-DMID. The structures of intermediates were also discussed by means of Material Studio calculations.

Prodegradant Additives Effect onto Comercial Polyolefins

Fil: Vazquez, Yamila Victoria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Bahia Blanca. Planta Piloto de Ingenieria Quimica. Universidad Nacional del Sur. Planta Piloto de Ingenieria Quimica; Argentina. Universidad Nacional del Sur. Departamento de Ingenieria Quimica; Argentina

The comparative study of two reusable phosphotungstic acid salts/reduced graphene oxides composites with enhanced photocatalytic activity

In this work, two recyclable phosphotungstic acid salts/reduced graphene oxides were successfully prepared. The prepared samples were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), Raman spectroscopy, and photoluminescence spectroscopy (PL). The structure and catalytic performance of two composites were comparatively investigated, and the reduced graphene oxide mass ratios in K3[PW12O40]/reduced graphene oxide (denoted as KPW-RGO) and (NH4)3[PW12O40]/reduced graphene oxide (denoted as NH4PW-RGO) were optimized and their roles in them were explored. The results indicate that the Keggin structures of KPW and NH4PW are still kept after being anchored on the RGO surface, but their morphologies change a lot in composites. The photocatalytic activities of KPW-3RGO (0.01989min-1) are 5.42 times than that of KPW (0.00367min-1), and NH4PW-1RGO (0.0184min-1) is 2.26 times than that of NH4PW (0.00814min-1). The enhanced photocatalytic activity is mainly ascribed to photo-induced interfacial charge transfer on the heterojunction between RGO and NH4PW or KPW and strong adsorption ability of RGO towards MO. Moreover, NH4PW-1RGO and KPW-3RGO had much better photocatalytic activity, good recyclable ability, and stability compared to HPW-RGO, which cannot be recycled.

N-doped graphene confined Pt nanoparticles for efficient semi-hydrogenation of phenylacetylene

N-doped graphene (N-graphene) confined Pt nanoparticles (NPs) with core-shell structure supported on carbon nanotubes (CN@Pt/CNTs) are prepared by a facile two-step process. The obtained N-graphene nanoshell ranging from 2 to 4 graphene layers and the Pt NPs covered within N-graphene are uniformly dispersed on the CNTs. The as-prepared CN@Pt/CNTs exhibits much higher styrene selectivity and robust recycle ability in selective hydrogenation of phenylacetylene, compared with that of traditional CNTs supported Pt NPs (Pt/CNTs). DFT calculation reveals that the high styrene selectivity is derived from the confinement effect of N-graphene, which facilitates desorption of styrene from Pt NPs surface, avoiding the over hydrogenation of styrene to benzylethane. The present method paves a new way to design high selective Pt based hydrogenation catalyst.

Infrared induced repeatable self-healing and removability of mechanically enhanced graphene-epoxy flexible materials.

A repeatable self-healing epoxy composite mechanically enhanced by graphene nanosheets (GNS) was prepared from an epoxy monomer with Diels–Alder (DA) bonds, octanediol glycidyl ether (OGE) and polyether amine (D230). The GNS/epoxy composites, with a maximum tensile modulus of 14.52 ± 0.45 MPa and elongation at break more than 100%, could be healed several times under Infrared (IR) light with the healing efficiency as high as 90% through the molecule chain mobility and the rebonding of reversible DA bonds between furan and maleimide. Also, they displayed excellent recyclable ability by transforming into a soluble polymer, which offers a wide range of possibilities to produce epoxy flexible materials with healing and removable abilities.

Photothermal-Induced Self-Healable and Reconfigurable Shape Memory Bio-Based Elastomer with Recyclable Ability.

Photothermal-induced self-healable and shape memory materials have drawn much attention due to the rapidly growing technical applications and environmental requirements. As epoxy natural rubber (ENR) is a kind of bio-based elastomer with good mechanical properties, weather resistance, and air impermeability, it is of great significance to incorporate ENR with recyclable, photothermal-induced self-healable and shape memory properties. In this study, we report a simple method to cross-link ENR with dodecanedioic acids (DAs) through esterification reaction, and during the cross-linking process, a little aniline trimer (ACAT, a kind of oligoaniline) was added at the same time. Then, the ENR-DA-ACAT vitrimers that were covalently cross-linked with recyclable, self-healable, and multiple responsive properties were obtained, which also possessed various functions. As a result of the transesterification reactions at elevated temperatures, the ENR-based vitrimers possess the ability to be reprocessed and self-healed, and the mechanical properties could be maintained even after three consecutive breaking/mold pressing cycles. Besides, the vitrimer is also responsive to near-infrared (NIR) light and pH with the introduction of ACAT, and we also find that ACAT can be used as a catalyst to accelerate the transesterification reaction. Moreover, it is demonstrated that the ENR-DA-ACAT vitrimer could also be used to construct the reconfigurable shape memory polymer; the shape fixing ratio and shape recovery ratio are both above 95% in the reconfiguration process, and the multistage shape memory performance can also be achieved by NIR irradiation, which will potentially lead to a wide application for ENR in the field of actuators.

Plant polyphenol-inspired nano-engineering topological and chemical structures of commercial sponge surface for oils/organic solvents clean-up and recovery

In our study, plant polyphenol-inspired chemistry is explored to nano-engineer the topological and chemical structures of commercial melamine sponge surface for preparing superhydrophobic sponges. Briefly, tannic acid (TA, a typical plant polyphenol) is applied to induce the co-assembly of silica nanoparticles (SiO2) and silver ions (Ag+) to form SiO2@TA@Ag nanostructures on a melamine sponge surface. After further chemical fluorination, the superhydrophobic sponge with a “lotus leaf-mimic” surface is formed. Surface topological/chemical structures, superhydrophobic property and anti-combustion characteristics of the sponge are examined by a series of characterization techniques, including scanning electron microscopy, X-ray photoelectron spectroscopy, water contact angle measurements, combustion/heating test, etc. The superhydrophobic sponge presents an adsorption capacity of 69–153 times of its own weight toward various oils/organic solvents, and exhibits excellent recycling ability evidenced by over 100-cycled uses. Continuous oil/water separation apparatus is also set up through equipping the superhydrophobic sponge on a peristaltic pump, realizing the clean-up of oils and organic solvents from water continuously. Together with the facile, easy-to-scale-up and substrate non-selective features of plant polyphenol-inspired chemistry, the superhydrophobic sponge and the surface nano-engineering method would hold great promise for the effective treatment of oil spillages and organic discharges, achieving high sustainability to energy and environment.

Synthesis of highly dispersed ultra-small cobalt nanoparticles within the cage-type mesopores of 3D cubic mesoporous silica via double agent reduction method for catalytic hydrogen generation

Ultra-small cobalt nanoparticles (NPs) are successfully confined within the mesopores of cubic mesoporous silica KIT-6 via a facile chemical reduction process using double reducing agents sodium borohydride (NaBH4) and ammonia borane (NH3BH3, AB). When the Co NPs embedded KIT-6 catalysts are used as catalysts for generation of hydrogen from hydrolysis of NH3BH3 a superior turnover frequency (TOF) of 20.05 molH2molCo-1min-1 and lower activation energy of 32.6 kJ mol−1, better than most of the Co-based catalysts, are achieved. The higher catalytic activity is mainly attributed to the ultra-small size (2.5 nm) of Co NPs and uniform dispersion of Co NPs in the mesopores of KIT-6. Co NPs are also prepared using KIT-6 as the support with another two synthesis routes, namely, single reducing agent NaBH4 and thermal reduction method for comparative study. However, the resulting Co NPs are much larger in size and hence have less catalytic activities. The Co NPs are synthesized within the hexagonal mesopores of SBA-15 as well using double reducing agents in order to study the effect of the pore structure of the support on hydrogen generation. KIT-6 supported Co NPs can produce hydrogen much faster than the SBA-15 supported Co NPs as the 3D interconnected porous structure of KIT-6 allows homogenous transportation and easy diffusion of NH3BH3 molecules to the active sites. The Co NPs in KIT-6 exhibits good recycle ability up to 5 cycles, and the catalyst can be recovered economically from the aqueous solution due to its magnetic nature.

ZnO/Ag–Ag2O microstructures for high-performance photocatalytic degradation of organic pollutants

Organic pollutants cause serious impacts on environment. A novel method to synthesize ZnO/Ag–Ag2O microstructures was developed for organic pollutant photocatalytic degradation. The 3D pompon-like Zn(OH)1.68(SO4)0.16·0.58H2O microspheres were firstly synthesized in a creative way by combining reaction in ethanol/water mixing layer and room-temperature self-assembly together. The length of nanosheets on Zn(OH)1.68(SO4)0.16·0.58H2O microspheres was controlled from ~ 0.8 to ~ 4.4 μm successfully. The method reduced both the processing temperature and reaction time compared with conventional ripening, which shortened catalysts’ production cycle, reduced production cost and simplified production condition. It holds great potential for industrial application. As traditional nanocatalysts are not easy to recycle and the residual nanocatalysts are also potential danger to the environment, our microsized ZnO/Ag–Ag2O photocatalysts inherit advantages of both nanoparticles and microspheres with enhanced removal efficiency and excellent recycle ability. Ag–Ag2O nanoparticles in ZnO/Ag–Ag2O microstructures were used to enhance the photocatalytic performance. 83.2% and 96.3% degradation efficiencies of Congo red were achieved by pure ZnO and ZnO/Ag–Ag2O microstructures after 80 min irradiation by UV light. 78.2% and 95.6% degradation efficiencies of methylene blue were achieved by pure ZnO and ZnO/Ag–Ag2O after 40 min under UV radiation. The degradation rate constants by ZnO/Ag–Ag2O microstructures are 0.04056 min−1 for Congo red and 0.07629 min−1 for methylene blue respectively. The ZnO/Ag–Ag2O photocatalyst showed excellent stability and reusability, since it was reused at least 5 times without any extra treatment. The ZnO/Ag–Ag2O microstructures may hold potential for organic pollutant treatments.

Synthesis of CeO2-modified activated carbon spheres by grafting and coordinating reactions for elemental mercury removal

Series of resin-based activated carbon spheres with well-dispersed CeO2 particles inside and high surface area were successfully prepared by the grafting of MMA and coordinating reactions of cerium(III) nitrate salt and steam activation. N2 adsorption isotherms, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction-meter and X-ray photoelectron spectroscopy were applied to study the textural and surface characteristics of the obtained activated carbon spheres, and the Hg0 removal performances were evaluated in a fixed bed reactor. The experimental results indicated that pore structure, surface chemical properties and Hg0 removal ability of activated carbon spheres were observably improved after the modification of grafting and coordinating reactions. The optimal cerium(III) nitrate loading value, reaction temperature and O2 content were 7%, 150 °C and 5%, respectively. Moreover, SO2 showed an obvious inhibitory effect on the Hg0 removal efficiency in the absence of O2, while it facilitated the Hg0 removal in the presence of O2. Nitrogen monoxide promoted the Hg0 removal with or without O2, while water vapor inhibited the Hg0 removal over ACS-M-7%Ce. In addition, both of stable removal performance and excellent recycling ability were shown for ACS-M-7%Ce in ten cycles. The Hg0 removal mechanism analysis indicated that introduced CeO2 significantly promoted the Hg0 removal ability of ACS-M-7%Ce by generating the active species (such as C=O or C–O) and the lattice oxygen through the Ce4+/Ce3+ redox couple, and catalytically oxidized Hg0 into HgO.

Self-templated synthesis of CoS2 hollow polyhedron with superior performance for removal of dye and heavy metal ion

Nanomaterials with hollow structures have been the focus of attention in recent years because of their widespread applications. In this article, we successfully developed an effective method to synthesize polyhedral CoS2 hollow nanostructure using ZIF-67 as the sacrificial template. When assessed as the adsorbents for fluorescein sodium and Pb(II) removal, the adsorption isotherm show a good fit with the Langmuir model, with the maximum adsorption capacities of 289 and 758 mg g−1, respectively. In addition, the as-prepared CoS2 also has a good recycling ability in the removal of fluorescein sodium dye, and the adsorption efficiency remains 98% after the four cycles. The superior performance for adsorption of dye and heavy metal ion make the polyhedral CoS2 hollow nanostructure have potential applications in water treatment.

Hydrophilic polyethylenimine modified magnetic graphene oxide composite as an efficient support for dextranase immobilization with improved stability and recyclable performance

Development of appropriate support for enzyme immobilization with approving loading capacity, stability and recyclable performance is a significant topic in enzyme chemistry. In this study, the hydrophilic polyethylenimine (PEI) modified magnetic graphene oxide (GO) composite (Fe3O4@PDA@GO-PEI) was fabricated and acted as an efficient solid support for the immobilization of dextranase to improve the stability and recyclable performance. The GO nanosheet component not only provided abundant binding sites for decorating PEI molecules and further increasing the loading capacity of immobilized dextranase, but also acted as a soft matrix for enhancing the stability of immobilized dextranase. In addition, in combination of the unique magnetic separation property, the recyclable ability of immobilized dextranase was further improved. The loading amount of immobilized dextranase on as-developed Fe3O4@PDA@GO-PEI was determined to be 305.1 mg g−1, which was 1.61 times that on the Fe3O4@PDA-PEI without GO component. Moreover, the as-developed Fe3O4@PDA@GO-PEI-dextranase exhibited high immobilization efficiency (76.27%) and enzymatic activity (83.67%), improved stabilities in wide temperature conditions and pH solutions, and excellent reusability (85.78% of its initial activity after 20 cycles). These experimental results suggest that the immobilized dextranase is promising for various applications in biocatalytic engineering fields.

Stable graphene oxide-based composite membranes intercalated with montmorillonite nanoplatelets for water purification

Graphene oxide (GO) membranes have great potential in separation technology. However, their instability under aqueous environments hinders their separation performance and practical application. Herein, we present a facile and environmentally friendly method to fabricate stable GO-based membranes via the intercalation of montmorillonite (MMT) nanoplatelets. The as-prepared membranes remain stable under water (neutral, acidic, and alkaline) in a fully hydrated state and exhibit a high pure-water flux up to 139.5 L·m−2·h−1 under 0.09 MPa. Furthermore, they also show high organic molecule rejection (98.75% for Congo red, 99.44% for rhodamine B, 99.90% for crystal violet, 99.94% for methylene blue, 96.26% for phenanthracene, and 51.32% for phenol) as well as good removal rate of heavy metal ions (100% for Ag(I), 100% for Cu(II), and 27.04% for Cr(VI)). Moreover, an outstanding recycling ability of the membranes also has been obtained. These significant performances make our membranes a good candidate in water purification.

Wet chemically synthesized ZnO structures for photodegradation of pre-treated palm oil mill effluent and antibacterial activity

Various ZnO structures including spherical-like, hexagonal rod-like, spindle-like and pompon-like structures engineering at different solution pHs were prepared using a facile and surfactant-free reflux fabrication technique. The samples were morphologically and structurally analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), Brunauer–Emmett–Teller (BET) surface area and photoluminescence (PL) spectroscopy. The growth mechanism of pompon-like ZnO was delineated by the self-assembly attachment technique. Photoactivities of ZnO samples with varying morphologies were employed for the UV degradation of pre-treated palm oil mill effluent (POME) and inactivation of Escherichia coli (E. coli). Especially, pompon-like ZnO synthesized at pH 12 showed excellent photoactivity as compared to those of other three samples. The PL spectra demonstrated that the pompon-like ZnO can efficiently separate the charge carrier. The cyclic and leakage of zinc ion tests showed that the pompon-like ZnO has stable recyclable ability up to five successive runs. Much effort was also emphasized on the ZnO photocatalytic inactivation of E. coli by assessing the antibacterial behaviour, biomolecule leakage and cell destruction assays. The trapping experiments implied that the hydroxyl radicals were the dominant reactive species for both photocatalytic and antibacterial activities. Overall, ZnO catalysts exceled in the distinct potential applications including photocatalysis and antibacterial activities with their tunable structures.

Adsorption performance and mechanism for phosphate removal by cerium hydroxide loaded on molecular sieve

Abstract Cerium hydroxide loaded on molecular sieve (CHMS) was investigated for phosphate (PO4) adsorption. As the initial phosphorus concentration was set as 5 mg L−1, CHMS possessed high PO4 adsorption capacity at 25 °C compared with COMS (ceria loaded on molecular sieve) and MS (molecular sieve), and can be extensively applied in wide pH range (4–11). Based on kinetics and isotherms analysis, the adsorption process was mainly chemisorption and multilayer adsorption procedure. In addition, most of the coexisting ions had little effect on PO4 adsorption, in spite of 2 orders of magnitude higher levels than PO4. CHMS showed the excellent regeneration (at least 5 times recycling) ability with 1 M NaOH. The proposed mechanisms were explicated by various analytical techniques XRD, TG, XPS, and NMR analysis and found that Ce(HPO4)2 and Ce3(PO4)4 were the main pathways after adsorption, and the activated site of adsorbent was dependent on the presence of cerium hydroxide. Consequently, CHMS was a promising adsorbent for PO4 removal from wastewater.

A novel crosslinked β-cyclodextrin-based polymer for removing methylene blue from water with high efficiency

In this work, a novel crosslinked porous β-cyclodextrin-based polymer containing carboxylic acid groups (CT-β-CD) was synthesized successfully and characterized by SEM, FTIR, 13C solid-state NMR, water-contact-angle measurement, and TGA. The resultant CT-β-CD with triple absorption effects including inclusion complextion, porous network capture, and electrostatic interaction was employed as an adsorbent for removing methylene blue dye from aqueous solution, which exhibited several advantages such as high absorption capacity (qmax = 672 mg/g), rapid absorption rate, good recyclable ability, and selective adsorption for cationic dyes. The influences of initial MB concentration, absorption time, and pH value on the absorption behavior of CT-β-CD for MB were also investigated. In addition, it was found that the pseudo-second-order kinetic and the Langmuir model for adsorption isotherm could be used to describe the MB absorption behavior of CT-β-CD.

Graphene aerogel for the removal of bad smells from recycling of post-consumer polymers

Graphene aerogel was fabricated by a facile chemical reduction of a graphene oxide dispersion. The chemical reduction of graphene oxide was confirmed by different techniques. The resulting graphene aerogel showed large specific surface area (163 m2 g-1), high absorption capacity to incorporate odour and superior absorption recyclability. When graphene aerogel was added to the melting waste plastics, all the GC peaks of classified VOCs were reduced in intensity: of about 85% alcohols and carboxyl acids compounds; of more than 70 % aldehydes, ketones, esters and ethers; and in a lower content (62 % and 68 %, respectively) aliphatic and aromatic compounds, i.e. they were absorbed by GA. Thus, it displays promising application prospects in the field of organic volatile compounds treatment techniques, while allowing the adsorption and removal of molecules responsible for bad smells.

Highly Advanced Degradation of Thiamethoxam by Synergistic Chemisorption-Catalysis Strategy Using MIL(Fe)/Fe-SPC Composites with Ultrasonic Irradiation.

MIL(Fe)/Fe-doped nanospongy porous biocarbon (Fe-SPC) composite was fabricated from MIL-100(Fe) via in situ growth on a unique Fe-doped nanospongy porous biocarbon (Fe-SPC) and was used as Fenton-like catalyst for advanced degradation of thiamethoxam (THIA). Fe was loaded on silkworm excrement and calcined to Fe-SPC with nanospongy and high sp2 C structure. The in situ growth strategy embedded the Fe-SPC into MIL-100(Fe) crystals and formed conductive heterojunctions with an intensified interface by Fe-bridging effect, which was confirmed by negative shift of Fe3+ binding energy in X-ray photoelectron spectroscopy. MIL(Fe)/Fe-SPC composites exhibited high degree of crystallinity and surface area (Brunauer-Emmett-Teller: 1730 m2/g). Liquid chromatography-mass spectrometry and density functional theory simulations demonstrated that THIA was converted to a relatively stable compound (C4H5N2SCl), which could be captured by MIL-100(Fe) with strong chemical bonding energy (Fe-N, -587 kJ/mol), followed by a significant geometric distortion, resulting in a thorough degradation. Efficient charge separation and synergistic chemisorption-catalysis strategy resulted in the high catalytic activity of MIL(Fe)/Fe-SPC. The composite catalyst concurrently exhibited high mineralization ratio with 95.4% total organic carbon removal (at 25 °C and 180 min) and good recycling ability under wider neutral/alkaline conditions. Endorsing to these intriguing properties, MIL(Fe)/Fe-SPC can be deemed an efficient contender for removal of hard-degradable pesticides and other environmental pollutants in practical applications.

Graphene and silver decorated ZnO composite synthesis, characterization and photocatalytic activity evaluation

Ag/ZnO/g-C3N4 (graphene), ZnO/g-C3N4 and Ag/ZnO composites were prepared using green method and characterized by XRD, SEM, FTIR and UV–Vis techniques. The photo-catalytic activity (PCA) was evaluated by degradation textile dye methyl blue (MB) under UV light irradiation. The ZnO with band gap of 3.4 eV and hexagonal wurtzite structure was successfully decorated with Ag and G-C3N4 moieties. The MB degradation was achieved in the range of 90–99% and efficiency of photocatalysts was recorded in following order; Ag/ZnO/G-C3N4 > ZnO/G-C3N4 > Ag/ZnO > ZnO and the PCA performance was found to be highly pH sensitive. Moreover, the prepared composites showed excellent recycling ability and retained PCA up to 96% after five consecutive cycles for the degradation of MB. Results revealed that ZnO composite with Ag and g-C3N4 are efficient photo-catalyst and might be potential class of catalysts for the degradation of textile dyes and textile wastewater.

Superhydrophobic/Superoleophilic Polycarbonate/Carbon Nanotubes Porous Monolith for Selective Oil Adsorption from Water

A superhydrophobic/superoleophilic porous polycarbonate/carboxyl-functionalized multiwalled carbon nanotubes (PC/cMWCNTs) monolith with novel hierarchical micronanostructure was facilely fabricated via a thermally impacted nonsolvent induced phase separation method. A novel porous microstructure endowed PC/cMWCNTs monolith had a high porosity of 90.1%. Based on excellent superhydrophobicity (water contact angle of 159°) and superoleophilicity (oil contact angle of 0°), this porous monolith could selectively adsorb various types of oils/organic solvents from the oil–water mixture. Additionally, the monolith exhibited outstanding oil/water separation performance including fast adsorption speed, high saturation capacity, and superior recycling ability. The equilibrium adsorption time and saturated adsorption capacity of soybean oil were 20 s and 12.62 g g–1, respectively. By simple centrifugation or evaporation, the recovered PC/cMWCNTs monolith could be reused for at least 10 cycles. Thus, porous PC/cMWCNTs...