Showing papers in "ACS Sustainable Chemistry & Engineering in 2013"
TL;DR: The use of plant biomass or extracts for the biosynthesis of novel metal nanoparticles (silver, gold, platinum, and palladium) would be more significant if the nanoparticles are synthesized extracellularly and in a controlled manner according to their dispersity of shape and size as discussed by the authors.
Abstract: In recent years, nanobiotechnology has emerged as an elementary division of modern science and a noval epoch in the fields of material science and is receiving global attention due to its ample applications. Various physical, chemical, and biological methods have been employed to synthesize nanomaterials. Biological systems such as bacteria, fungi, actinomycetes, yeasts, viruses, and plants have been reported to synthesize various metal and metal oxide nanoparticles. Among these, biosynthesis of nanoparticles from plants seems to be a very effective method in developing a rapid, clean, nontoxic, and eco-friendly technology. The use of plant biomass or extracts for the biosynthesis of novel metal nanoparticles (silver, gold, platinum, and palladium) would be more significant if the nanoparticles are synthesized extracellularly and in a controlled manner according to their dispersity of shape and size. Owing to the rich biodiversity of plants, their potential use toward the synthesis of these nobel metal na...
643 citations
TL;DR: In this article, the authors present a recent advance in optical, electrochemical and field-effect transistor sensors for heavy metal detection, focusing on colorimetric, fluorescent, surface-enhanced Raman scattering and surface plasmon resonance devices.
Abstract: Heavy metal pollution is one of the most serious environmental problems, which undermines global sustainability. Many efforts have been made to develop portable sensors for monitoring heavy metals in the environment. Incorporation of nanomaterials and nanostructures into sensors leads to significant improvement in the performance of devices in terms of sensitivity, selectivity, multiplexed detection capability and portability. In addition, small molecules, DNA, proteins and bacteria have been integrated with inorganic materials to selectively bind heavy metals as the molecular recognition probes. This review presents a recent advance in optical, electrochemical and field-effect transistor sensors for heavy metal detection. The optical sensors are focused on colorimetric, fluorescent, surface-enhanced Raman scattering and surface plasmon resonance devices. In addition, optofluidic devices which integrate optical components with microfluidic chips are discussed. Furthermore, nanoparticle-modified electrodes...
450 citations
TL;DR: The authors summarizes recent activity in this general area where environmentally friendly synthetic techniques are currently being explored for the synthesis of “greener” AgNPs including the use of plant extracts, biodegradable polymers, and enzymes/bacteria and alternative energy input systems, such as microwave irradiation.
Abstract: The use of silver nanoparticles (AgNPs) is gaining in popularity due to silver’s antibacterial properties. Conventional methods for AgNP synthesis require dangerous chemicals and large quantities of energy (heat) and can result in formation of hazardous byproducts. This article summarizes recent activity in this general area where environmentally friendly synthetic techniques are currently being explored for the synthesis of “greener” AgNPs including the use of plant extracts, biodegradable polymers, and enzymes/bacteria and alternative energy input systems, such as microwave irradiation. Microwave heating enables efficient formation of nanostructures of uniform small sizes in shorter reaction times with reduced energy consumption; preventing agglomeration of ensuing nanoparticles is an additional attribute.
326 citations
TL;DR: The need for renewable alternatives to traditional petroleum-derived plastics has driven recent interest in biobased composite materials that are sourced from carbon-neutral feedstocks, such as Lignin this article.
Abstract: The need for renewable alternatives to traditional petroleum-derived plastics has driven recent interest in biobased composite materials that are sourced from carbon-neutral feedstocks. Lignin, an ...
275 citations
TL;DR: In this paper, the authors presented the complete utilization of spent coffee grounds to produce biodiesel, bio-oil, and biochar, and evaluated the neat biodiesel and blended (B5 and B20) fuel properties against ASTM and EN standards.
Abstract: This study presents the complete utilization of spent coffee grounds to produce biodiesel, bio-oil, and biochar. Lipids extracted from spent grounds were converted to biodiesel. The neat biodiesel and blended (B5 and B20) fuel properties were evaluated against ASTM and EN standards. Although neat biodiesel displayed high viscosity, moisture, sulfur, and poor oxidative stability, B5 and B20 met ASTM blend specifications. Slow pyrolysis of defatted coffee grounds was performed to generate bio-oil and biochar as valuable co-products. The effect of feedstock defatting was assessed through bio-oil analyses including elemental and functional group composition, compound identification, and molecular weight and boiling point distributions. Feedstock defatting reduced pyrolysis bio-oil yields, energy density, and aliphatic functionality, while increasing the number of low-boiling oxygenates. The high bio-oil heteroatom content will likely require upgrading. Additionally, biochar derived from spent and defatted gro...
245 citations
TL;DR: In this article, a microencapsulated phase change composite of paraffin@SiO2 was prepared by in situ emulsion interfacial hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS).
Abstract: In this work, a novel microencapsulated phase change composite of paraffin@SiO2 was prepared by in situ emulsion interfacial hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS). The as-prepared paraffin@SiO2 composite was determined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), scanning electronic microscope (SEM), and transmission electron microscopy (TEM), respectively. The results showed that the paraffin@SiO2 composite is composed of quasi-spherical particles with diameters of 200–500 nm. The paraffin is encapsulated in a SiO2 shell, and there is no chemical reaction between them. The DSC results indicate that the melting temperature and latent heat of the composite are 56.5 °C and 45.5 J/g, respectively. The encapsulation ratio of paraffin was calculated to be 31.7% from the results of the DSC measurements, slightly lower than the loading content (32.5%) of paraffin in the microencapsulated composite from the TGA measurements. The as-prepared para...
243 citations
TL;DR: In this article, the authors developed a one-pot, solvent free, and rapid synthesis of smart magnetic graphene (SMG) by microwave irradiation of graphene oxide (GO) and ferrocene precursors.
Abstract: Bacterial infections, the toxicity of engineered nanomaterials, the presence of inorganic pollutants in the environment, and providing safe drinking water are the most threatening problems of the 21st century. To tackle these challenges, we develop a one-pot, solvent free, and rapid synthesis of smart magnetic graphene (SMG) by microwave irradiation of graphene oxide (GO) and ferrocene precursors. The SMG possesses increased adsorption sites with tunable superparamagnetic properties (50 emu/g, 1:7 wt %), facilitating the adsorption and magnetic separation of aqueous Cr(VI), As(V), and Pb(II) with ∼99% removal efficiencies down to the 1 ppb level. The X-ray photoelectron spectroscopy (XPS) analysis of SMG-Cr(VI) reveals the reduction of Cr(VI) to Cr(III), presumably due to the surface phenolic groups and unprotected ferrous ions on the SMG surface. The maximum adsorption capacity of SMG is 4.86, 3.26, and 6.00 mg/g for respectively Cr(VI), As(V), and Pb(II) at an initial concentration of 5.0 ppm. The addit...
232 citations
TL;DR: The RepRap as discussed by the authors is an open-source self-replicating rapid prototyper for low-cost 3D printing, which is now a technically viable form of distributed manufacturing.
Abstract: With the recent development of the RepRap, an open-source self-replicating rapid prototyper, low-cost three-dimensional (3D) printing is now a technically viable form of distributed manufacturing o...
217 citations
TL;DR: In this article, the authors examine the literature pertaining to the different interaction mechanisms between cellulose and non-derivatizing solvent systems with emphasis on the inorganic molten salt hydrates.
Abstract: During cellulose dissolution in non-derivatizing solvents, the inter- and intramolecular hydrogen bonds of the polymer are deconstructed. This occurs either by hydrogen bond formation between one or more components of the solvent systems and the hydroxyl groups of the cellulose or by coordination bond formation between the metal ion present in the medium and the hydroxyl group of cellulose molecules. None of the polymer molecules are actually chemically modified during dissolution. In the first part of this review, we examine the literature pertaining to the different interaction mechanisms between cellulose and non-derivatizing solvent systems with emphasis on the inorganic molten salt hydrates. In the second part of this effort, we further review inorganic molten salt hydrates from the point of view of the changes they impart to the physical properties of the cellulose and the various chemical reactions that can be performed in it.
213 citations
TL;DR: Exposure at 250 ppm CeO2 NPs significantly increased plant biomass, but at 500–2000 ppm, plant growth was decreased by up to 85% in a dose-dependent fashion, and total chlorophyll and MDA production were unaffected by In2O3 NPs exposure.
Abstract: The effects of cerium oxide (CeO2) and indium oxide (In2O3) nanoparticles (NPs) exposure on Arabidopsis thaliana (L.) Heynh. were investigated. After inoculation in half strength MS medium amended with 0–2000 ppm CeO2 and In2O3 NPs for 25 days, both physiological and molecular responses were evaluated. Exposure at 250 ppm CeO2 NPs significantly increased plant biomass, but at 500–2000 ppm, plant growth was decreased by up to 85% in a dose-dependent fashion. At 1000 and 2000 ppm CeO2 NPs, chlorophyll production was reduced by nearly 60% and 85%, respectively, and anthocyanin production was increased 3–5-fold. Malondialdehyde (MDA) production, a measure of lipid peroxidation, was unaffected by exposure to 250–500 ppm CeO2 NPs, but at 1000 ppm, MDA formation was increased by 2.5-fold. Exposure to 25–2000 ppm In2O3 NPs had no effect on A. thaliana biomass and only minor effects (15%) on root elongation. Total chlorophyll and MDA production were unaffected by In2O3 NPs exposure. Molecular response to NP exposu...
204 citations
TL;DR: In this paper, a new gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation.
Abstract: We suggest a new gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation. The hydrate formation reactions were carried out in an isobaric condition of 3.1 MPa to find the upper temperature limit of CO2 hydrate formation. Simulated produced water (8.95 wt % salinity) mixed with the hydrate formers shows an increased upper temperature limit from −2 °C for simple CO2 hydrate to 16 and 7 °C for double (CO2 + CP) and (CO2 + CH) hydrates, respectively. The resulting conversion rate to double hydrate turned out to be similar to that with simple CO2 hydrate at the upper temperature limit. Hydrate formation rates (Rf) for the double hydrates with CP and CH are shown to be 22 and 16 times higher, respectively, than that of the simple CO2 hydrate at the upper temperature limit. Such mild hydrate formation temperature and fast formation kinetics indicate increased energ...
TL;DR: In this paper, the authors evaluated four comparable lab-scale nanocellulose fabrication routes through a cradle-to-gate life cycle assessment (LCA) adopting the Eco-Indicator 99 method.
Abstract: Nanocellulose is a nascent and promising material with many exceptional properties and a broad spectrum of potential applications. Because of the unique and functional materials that can be created using nanocellulose, pilot-scale development for commercialization has begun. Thus a thorough understanding of its environmental impact, covering the whole life cycle of nanocellulose, becomes the foundation for its long-term sustainable success. In this current study, four comparable lab scale nanocellulose fabrication routes were evaluated through a cradle-to-gate life cycle assessment (LCA) adopting the Eco-Indicator 99 method. The results indicated that, for the chemical–mechanical fabrication routes, the majority of the environmental impact of nanocellulose fabrication is dependent upon both the chemical modification and mechanical treatment route chosen. For sonication, the mechanical treatment overshadows that from the chemical modifications. Adapting the best practice based on unit mass production was 2...
TL;DR: In this article, the authors investigated atmospheric hydrodeoxygenation (HDO) of guaiacol over Ni2P-supported catalysts, including alumina, zirconia, and silica.
Abstract: This study investigated atmospheric hydrodeoxygenation (HDO) of guaiacol over Ni2P-supported catalysts. Alumina, zirconia, and silica served as the supports of Ni2P catalysts. The physicochemical properties of these catalysts were surveyed by N2 physisorption, X-ray diffraction (XRD), CO chemisorption, H2 temperature-programmed reduction (H2-TPR), H2 temperature-programmed desorption (H2-TPD), and NH3 temperature-programmed desorption (NH3-TPD). The catalytic performance of these catalysts was tested in a continuous fixed-bed system. This paper proposes a plausible network of atmospheric guaiacol HDO, containing demethoxylation (DMO), demethylation (DME), direct deoxygenation (DDO), hydrogenation (HYD), transalkylation, and methylation. Pseudo-first-order kinetics analysis shows that the intrinsic activity declined in the following order: Ni2P/ZrO2 > Ni2P/Al2O3 > Ni2P/SiO2. Product selectivity at zero guaiacol conversion indicates that Ni2P/SiO2 promotes DMO and DDO routes, whereas Ni2P/ZrO2 and Ni2P/Al2O...
TL;DR: The proposed life cycle optimization framework is applied to a case study on the hydrocarbon biofuels through a spatially explicit model for the county-level supply chain in Illinois and the Pareto-optimal results show that the trade-off between the economic and environmental objectives is revealed.
Abstract: We propose a life cycle optimization framework for the design of sustainable product systems and supply chains considering the concept of “functional unit” under economic and environmental criteria. This general modeling framework integrates the life cycle analysis methodology with multiobjective optimization and measures both the economic and environmental performances based on a standard quantity of functional unit associated with final products. The Pareto-optimal frontier returned by the multiobjective optimization problem reveals the trade-off between the economic and environmental objectives. We also present tailored optimization algorithms for efficiently solving the mixed-integer linear fractional programming problems, which result from the life cycle optimization framework. We apply the proposed life cycle optimization framework to a case study on the hydrocarbon biofuels through a spatially explicit model for the county-level supply chain in Illinois. The Pareto-optimal results show that the env...
TL;DR: The formation of the BSA corona presented here provides a low-cost bio-compatible strategy for nanoparticle stabilization and transport in highly ionic environments.
Abstract: We find that citrate-stabilized gold nanoparticles aggregate and precipitate in saline solutions below the NaCl concentration of many bodily fluids and blood plasma. Our experiments indicate that this is due to complexation of the citrate anions with Na+ cations in solution. A dramatically enhanced colloidal stability is achieved when bovine serum albumin is adsorbed to the gold nanoparticle surface, completely preventing nanoparticle aggregation under harsh environmental conditions where the NaCl concentration is well beyond the isotonic point. Furthermore, we explore the mechanism of the formation of this albumin “corona” and find that monolayer protein adsorption is most likely ruled by hydrophobic interactions. As for many nanotechnology-based biomedical and environmental applications, particle aggregation and sedimentation are undesirable and could substantially increase the risk of toxicological side effects; the formation of the BSA corona presented here provides a low-cost biocompatible strategy f...
TL;DR: In this paper, a series of Ni/Al2O3 catalysts were synthesized using four different precursors, nickel nitrate, nickel chloride, nickel acetate, and nickel acetylacetonate.
Abstract: This paper describes an investigation regarding the influence of Ni precursors on catalytic performances of Ni/Al2O3 catalysts in glycerol steam reforming. A series of Ni/Al2O3 is synthesized using four different precursors, nickel nitrate, nickel chloride, nickel acetate, and nickel acetylacetonate. Characterization results based on N2 adsorption–desorption, X-ray diffraction, H2 temperature-programmed reduction, H2 chemisorption, transmission electron microscopy, and thermogravimetric analysis show that reduction degrees of nickel, nickel dispersion, and particle sizes of Ni/Al2O3 catalysts are closely dependent on the anion size and nature of the nickel precursors. Ni/Al2O3 prepared by nickel acetate possesses the moderate Ni reduction degree, high Ni dispersion, and small nickel particle size, which possesses the highest H2 yield. Reaction parameters are also examined, and 550 °C and a steam-to-carbon ratio of 3 are optimized. Moreover, coke deposition, mainly graphite species, leads to the deactivati...
TL;DR: In this article, the design of Ni/SiO2 catalysts obtained from a phyllosilicate precursor that possess high activity and stability for bioethanol steam reforming to sustainably produce hydrogen is described.
Abstract: This paper describes the design of Ni/SiO2 catalysts obtained from a phyllosilicate precursor that possess high activity and stability for bioethanol steam reforming to sustainably produce hydrogen. Sintering of metal particles and carbon deposition are two major issues of nickel-based catalysts for reforming processes, particularly at high temperatures; strong metal–support interaction could be a possible solution. We have successfully synthesized Ni-containing phyllosilicates by an ammonia evaporation method. Temperature programmed reduction results indicate that the metal–support interaction of Ni/SiO2 catalyst prepared by ammonia evaporation method (Ni/SiO2P) is stronger due to the unique layered structure compared to that prepared by conventional impregnation (Ni/SiO2I). With the phyllosilicate precursor nickel particles highly disperse on the surface, remaining OH groups in the unreduced phyllosilicates promote nickel dispersion and carbon elimination. We also show that high dispersion of Ni and str...
TL;DR: In this paper, the authors investigated the energy efficiency of this process for feed waters that passed a reverse electrodialysis cell once and waters that pass multiple cells or electrode segments, and they showed that the ion transport corresponding to the obtained energy and the electromotive force mutually influence each other, which enables capture of more than 50% (even up to 95%) of the theoretical energy.
Abstract: Renewable energy can be captured from the mixing of salt and fresh water in reverse electrodialysis. This paper investigates the energy efficiency of this process for feed waters that pass a reverse electrodialysis cell once and waters that pass multiple cells or electrode segments. So far, the maximum theoretical energy efficiency was considered to be 50% when the feed waters pass a single cell once; significantly higher efficiencies could only be obtained when the waters were recirculated or passed multiple electrodes. In this study, we show that the ion transport corresponding to the obtained energy and the electromotive force mutually influence each other, which enables capture of more than 50% (even up to 95%) of the theoretical energy, even when the feedwater streams pass a reverse electrodialysis cell only once.
TL;DR: In this article, the effects of engineered nanoparticles (ENPs) on aquatic ecosystems are evaluated. But the authors focus on the direct and indirect effects of ENPs on aquatic organisms.
Abstract: In order to assess the overall risk posed by engineered nanoparticles (ENPs), the biological effects of this emergent pollutant to aquatic ecosystems must be evaluated. We present findings from studies conducted with a diversity of ENPs (metallic, quantum dots) on a variety of freshwater and marine algae (phytoplankton) illustrating both their direct and indirect effects. We show that in general, while the surface properties of ENPs govern their aggregation behavior and ionic strength controls their dissolution, exopolymeric substances (EPS) produced by algae determine their potential to be toxic and thereby movement through the water column and food web. The production of EPS reduces the impact of ENPs (bioavailability and toxicity) and/or their ions on cellular activities of algae. It does not however directly reduce the aggregation and/or solubility of ENPs but rather affects their stability. Complicating understanding of these interactions is the great assortment of surface coatings for ENPs. This per...
TL;DR: In this paper, the cathode of a bio-electrochemical system can be used as the electron donor for the conversion of acetate into medium chain fatty acids, precursors for renewable fuels or chemicals.
Abstract: The use of mixed cultures to convert waste biomass into medium chain fatty acids, precursors for renewable fuels or chemicals, is a promising route. To convert waste biomass into medium chain fatty acids, an external electron donor in the form of hydrogen or ethanol needs to be added. This study investigated whether the cathode of a bioelectrochemical system can be used as the electron donor for the conversion of acetate into medium chain fatty acids. We show that medium chain fatty acids were produced in a bioelectrochemical system at −0.9 V vs NHE cathode potential, without addition of an external mediator. Caproate, butyrate, and smaller fractions of caprylate were the main products formed from acetate. In-situ produced hydrogen was likely involved as an electron donor for the reduction of acetate. Electron and carbon balances revealed that 45% of the electrons in electric current and acetate, and 31% of the carbon from acetate were recovered in the formed products. This study showed for the first time...
TL;DR: In this paper, an approach for comprehensive utilization of rice husk biomass was developed to obtain both lignocellulose and high quality porous silica nanoparticles from RHs.
Abstract: Rice husk (RH) biomass is a massive byproduct from rice milling. Applications of RHs have been very limited. Therefore, RHs are often considered as a biowaste. RHs are mainly composed of lignocellulose (ca. 72–85 wt %) and silica (ca. 15–28 wt %). The majority of previous explorations focused on the preparation of silica or other silicon based materials from RHs, while the lignocellulose in RHs was usually burnt and thus wasted. Herein, an approach for comprehensive utilization of RHs has been developed to obtain both lignocellulose and high quality porous silica nanoparticles from RHs. Most of the lignocellulose in RHs was first extracted by dissolving in ionic liquids. The dissolved lignocellulose was subsequently separated and collected. The remaining RH residue after extraction that contains a high concentration of silica was thermally treated to synthesize amorphous porous silica nanoparticles with a high purity and surface area. It was also found that, during the extraction of lignocellulose using i...
TL;DR: In this article, the authors characterized hydrochars derived from macroalgae Sargassum horneri to elucidate their potential as a valuable resource and found that they formed mainly through a dehydration reaction pathway and had carbon contents of 36.8-50.5% and higher heating values of 19.0-25.5%.
Abstract: Hydrochars derived from macroalgae Sargassum horneri were characterized physically and chemically to elucidate their potential as a valuable resource. Hydrochars were prepared by hydrothermal carbonization (HTC) of Sargassum horneri at temperatures of 180–210 °C with citric acid. The hydrochars were found to form mainly through a dehydration reaction pathway and had carbon contents of 36.8–50.5% and higher heating values of 19.0–25.1 MJ kg–1. The BET surface area of hydrochars remained low, in the range of 0.6–31.8 m2 g–1. On the basis of Taguchi’s experimental design, reaction temperature, reaction time, and particle size of feedstock were found to be the most important control factors for the chemical and physical properties of the hydrochars.
TL;DR: In this paper, the best fluorinated ionic liquids for the following applications were selected: recovery/recycling of perfluorocarbon contaminants such as greenhouse perfluors gases and perfluoroalkyl acids of industrial effluents that are persistent, bioaccumulative, and toxic, and the partial or total replacement of inert perffluorocarbons in oxygen therapeutic emulsions by enhancing the emulsion stability and increasing the solubility of respiratory gas.
Abstract: Ionic liquids have become a green media for engineering applications due to exceptional physicochemical properties, such as their practically nonvolatile nature, null flammability, low melting point, high ionic conductivity, and thermal and electrochemical stability. This work aimed to select the best fluorinated ionic liquids for the following applications: recovery/recycling of perfluorocarbon contaminants such as greenhouse perfluorocarbons gases and perfluoroalkyl acids of industrial effluents that are persistent, bioaccumulative, and toxic, and the partial or total replacement of inert perfluorocarbons in oxygen therapeutic emulsions by enhancing the emulsion stability and increasing the solubility of respiratory gas. With this dual goal in mind, thermodynamic and thermophysical properties of fluorinated ionic liquids (FILs) and their toxicity and biocompatibility are discussed so that the feasibility of the proposed applications can be evaluated. Herein, FILs are defined as ionic liquids with fluori...
TL;DR: In this article, the effect of incorporating 30 wt % lignocellulosic fibers into a biodegradable polymer matrix comprising a pre-blend of poly(3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV) and poly(butylene adipate co-terephthalate) (PBAT) has been investigated.
Abstract: This work has explored the potential use of lignocellulosic agricultural residues like soy stalk, corn stalk, wheat straw, and perennial grasses, like switchgrass and miscanthus, as reinforcement for engineering value-added biobased composite materials. The effect of incorporating 30 wt % lignocellulosic fibers into a biodegradable polymer matrix comprising a pre-blend of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(butylene adipate-co-terephthalate) (PBAT) has been investigated. Results of this work explain that fiber chemical composition and fiber length distribution provide a complementary effect on the mechanical and thermal properties of the resulting biobased composites. Comparing the effects of all the fiber types, miscanthus (MS)-based composites, showed slightly higher tensile strength, and Young’s modulus improved by 104%. The highest heat deflection temperature of 110 °C was obtained with PHBV/PBAT/MS composites. This study has revealed prospects for hybridization of these ligno...
TL;DR: In this article, a new hybrid clay adsorbent based on kaolinite clay and Carica papaya seeds with improved cation exchange capacity (CEC), rate of heavy metal ion uptake, and adsorption capacity for heavy metal ions were prepared.
Abstract: New hybrid clay adsorbent based on kaolinite clay and Carica papaya seeds with improved cation exchange capacity (CEC), rate of heavy metal ion uptake, and adsorption capacity for heavy metal ions were prepared. The CEC of the new material is ca. 75 meq/100 g in spite of the unexpectedly low surface area (≈9 m2/g). Accordingly, the average particle size of the hybrid clay adsorbent decreased from over 200 to 100 μm. The hybrid clay adsorbent is a highly efficient adsorbent for heavy metals. With an initial metal concentration of 1 mg/L, the hybrid clay adsorbent reduces the Cd2+, Ni2+, and Pb2+ concentration in aqueous solution to ≤4, ≤7, and ≤20 μg/L, respectively, from the first minute to over 300 min using a fixed bed containing 2 g of adsorbent and a flow rate of ≈7 mL/min. These values are (with the exception of Pb2+) in line with the WHO permissible limits for heavy metal ions. In a cocktail solution of Cd2+, and Ni2+, the hybrid clay shows a reduced rate of uptake but an increased adsorption capaci...
TL;DR: In this article, a hierarchical carbon nanotube membrane (HCNM) was used to prevent nanoparticles from aggregating and eliminate the need for separation, and the authors showed that HCNM-supported AuNPs retained 78% of their catalytic capability compared to suspended AuNs.
Abstract: Gold nanoparticles (AuNPs) have attracted increasing attention as catalysts for pollutant degradation because of their unique reactivity. Direct use of gold nanoparticles in water treatment faces prohibitive challenges from nanoparticle aggregation and post-treatment separation. To prevent nanoparticles from aggregating and eliminate the need for separation, we affixed AuNPs on hierarchical carbon nanotube membrane (HCNM) that was approximately 50 μm thin with 10 μm × 10 μm openings as pores for water passage. HCNM was fabricated by growing vertically aligned carbon nanotube (CNT) arrays on stainless steel mesh. Using p-nitrophenol (PNP) as model pollutant, we showed that in batch experiments HCNM-supported AuNPs retained 78% of their catalytic capability compared to suspended AuNPs. The slight reduction in reactivity was attributed to the blockage of part of the gold surface at the AuNP–CNT juncture. When the membrane was used in continuous flow-through operation, HCNM-supported AuNPs achieved 71% of the...
TL;DR: In this article, an alkaline treatment was applied to pinewood (PW), switchgrass (SG), and coastal bermuda grass (CBG) in order to extract hemicelluloses to subsequently produce a novel biosorbent.
Abstract: Hemicellulose material is an abundant and relatively under-utilized polymeric material present in lignocellulosic materials. In this research, an alkaline treatment was applied to pinewood (PW), switchgrass (SG), and coastal bermuda grass (CBG) in order to extract hemicelluloses to subsequently produce a novel biosorbent. Alkaline extraction at 75 °C recovered 23% of the biomass as a predominantly hemicellulose material with a number average degree of polymerization of ∼450. These hemicelluloses were grafted with penetic acid (diethylene triamine pentaacetic acid, DTPA) and were then cross-linked to chitosan. The effects of hemicellulose–DTPA concentration, reaction time, and temperature of reaction with chitosan on the resulting salt (sodium chloride, NaCl) uptake and weight loss in saline solutions were determined. A maximum salt uptake for the materials was ∼0.30 g/g of foam biosorbent. The foam biosorbent was characterized by FT-IR spectra, porosity, and dynamic mechanical analysis. Batch adsorption e...
TL;DR: In this paper, the pyrolysis of softwood kraft lignin in the presence of various H-ZSM-5 zeolites with different SiO2/Al2O3 mole ratios from 23/1-280/1 as additives were examined at 600 °C.
Abstract: The pyrolysis of softwood (SW) kraft lignin in the presence of various H-ZSM-5 zeolites with different SiO2/Al2O3 mole ratios from 23/1–280/1 as additives were examined at 600 °C. Nuclear magnetic resonance (NMR), including quantitative 13C, 31P NMR, and heteronuclear single-quantum correlation (HSQC)-NMR, and gel permeation chromatography (GPC) were used to characterize various pyrolysis oils. On the basis of the results of the 13C and 31P NMR for pyrolysis oils, the use of H-ZSM-5 zeolites during the pyrolysis process caused the near complete decomposition of aliphatic hydroxyl and carboxyl groups. With the exception of carboxylic acid, the H-ZSM-5 zeolite with a relatively higher SiO2/Al2O3 mole ratio was more effective at the elimination of methoxyl groups, ether bonds, and aliphatic C–C bonds, and dehydration of aliphatic hydroxyl groups during pyrolysis. However, the H-ZSM-5 zeolite with a very large SiO2/Al2O3 mole ratio, such as 280, has only limited effects on the properties of upgraded pyrolysis...
TL;DR: In this article, the structural modifications of castor oil, a renewable resource, to develop functional organic inorganic hybrid coatings were investigated, and a novel methodology has been developed to introduce hydrolyzable −Si−OCH3 groups in the castor-oil backbone that has been used subsequently for the development of polyurethane/urea-silica hybrid coatingings.
Abstract: This paper investigates the structural modifications of castor oil, a renewable resource, to develop functional organic inorganic hybrid coatings. A novel methodology has been developed to introduce hydrolyzable −Si–OCH3 groups in the castor oil backbone that has been used subsequently for the development of polyurethane/urea–silica hybrid coatings. The alkoxysilane functional castor oil (ASCO) was characterized by techniques such as 1H, 13C, and 29Si nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The ASCO was further reacted with different ratios of isophorone diisocyanate (IPDI) to get an isocyanate-terminated hybrid polyurethane prepolymer that was cured under atmospheric moisture to get the desired coating films. The glass transition temperatures (Tg) of the hybrid networks were found to be in the range of 29–70 °C, and the water contact an...
TL;DR: In this paper, the synthesis of new biobased polyols for rigid polyurethane (PU) foams through oxidation of side chain unsaturation is reported using the environmentally benign reagent hydrogen peroxide.
Abstract: Global efforts to find renewable feedstocks for the chemical industry are aimed at replacing fossil reserves and a reduction in global warming by employing environmently friendly technologies (green chemistry approaches) for specialty chemical manufacturing. Cardanol, obtained as a byproduct of the cashew processing industry, is an important renewable resource and a unique phenolic compound carrying a 15-carbon side chain in meta position with varying degrees of unsaturation. In this work, the synthesis of new biobased polyols for rigid polyurethane (PU) foams through oxidation of side chain unsaturation is reported using the environmentally benign reagent hydrogen peroxide. Polyols with hydroxyl values in the range of 350–400 mg KOH/g were prepared through epoxidation followed by hydrolysis and characterized for structure using IR,1H-NMR, 13C NMR, and mass spectroscopic techniques. The foaming characteristics were studied, and the polyols were successfully used in making rigid polyurethane foams with goo...