Rising environmental concerns and depletion of petro-chemical resources has resulted in an increased interest in biorenewable polymer-based environmentally friendly materials. Among biorenewable polymers, lignin is the second most abundant and fascinating natural polymer next to cellulose. Lignin is one of the three major components found in the cell walls of natural lignocellulosic materials. Lignin is widely available as a major byproduct of a number of industries involved in retrieving the polysaccharide components of plants for industrial applications, such as in paper making, ethanol production from biomass, etc. The impressive properties of lignin, such as its high abundance, low weight, environmentally friendliness and its antioxidant, antimicrobial, and biodegradable nature, along with its CO2 neutrality and reinforcing capability, make it an ideal candidate for the development of novel polymer composite materials. Considerable efforts are now being made to effectively utilize waste lignin as one of the components in polymer matrices for high performance composite applications. This article is intended to summarize the recent advances and issues involving the use of lignin in the development of new polymer composite materials. In this review, we have made an attempt to classify different types of lignin-reinforced polymer composites starting from synthetic to biodegradable polymer matrices and highlight recent advances in multifunctional applications of lignin. The structural features and functions of the lignin/polymer composite systems are discussed in each section. The current research trends in lignin-based materials for engineering applications, including strategies for modification of lignin, fabrication of thermoset/thermoplastic/biodegradable/rubber/foam composites, and the use of lignin as a compatibilizer are presented. This study will increase the interest of researchers all around the globe in lignin-based polymer composites and the development of new ideas in this field.
Green technology actively seeks new solvents to replace common organic solvents that present inherent toxicity and have high volatility, leading to evaporation of volatile organic compounds to the atmosphere. Over the past two decades, ionic liquids (ILs) have gained enormous attention from the scientific community, and the number of reported articles in the literature has grown exponentially. Nevertheless, IL "greenness" is often challenged, mainly due to their poor biodegradability, biocompatibility, and sustainability. An alternative to ILs are deep eutectic solvents (DES). Deep eutectic solvents are defined as a mixture of two or more components, which may be solid or liquid and that at a particular composition present a high melting point depression becoming liquids at room temperature. When the compounds that constitute the DES are primary metabolites, namely, aminoacids, organic acids, sugars, or choline derivatives, the DES are so called natural deep eutectic solvents (NADES). NADES fully represent green chemistry principles. Can natural deep eutectic solvents be foreseen as the next generation solvents and can a similar path to ionic liquids be outlined? The current state of the art concerning the advances made on these solvents in the past few years is reviewed in this paper, which is more than an overview on the different applications for which they have been suggested, particularly, biocatalysis, electrochemistry, and extraction of new data. Citotoxicity of different NADES was evaluated and compared to conventional imidazolium-based ionic liquids, and hints at the extraction of phenolic compounds from green coffee beans and on the foaming effect of NADES are revealed. Future perspectives on the major directions toward which the research on NADES is envisaged are here discussed, and these comprised undoubtedly a wide range of chemically related subjects.
Chitosan is among one of the most important and most studied natural polymers. The cationic nature of chitosan makes it a polymer of high importance from environmental and biomedical point of views among the other natural polysaccharides. However, it also suffers from a few disadvantages and requires further development to achieve the targeted results and desired range of efficiency. To overcome some of the disadvantages of the pristine chitosan, it is most imperative to functionalize it with suitable functional groups. Therefore, it is highly desired to understand the chemistry of the reactions used to alter the surface characteristics of chitosan. Among various techniques presently being used to tailor the surface characteristics of chitosan, graft copolymerization is of the utmost importance. The aim of the present perspective is to describe the recent advances in the graft copolymerization of chitosan with particular emphasis on atom transfer radical polymerization (ATRP). This perspective describes the synthesis, characterization, and multifunctional applications of different types of chitosan-based copolymers.
Evolution of the bioplastics industry has changed directions dramatically since the early 1990s. The latest generation is moving toward durable bioplastics having high biobased content. The main objective is to replace "fossil carbon" with "renewable carbon", a holistic strategy to mitigate climate change by minimizing the environmental impact of a product throughout its life cycle. Durable bioplastics is desired for multiuse long-term application in automotive, electronics and other industries. One necessary requirement for them is to be both tough and strong, yet the two attributes are often mutually exclusive. Does this mean a biobased and biodegradable polymer as polylactic acid (PLA) with its high strength but low toughness cannot be adopted for durable applications? Well, not exactly; this is where the concept of tailoring the properties of PLA to achieve stiffness toughness balance along with acceptable heat resistance comes into play. In this perspective, we summarize the recent research progress in addressing the toughness vs strength and heat resistance conflict inherent in PLA. Blends having super toughness and composites based on the toughened PLA blends formulated to obtain desired material properties are covered. Morphology and crystallinity that individually contribute to toughness and heat resistance have also been elucidated.
In this study, the binary transition metal sulfide NiCo2S4 with a novel hollow hexagonal nanoplate (HHNs) structure has been synthesized through a sacrificial template method based on the Kirkendall effect. The hollow nanoplates have an average diameter of about 200 nm, thickness of about SO nm, and shell thickness of about 10 nm. The resulting samples were characterized by means of XRD, XPS, EDX, SEM, TEM, and HRTEM. The electrochemical characterization results demonstrate that NiCo2S4 hollow hexag,onal nanoplates exhibit a high specific capacitance of 437 F g(-1) in a 3 M KOH aqueous electrolyte at a current rate of 1 A g(-1), along with a superior rate capability and Coulombic efficiency stability, indicating their potential application as electrode materials for supercapacitors.
Development of core/shell heterostructures and semiconductor p-n junctions is of great concern for environmental and energy applications. Herein, we develop a facile in situ deposition route for fabrication of a BiVO4/BiOI composite integrating both the core/shell heterostructure and semiconductor p-n junction at room temperature. In the BiVO4/BiOI core/shell heterostructure, the BiOI nanosheets are evenly assembled on the surface of the BiVO4 cores. The photocatalytic performance is evaluated by monitoring the degradation of the dye model Rhodamine B (RhB), colorless contaminant phenol, and photocurrent generation under visible-light irradiation. The heterostructured BiVO4/BiOI core/shell photocatalyst shows drastically enhanced photocatalysis properties compared to the pristine BiVO4 and BiOI. This remarkable enhancement is attributed to the intimate interfacial interactions derived from the core/shell heterostructure and formation of the p-n junction between the p-type BiOI and n-type BiVO4. Separation and transfer of photogenerated electron hole pairs are hence greatly facilitated, thereby resulting in the improved photocatalytic performance as confirmed by electrochemical, photoelectrochemical, radicals trapping, and superoxide radical (center dot O-2(-)) quantification results. Moreover, the core/shell BiVO4/BiOI also displays high photochemical stability. This work sheds new light on the construction of high-performance photocatalysts with core/shell heterostructures and matchable band structures in a simple and efficient way.
Visible-light-driven photocatalysts attract great interest because they can utilize more sunlight for reactions than conventional photocatalysts. A novel visible-light-driven photocatalyst AgI/Bismuth oxychloride (Bi12O17Cl2) hybrid was synthesized by a hydrothermal-precipitation method. Several characterization tools, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS) were employed to study the phase structures, morphologies, and optical properties of the fabricated photocatalysts. These characterizations indicated that AgI nanoparticles were evenly distributed on the surface of Bi12O17Cl2, and heterostructures were formed. The photochemical characterizations demonstrated that the promoted separation of carrier transfer in the AgI/Bi12O17Cl2 heterojunction was achieved. The degradation rate of sulfamethazine (SMZ) by AgI/Bi12O17Cl2 was about 7.8 times and 35.2 times higher than that of pristine Bi12O17Cl2 and BiOCl under visible-light-driven photocatalysts, respectively. It was also found that the amount of AgI in the AgI/Bi12O17Cl2 composites played an important role in photocatalytic activity, and the optimized ratio was 25%. The AgI/Bi12O17Cl2 shows good catalytic stability and maintains similar reactivity after four cycles. Furthermore, the degradation intermediates of SMZ were identified by HPLC-MS, and the photocatalytic mechanism was proposed. These findings highlight the role of Bi12O17Cl2 on contaminant elimination and open avenues for the rational design of highly efficient photocatalysts.
A Z-scheme g-C3N4/Ag/MoS2 ternary plasmonic photocatalyst in a flowerlike architecture of diameter about 0.40.6 pm is successfully synthesized by a reliable and effective method. The as-synthesized g-C3N4/Ag/MoS2 photocatalyst showed excellent improvement for visible-light absorption and separation efficiency of photoinduced electron hole pairs. The g-C3N4/Ag/MoS2 system exhibits optimum visible-light-induced photocatalytic activity in degrading Rhodamin B (RhB), which is 9.43 fold and 3.56-fold of Ag/MoS2 and g-C3N4/MoS2 systems, and 8.78-fold and 2.08-fold in the production of hydrogen (H-2) out of water, respectively. The excellent photocatalytic activities are attributed to the synergetic effects of Ag, g-C3N4, and MoS2 nanophase structures in the g-C3N4/Ag/MoS2 composites, which result in a Z-scheme-mechanism-assisted fast separation and slow recombination of photoinduced electron hole pairs and thereby higher photocatalytic activity.
Two-dimensional (2D) carbon nanomaterials generally display some limitations in adsorption applications due to easy agglomeration. To solve this problem, as-synthesized sandwiched nanocomposites made of Fe3O4 nanoparticles, poly(allylamine) hydrochloride molecules, and carboxylate graphene oxide sheets were prepared using a layer-by-layer (LbL) self-assembly method. The successfully synthesized sandwiched structures in the present nanocomposites have outstanding organic dye adsorption performance, stability, and recycling. The agglomeration of carboxylate graphene oxide was reduced with increased specific surface area because the Fe3O4 nanoparticles play important roles in interpenetrating and supporting graphene oxide sheets layers. In comparison with other kinds of composite adsorbents, the preparation process of the present new sandwiched composite materials is facile to operate and regulate, which demonstrates potential large-scale applications in wastewater treatment and dye removal.
Constructing two-dimensional (2D) composites using layered materials is considered to be an effective approach to achieve high-efficiency photocatalysts. Herein, a 2D/2D g-C3N4/MnO2 heterostructured photocatalyst was synthesized via in situ growth of MnO2 nanosheets on the surface of g-C3N4 nanolayers using a wet-chemical method. The hybrid nanomaterial was characterized by a range of techniques to study its micromorphology, structure, chemical composition/states, and so on. The g-C3N4/MnO2 nanocomposite exhibited greatly improved photocatalytic activities for dye degradation and phenol removal in comparison to the single g-C3N4 or MnO2 component. On the basis of the electron paramagnetic resonance spectra, X-ray photoelectron spectra, and the Mott Schottky measurements, we consider that a Z-scheme heterojunction was generated between the g-C3N4 nanosheets and MnO2 nanosheets, wherein the photoinduced electrons in MnO2 combined with the holes in g-C3N4, leading to enhanced charge carrier extraction and utilization upon photoexcitation. This work provides an effective approach to construct the 2D/2D heterojunctions for the application in solar-to-fuel conversion and photocatalytic water treatment.
The use of vanillin as a building block for the chemical industry is discussed in this article. Vanillin is currently one of the only molecular phenolic compounds manufactured on an industrial scale from biomass. It has thus the potential to become a key-intermediate for the synthesis of bio-based polymers, for which aromatic monomers are needed to reach good thermo-mechanical properties. After a first part dedicated to the current sourcing of vanillin, this article focuses on the alkaline oxidation lignin-to-vanillin process, reporting advantages and limits, discusses the various postdepolymerization methods for product isolation and finally examines the outlook for the wider use of vanillin as a key building block for the chemical industry.
The combination of cobalt redox catalysis and carbon nitride photocatalysis to construct a cascade photoreaction system has been developed for the deoxygenative reduction of CO2 to CO with visible light. The graphitic carbon nitride has been demonstrated to function both as a capture/activation substrate of CO2 and a photocatalyst, whereas the introduced cobalt species act as reductive and oxidative promoters to accelerate charge-carrier separation and transfer kinetics. This hybrid photosystem contains inexpensive substances that synergetically catalyze CO2-to-CO conversion at mild conditions, with a high stability of catalysts. The optimization in the surface and texture structures as well as reaction conditions has been demonstrated. The results represent an important step toward artificial photosynthesis by using cost-acceptable materials.
A high efficiency and eco-friendly porous cellulose-based bioadsorbent was synthesized by grafting acrylic acid and acrylamide to remove anionic dye acid blue 93 (AB93) and cationic dye methylene blue (MB) from single and binary dye solutions. The effects of initial dye concentration, bioadsorbent dosage, contact time, solution pH value, temperature, ionic strength and surfactant content on the adsorption capacity of the bioadsorbent were investigated. The maximum adsorption capacities of the bioadsorbent for both AB93 and MB were 1372 mg g(-1) at an initial concentration of 2500 mg L-1. The conditions dependent adsorption characteristics of the bioadsorbent indicated a high efficiency of dyes removal. The appropriate isotherm model for the equilibrium process was the Freundlich, and the kinetic studies revealed that the adsorption of AB93 and MB followed the pseudo-second-order kinetic models. The adsorbent behaviors were dominated by the electrostatic interactions between the bioadsorbents and the dye molecules. Moreover, the recyclability experiments showed that the bioadsorbent could be reused for at least three cycles with stable adsorption capacity even in complex systems containing binary dyes, salt, and surfactant Thus, the cellulose based bioadsorbent can be effectively used for the removal of dyes from industrial textile wastewater.
A stable magnetic carbon was synthesized using activated sludge as the carbon precursor. The ultrasonic pretreatment was used to destroy the cells in the activated sludge and to release the soluble carbon source, which was responsible for the improved stability of the synthesized magnetic carbon. 800 W was demonstrated as the optimized ultrasonication power for the pretreatment of activated sludge. Then, the carbonization parameters, such as pyrolysis temperature, heating rate, and dwell time were optimized as 800 degrees C, 10 degrees C/min, and 60 min, respectively. To be more specific, this activated sludge derived magnetic carbon can reduce almost all the hexavalent chromium (Cr(VI)) (2.0 mg/L) in 10 min and has a maximum capacity as high as 203 mg/g. The iron release rate of the synthesized activated sludge derived magnetic carbon was decreased, which improved the electron utilization of zerovalent iron (ZVI). This composite was demonstrated to have a good stability and recyclability as well. Finally, the Cr(VI) removal mechanisms were clarified under the acidic and the natural conditions.
The design and decoration of plasmonic metal hybrid photoanodes provide an effective strategy for highly efficient photoelectrochemical (PEC) water splitting. In this work, an Au nanoparticle (NP) decorated highly ordered ZnO/CdS nanotube arrays (ZnO/CdS/Au NTAs) photoanode has been rationally designed and successfully synthesized. By virtue of the favorable band alignment and specific nanotube structure of ZnO/CdS as well as the surface plasmonic effect of Au NPs, the ZnO/CdS/Au NTAs photoanode shows significantly enhanced PEC performance as compared to the ZnO/CdS/Au and ZnO/CdS nanorod arrays (NRAs). Impressively, the optimized ZnO/CdS/Au NTAs photoanode exhibits the highest photocurrent density of 21.53 mA/cm(2) at 1.2 V vs Ag/AgCl and 3.45% photoconversion efficiency (PCE) among the parallel photoanodes under visible light illumination (lambda > 420 nm).
In recent years, nanobiotechnology has emerged as 1 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 nanoparticles is yet to be explored. The aim of this review is to provide the recent trends involved in the phytosynthesis of nobel metal nanoparticles in the past decade.
Recently, many studies concerning the environmental impact of ionic liquids (ILs) have shown that despite their unique properties and clear advantages in an ever wide range of applications and processes, ILs are not intrinsically green. In a search for biodegradable and low toxicity, a new type of as has been developed, the deep eutectic solvents (DESs). In this context, the aim of this work is to provide accurate densities, viscosities, and refractive indices for DESs prepared using cholinium chloride as the hydrogen bond acceptor and several carboxylic acids (levulinic, glutaric, malonic, oxalic, and glycolic) as the hydrogen bond donors. The impact of two different synthetic methodologies, heating and grinding, in the thermophysical properties of the prepared DESs was assessed. The obtained DESs were analyzed using NMR spectroscopy, FTIR, and electrospray ionization mass spectrometry in order to check their structures and purities. Thermophysical properties, densities, viscosities, and refractive indices were rationalized in terms of the chemical structure of the prepared DESs. The effect of the presence of water in the thermophysical properties of the compounds was also evaluated. Finally, comparisons between the DESs and the corresponding ILs are presented.
In the present paper, one-pot green syntheses of novel hydrophilic and superparamagnetic molecularly imprinted polymers (MMIPs) for the cleanup and extraction of hydrochlorothiazide (HCT) in human urine are described. The MMIPs were prepared via a sol gel process using Fe3O4 magnetite as a magnetic component, HCT as a template, tetraethyl orthosilicate (TEOS) as the cross-linker, and 3-aminopropyl trimethoxysilane (APTMS) as the functionalized monomer, which could simplify the imprinting process. During the synthesis process, a surfactant was especially used to graft the silica-imprinted nanoparticles. The key step of this research is mild working temperature without consuming any organic solvent during the synthesis of MMIPs in addition to its ability for efficient and highly selective enrichment of HCT in complicated human urine. The morphology, structure, and magnetic properties of the MMIPs were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometry (VSM). The prepared MMIPs were found to be superparamagnetic, which makes them easy to be quickly separated from the sample solution and thus decreases the extraction time. After the dispersive solid phase extraction (d-SPE) by the prepared MMIPs, high performance liquid chromatography (HPLC) was used to determine the target analyte, HCT. Several factors affecting the extraction efficiency, including the pH of the sample solution, the amount of adsorbent, sonication time, eluent, and washing solvent volumes, were evaluated, and the optimum conditions were obtained using the experimental design methodology. Under the optimized conditions, the developed MMIPs-d-SPE linearly responded over 2.5-1000 mu g L-1 while a detection limit of 0.75 mu g L-1 was obtained. The high selectivity of this method makes it suitable for successful monitoring of analyte in a real sample such as urine with satisfactory recoveries of 90.7-110.0% with the precision of 0.8-6.6%.