Green Chemistry Perspective Research Articles

Fe3O4 nanoparticles coated by new functionalized tetraaza-2,3 dialdehyde micro-crystalline cellulose: synthesis, characterization, and catalytic application for degradation of Acid Yellow 17

In this study, we developed an original approach for preparing cellulose-coated magnetite nanoparticles (NPs). Two novel Schiff bases (PDA-g-DAC) and [Bz-(PDA-g-DAC)] were synthesized via condensation reactions of periodate oxidized micro-crystalline cellulose (DAC) with o-phenylene diamine (PDA) to obtain its azomethine derivative with 85% yield. Subsequently, the functionalization of (PDA-g-DAC) with benzil (Bz) yields the tetraaza macrocycle [Bz-(PDA-g-DAC)]. The physicochemical characterization of the condensation products was performed using 13CNMR, FTIR, ATG, DSC, and X-ray diffraction techniques. Magnetic nanomaterial-based Schiff base cellulose was successfully prepared using in situ chemical co-precipitation of coordinated ferric and ferrous ions in cellulose Schiff base matrix under optimized conditions, and then, its magnetic properties were characterized. The results demonstrated that the Fe3O4 NPs coated with [Bz-(PDA-g-DAC)] were homogeneously coated in the matrix under ultrasonic irradiation with the saturation magnetization of 69.50 emu g−1. In addition, XRD line broadening analysis showed that the average particle size of the NPs was 37.3 nm. Furthermore, FTIR spectra demonstrated that [Bz-(PDA-g-DAC)] concavity was anchored to magnetite Fe3O4 NPs through azomethine groups. Vibrating sample magnetometry (VSM) of [Bz-(PDA-g-DAC)@Fe3O4] magnetic nanocomposite samples showed the typical behavior of ferromagnetism. This study provided a green and facile method to inhibit magnetic nanoparticle aggregation. Activity results revealed that the prepared [Bz-(PDA-g-DAC)@Fe3O4] catalyst shows the maximum activity for degradation of Acid Yellow 17 (AY17) compared to other prepared catalysts. After degradation reaction, the [Bz-(PDA-g-DAC)@Fe3O4] catalyst was recovered from the reaction mixture via an external magnet and used for further five consecutive cycles with excellent catalytic activity, successively, which was comparable to the fresh catalyst. The catalyst degradation efficiency and its easy separation exhibited that [Bz-(PDA-g-DAC)@Fe3O4] catalyst is a promising material for the removal of AY17 from aqueous solutions in green chemistry perspectives.

Green methods for the synthesis of metal nanoparticles using biogenic reducing agents: a review

Abstract Metal nanoparticles are being extensively used in a variety of sectors, including drug delivery, cancer treatment, wastewater treatment, DNA analysis, antibacterial agents, biosensors and catalysts. Unlike chemically produced nanoparticles, biosynthesized metal nanoparticles based on green chemistry perspectives impose limited hazards to the environment and are relatively biocompatible. This review is therefore focused on green methods for nanoparticle synthesis by emphasizing on microbial synthesis using bacteria, fungi, algae, and yeasts, as well as phytosynthesis using plant extracts. Furthermore, a detailed description of bioreducing and capping/stabilizing agents involved in the biosynthesis mechanism using these green sources is presented.

Biocatalytic aminolysis of ethyl (S)-mandelate by lipase from Candida antarctica

Enzymes play many roles in the advancement of biotechnology, discovery of new therapeutic agents and industrial processes. In this perspective, aminolysis reactions using lipase from Candida antarctica (CAL-B) were performed from ethyl (S)-mandelate and several aliphatic amines (45°C, hexane, 3–6h). By means of optimized conditions, amides with excellent isolated yields (60–97%) were synthetized. The biotechnological potential of CAL-B as a promising approach for the synthesis of organic compounds in a more sustainable, rapid, efficient and green chemistry perspective was verified on these results.

Highly Selective Solid Acid Catalyst H1−xTi2(PO4)3−x(SO4)x for Non-Oxidative Dehydrogenation of Methanol and Ethanol

The conversion of alcohols towards aldehydes in the presence of catalysts by non-oxidative dehydrogenation requires special importance from the perspective of green chemistry. Sodium (Na) super ionic conductor (NASICON)-type hydrogen titanium phosphate sulfate (HTPS; H1−xTi2(PO4)3−x(SO4)x, x = 0.5–1) catalysts were synthesized by the sol-gel method, characterized by N2 gas sorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), NH3 temperature-programmed desorption (NH3-TPD), ultraviolet–visible (UV-VIS) spectroscopy, and their catalytic properties were studied for the non-oxidative dehydrogenation of methanol and ethanol. The ethanol is more reactive than methanol, with the conversion for ethanol exceeding 95% as compared to methanol, where the conversion has a maximum value at 55%. The selectivity to formaldehyde is almost 100% in methanol conversion, while the selectivity to acetaldehyde decreases from 56% to 43% in ethanol conversion, when the reaction temperature is increased from 250 to 400 °C.

Sequestration of Methylene Blue and Lead ions by MWCNT Modified with Polyconducting Polymers

Taking into consideration the perspective of green chemistry, an attempt was made to investigate regenerative material for carbon nanotubes (CNTs) with high productivity. The special properties of CNTs, such as easy functionalization ability, high surface area, and unique thermal, mechanical, and electrical properties, make them an appealing component for composite materials, which resulted in the attraction of great interest on CNT-based composites. This research work focuses mainly on multiwall carbon nanotubes (MWCNTs) synthesized from camphor over iron nitrate catalyst supported on alumina by wet impregnation method. The formation of MWCNTs and incorporation of poly conducting polymers (o- and m-Toluidine) on the surface of MWCNTs was confirmed by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Ultraviolet visible spectroscopy (UV-Vis), low temperature nitrogen adsorption and Thermo-Gravimetric analysis (TGA). The performance evaluation of as-synthesized MWCNTs and their nanocomposites towards adsorption of methylene blue (MB) dye and Pb(II) was also highlighted. MWCNTs and their nanocomposites pose a great potential as a promising material for application in adsorption from aqueous solution.

Fe3O4-CeO2 metal oxide nanocomposite as a Fenton-like heterogeneous catalyst for degradation of catechol

Magnetically separable Fe3O4-CeO2 metal oxide nanocomposite materials were prepared by co-precipitation method keeping the view of developing an efficient Fenton-like heterogeneous catalyst for the degradation of organic pollutants at simple reaction conditions. The prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Thermogravimetric analysis (TGA), BET analysis, Field emission scanning electron microscope (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM). These materials were used as heterogeneous catalyst for the degradation of catechol from aqueous solutions in the presence of hydrogen peroxide (H2O2) at room temperature to evaluate the catalytic activities. The degradation of catechol was monitored by UV–Vis spectrophotometer and the formation of degraded products like 2-hydroxy-1,4-benzoquinone, acetic acid, β-ketoadepic acid, Glyoxilic acid and Glutaconic acid were identified with the help of Liquid chromatography mass spectrometry (LC–MS) studies. The catalytic activities were evaluated in terms of reaction parameters like pH, amount of catalyst and H2O2 concentration. Activity results revealed that the prepared Fe3O4-CeO2 (15wt%) catalyst shows the maximum activity for degradation of catechol as compared to the other prepared catalysts. After the degradation reaction the Fe3O4-CeO2 catalyst was recovered from the reaction mixture by using an external magnet and successively used for five consecutive cycles with excellent catalytic activity which is comparable to the fresh catalyst. The efficiency in degradation and easy separation of the catalyst exhibits that Fe3O4-CeO2 (15%) catalyst is promising for the removal of catechol from aqueous solutions from green chemistry perspectives.

Sample Treatment in Organic Compound Determination: A Green Chemistry Perspective

Sample Treatment in Organic Compound Determination: A Green Chemistry Perspective

ChemInform Abstract: Ionic Liquids in Chromatographic and Electrophoretic Techniques: Toward Additional Improvements in the Separation of Natural Compounds

AbstractReview: 95 refs.

Comparing Amide-Forming Reactions Using Green Chemistry Metrics in an Undergraduate Organic Laboratory

In this laboratory experiment, upper-division undergraduate chemistry and biochemistry majors investigate amide-bond-forming reactions from a green chemistry perspective. Using hydrocinnamic acid and benzylamine as reactants, students perform three types of amide-forming reactions: an acid chloride derivative route; a coupling reagent promoted method; and a boric acid catalyzed condensation. After isolation of the common product, students assess the reactions using the 12 Principles of Green Chemistry and several green chemistry metrics: atom economy; reaction mass efficiency; process mass intensity; and the EcoScale. In addition to assessing what route is the greenest, students also compare the metrics to discern what aspects of green chemistry each metric captures. In order to extend sustainability to economic considerations, the projected “front-end” cost of synthesizing a kilogram of the amide is calculated based on data from each reaction. The experimental work is conducted over two 3 h laboratory pe...

Nobel metal free, oxidant free, solvent free catalytic transformation of alcohol to aldehyde over ZnO-CeO2 mixed oxide catalyst

The catalytic transformation of alcohols to aldehydes under oxidant-free condition has drawn significant attention from the perspective of green chemistry. In this work, we designed noble metal free ZnO-CeO2 mixed oxide catalyst in four different ratios and tested for vapor phase benzyl alcohol dehydrogenation reaction as a model reaction under oxidant free condition. The ZnO-CeO2 mixed oxide catalyst having ratio Zn/Ce=30/70 composition showed highest selectivity towards formation of benzaldehyde. Interestingly in addition to benzaldehyde, toluene was formed in the reaction due to hydrogenolysis of benzyl alcohol. The lowest Ce3+/Ce4+ ratio was observed from the XPS analysis of Ce(3d) core electron for the catalyst having Zn/Ce=30/70 composition compared to others. CO2-TPD results proved that mostly the medium strength basic sites were responsible for hydrogen abstraction from benzyl alcohol producing benzaldehyde. H2-TPR results showed that ZnO-CeO2 catalyst (Zn/Ce=30:70) had lowest reduction temperature which is in the 673K to 573K temperature range. The amount of toluene was higher for the ZnO-CeO2 catalyst having Zn/Ce=40:60 ratio which had less basic sites and higher fraction of Ce3+ ion. The ZnO-CeO2 catalyst (Zn/Ce=30:70) did not deactivate for a reaction time up to 2h. While successive regenerations of the catalyst, toluene selectivity were increased. This may be due to the reduction of Ce4+ to Ce3+ by adsorbed hydrogen species. Also the ZnO-CeO2 catalyst (Zn/Ce=30/70) showed activity for the formation of ethanal, propanal, butanal and octanal along with corresponding alkanes from ethanol, 1-propanol, 1-butanol and 1-octanol in oxidant free condition demonstrating the in-situ generation of hydrogen. The micro kinetic analysis showed that there is no external and internal mass transfer limitation in the present case.

Green Synthesis of Gold Nanoparticles Using Tamarindus indica Extract as a Bioreductant

Over the last few decades, economically viable, straightforward and green route for the synthesis of nanomaterial has drawn the attention of researchers in the area of nanoscience and technology. Applications of economical and non-toxic chemicals, environmentally safer solvents and renewable products materials are the advantages of nanoscience and technology considering researchers to use green route for large scale manufacturing. It is well documented that the synthesis and stabilization of nanomaterials usually depends upon reaction medium, reducing agents (RA) and capping agent, that is why these three factors must be taken into the consideration comprehensively from an economic and green chemistry perspective. A novel green approach for the synthesis of gold nanoparticles has been proposed over here by using fruit extract of Tamarindus indica fruit extract (TIFE). When 2 mL of TIFE was added into 2 mL of 1 mM tetrachloroauric acid solution the color changed from light yellow to purple brown was observed indicating the formation of Gold nanoparticles. It was confirmed by UV-Visible spectroscopy showing a sharp peak at 540 nm. Transmission Electron Microscopy (TEM) an EDAX analyses indicated that the shapes and sizes of formed gold nanoparticles were depending upon the reaction conditions. X-Ray diffraction pattern indicated that the synthesized nanoparticles were purely face centered cubic crystal. The gold nanoparticles were found to have significant in vitro stability. The mechanism of formation of gold nanoparticles has been explored and it was found that tartaric acid and glucose which were the major active constituents of the TIFE, were behaving as a bioreductants as well as capping agents. Keywords: Bioreductant, green synthesis, gold nanoparticles, stabilizers, tamarind extract.

A room temperature synthesizable and environmental friendly heterogeneous ZIF-67 catalyst for the solvent less and co-catalyst free synthesis of cyclic carbonates

Catalysts capable of materializing high performance without compromising the green credentials are a pre-requisite for the establishment of a sustainable process. Herein, ZIF-67, a cobalt based zeolitic imidazolate framework possessing acid-base bifunctionalities, is reported for its application in the artificial fixation of CO2 via cyclic carbonate synthesis. The ZIF-67 is synthesizable in water at room temperature with inexpensive precursors in less than 3h. The heterogeneous ZIF-67 was found catalytically efficient towards CO2-oxirane coupling under moderate reaction conditions with nearly complete selectivity towards five membered cyclic carbonates under solvent free and co-catalyst free conditions and it exhibited good reusability, outperforming the previously reported ZIF catalyst systems on efficiency and economic-environmental aspects. Crystal defects on the surface of the catalyst supposedly assumed to exert opportunistic catalytic roles in this liquid phase cycloaddition reaction and the plausible mechanism with multiple physico-chemical characterizations was proposed. In comparison with the previously reported heterogeneous catalysts synthesized by complicated multistep synthesis involving organic solvents and high temperature, the facile one-pot water mediated room temperature synthesis of ZIF-67 with acido-basic dual active sites makes it more practical for high-performance heterogeneous catalysis ensuring green chemistry perspectives.

Expedient Access to Unsymmetrical Diarylindolylmethanes through Palladium-Catalyzed Domino Electrophilic Cyclization-Extended Conjugate Addition Approach.

A palladium-catalyzed domino process to access unsymmetrical diarylindolylmethanes has been developed through the annulation of o-alkynylanilines followed by 1,6-conjugate addition with p-quinone methides (p-QMs) under relatively mild conditions. The broad substrate scope of this methodology was demonstrated through the use of a wide range of substituted o-alkynylanilines and p-quinone methides, and in most cases, the unsymmetrical diarylindolylmethanes could be prepared in moderate to excellent yields. Notably, this method does not require any amino group protection. Moreover, 100% atom economy makes this transformation attractive from a green chemistry perspective.

A facile preparation method for synthesis of silica sulfuric acid/poly(o‐methoxyaniline) core–shell nanocomposite

A new nanocomposite of poly(o‐methoxyaniline) (POMA) is introduced by overlayer formation of POMA on silica. The key appealing feature of the synthesis is the role of silica sulfuric acid (SSA) both as solid acid dopant and template in overlayer self‐assembly of POMA on silica surface. Hereon siloxide group (Si―O−) of silica surface is replaced with dopant anion of SSA (≡Si―O―SO3−), which leads to formation of a overlayer of POMA on the silica surface. The composite particles are spherical in the nanoscale range of 50 nm without application of any external template (no‐template synthesis). Nanocomposite was fully characterized by various instrumentation methods: Fourier transform infrared (FT‐IR), ultraviolet–visible (UV–vis), thermogravimetric analysis (TGA), diffrential thermal analysis (DTA), elemental analysis (CHNS), energy dispersive X‐ray (EDX), X‐ray photoelectron spectroscopy (XPS) and X‐ray difraction (XRD). Based on XPS and CHNS results, it is demonstrated that the doping level of POMA is as high as 50% and for the first time the ratio of 4:2:2 is obtained for ―NH― (amine): ―HN.+― (polarons): HN+― (bipolarons), respectively. In fact, bipolarons may also coexist with polarons with a 1:1 ratio of them. Moreover, the synthesis benefits from the perspective of green chemistry which is preparation under solid‐state (solvent‐free) condition. Copyright © 2015 John Wiley & Sons, Ltd.

Green synthesis of calcium silicate bioceramic powders

Calcium silicates have proven to be potential candidates for biomedical applications because of their osteogenic properties. Sol–gel methods are typically used for the preparation of calcium silicate powders. However, in the sol–gel route, an acid or base and ethanol are used to catalyze the precursors. From the perspective of green chemistry, it is better to avoid the use of organic solvents. The objective of this study was to prepare calcium silicate powders using a green synthesis route (hydrothermal method) without organic solvents. The powders were also prepared via the sol–gel process using tetraethoxysilane (TEOS) and calcium nitrate as the raw materials for the purpose of comparison. The powders were sintered at temperatures ranging from 600 to 1000°C after the application of both methods. To understand the feasibility of using the resulting materials in medical applications for bone repair, the powders were mixed with water to form cements. The results indicated that the powder composition was not significantly affected by the different techniques but was dependent on the Ca:Si ratio of the precursors and on the sintering temperature. The different techniques produced no differences in powder morphology. In addition, the setting times of the powder-derived cements were found to be independent of the sintering temperature and synthesis technique, but it was affected by the Ca:Si ratio of the precursors. The mechanical strength of the cements was similar. These encouraging results suggest that the hydrothermal method is a potentially beneficial alternative to the sol–gel route for the production of calcium silicate powders.

Conventional to Nano-Green Adsorbents for Water Pollution Management - A Review

Pure and clean water is a must for living a healthy life. However, the increasing influence of urbanization, industrialization, domestic and agricultural activities, is continuously adding both conventional and newly emerging pollutants to the earth's water bodies, seriously affecting both the terrestrial and aquatic flora and fauna. Thus water pollution has become a major issue in the global perspectives. In the last few decades, numerous methods, such as chemical precipitation, filtration, oxidation, ion exchange treatment and adsorption have been proposed for the purification of contaminated water. Among these methods, adsorption has taken an important position in water purification technology. This is because of its ease of operations, cost-effective maintenance, and availability of adsorbents in various forms with high surface area, porous structure and specific surface reactivity. Instead of having many attractive properties, many adsorbents have failed to achieve a good acceptability at commercial levels. In the recent years, nanotechnology approaches have introduced nanoadsorbent which is capable of removing water pollutants more efficiently. In this review, various water treatment techniques with their shortcomings followed by efficiency of adsorption and nanoadsorbent for pollutant removal are discussed with green chemistry perspectives.

Titanium Catalyzed Enantioselective Oxidation of Thioethers with Hydrogen Peroxide

Catalytic asymmetric oxidation of prochiral sulfides has been a challenging goal for years, which reflects the importance of sulfinyl group as a chiral controller in many organic transformations, as well as the existence of natural and synthetic biologically active products that need a sulfinyl group with a defined stereoconfiguration. 30 years ago, owing to the milestone discoveries of Kagan and Modena, titanium-dialkyltartrate/alkyl hydroperoxide catalyst systems emerged as the protagonists in this area. In the last decade, various types of novel titanium based catalyst systems were developed, exploiting ‘green’ hydrogen peroxide as the terminal oxidant. This mini-review is aimed at discussing recent advances in enantioselective sulfoxidations with H2O2 in the presence of new generation chiral titanium catalysts, demonstrating high reactivity, efficiency, and enantioselectivity, which are likely to contribute to preparative syntheses of biologically active sulfoxides in near future. Peculiarities of their behavior and mechanisms of their catalytic action are discussed. Their viability is analyzed from the industrial and green chemistry perspectives. Keywords: Asymmetric synthesis, homogeneous catalysis, hydrogen peroxide, kinetic resolution, mechanism, sulfoxides, titanium.

Interactions of microorganisms with rare earth ions and their utilization for separation and environmental technology

In recent years, rare earth elements (REEs) have been widely used in various modern technological devices and the global demand for REE has been increasing. The increased demand for REEs has led to environmental exposure or water pollution from rare earth metal mines and various commercial products. Therefore, the development of a safe technology for the separation and adsorption of REEs is very important from the perspective of green chemistry and environmental pollution. In this review, the application and mechanisms of microorganisms for the removal and extraction of REEs from aqueous solutions are described. In addition, the advantages in using microorganisms for REE adsorption and future studies on this topic are discussed.

Expanding GREENSCOPE beyond the gate: a green chemistry and life cycle perspective

Industrial processes, particularly those within the chemical industry, contribute products and services to improve and increase society’s quality of life. However, the transformation of raw materials into their respective final goods involves the consumption of mass and energy and the possible generation of by-products and releases. To address these issues, the new approach for chemical processing is focused on sustainable production: minimize raw material consumption and energy loads, minimize/eliminate releases, and increase the economic feasibility of the process. To evaluate these advances, a sustainability assessment methodology, GREENSCOPE, has been developed into a tool to evaluate and assist in the synthesis and design of chemical processes. New process sustainability indicators have been proposed based on input/output process data, and the base-case ratio approach is implemented to predict process changes from known process performance data and design relationships. In addition, a discussion regarding the implications of using sustainability evaluations beyond the process boundaries, applying the principles of green chemistry in all steps of chemical process development, and a description of their benefits to the life cycle inventory and the subsequent life cycle assessment is included. Finally, a new methodology approach to integrate GREENSCOPE into a life cycle inventory to develop sustainable systems is introduced.

ChemInform Abstract: Green Chemistry Oriented Organic Synthesis in Water

AbstractReview: 72 refs.