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Per- and polyfluoroalkyl substances (PFAS) are oxidatively recalcitrant organic synthetic compounds. PFAS are an exceptional group of chemicals that have significant physical characteristics due to the presence of the most electronegative element (i.e., fluorine). PFAS persist in the environment, bioaccumulate, and have been linked to toxicological impacts. Epidemiological and toxicity studies have shown that PFAS pose environmental and health risks, requiring their complete elimination from the environment. Various separation technologies, including adsorption with activated carbon or ion exchange resin; nanofiltration; reverse osmosis; and destruction methods (e.g., sonolysis, thermally induced reduction, and photocatalytic dissociation) have been evaluated to remove PFAS from drinking water supplies. In this review, we will comprehensively summarize previous reports on the photodegradation of PFAS with a special focus on photocatalysis. Additionally, challenges associated with these approaches along with perspectives on the state-of-the-art approaches will be discussed. Finally, the photocatalytic defluorination mechanism of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) following complete mineralization will also be examined in detail.

The synthetic dye discharge is responsible for nearly one-fifth of the total water pollution from textile industry, which poses both environmental and public health risks. Herein, a solid substrate inoculated with fungi is proposed as an effective and environmentally friendly approach for catalyzing organic dye degradation. Pleurotus ostreatus was inoculated onto commercially available solid substrates such as sorghum, bran, and husk. Among these, P. ostreatus grown on sorghum (PO-SORG) produced the highest enzyme activity and was further tested for its dye biodegradation ability. Four dye compounds, Reactive Blue 19 (RB-19), Indigo Carmine, Acid Orange 7, and Acid Red 1 were degraded by PO-SORG with removal efficiencies of 93%, 95%, 95%, and 78%, respectively. Under more industrially relevant conditions, PO-SORG successfully degraded dyes in synthetic wastewater and in samples collected from a local textile factory, which reveals its potential for practical usage. Various biotransformation intermediates and end-products were identified for each dye. PO-SORG exhibited high stability even under relatively extreme temperatures and pH conditions. Over 85% removal of RB-19 was achieved after three consecutive batch cycles, demonstrating reusability of this approach. Altogether, PO-SORG demonstrated outstanding reusability and sustainability and offers considerable potential for treating wastewater streams containing synthetic organic dyes.

Per- and polyfluoroalkyl substances (PFAS) are a set of synthetic chemicals which contain several carbon-fluorine (C‒F) bonds and have been in production for the past eight decades. PFAS have been used in several industrial and consumer products including nonstick pans, food packaging, firefighting foams, and carpeting. PFAS require proper investigations worldwide due to their omnipresence in the biotic environment and the resulting pollution to drinking water sources. These harmful chemicals have been associated with adverse health effects such as liver damage, cancer, low fertility, hormone subjugation, and thyroid illness. In addition, these fluorinated compounds show high chemical, thermal, biological, hydrolytic, photochemical, and oxidative stability. Therefore, effective treatment processes are required for the removal and degradation of PFAS from wastewater, drinking water, and groundwater. Previous review papers have provided excellent summaries on PFAS treatment technologies, but the focus has been on the elimination efficiency without providing mechanistic understanding of removal/degradation pathways. The present review summarizes a comprehensive examination of various thermal and non-thermal PFAS destruction technologies. It includes sonochemical/ultrasound degradation, microwave hydrothermal treatment, subcritical or supercritical treatment, electrical discharge plasma technology, thermal destruction methods/incinerations, low/high-temperature thermal desorption process, vapor energy generator (VEG) technology and mechanochemical destruction. The background, degradation mechanisms/pathways, and advances of each remediation process are discussed in detail in this review.

Advanced catalysts are crucial for a wide range of chemical, pharmaceutical, energy, and environmental applications. They can reduce energy barriers and increase reaction rates for desirable transformations, making many critical large-scale processes feasible, eco-friendly, energy-efficient, and affordable. Advances in nanotechnology have ushered in a new era for heterogeneous catalysis. Nanoscale catalytic materials are known to surpass their conventional macro-sized counterparts in performance and precision, owing it to their ultra-high surface activities and unique size-dependent quantum properties. In water treatment, nanocatalysts can offer significant promise for novel and ecofriendly pollutant degradation technologies that can be tailored for customer-specific needs. In particular, nano-palladium catalysts have shown promise in degrading larger molecules, making them attractive for mitigating emerging contaminants. However, the applicability of nanomaterials, including nanocatalysts, in practical deployable and ecofriendly devices, is severely limited due to their easy proliferation into the service environment, which raises concerns of toxicity, material retrieval, reusability, and related cost and safety issues. To overcome this limitation, matrix-supported hybrid nanostructures, where nanocatalysts are integrated with other solids for stability and durability, can be employed. The interaction between the support and nanocatalysts becomes important in these materials and needs to be well investigated to better understand their physical, chemical, and catalytic behavior. This review paper presents an overview of recent studies on matrix-supported Pd-nanocatalysts and highlights some of the novel emerging concepts. The focus is on suitable approaches to integrate nanocatalysts in water treatment applications to mitigate emerging contaminants including halogenated molecules. The state-of-the-art supports for palladium nanocatalysts that can be deployed in water treatment systems are reviewed. In addition, research opportunities are emphasized to design robust, reusable, and ecofriendly nanocatalyst architecture.

This research work explored the synthesis and characterization of magnetic manganese ferrites using a simple combustion method. The purpose of creating the magnetic manganese ferrites was for their planned use as ozonation catalysts. Their magnetic properties allow for their recovery from the treatment system. Magnetic manganese ferrites were prepared by mixing manganese nitrate and iron nitrate in a stoichiometric ratio of 1:2. Polyvinyl alcohol was added to the mixed metal salt solution and the ratio of PVA: total nitrate salt added was varied from 1:1 up to 1:2 by weight. The resulting particles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), tunneling electron microscope (TEM), and Ultraviolet–Visible spectroscopy (UV/Vis). Keywords: Synthesis, Magnetic particles, Water treatment

In recent years, the primary power sources for portable electronic devices are lithium ion batteries. However, they suffer from many of the limitations for their use in electric means of transportation and other high level applications. This mini-review discusses the recent trends in electrode materials for Li-ion batteries. Elemental doping and coatings have modified many of the commonly used electrode materials, which are used either as anode or cathode materials. This has led to the high diffusivity of Li ions, ionic mobility and conductivity apart from specific capacity. Many of the newly reported electrode materials have been found to deliver a better performance, which has been analyzed by many parameters such as cyclic stability, specific capacity, specific energy and charge/discharge rate. Hence, the current scenario of electrode materials of Li-ion batteries can be highly promising in enhancing the battery performance making it more efficient than before. This can reduce the dependence on fossil fuels such as for example, coal for electricity production. Keywords: Li-ion, Battery, Cathode, Anode, Electrode

Municipal wastewater has been identified as a potential source of natural phosphorus (P) that is projected to become depleted in a few decades based on current exploitation rates. This paper focuses on combining a bench-scale anaerobic/anoxic/aerobic membrane bioreactor (MBR) and magnesium carbonate (MgCO3)-based pellets to effectively recover P from municipal wastewater. Ethanol was introduced into the anoxic zone of the MBR system as an external carbon source to improve P release via the enhanced biological phosphorus removal (EBPR) mechanism, making it available for adsorption by the continuous-flow MgCO3 pellet column. An increase in the concentration of P in the MBR effluent led to an increase in the P adsorption capacity of the MgCO3 pellets. As a result, the anaerobic/anoxic/aerobic MBR system, combined with a MgCO3 pellet column and ethanol, achieved 91.6% P recovery from municipal wastewater, resulting in a maximum P adsorption capacity of 12.8 mg P/g MgCO3 through the continuous-flow MgCO3 pellet column. Although the introduction of ethanol into the anoxic zone was instrumental in releasing P through the EBPR, it could potentially increase membrane fouling by increasing the concentration of extracellular polymeric substances (EPSs) in the anoxic zone.

Abstract A titanium-based zeolitic thiophene-benzimidazolate framework has been designed for the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide. The developed catalyst activates carbon dioxide and delivers over 16% yield of DMC without the use of any dehydrating agent or requirement for azeotropic distillation.

A greener synthesis protocol for noble nanometals is developed using vitamin B12 as a reducing and capping agent in conjunction with the use of microwaves. Successful assembly of nanoparticles or microparticles with varied shapes and sizes have been demonstrated. The synthesized Ag, Au, and Pd samples were thoroughly characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission microscopy, and UV-visible spectrophotometry, confirming that metallic Ag, Au, and Pd were synthesized by the green chemistry method.

Various compositions of barium carbonate (BaCO3) loaded polycaprolactone (PCL) composites were prepared, including 2.5/97.5, 10/90, 30/70, 50/50 and 90/10 (PCL/BaCO3), via re-precipitation technique. Small-scale column tests were conducted to study the efficiency of sulfate removal using the PCL/BaCO3 composites. The composites before and after their use to remove sulfate were extensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and thermogravimetric analysis (TGA). As PCL is a biodegradable polymer, these composites are environmentally friendly and have several advantages over barium sulfate precipitation in overcoming clogging issues in filters or resins due to collection of natural organic matter (NOM). The media used in this study exhibited high capacity and was able to remove more than 90% sulfate from synthetic sulfate containing waters and NOM samples collected from the Ohio River.

Combustion synthesis of iron oxide/iron coated carbons such as activated carbon, anthracite, cellulose fiber, and silica is described. The reactions were carried out in alumina crucibles using a Panasonic kitchen microwave with inverter technology, and the reaction process was completed within a few minutes. The method used no additional fuel and nitrate, which is present in the precursor itself, to drive the reaction. The obtained samples were then characterized with X-ray mapping, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), selected area diffraction pattern (SAED), transmission electron microscopy (TEM), X-ray diffraction (XRD), and inductively coupled plasma (ICP) spectroscopy. The size of the iron oxide/iron nanoparticle-coated activated carbon, anthracite, cellulose fiber, and silica samples were found to be in the nano range (50–400 nm). The iron oxide/iron nanoparticles mostly crystallized into cubic symmetry which was confirmed by SAED. The XRD pattern indicated that iron oxide/iron nano particles existed in four major phases. That is, γ-Fe2O3, α-Fe2O3, Fe3O4, and Fe. These iron-coated activated carbon, anthracite, cellulose fiber, and silica samples were tested for arsenic adsorption through batch experiments, revealing that few samples had significant arsenic adsorption.

A “green” protocol was used for the rapid generation of nanoscale zerovalent iron (NZVI) particles using tea polyphenols. The NZVI particles were subsequently examined for in vitrobiocompatibility using the human keratinocyte cell (HaCaT) line as a representative skin exposure model. The cells were exposed to NZVI for time periods of 24 and 48 h. Biocompatibility was assessed using the methyl tetrazolium, or MTS, (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)) and lactate dehydrogenase (LDH) assays to determine in vitrocytotoxicity. The evaluation of mitochondrial function (MTS) and membrane integrity (LDH) in human keratinocytes showed that these “green” synthesized NZVI particles were nontoxic in the human keratinocytes exposed when compared with control samples synthesized using a borohydride protocol. In fact, in most cases, these “green” nanoparticles induced a prolific response in the cellular function even at the highest concentration (100μg ml−1). [ABSTRACT FROM AUTHOR]

There are several factors which influence the corrosion rate of lead, which in turn morphs into different crystal shapes and sizes. Some of the important factors are alkalinity, pH, calcium, orthophosphate, and silica. Low to moderate alkalinity decreases corrosion rates, while higher alkalinities have a tendency to increase the corrosion rates of lead. This work describes the effect of orthophosphate inhibitor and pH on the formation of different structures of lead phosphate/carbonate nanorods, nanobelts, microrods, and dendritic structures. The experiments were carried out at different pHs both with and without orthophosphate inhibitor under laboratory conditions, which were intended to represent actual drinking water distribution system (DWDS) conditions. The surface morphology and crystal structure of the different crystals were obtained using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), transmission electron microscopy (TEM), and selected area diffraction pattern (SAED). The phase identification was done using powder X-ray diffraction (PXRD). With the increase in pH from 6.5 to 8.5, the formation of uniform thickness coating of phosphate containing minerals was observed, which was in contrast to the different crystal growth under low pH conditions. The XRD patterns indicate that the surface solids contain a mixture of many phases. [ABSTRACT FROM AUTHOR]

An environmentally friendly one-step method to synthesize palladium (Pd) nanobelts, nanoplates and nanotrees using vitamin B1without using any special capping agents at room temperature is described. This greener method, which uses water as a benign solvent and vitamin B1as a reducing agent, can be extended to prepare other noble nanomaterials such as gold (Au) and platinum (Pt). Depending upon the Pd concentration used for the preparation, Pd crystallized in different shapes and sizes. A lower Pd concentration yielded a plate-like structure where thickness of these plates varied from 100 nm to 250 nm with a length of several microns. An increase in concentration of Pd resulted in the formation of tree-like structures. The Pd plates are grown on a single Pd nanorod backbone mimicking the leaf-like structures. Upon further increase in Pd concentration, Pd nanoplates started becoming thicker by vertically aligning themselves together to form ball-like structures. The synthesized self-assembled Pd nanoparticles were characterized using, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV spectroscopy. The Pd nanoparticles showed excellent catalytic activity for several C–C bond forming reactions such as Suzuki, Heck and Sonogashira reactions under microwave (MW) irradiation conditions. [ABSTRACT FROM AUTHOR]

The copper–carbon substrate of a transmission electron microscopy (TEM) grid reacted with aqueous silver nitrate solution within minutes to yield spectacular tree-like silver dendrites, without using any added capping or reducing reagents. These results demonstrate a facile, aqueous, room-temperature synthesis of a range of noble metal nano- and meso-structures that have widespread technological potential in the design and development of next-generation fuel cells, catalysts, and antimicrobial coatings. [ABSTRACT FROM AUTHOR]

The use of emerging microwave (MW)-assisted chemistry techniques in conjunction with benign reaction media is dramatically reducing chemical waste and reaction times in several organic syntheses and chemical transformations. The present review summarizes recent developments in MW-assisted synthesis, name reactions and organic transformations, and rapid generation of nanoparticles with uniform size distribution. Greener protocols have been developed for the synthesis of various bio-active heterocycles, namely 1,3,4-oxadiazoles, 1,3,4-thiadiazoles, 1,3-dioxanes, pyrazoles, hydrazones and 3,4-dihydropyrimidin-2(1H)-ones, which proceed under the influence of microwaves and using eco-friendly conditions. These high-yielding methods were catalyzed efficiently by solid-supported Nafion NR50 under solvent-free conditions and polystyrene sulfonic acid in aqueous media. The eco-friendly nucleophilic substitution chemistry in water to generate cyclic amines via double N-alkylation of primary amines or hydrazines by dihalides or tosylates enables the greener synthesis of a range of pharmaceutically active heterocycles. Similarly, efficient MW synthesis of various azides, thiocyanates, and sulfones in aqueous medium occurs wherein nucleophilic substitution reaction takes place in the absence of a phase-transfer catalyst. Bulk and shape-controlled synthesis of noble nanostructures via MW-assisted spontaneous reduction of noble metal salts using α-d-glucose, sucrose, and maltose is described. MW method also accomplishes the cross-linking reaction of poly(vinyl alcohol) with metallic systems such as Pt, Cu, and In; bimetallic systems, namely Pt–In, Ag–Pt, Pt–Fe, Cu–Pd, Pt–Pd, and Pd–Fe; and single-walled nanotubes, multi-walled nanotubes, and buckminsterfullerenes (C-60). The strategy is extended to the formation of biodegradable carboxymethyl cellulose (CMC) composite films with noble nanometals; such metal decoration and alignment of carbon nanotubes in CMC is possible using a MW approach that also enables the shape-controlled bulk synthesis of Ag and Fe nanorods in poly(ethylene glycol). [ABSTRACT FROM AUTHOR]

An extremely simple green approach that generates bulk quantities of nanocrystals of noble metals such as silver (Ag) and palladium (Pd) using coffee and tea extract at room temperature is described. The single-pot method uses no surfactant, capping agent, and/or template. The obtained nanoparticles are in the size range of 20–60 nm and crystallized in face centered cubic symmetry. The method is general and may be extended to other noble metals such as gold (Au) and platinum (Pt). [ABSTRACT FROM AUTHOR]

Bulk syntheses of silver (Ag) and iron (Fe) nanorods using poly(ethylene glycol) (PEG) under microwave irradiation conditions are reported. Favorable conditions to make Ag nanorods were established and can be extended to make Fe nanorods with uniform size and shape. The nanorods formation depended upon the concentration of PEG used in the reaction with Ag salt. The obtained Ag and Fe nanorods were characterized using scanning electron microscopy, transmission electron microscopy, and UV–visible spectroscopy. Ag and Fe nanorods crystallized in face centered cubic symmetry. The method uses no surfactant or reducing agent and is greener in nature which could open a myriad of applications. [ABSTRACT FROM AUTHOR]

A greener method to fabricate novel core (Fe and Cu)-shell (noble metals) metal nanocrystals using aqueous ascorbic acid (vitamin C) is described. Transition metal salts such as Cu and Fe were reduced using ascorbic acid, a benign naturally available antioxidant, and then addition of noble metal salts resulted in the formation of the core–shell structure depending on the core and shell material used for the preparation. Pt yielded a tennis ball kind of structure with a Cu core, whereas Pd and Au formed regular spherical nanoparticles. Au, Pt, and Pd formed cube-shaped structures with Fe as the core. Inversely, transition metals with noble metals, such as Pd, as the core also formed interesting structures; these structures were brushlike with indium as the shell and needle-like when Cu was employed as the shell. The method is general uses no surfactant or capping agent and can be extended to noble metals as cores and transition metals as shells. The core–shell nanocrystals were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), and UV–vis spectroscopy. These nanocrystals have unique properties that are not originally present in either the core or shell materials and may have potential functions in catalysis, biosensors, energy storage systems, nanodevices, and ever-expanding other technological applications. [ABSTRACT FROM AUTHOR]

A green approach is described that generates bulk quantities of nanocomposites containing transition metals such as Cu, Ag, In, and Fe at room temperature using a biodegradable polymer, carboxymethyl cellulose (CMC), by reacting respective metal salts with the sodium salt of CMC in aqueous media. These nanocomposites exhibit broader decomposition temperatures when compared with control CMC, and Ag-based CMC nanocomposites exhibit a luminescent property at longer wavelengths. The noble metals such as Au, Pt, and Pd do not react at room temperature with aqueous solutions of CMC, but do so rapidly under microwave irradiation (MW) conditions at 100 °C. This environmentally benign approach, which provides facile entry to the production of multiple shaped noble nanostructures without using any toxic reducing agent such as sodium borohydride (NaBH4), hydroxylamine hydrochloride, and so forth, and/or a capping/surfactant agent, and which uses a benign biodegradable polymer CMC, could find widespread technological and medicinal applications. The ensuing nanocomposites derived at room temperature and MW conditions were characterized using scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, UV−visible spectroscopy, X-ray mapping, energy-dispersive analysis, and thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

Dendritic nanoferrites with a micro-pine morphology have been synthesized for the first time under microwave irradiation conditions without using any reducing or capping reagent; the nanoferrites were then functionalized and coated with Pd metal, which catalyzes various organic transformations. [ABSTRACT FROM AUTHOR]