Degradation Of Contaminants In Water Research Articles

Photo responsive single layer MoS2 nanochannel membranes for photocatalytic degradation of contaminants in water

The major polluting aspects of our global fashion industries are the textile wastewater that turns black all our freshwater reservoirs. Nano-filtration through membrane technology is one of the biggest solutions of industrial wastewater treatment but the fouling of membrane is the major limitation of previous work. In this research, novel PVDF/MoS2-TNT (PMT) nanocomposite membranes were fabricated through a modified In-situ polymerisation phase inversion method. X-ray diffraction (XRD) analysis also confirmed the β-phase of PVDF within the developed PVDF/MoS2-TNT membrane. XPS analysis provides evidence about the presence of a specific chemical states of titanium nanotube and molybdenum disulphide which is involved in the photocatalytic degradation of pollutant molecules. Scanning electron microscope (SEM) shows that our membranes are porous in nature. PVDF/MoS2-TNT membranes exhibit excellent filtration efficiency (∼97%) for textile wastewater. The results and outcomes of the research demonstrate that PMT membranes have enormous potential in the commercial application of textile wastewater treatment.

Electro-activation of peroxymonosulfate using a carbon fiber membrane anode for high-efficient degradation of antibiotic wastewater: The dominant role of singlet oxygen

A flow-through peroxymonosulfate (PMS) electro-activation system with a polyacrylonitrile-based carbon fiber (PCF) membrane anode (denoted as E-PCF-PMS system) was developed. The introduction of the PCF membrane anode enabled the flow-through electrocatalytical system to achieve a remarkable tetracycline (TC) removal of 96.0 ± 0.2 % within 15 min, with a degradation rate of 0.273 min−1. Scavenging investigations revealed that singlet oxygen (1O2) was the dominant reactive oxygen species for TC degradation in the E-PCF-PMS system, and this finding was confirmed by electron paramagnetic resonance tests. Potential degradation pathways of TC were identified according to the detected intermediates and calculations of density functional theory, and a decreasing trend in the toxicity of TC intermediates was discovered. Thanks to the 1O2-dominated pathway, the constructed E-PCF-PMS system could achieve efficient TC degradation under different concentrations of several common anions (Cl−, NO3−, HPO42−, and HCO3−) and humic acid (HA). General applicability and reusability tests demonstrated the excellent practicability of the proposed system. The PMS electro-activation system offers a potential technique for high-efficient degradation of contaminants in water and wastewater.

Retraction: Water Science & Technology 86 (9), 2303-2335: Synthesis characterization of Zn-based MOF and their application in degradation of water contaminants, Saade Abdalkareem Jasim, Hawraz Ibrahim M. Amin, Ahmad Rajabizadeh, Marcos Augusto Lima Nobre, Fariba Borhani, Abduladheem Turki Jalil, Marwan Mahmood Saleh, Mustafa M. Kadhim and Mehrdad Khatami, https://doi.org/10.2166/wst.2022.318.

Retraction: Water Science & Technology 86 (9), 2303-2335: Synthesis characterization of Zn-based MOF and their application in degradation of water contaminants, Saade Abdalkareem Jasim, Hawraz Ibrahim M. Amin, Ahmad Rajabizadeh, Marcos Augusto Lima Nobre, Fariba Borhani, Abduladheem Turki Jalil, Marwan Mahmood Saleh, Mustafa M. Kadhim and Mehrdad Khatami, https://doi.org/10.2166/wst.2022.318.

Asymmetrically Coordinated CoB1 N3 Moieties for Selective Generation of High-Valence Co-Oxo Species via Coupled Electron-Proton Transfer in Fenton-like Reactions.

High-valence metal species generated in peroxymonosulfate (PMS)-based Fenton-like processes are promising candidates for selective degradation of contaminants in water, the formation of which necessitates the cleavage of OH and OO bonds as well as efficient electron transfer. However, the high dissociation energy of OH bond makes its cleavage quite challenging, largely hampering the selective generation of reactive oxygen species. Herein, an asymmetrical configuration characterized by a single cobalt atom coordinated with boron and nitrogen (CoB1 N3 ) is established to offer a strong local electric field, upon which the cleavage of OH bond is thermodynamically favored via a promoted coupled electron-proton transfer process, which serves an essential step to further allow OO bond cleavage and efficient electron transfer. Accordingly, the selective formation of Co(IV)O in a single-atom Co/PMS system enables highly efficient removal performance toward various organic pollutants. The proposed strategy also holds true in other heteroatom doping systems to configure asymmetric coordination, thus paving alternative pathways for specific reactive species conversion by rationalized design of catalysts at atomic level toward environmental applications and more.

A review on nanomaterial-based heterogeneous photocatalysts for removal of contaminants from water

The rising concentration of pollutants in the environment due to partially treated or untreated wastewater entering the surface waters has seriously challenged the integrity of the ecosystem and the quality of water for human health. Therefore, it is crucial to establish a productive and economical process to degrade recalcitrant pollutants from various water matrices owing to the ineffectual removal of these contaminants by conventional treatment methods. In this regard, advanced oxidation processes (AOPs), especially photocatalysis, have gained much attention due to their unique properties, such as low-cost, easy synthesis, and ability to produce reactive radicals under light irradiation with complete mineralization of recalcitrant pollutants. In this review, heterogenous photocatalysts, their fundamental properties, and their working mechanism have been described, along with their applications in the degradation of contaminants in water. Recent progress on pristine and modified nanomaterial-based photocatalysts for the degradation of various pollutants in water has been discussed. In particular, the removal of toxic heavy metals, pesticides, dyes, pathogens, pharmaceuticals, and other miscellaneous contaminants from water using a wide variety of nanomaterial-based heterogeneous photocatalysts has been summarized. The effect of temperature, solution pH, and loading of photocatalysts was found to be the most critical factors influencing the photocatalytic degradation of pollutants. Subsequently, the photocatalyst immobilization process using various support materials including carbon-based materials, glass, zeolites, and polymers in designing the efficient photocatalysts and future perspectives have been outlined.

Boosted Activity of g-C3N4/UiO-66-NH2 Heterostructures for the Photocatalytic Degradation of Contaminants in Water.

The combination of graphitic carbon nitride and the metal-organic framework UiO-66-NH2 has been developed with the aim to enhance the photocatalytic activity of pure semiconductors. Different proportions of g-C3N4 and UiO-66-NH2 were combined. Complete characterization analysis of the resulting photocatalytic materials was conducted, including N2 adsorption isotherms, XRD, FTIR, STEM-EDX microscopy, DRS-UV-visible, and photoluminescence. The photocatalytic activity was tested in an aqueous solution for the removal of acetaminophen as the target pollutant. From the obtained results, less than 50% of UiO-66-NH2 incorporated in the g-C3N4 structure enhanced the photocatalytic degradation rate of both bare semiconductors. Concretely, 75% of g-C3N4 in the final g-C3N4/UiO-66-NH2 heterostructure led to the best results, i.e., complete acetaminophen elimination initially at 5 mg·L-1 in 2 h with a pseudo-first order rate constant of ca. 2 h-1. The presence of UiO-66-NH2 in the g-C3N4 enhanced the optoelectronic properties, concretely, the separation of the photo-generated charges was improved according to photoluminescence characterization. The better photo-absorption uptake was also confirmed by the determination of the quantum efficiency values of the heterostructure if compared to either pure g-C3N4 or UiO-66-NH2. This photocatalyst with the best activity was further tested at different pH values, with the best degradation rate at a pH close to the pHpzc ~4.15 of the solid. Sequential recycling tests demonstrated that the heterostructure was stable after five cycles of use, i.e., 15 h. A high contribution of photo-generated holes in the process of the degradation of acetaminophen, followed marginally by superoxide radicals, was suggested by scavenger tests.

A portable architectonics of Al/carbon nitride/metal-organic frameworks anchored Ag nanoparticles for SERS detection and photocatalytic degradation of fungicide

In recent years, it is urgent to develop bi-functional materials for highly sensitive SERS detection and photocatalytic degradation of contaminants in water of fish pond. Herein, using 5-mercapto-1-methyltetrazole as the ligand, the tree-trunk like zeolitic imidazolate framework (ZIF-8) is induced and in-situ grown on the surface of aluminum/flower carbon nitride (Al/f-C3N4). Then, AgNPs are tightly anchored in ZIF-8 of Al/f-C3N4/ZIF-8 by strong Ag-N and Ag-S bonds, and a portable architecture of Al/f-C3N4/ZIF-8/Ag is successfully prepared. Results indicate that the Al/f-C3N4/ZIF-8/Ag architecture exhibits excellent SERS activity and the detection limit can as low as 2.15 × 10−11 mol⋅L−1 for crystal violet (CV, a typical fungicide). Also, the Al/f-C3N4/ZIF-8/Ag substrate presents good photocatalytic activity for CV molecule, and the degradation efficiency reaches 98.58% after illumination for 90 min. This is mainly due to the good adsorption capacity of ZIF-8 which can enrich more CV molecules and pull them to “hot spots” generated by Ag in Al/f-C3N4/ZIF-8/Ag, and thus SERS response are enhanced significantly. Besides, the strong synergistic effect of f-C3N4, ZIF-8 and AgNPs is also important which facilitates the separation of photogenerated electrons and holes. Thus, the designed portable and bi-functional substrate could be used as a potential material for the detection and removal of CV in practical application.

Synthesis and enhanced photocatalytic performance of Ni2+-doped Bi4O7 nanorods with broad-spectrum photoresponse

To fully utilize the solar energy, developing a suitable photocatalyst with broad-spectrum photoresponse is crucial in the degradation of water contaminants. In this work, Ni2+-doped Bi4O7 nanorods are prepared through a facile hydrothermal procedure. Various characterization techniques are adopted to explore the structure‐photocatalytic performance relationships of the obtained materials in degrading organic dye rhodamine B (RhB) and antibiotic ciprofloxacin (CIP). Compared with that of the pristine Bi4O7, the Ni2+-doping enlarges the specific surface area, lowers the band gap energy and reduces the electrons-holes recombination, thus improving photocatalytic performance. Catalyzed by the optimal 4 % Ni/Bi4O7 (20.0 mg), the elimination efficiencies of RhB and CIP (10.0 mg/L, 50.0 mL) are 97 % and 96 % within 2 h irradiated by visible light, respectively, which are obviously higher than that of Bi4O7. Also, the doped semiconductor exhibits satisfactory cycling stability. In addition, the possible photocatalytic degradation procedures of the pollutants and the plausible photocatalytic mechanism of the resulting composites are proposed. The excellent photocatalytic performance, low cost and facile preparation strategy endow the as-prepared 4 % Ni/Bi4O7 with broad-spectrum photoresponse a promising potential in environmental remediation.

One-Pot Fabrication of K-Doped g-C3N4/SiO2Composite with Enhanced Photocatalytic Activity for Degradation of Tetracycline

K-doped g-C3N4/SiO2composite (SiO2/K-CN) was synthesized by a facile thermal polymerization with potassium chloride, melamine and nano-silica as raw materials. The as-prepared SiO2/K-CN was characterized by various measures. The photocatalytic activity of SiO2/K-CN was tested via the photocatalytic degradation of tetracycline under visible-light irradiation. The results showed that the specific surface area of SiO2/K-CN catalyst was 28.16m2/g, which is larger than that of pristine K-doped g-C3N4. Both K-doping and silica-combination can reduce the recombination rate of photo-generated electrons-holes pairs and broaden the region of visible light-harvesting. Compared with the pristine K-doped g-C3N4 and composite SiO2/g-C3N4, SiO2/K-CN exhibits distinctly higher photocatalytic activity for degradation of tetracycline. The enhanced photocatalytic performance of SiO2/K-CN is attributed to the increased specific surface area and the synergistic effect of K-doping and silica-combination in both accelerating separation of charged carries and improving visible light-absorption. During photocatalytic degradation of tetracycline, superoxide radicals play the most important role, followed by holes.SiO2/K-CN complex has excellent stability and shows promising application in photocatalytic degradation of organic contaminants in water.

N,Fe-Doped Carbon Dot Decorated Gear-Shaped WO3 for Highly Efficient UV-Vis-NIR-Driven Photocatalytic Performance

The development of efficient and non-toxic photocatalysts with a full spectrum response is a primary strategy in the area of photocatalytically mediated pollutant elimination. Herein, we report the preparation of novel nitrogen and iron co-doped carbon dots/gear-shaped WO3 (N,Fe-CDs/G-WO3) with significantly improved broad-spectrum utilization. Characterization results demonstrated that the gear-shaped G-WO3, decorated by N,Fe-CDs with excellent electron transfer/reservoir properties, possessed abundant oxygen vacancies, had large specific surface areas, had multiple light-reflections and had a narrow band gap. As a result, the N,Fe-CDs/G-WO3 composite exhibited excellent photocatalytic activity towards the degradation of water contaminants under full spectrum irradiation. For example, the photodegradative efficiencies of rhodamine B (RhB) reached 81.4%, 97.1%, and 75% in 2 h, under ultraviolet, visible, and near-infrared (UV, vis, and NIR) light irradiation, respectively. Moreover, the N,Fe-CDs/G-WO3 composite also exhibited an outstanding photocatalytic degradation efficiency for other dyes, pharmaceuticals, and personal care products (PPCPs) like methylene blue (MB), ciprofloxacin (CIP), tetracycline hydrochloride (TCH), and oxytetracycline (OTC) (91.1%, 70.5%, 54.5%, and 47.8% in 3 h, respectively). The radical trapping experiments indicated that h+ and ·OH were the main reactive oxidative species (ROS), and the conversion between Fe (III) and Fe (II) played a key role in the photocatalytic reactions. Such a N,Fe-CD decorated material with brilliant photocatalytic activity has tremendous potential for application in environmental remediation.

Magnetic properties of TiO2/graphitic carbon nanocomposites

AbstractTiO2 is the most promising oxide semiconductor extensively used as photocatalyst in solar energy conversion into hydrogen and electric energy as well as in degradation of contaminants in water. To increase its efficiency, carbon dopants are applied. A series of TiO2/graphitic carbon nanocomposites with enhanced photocatalytic performance was synthesized at different temperatures in the 300 – 850°C range in the presence of benzene vapours. To investigate the magnetic properties of these nanocomposites, the dc magnetic susceptibility and electron paramagnetic resonance (EPR) measurementswere carried out. Magnetometry revealed the presence of three very different components: a temperature independent and easily recognized in the high-temperature range, another one in 20 – 100 K range displaying a slow increase with temperature decrease and saturation at low temperatures, and the third one observed at T < 20 K showing a sharp increase with decreasing temperature. Five types of EPR spectra were detected in the investigated samples and attributed to various paramagnetic centres. The role of TiO2 phase composition, nanocrystalline sizes, carbon content in its different forms in establishing static and dynamic magnetic response of our samples will be discussed.

Removal of organic dye by biomass-based iron carbide composite with an improved stability and efficiency.

The efficiency of zero-valent iron (Fe0) for the degradation of contaminants in water or soil can be highly reduced by side reactions with oxygen or water. This work was conducted to test whether this drawback can be effectively suppressed by the carbonation of Fe0 with pyrolyzed biomass, which forms a Fe3C composite. The composite Fe3C was characterized and its reactivity and stability were assessed in batch tests with methyl orange (MO) as a model pollutant. The results indicated that the removal rate of MO on Fe3C composite was higher than that of Fe0 (7.587 mg/(g·min) vs. 4.306 mg/(g·min)) at pH 4, where the degradation mechanism was confirmed by high-performance liquid chromatography-mass spectrometry. More importantly, the produced iron oxide in the Fe3C composite was highly suppressed. Regeneration studies showed that after three times of cycling, the removal efficiency of MO on Fe3C composite was kept to 99.42%, but Fe0 almost lost its reactivity. In situ chemical reduction of a colorimetric redox probe (indigo-5, 5'-disulfonate, I2S) quantitatively demonstrated that Fe3C composite has the reduction kinetics of I2S obviously slower than Fe0, indicating that Fe3C composite improved the stability of incorporated Fe0 to resist the side oxidation.

Theoretical studies of photocatalytic behaviors of isoelectronic C/Si/Ge/Sn-doped TiO2: DFT + U

The electronic structures and absorption spectra have been studied with density functional theory plus U for isoelectronic impurities C/Si/Ge/Sn-doped anatase TiO2. Our theoretical results show silicon atoms can attract electrons from the surrounding oxygen atoms due to their greater electronegativity than that of titanium atoms which leads to increasing the energy of 2p orbitals of the surrounding oxygen atoms and then forming new acceptor impurity level composed of oxygen 2p orbitals near the top of TiO2 valence band. This new acceptor level can easily bind the photoexcited holes for a period of time, thus effectively preventing the recombination of photo-excited electron-hole pairs, which play a key role in achieving higher light photocatalytic activity than pure TiO2 for degradation of contaminants in water. We also systematically described the electronic structure and optical properties of the germanium doped system and then explained experimental observations of absorption spectra with red-shift at a suitable Ge dopant concentration. Especially, compared with pure TiO2, Sn-doped TiO2 has better photocatalytic activity because of the synergistic effect of Sn atoms and oxygen vacancies. Our theoretical calculations not only explained the key role of isoelectronic defect in preventing the recombination of photo-excited electron-hole pairs but also provided a new way for enhance of photocatalytic activity.

Photocatalytic degradation of recalcitrant micropollutants by reusable Fe 3 O 4 /SiO 2 /TiO 2 particles

Abstract Photocatalysis promotes the degradation of contaminants in water, transforming them into by-products with lower or no toxicity. The photocatalysts can be applied in suspension or immobilized onto a support. The aim of using the immobilized form against the suspension form is that the costly extra final filtration process can be avoided, which is particularly important in water decontamination. This work reports on reusable Fe3O4/SiO2/TiO2 particles and the assessment of their photocatalytic activity on the degradation of methylene blue (MB), ciprofloxacin (CIP), norfloxacin (NOR) and ibuprofen (IBP). To achieve the most efficient photocatalyst it is necessary to determine the optimal thermal treatment parameters therefore, the Fe3O4/SiO2/TiO2 particles were calcined at different temperatures (500 °C and 600 °C) and times (30 min and 60 min). Higher degradation rates were achieved with calcination at 600 °C, reaching a total degradation of CIP, NOR, and MB, and half of IBP. The reuse of the magnetic particles is an economic and eco-friendly way to treat polluted water. The produced Fe3O4/SiO2/TiO2 particles showed a remarkable photocatalytic degradation of recalcitrant micropollutants, without significant efficiency loss after five uses. In addition, no other works reporting on the degradation of recalcitrant micropollutants using similar magnetic particles were found in the literature.

Size dependence of uniformed carbon spheres in promoting graphitic carbon nitride toward enhanced photocatalysis

Recently, graphitic carbon nitride (GCN) has been extensively employed as a metal-free, visible-light-responsive photocatalyst. The strong recombination rate of photo-induced charges and small surface area limit its wide applications. In this study, monodisperse carbon nanospheres (CS) with a uniform size were synthesized from resorcinol-formaldehyde resin using different surfactants and then loaded onto GCN via a hydrothermal treatment. It was found that the size of CS influenced the properties and photocatalytic performances of the CS/GCN hybrids. All the CS/GCN catalysts exhibited higher photocatalytic activities in degradation of water contaminants, antibiotic sulfachloropyridazine and methylene blue, under visible light irradiations. Photoluminescence spectra and photocurrent analysis indicated that hybridization with the carbon spheres at 200–500nm will significantly reduce the electrocarrier recombination of carbon nitride while increase the photocurrent intensity, resulting in much better photocatalysis.

Solar degradation of contaminants in water: TiO2 solar photocatalysis assisted by up-conversion luminescent materials

Solar energy, along with other renewable resources, could potentially solve environmental problems, as demonstrated by recent developments in the use of solar energy, such as solar photocatalysis. Solar photocatalytic technology has been demonstrated to be effective for treating groundwater, drinking water, wastewater and air and soil pollution. In this study, a solar photocatalytic application for wastewater decontamination is presented. Luminescent material has been evaluated as up-conversion material for enhancing the photocatalytic activity. Wastewater decontamination by heterogeneous photocatalysis has been developed in a slurry photo-reactor, using TiO2 as a photocatalyst. The photoactivity of TiO2 under several sun irradiation conditions was investigated. The up-conversion luminescence agent ZBLAN, a rare-earth (Yb-Er-Tm) co-doped fluoride glass (ZrF4– BaF2–LaF3–AlF3–NaF), was incorporated to enhance the solar-driven activity of TiO2 because this material could transform the unused near-infrared sunlight tail into UV–vis radiation available for photoreaction activation. The use of ZBLAN has demonstrated an improvement over ordinary titanium dioxide photocatalytic activity under sunlight irradiation for the photocatalytic degradation of pollutants in wastewater. Our results demonstrating the contribution of up-conversion luminescence to the improved photoactivity of titanium dioxide suggest that it can be used to develop new technologies for treating wastewater using solar light.

A comparative study of photocatalytic degradation and mineralisation of an azo dye using supported and suspended nano-TiO2 under UV and sunlight irradiations

Purpose – This paper aims to introduce two methods for immobilisation of TiO2 nanoparticles on a glass plate by means of silicon resin as a medium. Then, to ensure the effectiveness of these stabilisation methods, the photocatalytic degradation and mineralisation of the dye C.I. Reactive Blue 21 (RB21), as a model organic pollutant, were compared using these immobilised systems and the suspended one utilizing UV and sunlight irradiations individually. Design/methodology/approach – TiO2 nanoparticles were supported onto a glass support by silicon resin as an adhesion agent by spraying of TiO2 nanoparticles on the resin surface, which covered the glass plate or brushing the mixture of TiO2 and the resin onto the glass. The characteristics of the applied nano-TiO2 were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer – Emmett–Teller. Photocatalytic degradation and mineralisation of C.I. Reactive Blue 21 (RB21) by two immobilised systems were compared with suspended system in a batch mode under UV and sunlight irradiations after 2 h of treatment. Findings – The results showed that these immobilised modes had efficiencies, including 82-87 per cent degradation of RB21 and 52-58 per cent decrease in chemical oxygen demand (COD) for the operational time of 120 min, comparable to that of the suspended mode (91 per cent degradation of RB21 and, consequently, COD is decreased by 65 per cent). Comparison between photocatalytic efficiencies of two immobilised systems revealed that coating by spraying method performed better than brushing one due to more available surface area of TiO2. Finally, the results obtained from the mentioned supported systems under sunlight indicated the efficiencies about 87 to 89 per cent in comparison of the suspension system regardless of the reaction time enhancement up to 15 h compared to the UV irradiation. Research limitations/implications – In this research, the fixation of TiO2 nanoparticles on a substrate such as normal glass by an easy, inexpensive, durable, repairable and repeatable technique for wastewater treatment was introduced. Due to the simplicity and cheapness of these stabilisation methods and as these stabilisation methods are applicable on other substrates such as concrete, ceramics, etc., you can use these methods in major scales for purification of contaminated water, for example for stabilisation of TiO2 nanoparticles on wall pool utilized for water purification can be used. Originality/value – Two introduced immobilisation methods in this study are novel. The photocatalytic efficiency of these immobilised systems in degradation of water contaminants was investigated by using these systems in degradation and mineralisation of the dye C.I. Reactive Blue 21 (RB21), as a model organic pollutant compared with same TiO2 nanoparticles in an aqueous suspension system under UV light. Furthermore, this paper investigated replacing of inexpensive sources of UV light instead of UV lamps, and then the same photocatalytic reactions were carried out under sunlight as a UV source and degradation efficiencies by two UV sources were compared.

Photocatalytic microfluidic reactors utilizing titania nanotubes on titanium mesh for degradation of organic and biological contaminants

Microfluidic reactors have gained considerable interest for photocatalytic degradation of contaminants in water. These systems have advantages such as large surface-area-to-volume ratio and high control of fluid flow, yet still suffer from drawbacks due to limited mass transport associated with laminar flow. The use of titania nanotubes synthesized on a mesh substrate shows improved photocatalytic performance in comparison to nanotubes synthesized on a foil substrate in a microreactor. At the lowest flow rate (25μL/min), the area normalized fractional conversion of methylene blue increased from 20% for foil to 46% in the case of nanotubes on mesh. The enhanced photocatalytic performance of the mesh is due to shorter diffusion distance and induction of flow perturbation. Also, the radially outward oriented nanotubes formed over the circumference of the titanium wire leads to the efficient capture of both reflected and refracted light. The device was also applied for inactivation of Escherichia coli O157:H7. At a flow rate of 50μL/min, the titania nanotubes on a mesh microreactor were able to achieve >99% inactivation of E. coli under AM 1.5 (≈100mW/cm2) simulated solar light.

Mesoporous carbon-supported cobalt catalyst for selective oxidation of toluene and degradation of water contaminants

Mesoporous carbon-supported cobalt (Co-MC) catalysts are widely applied as electrode materials for batteries. Conversely, the development of Co-MC as bifunctional catalysts for application in organic catalytic reactions and degradation of water contaminants is slower. Herein, the catalyst displayed high activity in the selective oxidation of toluene to benzaldehyde under mild conditions, attaining a high selectivity of 92.3%. Factors influencing the catalytic reaction performance were also investigated. Additionally, Co-MC displayed remarkable catalytic activity in degrading dyes relative to the pure metal counterpart. Moreover, the catalyst exhibited excellent reusability, as determined by the cyclic catalytic experiments. The paper demonstrates the potential of Co-MC as a bifunctional catalyst for both toluene selective oxidation and water contaminant degradation.

Environmental applications and implications of nanotechnologies

Since the launch of the U.S. National Nanotechnology Initiative (NNI) in 2000, research and development in nanotechnology innovation has come a long way worldwide. Based on the Web of Science database, the total SCIindexed papers surged from 971 in 2000 to 13, 546 in 2014, and the momentum remains strong. One of the most active and productive research fields has been environmental applications and implications of nanomaterials and nanotechnologies. Environmental nanotechnologies have shown great potential to fundamentally change the conventional practices in environmental cleanup. While the development of innovative cleanup technologies continues to evolve, our understanding of the environmental implications/impacts associated with the booming applications of nanotechnologies in various fields has also deepened. The objectives of this special issue were to: 1) promote exchanges of ideas and information on the latest development of environmental nanotechnologies, 2) facilitate development of more cost-effective and “greener” cleanup technologies based on innovative nanomaterials and nanotechnologies, 3) address limitation and potential environmental impacts of nanotechnologies and nanomaterials, and 4) identify major knowledge gaps and research directions. Due to the capacity limit, we can only include 20 papers in this issue from a large pool of high-quality submissions, including 14 research papers addressing applications, four papers on environmental impacts/implications, and two critical review papers. The applications are focused on adsorption, and redox or catalytic degradation of contaminants in water and potentially in soil. The nanomaterials encompass carbonaceous nanomaterials including carbon nanotubes, hydroxyapatite, metal oxides, zero-valent metals including iron, metal catalysts, iron-carbon composite microspheres, and TiO2 nanotubes. The implication papers address interactions of carbonaceous materials with wastewater biomass, effects of zinc oxide on soil microorganisms, effects of nano-silicon on lead in rice cultivars, and toxicity of engineered TiO2 nanoparticles, whereas the critical reviews thoroughly examine applications of nano-sized magnetite and hollow nanomaterials. While most of these works deal with water treatment, it appears that more research is needed to develop novel in situ nanotechnologies for remediation of soil and groundwater and to address impacts of nanoparticles in the subsurface on the biogeochemical conditions. As environmental nano-research continues to thrive, we hope this special issue will inspire even greater innovation and discoveries in the field. We thank all authors, reviewers, and the editorial staff of FESE for their time and contributions to this issue. In particular, we are grateful to Professor Xia Huang for her support and meticulous guidance throughout the process.