MXene, comprised of two-dimensional transition metal carbides/nitride, has emerged as a novel material suitable for environmental remediation of toxic compounds. Due to their inherent and superior ...physical and chemical properties, MXene is employed in separation techniques like photocatalysis, adsorption, and membrane separation. MXene is equipped with a highly hydrophilic surface, ion exchange property, and robust surface functional groups. In this review paper, a comprehensive discussion on the structural patterns, preparation, properties of MXene and its application for the removal of toxic pollutants like Radionuclide, Uranium, Thorium, and dyes is presented. The mechanism of removal of the pollutants by MXene is extensively reviewed. Synthesis of MXene based membranes, their properties, and application for water purification and properties were also discussed. This review will be highly helpful to understand critically the methods of synthesis and use of MXene material for priority environmental pollutants removal. In addition, the challenges behind the synthesis and use of MXene for decontamination of pollutants were reviewed and reported.
•The structural patterns of MXene and its different formula are reviewed.•The synthesis of 2D MXenes by primary techniques (Top-down and Bottom-up) was briefly reviewed.•Mechanical, Electronic, Optical, Oxidative stability, Magnetic nature and Hydrogen storage properties of MXene are reviewed.•This review emphasis the environmental application of toxic pollutant removal on MXene.
The presence of toxic metals such as vanadium in water resources has attracted considerable attention as a new concern in international health. Systematic review and meta-analysis were performed to ...assess the concentration of vanadium in water resources along with the relevant ecological risk assessment. Databases of Scopus, PubMed, and Embase were investigated to retrieve the related articles from January 01, 1974 to December 25, 2019. Twenty-eight articles containing 152 samples from 24 countries were included. Furthermore, the meta-analysis was conducted by the approach of z-score to estimate differences in the effect size. In addition, the mean of concentrations of vanadium was applied to calculate the risk assessment only to the water surface and choose the maximum environmental concentration (MEC) for demonstrate a worst-case scenario. Here, the risk assessment approach was used to show that the MEC of vanadium confirm the risk it for aquatic ecosystems, being fish (e.g., Danio rerio) our model organism due to their sensibility. According to findings, the MEC of vanadium in surface water varied from 0.010 μg L−1 (USA) and 68 μg L−1 (China), with an overall mean of 6.21 ± 13.3 μg L−1 (mean ± standard deviation). The ecological risk assessment demonstrated that people living in some countries such as China and Japan were at an adverse ecological risk of vanadium in the water resources. Hence, essential control plans besides adequate removal techniques must be implemented for significant deracination of heavy metals like vanadium.
Display omitted
•Twenty eight articles with 152 samples were included in the study.•Maximum environmental concentration (MEC) of Vanadium in water was varied from 0.010 μgL−1 (USA) and 68 μgL−1 (China).•China and Japan are exposed to adverse vanadium ecological risk in the water.•The order of sensitivity to vanadium-based on SSD was as R. subcapitata > D. magna > O. mykiss.
Electrode stability, lifetime and electrochemical oxidation.▪
Display omitted
•Comprehensive and state-of-the-art information on the stability and service life of electrodes are provided.•The ...degradation mechanisms of pollutants on different EAOPs electrodes were discussed.•Electrodes composed of intermediate compounds have a higher lifetime than binary oxides.•The coating of electrodes with noble metals usually improves stability.
In recent years, novel advanced oxidation processes (AOPs) based on electrochemical technology known as electrochemical advanced oxidation processes (EAOPs) have been applied to the degradation of a wide range of persistent organic pollutants (POPs). EAOPs produce in situ hydroxyl radicals (•OH) capable of degrading POPs and their mineralization by producing stable electrode materials (e.g., boron-doped diamond (BDD), doped-SnO2, PbO2, and substoichiometric- and doped-TiO2). Moreover, ozone and sulfate radicals could be produced, based on electrolyte type, which cause the degradation of POPs. Although EAOPs are promising novel technologies, various parameters related to the types of electrodes in the POPs oxidation have not been fully addressed. In order to provide a full and comprehensive picture of the current state of the art, and improve the treatment efficiency and motivate new researches in these areas, this study analyzed the research covering EAOPs aspects, with a focus on the comparison of stability, lifetime and service life of electrodes. Electro-chemical stability and longer life are the major concerns in the EAOPs. Since electrodes must be highly efficient for long periods of time, the determination of their lifetime is essential. On the other hand, in real-life situations, lifetime determination is difficult. The oxidation ability and durability of electrodes during the reactions depended on the structural properties of them. Electrodes composed of intermediate compounds had a higher lifetime than binary oxides. Another factor affecting the stability of the electrodes was the structure of the expanded mesh style anodes to better control the bubble growth through a polygonized structure. Anodes with irregular shapes at the surface were more likely to discharge the bubbles and reduce the negative effects of the high pressure on the surface of the electrode. The electrodes having high oxidation strength and stability, had a shorter service life value. Furthermore, the calcination temperature and the amount of applied current directly affected the lifetime of the electrodes. On the other hand, the electrical resistance of the synthesized electrode was effective in the lifetime. Coating of electrodes with noble metals such as tantalum, titanium, niobium, zirconium, hafnium, vanadium, molybdate and tungsten improved the electrode stability.
Microplastics are gaining growing research interest due to their significant potential threats to ecosystems and public health. Physical techniques have been proposed as a promising strategy for ...removing microplastics from the environment. This work innovatively proposes a process of microplastic removal by froth flotation and subsequent carbonization for synthesis of heterogeneous Fenton catalyst. The feasibility of separating different microplastics from water was verified by froth flotation, and iron-loaded carbon derived from separated microplastics was fabricated as catalyst. Carbon material was obtained by carbonization of microplastics, and iron loading was conducted to improve catalytic ability. The catalyst of iron-loaded iron was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The degradation of tetracycline hydrochloride in the heterogeneous Fenton system was evaluated by single factor experiment and kinetic analysis. The catalytic performance was mainly influenced by H
2
O
2
concentration, solution pH, and co-existing ions. Under the conditions of catalyst 20 mg/L, H
2
O
2
concentration 0.99 mmol/L, initial tetracycline hydrochloride concentration 20 mg/L, pH 4.0, and temperature 25 °C, the removal rate of tetracycline hydrochloride within 15 min reached 81.6%, and the rate constant was 0.138min
−1
. The catalytic mechanism dominated by hydroxyl radical was verified for the degradation of tetracycline hydrochloride. This work offers insights into the management of microplastics and sustainable treatment of antibiotic wastewater.
Cereal-based foods are utilized as an essential food segment worldwide. Nevertheless, their contamination by mycotoxins, also fumonisins, could pose a critical health risk. The present research ...provides the first systematic review regarding the prevalence and concentration of fumonisins in cereal-based food with the aid of a meta-analysis. In this regard, some international databases PubMed, Web of Science, Google Scholar, and Scopus were explored during the last 30 years. Among 9729 screened articles, 73 articles (which meet the proposed inclusion criteria), including 11,132 data, were incorporated in the performed meta-analysis. The overall rank order regarding the concentration of fumonisins in cereal-based foods was corn-based foods > wheat-based foods > other cereal foods > barley-based foods > rice-based foods > oat-based foods. Based on the prevalence of fumonisins, the overall rank order was other cereal foods > corn-based foods > rice-based foods > wheat-based foods > oat-based foods > barley-based food. The present meta-analysis results can be a beneficial database for risk assessment model progress, which can help industries and organizations decrease the presence of fumonisins in cereal-based food.
Graphical abstract
Schematic of pollutants degradation in PFC.
Display omitted
Wastewater contains organic compounds (fatty acids, amino acids, and carbohydrates) that have a significant amount of chemical energy. In ...this regard, the use of wastewater for recovering energy by some appropriate energy conversion technologies can be considered as an appropriate approach to simultaneously achieve the reduction of environmental contamination and increasing supply of energy. The Photocatalytic Fuel Cell (PFC) can provide a new approach in developing technology for simultaneous organic pollutants removal from wastewaters and power generation, but it also has disadvantages, such as requires higher voltage, more cost and complexity. To present a comprehensive vision of the current state of the art, and progress the treatment efficiency and agitate new studies in these fields, this review discussed the study covering PFC aspects, with a focus on the comparison of pollutant degradation, power generation, different photoanode and photocathode materials as well as the application of the Fenton process in PFCs.
Dry reforming of hydrocarbons, alcohols, and biological compounds is one of the most promising and effective avenues to increase hydrogen (H2) production. Catalytic dry reforming is used to ...facilitate the reforming process. The most popular catalysts for dry reforming are Ni-based catalysts. Due to their inactivation at high temperatures, these catalysts need to use metal supports, which have received special attention from researchers in recent years. Due to the existence of a wide range of metal supports and the need for accurate detection of higher H2 production, in this study, a systematic review and meta-analysis using ANNs were conducted to assess the hydrogen production by various catalysts in the dry reforming process. The Scopus, Embase, and Web of Science databases were investigated to retrieve the related articles from 1 January 2000 until 20 January 2021. Forty-seven articles containing 100 studies were included. To determine optimal models for three target factors (hydrocarbon conversion, hydrogen yield, and stability test time), artificial neural networks (ANNs) combined with differential evolution (DE) were applied. The best models obtained had an average relative error for the testing data of 0.52% for conversion, 3.36% for stability, and 0.03% for yield. These small differences between experimental results and predictions indicate a good generalization capability.
Synthesis and fabrication of Cu-MOF/HNTs/rGO nanocomposite.
Display omitted
•Cu-MOF/HNTs/rGO was used for simultaneous sensing of dopamine and paracetamol.•The presence of Cu2+ was attracted by ...siloxane (Si-O-Si) groups in HNTs.•Cu-MOF/HNTs/rGO was demonstrated the superior electrochemical signal.•The developed sensor was exhibited the linear ranges of 0.1–130 µM and LOD 0.03 µM for dopamine.•The developed sensor was exhibited the linear ranges of 0.5–250 µM and LOD 0.15 µM for paracetamol.
Three-dimensional (3D) metal–organic frameworks (MOFs) a class of porous materials with tunable structure and surface functionality has arisen as electrode materials especially, for electrochemical sensing of analytes. However, MOFs possess intrinsic drawbacks such as poor conductivity with an agglomeration of particles, which restricted the electrochemical signal response in terms of sensitivity and detection limits. In this regard, the present work aims to develop conducting Cu-MOF on HNTs, a good substate for in-situ growth of MOF nanostructures due to the existence of abundant negatively charged Si-OH that can help the growth of nanosized MOFs. The negatively charged siloxane (Si-O-Si) groups on the surface of HNTs can be attracted by positive charged Cu2+ ions present in the reaction mixture through strong electrostatic attraction. When subjected to hydrothermal treatment, the Cu2+ ions can form nano-sized Cu-MOF particles with assistance from 2-methylimidazole. Moreover, the presence of graphene oxide (GO) can improve the electrical conductivity, large surface area, and thus resulting in the formation of conducting Cu-MOF/HNTs/rGO nanocomposite. Owing to the synergetic desirable properties of active metal sites and high porosity offered by Cu-MOF, the high conductivity of rGO, and the large surface area of HNTs, the resultant Cu-MOF/HNTs/rGO modified GC electrode demonstrates superior electrochemical signal response towards dopamine and paracetamol. Moreover, the developed sensor exhibits wide linear ranges of 0.1 µM–130 µM and 0.5–250 µM, with a low detection limit of 0.03 µM and 0.15 µM for dopamine and paracetamol, respectively.
In this study, three types of electrodes based on polyvinyl alcohol (PVA)/ polyaniline (PANI) are synthesized and their effects on the electro-oxidation of methanol (MeOH) are investigated. Composite ...electrodes of PVA/PANI-Ni, PVA/PANI-Cu, and PVA/PANI-NiCu are synthesized via the in-situ polymerization of aniline, Cu, Ni, and NiCu (Ni80Cu20 alloy) particles in the presence of PVA. Optical and chemical compositions and morphological characteristics of composite films are determined using UV–Vis, FTIR, SEM, and TGA analysis. The electrode degradation efficiency of MeOH following oxidation and the elimination of toxins from the solution by voltammetry and chronopotentiometry is also investigated. The results indicate that PVA/PANI-NiCu performs better than PVA/PANI-Ni electrode. The degradation of MeOH in an alkaline medium is monitored using UV–visible spectroscopy under a current density of 2.18 mAcm−2 with a stock solution of 0.1 M MeOH for 120 min. The toxicities of MeOH and the generated by-products were tested and confirmed through a growth-inhibition test against Staphylococcus aureus ATCC 6538 using the disk-diffusion method; the obtained results confirmed the effectiveness of our process.
Global warming is the result of traditional fuel use and manufacturing, which release significant volumes of CO2 and other greenhouse gases from factories. Moreover, rising energy consumption, ...anticipated limitations of fossil fuels in the near future, and increased interest in renewable energies among scientists, currently increase research in biofuels. In contrast to biomass from urban waste materials or the land, algae have the potential to be a commercially successful aquatic energy crop, offering a greater energy potential. Here we discuss the importance of Anaerobic Digestion (AD) for enhanced biogas yield, characterization, and comparisons between algae pretreatment methods namely, mechanical, thermal, microwave irradiation, and enzymatic and catalytic methods. The importance of anaerobic digestion enhances biogas yield, characterization, and comparisons between mechanical, thermal, microwave irradiation, and enzymatic and catalytic treatment. Additionally, operational aspects such as algal species, temperature, C/N ratio, retention period, and particle size impact biofuel yield. The highest algal biogas yield reported was 740 mL/gVS, subtracted from Taihu de-oiled algae applying thermos-chemical pretreatment under conditions of temperature, time, and catalyst concentration of 70 °C, 3 h, and 6%, respectively. Another high yield of algal-based biogas was obtained from Laminaria sp. with mechanical pretreatment under temperature, time, and VS concentration of 38 ± 1 °C, 15 min, and 2.5% respectively, with a maximum yield of 615 ± 7 mL/g VS. Although biofuels derived from algae species are only partially commercialized, the feedstock for biogas might soon be commercially grown. Algae and other plant species that could be cultivated on marginal lands as affordable energy crops with the potential to contribute to the production of biogas are promising and are already being worked on.
PDF
