The demand of wet wipes and masks has been rising worldwide since the outbreak of global COVID-19; however, with more reports about improper handling of wipes and masks, their potential threats to ...the environment are gradually emerging. Wipes and masks are made of a large number of plastic fibers, which are easily broken and fragmented into microplastic fibers under the influence of environmental factors. Weathered wipes or masks can release billions of microplastic fibers, which is a great challenge to the local ecological security. Wipes and masks as new microplastic pollution sources and their potential role in the ecosystem have not been fully recognized and considered. Microplastic fiber pollution is a huge environmental issue, and how to prevent a large number of discarded wipes and masks from entering the environment and how to deal with them are an important issue for all countries and regions in the world. In the post era of global COVID-19, disposable wipes and masks, as new sources of environmental microplastic fiber pollution, should be given concern. It is urgent to recognize this potential environmental threat and prevent it from becoming the next microplastic problem.
Graphical abstract
Capacitive deionization (CDI) and membrane capacitive deionization (MCDI) are the most common cell architectures in the use of CDI for water treatment. In this work, the Faradaic reactions occurring ...in batch-mode CDI and MCDI processes were compared by investigating the variation of H2O2 and dissolved oxygen (DO) concentrations, pH, conductivity and current during charging and discharging under different charging voltages. During charging, the H2O2 concentration in CDI increased rapidly and then decreased while almost no H2O2 was generated in MCDI due to the inability of oxygen to penetrate the ion exchange membrane. Chemical kinetic models were developed to quantitatively describe the variation of H2O2 concentration and found to present satisfactory descriptions of the experimental data. The pH drop during charging could be partially explained by Faradaic reactions with proton generation associated with oxidation of the carbon electrodes considered to be the major contributor. The electrode potentials required for the induction of Faradaic reactions were analyzed with this analysis providing robust thermodynamic explanations for the occurrence of carbon oxidation at the anode and H2O2 generation at the cathode during the ion adsorption process. Finally, electrochemically-induced ageing of the carbon electrodes and the resulting performance stability were investigated. The findings in this study contribute to a better understanding of Faradaic reactions in CDI and MCDI and should be of value in optimizing CDI-based technologies for particular practical applications.
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•Faradaic reactions occurring in CDI and MCDI have been compared.•Oxygen reduction at the cathode is inhibited by cation exchange membranes.•Electrode potentials were analyzed to reveal the mechanism behind Faradaic reactions.•H2O2 concentration changes during charging and discharging satisfactory modeled.•Original and ageing carbon electrodes were characterized.
Water pollution and freshwater scarcity are two of the most important environmental problems faced by human around the globe in the 21st century. Capacitive deionization (CDI), as a promising ...electrochemical water treatment technology, has attracted large attention over the past decade for the facile removal of ions from water with the advantages of environmental friendliness, cost effectiveness, low energy consumption, and convenient electrode regeneration. Enormous progress has been made in the CDI research field and now CDI encompasses various cell architectures assembled with either capacitive electrodes or battery electrodes. These scientific advances are accompanied by a diverse application of CDI-based technologies. This work is intended to summarize the versatile applications of CDI and highlight the representative achievements in each of the applications primarily covering water desalination, water purification, water disinfection, resource recovery and synergistic combination with other technologies. Emerging application areas of CDI such as energy harvesting and CO2 capture are also presented. Lastly, the challenges and future outlook for CDI practical applications are discussed. This work should be of value in promoting CDI-based technologies to develop into a competitive option for coping with multiple water or energy-related issues.
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•Versatile applications of CDI were comprehensively reviewed.•Representative achievements in each of the applications were highlighted.•Challenges and future outlook for CDI practical applications are discussed.
As a newly emerging class of porous materials, covalent organic frameworks (COFs) have attracted much attention due to their intriguing structural merits (
e.g.
, total organic backbone, tunable ...porosity and predictable structure). However, the insoluble and unprocessable features of bulk COF powder limit their applications. To overcome these limitations, considerable efforts have been devoted to exploring the fabrication of COF thin films with controllable architectures, which open the door for their novel applications. In this critical review, we aim to provide the recent advances in the fabrication of COF thin films not only supported on substrates but also as free-standing nanosheets
via
both bottom-up and top-down strategies. The bottom-up strategy involves solvothermal synthesis, interfacial polymerization, room temperature vapor-assisted conversion, and synthesis under continuous flow conditions; whereas, the top-down strategy involves solvent-assisted exfoliation, self-exfoliation, mechanical delamination, and chemical exfoliation. In addition, the applications of COF thin films including energy storage, semiconductor devices, membrane-separation, sensors, and drug delivery are summarized. Finally, to accelerate further research, a personal perspective covering their synthetic strategies, mechanisms and applications is presented.
This review presents a comprehensive summary of the synthesis and applications of covalent organic framework thin films.
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•Application of carbon nanomaterials for pollutants removal.•Toxicity impact of carbon nanomaterials.•Degradation of carbon nanomaterials.•Future perspectives of graphene based ...adsorbents.
Carbon nanomaterials (CNMs) are novel nanomaterials with excellent physicochemical properties, which are widely used in biomedicine, energy and sensing. Besides, CNMs also play an important role in environmental pollution control, which can absorb heavy metals, antibiotics and harmful gases. However, CNMs are inevitably entering the environment while they are rapidly developing. They are harmful to living organisms in the environment and are difficult to degrade under natural conditions. Here, we systematically describe the toxicity of carbon nanotubes (CNTs), graphene (GRA) and C60 to cells, animals, humans, and microorganisms. According to the current research results, the toxicity mechanism is summarized, including oxidative stress response, mechanical damage and effects on biological enzymes. In addition, according to the latest research progress, we focus on the two major degradation methods of chemical degradation and biodegradation of CNTs, GRA and C60. Meanwhile, the reaction conditions and degradation mechanisms of degradation are respectively stated. Moreover, we have prospects for the limitations of CNM degradation under non-experimental conditions and their potential application.
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•P-doped porous carbon derived from pinecones was prepared by H3PO4 activation.•Activation temperature had an important impact on properties of PPCP electrodes.•PPCP800 electrode ...exhibited high deionization capacity with a fast salt removal rate.•PPCP electrodes might be good candidates for CDI applications.
Electrochemical salt removal performance from water is greatly affected by the characteristics of porous carbon electrode materials. Nevertheless, facile eco-friendly synthesis of electrode materials with low cost for efficient salt electrosorption performance is still a huge challenge. Here, we readily prepared phosphorus-doped porous carbon derived from pinecones (PPCP), an abundant biomass waste, by using H3PO4 as the activating agent at appropriate activation temperature. The PPCP samples displayed an increase of the specific surface area and pore volume with rising activation temperature (700 − 900 °C). It has been demonstrated that the PPCP800 electrode displayed the highest specific capacitance due to relatively high specific surface area and degree of graphization, superior porous structure, the highest phosphorus content and lowest charge transfer resistance. Besides, the PPCP800 electrode displayed a high deionization capacity of 14.62 mg g−1 at 1.2 V in 1000 mg L−1 NaCl solution with the fastest salt removal rate. Furthermore, the prepared PPCP800 electrode exhibited good reproducibility in long-term consecutive operation. Hence, the phosphorus-doped porous carbons derived from pinecones might be promising candidates for capacitive deionization applications.
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•Surfactant-assisted synthesis is a promising method for photocatalyst synthesis.•Surfactant would efficiently enhance the photocatalytic activity of photocatalysts.•Surfactant can ...regulate the morphology and structure of photocatalysts.•Influencing factors and recent advances are highlighted.
The presence of large amounts of contaminants in the environment would result in ecological and health hazards. The photocatalytic technologies have been developed to use sunlight to remove contaminants in recent years. Researchers are primarily focused on developing high-performance photocatalysts. This review discusses the effects of surfactant on the structural morphology, physicochemical properties and contaminant removal performance of photocatalysts. The mechanism and synthesis method of surfactant-assisted photocatalysts are reviewed. Meanwhile, the effects of surfactant type, surfactant concentration, solution pH, synthesis method and calcination temperature on the photocatalysts are also discussed in detail. In addition, we summarized the recent advances and the application of surfactant-assisted photocatalysts in the environmental remediation. Finally, the future researches on surfactant-assisted photocatalysts are also proposed. This review provides new insights into the use of surfactants to prepare photocatalysts with well-defined shape and excellent performance to enhance photocatalytic efficiency for removing pollutants.
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•Ion removal performance of FCDI was greatly enhanced via cathodic iodide redox couple.•A similar positive effect noticed during desorption upon polarity reversal.•The system ...exhibited a stable behavior over multi-cycle consecutive runs.•The approach holds great promise in treatment of iodide-containing saline wastewater.
Flow-electrode capacitive deionization (FCDI) is attracting growing attention owing to its advantages such as effective ion removal capacity and easy management of the electrodes. Optimization of the flow-electrode comprising carbon materials and aqueous electrolyte is always a research hotspot aimed at improving FCDI performance. Herein, we innovatively introduced appropriate amount of KI3 into the cathodic flow-electrode to provide a highly efficient means of enhancing FCDI desalination performance with a stable behavior in salt electrosorption and desorption over multi-cycle consecutive runs. The accelerated salt removal rate originated from the reversible redox reaction of I3−/I− and the maintenance of the electro-neutrality of the global electrolyte. Although possible minor release or leakage of I−/I3− through the cation-exchange membrane and into the treated water occurred, which makes the proposed approach not quite suitable for potable water production, we demonstrated that this system has great application prospects in treatment of iodide-containing saline wastewater without causing secondary pollution.
Magnetic target localization using the magnetic gradient tensor (MGT) plays a significant role in underwater localization. However, this method inherently has a localization dead zone, which presents ...challenges for real-world applications. This paper delves into the root cause of this dead zone, identifying the non-invertibility of the MGT when the magnetic moment vector is orthogonal to the position vector from the target to the observation point. To tackle this issue, a method based on the eigenvector constraints is proposed. By constructing an objective function with eigenvector constraints and leveraging the property that its gradient at the observation point is zero, we derive an equivalent expression for the inverse of MGT that always holds and further develop a dead-zone-free localization method. To validate the robustness and efficacy of the proposed localization method, a comparative analysis with other methods is conducted. Simulation results in a 10 m × 10 m area under Gaussian noise demonstrate the proposed method’s capability to eliminate the dead zone and achieve an average localization error of 0.032 m. Experimental results further demonstrate that the proposed method eliminates the localization dead zone and exhibits greater robustness than the dominant method in the normal region. In summation, this paper provides an effective method for eliminating localization dead zone, offering a more stable and reliable method for magnetic target localization in practice.
Herein, we reported here a promising biosensor by taking advantage of the unique ordered mesoporous carbon nitride material (MCN) to convert the recognition information into a detectable signal with ...enzyme firstly, which could realize the sensitive, especially, selective detection of catechol and phenol in compost bioremediation samples. The mechanism including the MCN based on electrochemical, biosensor assembly, enzyme immobilization, and enzyme kinetics (elucidating the lower detection limit, different linear range and sensitivity) was discussed in detail. Under optimal conditions, GCE/MCN/Tyr biosensor was evaluated by chronoamperometry measurements and the reduction current of phenol and catechol was proportional to their concentration in the range of 5.00×10−8–9.50×10−6M and 5.00×10−8–1.25×10−5M with a correlation coefficient of 0.9991 and 0.9881, respectively. The detection limits of catechol and phenol were 10.24nM and 15.00nM (S/N=3), respectively. Besides, the data obtained from interference experiments indicated that the biosensor had good specificity. All the results showed that this material is suitable for load enzyme and applied to the biosensor due to the proposed biosensor exhibited improved analytical performances in terms of the detection limit and specificity, provided a powerful tool for rapid, sensitive, especially, selective monitoring of catechol and phenol simultaneously. Moreover, the obtained results may open the way to other MCN–enzyme applications in the environmental field.
•Mesoporous carbon nitride (MCN) was synthesized, and then applied to construct the biosensor with the immobilized enzyme firstly.•Fabrication process, characterizations, and sensing mechanism (the lower detection limit, different linear range and sensitivity) of the enzyme-based biosensor based on MCN are revealed.•Searching for the interference effect between catechol and phenol, and other interferent especially hydroquinone firstly.•The enzyme-based biosensor has potential applications in detecting catechol and phenol in compost extracts.
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