Adsorption of organic contaminants onto aged microplastics (MPs) may be important in understanding their transport potential and ecological risks in aquatic environment. Cations of Na+ and Ca2+ are ...common electrolytes in water, which can greatly influence the adsorption behavior of MPs by impacting the electrostatic interaction between MPs and organic contaminants. The results of this study showed that aged isotactic polypropylene (iPP) MPs exhibited higher adsorption capacity to triclosan (TCS) than pristine ones, and the sorption affinity was enhanced with the increase of ionic concentrations. The crucial influence of cations on the adsorption behavior of aged MPs mainly depended on the changed properties of TCS and interactions between MPs and TCS. Salting out effect induced the precipitation of TCS from water and facilitated the partition of TCS onto MPs in high salinity water. Besides, compressing electrostatic double layer of MPs via squeezing out effect and bridging effect between functional groups of aged MPs and contaminants may also be significant factors in the sorption process. These findings will be helpful for understanding the role of cations on the transport of pollutants, the fate of MPs and their associated environmental risks in aquatic ecosystems.
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•Aged polypropylene microplastics exhibited higher sorption capacity to TCS in water.•Cations related ionic strength strengthen the sorption of TCS on aged microplastics•Both TCS solubility and electrostatic double layer of plastic affect the adsorption.
Microplastic (MP) pollution is a raising global concern in recent years due to its wide distribution. Additionally, most of the MPs have undergone extensive weathering in the environment, and ...weathered MPs may exhibit different physicochemical properties from pristine ones. The review reveals the change in physicochemical properties (e.g. size, color, crystallinity, mechanical property and oxygen-containing groups) and the release of additives and MP-derived intermediates (i.e. oligomers and oxygenated compounds) during weathering processes. Weathering further affects the sorption behavior of MPs for environmental pollutants because of the changed crystallinity, specific surface area and oxygen functional groups. The interaction mechanisms of pristine and weathered MPs with pollutants are summarized, and how weathering processes affect sorption behavior is critically revealed. Because of the changed size, color and surface charges, weathered MPs might be ingested by aquatic organisms in different ways from the pristine ones. The detailed effects of weathering on the ingestion of MPs are discussed, and the potential toxicity of leachates from weathering processes is evaluated. In addition, the environmental components (e.g. natural organic matter and salinity) and biofilm correlated to the sorption behavior of MPs are reviewed. As for the knowledge gap, further studies should focus on the long-term weathering of MPs and the relationships between weathering properties and sorption capacities toward pollutants. The potential risks of weathered MPs and leachates on organisms should be explored.
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•Weathering significantly changes the physicochemical properties of microplastics.•Surface area, oxygen groups and crystallinity critically affect sorption of pollutants.•Effects of weathering on the risks of microplastics and leachates are revealed.•NOM, salinity and biofilms involved in the environmental behavior are reviewed.
The development of an efficient approach to construct fused polycyclic systems bearing a quaternary carbon center represents a great challenge to synthetic chemistry. Herein, we report a ...Rh(III)-catalyzed 4 + 1 annulation of propargyl alcohols with various heterocyclic scaffolds under an air atmosphere. Diverse fused heterocycles containing a quaternary carbon center were obtained in moderate to good yields. Additionally, this method features a high atom-economy, metal oxidant free, simple operation, and compatibility with various functional groups.
Layer stacking and chemical stability are crucial for two-dimensional covalent organic frameworks (2D COFs), but are yet challenging to gain control. In this work, we demonstrate synthetic control of ...both the layer stacking and chemical stability of 2D COFs by managing interlayer steric hindrance via a multivariate (MTV) approach. By co-condensation of triamines with and without alkyl substituents (ethyl and isopropyl) and a di- or trialdehyde, a family of two-, three-, and four-component 2D COFs with AA, AB, or ABC stacking is prepared. The alkyl groups are periodically appended on the channel walls and their contents, which can be synthetically tuned by the MTV strategy, control the stacking model and chemical stability of 2D COFs by maximizing the total crystal stacking energy and protecting hydrolytically susceptible backbones through kinetic blocking. Specifically, the COFs with higher concentration of alkyl substituents adopt AB or ABC stacking, while lower amount of functionalities leads to the AA stacking. The COFs bearing high concentration of isopropyl groups represent the first identified COFs that can retain crystallinity and porosity in boiling 20 M NaOH solution. After postsynthetic metalation with an iridium complex, the 2,2′-bipyridyl-derived COFs can heterogeneously catalyze C–H borylation of arenes, whereas the COF with isopropyl groups exhibits much higher activity than the COFs with ethyl groups and nonsubstituents due to the increased porosity and chemical stability. This work underscores the opportunity in using steric hindrance to tune and control layer stacking, chemical stability and properties of 2D COFs.
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•Aging of polystyrene (PS) microplastics was accelerated by photo-Fenton reaction.•The intermediates released from aging process of PS were analyzed.•Aging process significantly ...changed the adsorption mechanism of PS for pharmaceuticals.•Aging intermediates affected the adsorption of PS microplastics for pharmaceuticals.•Impact of aging intermediates mainly depended on their electrostatic interaction with PS.
In the environment, aging obviously changes physicochemical properties of microplastics (MPs), but the effects of aging process on adsorption behavior of MPs are not fully understood. In this study, the aging of polystyrene (PS) was accelerated by photo-Fenton reaction. The adsorption mechanism of different aged PS toward atorvastatin (ATV) and amlodipine (AML) and the role of PS-derived intermediates in adsorption process were investigated. Results showed that the adsorption of pristine PS toward pharmaceuticals relied on hydrophobic and π-π interaction, while for aged PS, electrostatic interaction and hydrogen bonding controlled the adsorption. The study revealed that the intermediates released from aging process in high concentration (TOC of 10 mg/L) significantly decreased the adsorption of ATV (10 mg/L) on PS (5.0 g/L) but increased the adsorption of AML (10 mg/L). However, those intermediates at environmental concentration (0.1 mg/L) exhibited low effects on adsorption of pharmaceuticals (1.0 mg/L) on MPs (0.5 g/L of PS). The impact mainly depended on electrostatic interaction between MPs and aging intermediates. Besides, the adsorption of low-degree aged PS was more susceptible to the aging intermediates than that of high-degree aged ones. These findings highlight significant implication of MP-derived intermediates in aquatic environments.
There have been breakthroughs in the development of covalent organic frameworks (COFs) with tunability of composition, structure, and function, but the synthesis of chiral COFs remains a great ...challenge. Here we report the construction of two-dimensional COFs with chiral functionalities embedded into the frameworks by imine condensations of enantiopure TADDOL-derived tetraaldehydes with 4,4′-diaminodiphenylmethane. Powder X-ray diffraction and computer modeling together with pore size distribution analysis show that one COF has a twofold-interpenetrated grid-type network and the other has a non-interpenetrated grid network. After postsynthetic modification of the chiral dihydroxy groups of TADDOL units with Ti(O i Pr)4, the materials are efficient and recyclable heterogeneous catalysts for asymmetric addition of diethylzinc to aldehydes with high enantioselectivity. The results reported here will greatly expand the scope of materials design and engineering for the creation of new types of functional porous materials.
Originating from the Luria–Delbrück experiment in 1943, fluctuation analysis (FA) has been well developed to demonstrate random mutagenesis in microbial cell populations and infer mutation rates. ...Despite the remarkable progress in its theory and applications, FA often faces difficulties in the computation perspective, due to the lack of appropriate simulators. Existing simulation algorithms are usually designed specifically for particular scenarios, thus their applications may be largely restricted. There is a pressing need for more flexible simulators that rely on minimum model assumptions and are highly adaptable to produce data for a wide range of scenarios. In this study, we propose SimuBP, a simulator of population dynamics and mutations based on branching processes. SimuBP generates data based on a general two-type branching process, which is able to mimic the real cell proliferation and mutation process. Through simulations under traditional FA assumptions, we demonstrate that the data generated by SimuBP follow expected distributions, and exhibit high consistency with those generated by two alternative simulators. The most impressive feature of SimuBP lies in its flexibility, which enables the simulation of data analogous to real fluctuation experiments. We demonstrate the application of SimuBP through examples of estimating mutation rates.
Mimicking cellular transport mechanisms to make solid-state smart nanochannels has long been of great interest for their diverse applications, but it poses a critical synthetic challenge. Covalent ...organic frameworks (COFs) are porous crystalline materials with tailor-made nanochannels and hold great potential for ion and molecule transport. We demonstrate here for the first time that 2D COFs possess the necessary merits to be promising solid-state nanochannels for selective transport of amino acids, which are the basis for life. By imine condensations of a C 3-symmetric trialdehyde and a mixture of diamines with and without divinyl groups, two vinyl-functionalized 2D COFs are crystallized. Both multivariant COFs afford straight 1D mesoporous channels formed by AA or AB stacking of layered hexagonal networks. After postmodification with chiral β-cyclodextrin (β-CD) via thiol–ene click reactions, the COFs are further fabricated into free-standing mixed matrix membranes (MMMs) that can selectively transport amino acids, as revealed by monitoring not only transmembrane ionic current signature but also concentration changes of permeated substrates. Specially, in the membrane system, the AA stacked COF exhibits higher chiral recognition capability toward histidine enantiomers than the AB stacked COF because of its uniform open channels decorated with β-CD. This work highlights the great potential of COF nanochannels as a platform for accumulating functional groups for selective transport of small molecules and even biomolecules in the solid state.
Herein, rhodium(III)-catalyzed C–H activation/subsequent 4 + 1 cyclization reactions between benzamides and propargyl alcohols are reported in which propargyl alcohols serve as unusual one-carbon ...units. This title transformation led to a series of isoindolinones bearing a quaternary carbon with moderate to good yields without the requirement for external metal oxidants. Due to the mild and simple reaction conditions, this reaction is compatible with various functional groups.
After being discarded into the environment, the microplastics (MPs) will undergo weathering effects. However, the low degradation rate of MPs in natural processes greatly limits the understanding of ...long-term aging behavior. By critically reviewing 82 articles in Web of Science from 2015 to 2020, the paper summarized different laboratory technologies including light irradiation, chemical oxidation, heat treatment and γ-ray irradiation to simulate and accelerate the aging of MPs, and evaluated the feasibility by comparison with natural processes. The advantages of laboratory technologies are that aging conditions can be artificially controlled and that the labor and time costs can be saved, whereas the laboratory system is too simple to simulate complex aging processes in the environment. We further reviewed the potential impacts of aging process on the risks of MPs (i.e. physical injury, combined toxicity with external pollutants and chemical risk of additives and low-molecular products). The overall risks are seemingly enhanced by aging process due to the high ingestion by organisms, the strong interaction with pollutants and the release of MP-derived organic compounds. Further studies on the aging behavior of MPs should be focused on the laboratory techniques that can simulate multiple processes of natural aging, the long-term fragmentation behavior of MPs, the effect of aging on growth rate of biofilm in MPs and ingestion property by organisms, and the relationship between aging property of MPs and release rate of chemicals in leachates.
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•Natural and laboratory-accelerated aging processes of microplastics were reviewed.•Advantage of laboratory process is artificially-controlled condition and time-cost saved.•Light irradiation is the mostly selected technology to accelerate the microplastic aging.•Aging increases the risks of microplastics from physical, combined and leachate toxicities.•Laboratory technology that can simulate multiple aging factors should be developed.
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