•Low-molecular-weight organic acids have significant influence on PAHs photolysis.•Chelating ability of LMWOAs with Fe are critical to their roles in Phe photolysis.•Presence of oxalic and malic ...acids favor Phe photodegradation on Fe(III)–clay.•EDTA or nitrilotriacetic acid inhibits both Fe(II) formation and Phe photolysis.•Reductive CO2− radicals involved in Phe photodegradation are supported by EPR.
The photolysis of polycyclic aromatic hydrocarbons (PAHs) is potentially an important process for its transformation and fate on contaminated soil surfaces. In this study, phenanthrene is employed as a model to explore PAH photodegradation with the assistance of Fe(III)–smectite under visible-light while focusing on roles played by five low-molecular-weight organic acids (LMWOAs), i.e., malic acid, oxalic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic acid. Our results show that oxalic acid is most effective in promoting the photodegradation of phenanthrene, while only a slight increase in the rate of phenanthrene photodegradation is observed in the presence of malic acid. Electron paramagnetic resonance experiments confirm the formation of CO2− radicals in the presence of malic and oxalic acid, which provides strong evidence for generating OH and subsequent photoreaction pathways. The presence of EDTA or nitrilotriacetic acid significantly inhibits both Fe(II) formation and phenanthrene photodegradation because these organic anions tend to chelate with Fe(III), leading to decreases in the electron-accepting potential of Fe(III)–smectite and a weakened interaction between phenanthrene and Fe(III)–smectite. These observations provide valuable insights into the transformation and fate of PAHs in the natural soil environment and demonstrate the potential for using some LMWOAs as additives for the remediation of contaminated soil.
Abstract Excessive Cu 2+ intake can cause neurological disorders (e.g. Wilson’s disease) and adversely affect the gastrointestinal, liver, and kidney organs. The presence of Cu 2+ is strongly linked ...to the emergence and progression of Wilson's disease (WD), and accurately measuring the amount of copper is a crucial step in diagnosing WD at an early stage in a clinical setting. In this work, CQDs were fabricated through a facile technique as a novel fluorescence-based sensing platform for detecting Cu(II) in aqueous solutions, and in the serum samples of healthy and affected individuals by WD. The CQDs interact with Cu(II) ions to produce Turn-on and Turn-off states at nano-molar and micro-molar levels, respectively, with LODs of 0.001 µM and 1 µM. In fact, the Cu 2+ ions can act like a bridge between two CQDs by which the charge and electron transfer between the CQDs may increase, possibly can have significant effects on the spectroscopic features of the CQDs. To the best of our knowledge, this is the first reported research that can detect Cu(II) at low levels using two different complexation states, with promising results in testing serum. The potential of the sensor to detect Cu(II) was tested on serum samples from healthy and affected individuals by WD, and compared to results obtained by ICP-OES. Astonishingly, the results showed an excellent correlation between the measured Cu(II) levels using the proposed technique and ICP-OES, indicating the high potential of the fluorimetric CQD-based probe for Cu(II) detection. The accuracy, sensitivity, selectivity, high precision, accuracy, and applicability of the probe toward Cu(II) ions make it a potential diagnostic tool for Wilson's disease in a clinical setting.
► Organic cation modified smectite-templated zero-valent iron (ZVI) was developed for improved stability and efficiency of nanosized-ZVI. ► Remediation of 2,4-DCP to phenol by organo-smectite-ZVI ...proceeds via adsorption–dechlorination processes. ► Hydrophobic interlayer environment could sustain the reactivity of ZVI and thus increase its efficiency.
Controlling the reactivity of nano-scale zero-valent iron (nZVI) remains a challenge for its practical application. In the present study, smectite-templated nZVI is hydrophobized by adding N,N,N-trimethyl-1-dodecanaminium salt (DTA+) to yield organo-smectite-ZVI. The obtained material was characterized by XRD, TEM and FTIR. Its reactivity was evaluated for the aqueous removal of 2,4-DCP. Results show that (i) nanosized ZVI clusters of <5nm are intercalated into the clay interlayers; (ii) hydrophobization of smectite surfaces occurs after binding of DTA+ to the clay minerals; (iii) aqueous 2,4-DCP could be rapidly accumulated in the vicinity of the solid phase; (iv) accumulated 2,4-DCP is then gradually dechlorinated. This demonstrates that hydrophobic conditions in clay interlayer facilitate the 2,4-DCP adsorption. In a 2,4-DCP successive addition systems, dechlorination can be maintained even after five cycles for organo-smectite-ZVI, but just two cycles for smectite-ZVI. This indicates that the hydrophobization of smectite-ZVI could significantly sustain its reactivity and inhibit the rapid consumption of ZVI in the Fe0/H2O system. This statement is supported by XPS analysis. Furthermore, organo-smectite-ZVI provides strong adsorptive affinity to 2,4-DCP and its reaction products. This is beneficial for the long-term stability of removed contaminants.
Water pollution caused by heavy metals has dramatically impacted ecosystems in recent years. For instance, 45.4% of lakes in China are in the category of moderate to high risk of toxic ...metal pollution, due to excessive mining. There is, therefore, a need for efficient techniques of metal decontamination. Hydrogels are gaining interest as heavy metal adsorbents because of their easy separation, but hydrogel applications are limited due to their poor mechanical property. Here we solve this problem by introducing natural attapulgite into the sodium alginate–poly(acrylic acid) semi-interpenetrating polymer network of the hydrogel. Results show that the compressive stress of the hydrogel with 10% attapulgite, of 1.230 Mpa, was 4.1 times higher than that of pure hydrogel, of 0.299 MPa. The adsorption capacity of hydrogel with 10% attapulgite was high, of 272.8 mg/g for Cu
2+
and 391.7 mg/g for Pb
2+
. Even after five cycles of adsorption, the hydrogel with 10% attapulgite still adsorbs 261.7 mg/g Cu
2+
and 368.1 mg/g Pb
2+
. Our findings thus reveal that network-structured sodium alginate–poly(acrylic acid)/attapulgite hydrogel holds great potential as an efficient and recyclable adsorbent for heavy metal removal.
Roles of exchangeable cations in PAHs photodegradation on clay surafces under visible light.
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•Photolysis rate are strongly dependent on the type of cations on clay surface.•The ...strength of “cation–π” interactions governs the photodegradation rate of PAHs.•Several exchangeable cations could cause a shift in the absorption spectrum of PAHs.•Exchangeable cations influence the type and amount of reactive intermediates.
Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe3+>Al3+>Cu2+>>Ca2+>K+>Na+, which is consistent with the binding energy of cation–π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation–π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na+-smectite and K+-smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe3+, Al3+, and Cu2+ are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O2− , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation.
Abstract
Silver-based antibacterial agents have obtained wide attention due to the fact that bacteria in the environment is ubiquitous, which has become one of the most difficult problems for human ...health. However, the antibacterial mechanism and process are still inconclusive. Here, Ag
2
O nanoparticles (NPs) with uniform spherical morphology and small size (around 30 nm) were prepared. The as-prepared Ag
2
O NPs induced high antibacterial activity (100% inhibition ratio) against
E. coli
. A two-step antibacterial process was proposed and confirmed, which divided into inhibition and sterilization steps. The optical density measurement, malondialdehyde concentration detection, morphologic imaging with electronic microscopy and Fourier transform infrared spectroscopic analysis unveiled the interaction of Ag
2
O NPs with
E. coli
, which verified the inhibition–sterilization process we proposed.
Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth ...nanoparticles from the precursor compound SrBi
Ta
O
under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction-relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes.
Photocatalytic hydrogen evolution is an attractive field for future environment-friendly energy. However, fast recombination of photogenerated charges severely inhibits hydrogen efficiency. ...Single-atom cocatalysts such as Pt have emerged as an effective method to enhance the photocatalytic activity by introduction of active sites and boosting charge separation with low-coordination environment. Herein, we demonstrated a new strategy to develop a highly active Pd single atom in carbon-deficient g-C
3
N
4
with a unique coordination. The single-atom Pd–N
3
sites constructed by oil bath heating and photoreduction process were confirmed by HADDF-STEM and XPS measurements. Introduction of single-atom Pd greatly improved the separation and transportation of charge carriers, leading to a longer lifespan for consequent reactions. The obtained single-atom Pd loaded on the carbon-deficient g–C
3
N
4
showed excellent photocatalytic activity in hydrogen production with about 24 and 4 times higher activity than that of g–C
3
N
4
and nano-sized Pd on the same support, respectively. This work provides a new insight on the design of single-atom catalyst.
In the context of the circular economy, the huge amounts of biomass waste should be converted into value-added materials and energy to diminish pollution, atmospheric CO2 levels and costly waste ...disposal. Biological imaging usually uses expensive and toxic chemicals e.g., organic dyes, semiconductor quantum dots, calling for safer, greener, cheaper fluorescent probes for biological imaging in vitro and in vivo. In these regards, carbon quantum dots (CQDs)-based fluorescent probes using biomass waste as a precursor may have much higher potential. Here we transformed the biomass waste of peach leaves into value-added fluorescent CQDs through a low-cost and green one-step hydrothermal process. The obtained CQDs show excitation-dependent photoluminescence properties with a fluorescence lifetime of 5.96 ns and a quantum yield of 7.71% without any passivation. In addition, the CQDs have a fine size of 1.9 nm with good hydrophilicity and high fluorescent stability over pH 4.0–11.0 range. Fluorescence imaging of in vitro cell cultures and in vivo with zebrafish show that CQDs possess ultra-low toxicity and remarkable performance for biological imaging. Even when CQDs present at a concentration as high as 500 µg/mL, the organism can still maintain more than 90% activity both in vitro and in vivo, and present bright fluorescence. The cheaper, greener, ultra-low toxicity CQDs developed in this work is a potential candidate for biological imaging in vitro and in vivo.
Green extraction of value-added carbon quantum dots from peach leaves waste with ultra-low toxicity and excellent photoluminescence properties: A potential candidate for biological imaging in vitro and in vivo. Display omitted
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