Magnesia‐alumina layered double hydroxide (Mg‐Al LDH) films grown in situ on LA43M magnesium‐lithium (Mg‐Li) alloy were synthesized utilizing the hydrothermal method. Scanning electron microscopy ...(SEM), energy‐dispersive spectrometry (EDS), and X‐ray diffraction (XRD) were used to characterize the surface morphologies, composition, and phase of the Mg‐Al films. The corrosion resistance of the Mg‐Al films was estimated via immersion experiment and hydrogen evolution test, and the tribological properties were investigated using tribological wear tests. The results showed that the thickness of the Mg‐Al LDH film enhanced, and the size of the LDH sheets increased as the hydrothermal temperature raised, resulting in the improvement of the corrosion and wear resistance. When the hydrothermal temperature reached 110°C, interlayer anions were loaded the most, and the film achieved the optimal thickness. The Mg‐Al LDH film had the optimum corrosion resistance and tribological properties. At this point, the weight loss of the film was 1.3560 mg·cm–2, and the average friction coefficient was .149. It demonstrated that synthesizing Mg‐Al LDH at a hydrothermal temperature of 110°C was an effective approach to improve the corrosion resistance of LA43M.
Abstract
An excellent anticorrosion Mg–Al layered double hydroxide (LDH) composite coating was successfully fabricated on LA43M magnesium alloy substrates via an in situ steam coating (SC) process ...and a subsequent hydrothermal treatment at different temperatures. The microstructure, composition and phase formation of the composite coatings were studied via X‐ray diffractometer, energy disperse spectroscopy, and scanning electron microscope, respectively. The corrosion resistance of composite coatings was further investigated using electrochemical measurements and corrosion test. The results showed that LDH/SC composite coating has typical nanosheets microstructure, which effectively seal the defects of SC. As the hydrothermal temperature increases, the thickness and density of nanosheets increases, and the corrosion resistance was significantly improved. Especially, the Mg–Al LDH/SC composite coating prepared at 100°C was the most dense and thickness, and exhibited the optimal and long‐term anticorrosion resistance in 3.5 wt.% NaCl soultion. It has the lowest
I
corr
(1.767 × 10
−8
A/cm
2
), which decreased by three and two orders of magnitude compared with the bare substrate and SC. Furthermore, it can maintain good chemical stability after immersion in the corrosion medium for 192 h and its hydrogen evolution rate (0.00416 mL·cm
−2
·h
−1
) and weight lost rate (0.00266 mg·cm
−2
·h
−1
) were the lowest compared with other samples.
The increasing production and applications of graphene oxide (GO) inevitably lead to its entry into the environment. However, its potential toxicity to soil invertebrates is not yet completely known. ...Herein, the harmful effects of GO on the growth, survival, reproduction, and ultrastructure of earthworms were thoroughly evaluated through acute and chronic toxicity experiments. In the acute toxicity experiments, earthworms were exposed to different concentrations of GO using two test methods: filter paper contact test and natural soil contact test. The lethal concentrations (LC50) for GO at 24-h and 48-h exposure were 2.52 and 2.36 mg mL-1, respectively, in the filter paper contact test and the LC50 on day 14 was 68.8 g kg-1 in the natural soil test. Histopathological observation demonstrated that serious skin and intestinal damage occurred with increasing GO concentrations. In the chronic toxicity test, earthworm growth rate and reproduction were investigated after exposure to 0, 5, 10, 20 and 30 g kg-1 GO in natural soil for 28 and 56 d. Earthworm growth was significantly inhibited after 7, 14, 21 and 28 d of GO exposure. The effect was more significant with increasing GO concentrations and exposure days. Moreover, GO exposure significantly decreased the reproductive capacity of earthworms. When earthworms were exposed to 20 g kg-1 GO for 56 d, the number and hatching rate of cocoons and the number of juveniles decreased by approximately half compared with the control. These findings indicate the potential health risk of GO to E. fetida under high concentrations and long exposure times in soil. Thus, the potential risks associated with the application of GO should receive considerable attention. This study can provide valuable information for assessing the toxicity of carbon nanomaterials in terrestrial ecosystems.
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•Data on acute and chronic toxicity of GO to Eisenia fetida were provided.•GO caused serious damages in the skin and intestine with increasing GO concentration.•The growth and reproduction of earthworms were significantly inhibited after GO exposure.•GO may pose a threat to E. fetida as it accumulates in the soil environment.
Carbon nanomaterials (CNMs) are novel engineered nanomaterials and have been used widely. Their toxic effects on terrestrial plants in soil matrix require careful investigation. In this study, white ...clover (Trifolium repens L.) was grown in a potted soil with graphene oxide (GO) at levels of 0.2%, 0.4% and 0.6% and the effects of GO on the growth and nutrient uptake of white clover were evaluated after 50 and 100 days of exposure. GO exposure showed adverse effects on seedling growth, photosynthetic parameters and nutrient uptake in shoots, and the effect was more significant with increasing concentration and exposure time. Compared with the control, GO at the highest level of 0.6% decreased plant height, leaf and stem dry weights, total chlorophyll content and net photosynthetic rate by 43.7%, 45.7%, 43.4%, 32% and 85.7%, respectively, after 100 d of exposure, and N, K, Cu, Zn, Fe, Mo, B, Si contents decreased by 19.5%, 20.1%, 12.6%, 25.0%, 12.9%, 26.0%, 18.9%, 23.0%, respectively. Furthermore, the electrolyte leakage, lipid peroxidation, reactive oxygen species, antioxidant enzyme activities were all increased by GO, especially at high dose and long exposure. These results indicate that GO can suppress plant growth by oxidative stress, photosynthesis inhibition, and nutrient imbalance.
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•Data on the toxicity of graphene oxide (GO) to white clover in soil matrix were provided.•GO adversely affected plant growth and photosynthesis.•GO induced oxidative stress in white clover.•A decrease in nutrient levels was observed in white clover after GO exposure.
The increasing application of carbon nanomaterials has resulted in their inevitable release into the environment. Their toxic effects on plant roots require careful investigation. In the present ...study, alfalfa (Medicago sativa L.) was exposed to graphene oxide (GO) at levels of 0.2 %, 0.4 %, and 0.6 % (w/w) in potting soil. This study aims to better understand the impact of GO on the root growth, structure, and physiology of alfalfa in the soil matrix. The results demonstrated that GO significantly affected the development and structure of alfalfa roots, and the effect varied with GO level. The highest level of GO (0.6 %) reduced the root length, diameter, volume, dry weight, number of lateral roots, and root activity by 36.1 %, 31.3 %, 60.0 %, 89.6 %, 55.8 %, and 72.3 % (p < 0.05), respectively, and the vascular cylinder diameter, periderm thickness, vessel diameter, and phellem thickness decreased by 51.5 %, 50.7 %, 80.9 %, and 49.1 % (p < 0.05), respectively. These observations might be associated with GO-induced oxidative stress, which was indicated by the activity of antioxidant enzymes. Furthermore, high GO levels (0.4 % and 0.6 %) inhibited the uptake of N, P, K, Mg, Zn, Fe, Mo, Si, and B in roots. Our findings indicate that GO at high levels has a negative impact on root growth and development by inducing oxidative stress, structural impairment, and nutritional imbalance. Careful soil GO management should be emphasized.
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•GO changes root anatomy and inhibits root growth and development.•GO induces oxidative stress in alfalfa roots.•High concentrations of GO hinder nutrient uptake by alfalfa roots.
A column experiment with horizontal permeable barriers was conducted to investigate phytoextraction of heavy metals by
Lolium perenne L. from municipal solid waste compost following EDTA application, ...as well as to study the effects of
L. perenne and permeable barriers on preventing metal from leaching. In columns with barriers, EDTA addition yielded maximum concentrations of Cu, Zn and Pb of 155, 541 and 33.5
mg
kg
−1 in shoot, respectively. This led to 4.2, 2.1 and 7.4
times higher concentrations of Cu, Zn and Pb compared to treatment with no chelating agent, respectively. In treatments with 10
mmol
kg
−1 EDTA, the barriers reduced leaching of Cu, Zn and Pb by approximately three times, respectively, resulting in leaching of total initial Cu, Zn and Pb by 27.3%, 25.2% and 28.8%, respectively, after four times’ irrigation. These results indicate that
L.
perenne and permeable barriers are effective to reduce leaching of heavy metals and minimize the risk of contaminating groundwater in EDTA-enhanced phytoremediation. Thus these findings highlight that turfgrass and permeable barriers can effectively prevent metal leaching.
Carbon nanomaterials have been widely used in industry and inevitably enter the environment. However, there is little information about their influence on the abundance and diversity of soil nematode ...community. We evaluated the impact of three kinds of carbon nanomaterials (graphene, graphene oxide, and carbon nanotubes) on the abundance and diversity of soil nematodes after growing tall fescue for 130 d using a laboratory pot experiment. A total of 29 genera of nematodes were identified in all the treatments. Carbon nanomaterials significantly increased the abundance of total nematodes and plant parasites. The presence of graphene and graphene oxide increased the numbers of bacterivores, and graphene benefited fungivores. The total nematode abundance was 1.9–2.9 times greater in the carbon nanomaterial treatments than in the control with no carbon nanomaterial addition. However, graphene oxide and carbon nanotubes decreased the values of nematode community parameters, e.g., diversity, species richness, and structure index. Compared with the control, the addition of graphene resulted in a community with a higher plant-parasitic index (i.e., the maturity index of the plant-parasitic nematodes). Overall, our findings highlight that the addition of carbon nanomaterials has a negative influence on the composition and diversity of the nematode community, simplifying the community structure.
Nanoscale materials have been produced with unprecedented speed due to their widespread use, and they may eventually be released into the environment. As effective adsorbents for heavy metals, carbon ...nanomaterials can be used to immobilize metals in contaminated soil, but little information is available regarding their effects on soil microarthropods. This study was designed to investigate the influence of three types of carbon nanomaterials, graphene (G), graphene oxide (GO) and carbon nanotubes (CNTs) on soil microarthropod communities under turfgrass growth conditions. The application of carbon nanomaterials resulted in increased abundance of all soil microarthropods, especially in the GO and CNT treatments. GO also significantly increased the abundances of multiple trophic functional groups, including predators, detritivores, herbivores and fungivores. Further, the dominant genera varied among the treatments. Herbivorous microarthropods predominated in the control, whereas predatory species predominated in the carbon nanomaterial treatments. Carbon nanomaterials also increased the total taxonomic richness, Shannon diversity index, and dominance index of the microarthropod community, but they decreased the evenness index. Higher diversity of soil microarthropods indicates an environment suitable for soil mesofauna and for enhanced decomposition and nutrient cycling in the soil food web.
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