Layered double hydroxides (LDH) have been extensively studied because of their unique characteristics. The available reviews have dealt with the applications of LDH normally prepared with aqueous ...solution approaches. Recently mechanochemical ways to synthesize LDH and intercalated LDH have received more and more attention from researchers and several mechanochemical processes have been reported. This article reviews the recent advances in the preparation and intercalation of layered double hydroxides by mechanochemical approaches. Although conventional solution methods for the syntheses of LDH were widely studied, several problems remain to be resolved; such as treatment of aqueous waste, high energy consumption, complex operation etc. It is believed that mechanochemical methods may have potentials to effectively overcome the difficulties and also to synthesize various new types of LDH with further development of this new technique.
•The syntheses of LDH by mechanochemistry, the processes and the characterization methods of the products have been reviewed.•The mechanochemical intercalations of LDH with and without solvent have been compared.•The characterization techniques used in mechanochemical approaches to synthesize LDH has been summarized.•The mechanochemical approaches may contribute new applications for LDH.
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•Methane production were improved with addition of biochar, magnetic biochar and Fe3O4.•The cumulative methane yield was increased by 60.47% with 5 g/kg of Fe3O4.•The direct ...interspecies electron transfer (DIET) was enhanced by Fe3O4.•The strategy of recycling Fe3O4 additive has the best economic benefit.
The co-digestion of corn straw and sewage sludge with different additives (biochar, magnetic biochar, Fe3O4) were investigated. The highest cumulative methane yield of 245.15 mL/g VSadded was obtained with the Fe3O4 addition ratio of 5 g/kg, which was 60.47% higher than that of the control run (without additives). The lag phase time was shortened from 5.46 to 3.82 days with a biochar dosage of 5 g/kg. The performance of Fe3O4 on methane production from the co-digestion process was better than that of the biochar and magnetic biochar. The direct interspecies electron transfer (DIET) was enhanced with regard to the increased concentration of acetic acid and decreased concentration of propionic acid. Microbial community analysis showed that the Geobacter and Methanosarcina were selectively enriched on the surface of Fe3O4, promoting the DIET and acetoclastic methanogenesis pathway. The cost-benefit analysis proved that the strategy of recycling Fe3O4 additive has the best economic benefit.
Precursor of MgAl LDH was simply obtained by dry milling of Al(OH)3 and Mg(OH)2 in two-step process and used as adsorbent to remove phenol and p-nitrophenol from water. The precursor samples before ...and after adsorption were characterized through Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR). The equilibrium adsorption data were well fitted to Langmuir model and were characterized with excellent adsorption capacities of 82.6 mg/g phenol and 356.4 mg/g p-nitrophenol, respectively. Pseudo-second-order kinetic model indicated that phenols were well adsorbed on the precursor. The enhanced adsorption mechanism was investigated and observed that the disorderly precursor have more active sites than the other adsorbents with stable crystalline structures. Comparison between the precursor and LDH product clearly demonstrated the advantage of precursor over the LDH, providing a new concept of using the easily obtained precursor as efficient adsorbent for wastewater treatment.
This study evaluated the associations of solid fuels with incidence of falls and fall-related injuries.
Data were taken from wave 1∼4 of the China Health and Retirement Longitudinal Study, including ...15,651 participants aged 45 years and older. Modified Poisson regression was used to examine the associations of solid fuels with falls and fall-related injuries.
Modified Poisson regression analysis showed that solid fuels users for cooking had an increasing incidence of falls and fall-related injuries, with RR of 1.211 (95% CI: 1.124, 1.305) and 1.248 (95% CI: 1.107, 1.408); for heating had an incidence, with RR of 1.178 (95% CI: 1.062, 1.306) and 1.134 (95% CI: 0.963, 1.335); combined for cooking and heating, with RR of 1.247 (95% CI: 1.105, 1.408) and 1.185 (95% CI: 0.982, 1.431).
Our study suggests that solid fuel use is associated with a higher incidence of falls and fall-related injuries among adults aged 45 years and older in China. It is necessary to restrict solid fuel use to reduce household air pollution and make stronger environmental protection policies to improve household environment.
This study presents an interesting phenomenon of the simultaneous occurrence of adsorption and synthesis of Mg–Al layered double hydroxide (Mg–Al–LDH) by stirring a precursor in an aqueous solution ...with methyl orange (MO) as target adsorbate with the precursor prepared by first milling Mg(OH)2 for 1 h followed by another 3 h milling with Al(OH)3.The prepared precursor and LDH samples were characterized by a set of analytical methods including X‐ray diffraction (XRD), thermogravimetry/differential scanning calorimetry (TG–DSC), and Fourier‐transform infrared (FT–IR). The maximum adsorption capacity (Qm) of MO by the prepared precursor sample was 1110.2 mg/g, much higher than that from the synthesized LDH sample. Engineering application may be expected from the easy preparation of such precursor as adsorbent to purify the tremendous amounts of dye wastewater.
The limbic system plays a pivotal role in stress-induced anxiety and intestinal disorders, but how the functional circuits between nuclei within the limbic system are engaged in the processing is ...still unclear. In our study, the results of fluorescence gold retrograde tracing and fluorescence immunohistochemistry showed that the melanin-concentrating hormone (MCH) neurons of the lateral hypothalamic area (LHA) projected to the basolateral amygdala (BLA). Both chemogenetic activation of MCH neurons and microinjection of MCH into the BLA induced anxiety disorder in mice, which were reversed by intra-BLA microinjection of MCH receptor 1 (MCHR1) blocker SNAP-94847. In the chronic acute combining stress (CACS) stimulated mice, SNAP94847 administrated in the BLA ameliorated anxiety-like behaviors and improved intestinal dysfunction via reducing intestinal permeability and inflammation. In conclusion, MCHergic circuit from the LHA to the BLA participates in the regulation of anxiety-like behavior in mice, and this neural pathway is related to the intestinal dysfunction in CACS mice by regulating intestinal permeability and inflammation.
Conventional chemical soil amendments and novel material biochars have been widely reported for the immobilisation of cadmium (Cd) and lead (Pb) in polluted soil. However, information regarding their ...comparative effectiveness is poor. In the present study, rice husk biochar (RHB) was compared with two chemical soil amendments including hydroxyapatite (HAP) and hydrated lime (HDL) for their effectiveness to enhance plant growth and the reduction of Cd uptake and translocation by
Triticum aestivum
L. grown in heavy-metal-polluted soil. Compared with control and two chemical soil amendments, RHB rapidly improved wheat growth. The HAP, HDL, and RHB treated plants retained Cd and Pb in roots and restricted their translocation. The RHB treatment had the best effect on growth, yield promotion and the reduction of Cd and Pb in wheat grain. Furthermore, the soils treated with RHB and HAP showed lower DTPA-extracted Cd concentrations, and the maximum reduction was observed in HAP-amended soil. However, the DTPA-extracted Pb concentration was not significantly decreased after the application of two chemical soil amendments for 40 days; the maximum reduction was found in soil treated with RHB for 80 days. In all treatments, Cd in post-harvest soil was mainly present in exchangeable, carbonate bound, and Fe-Mn oxide Cd, while the dominant chemical form of Pb was Fe-Mn oxide Pb. Three soil amendments application decreased exchangeable and organic bound- Cd and Pb levels. HAP and RHB displayed significantly immobilisation for soil Cd and reduced translocation of heavy metal as well as its availability in soil, but the HAP had significant inhibition on growth of wheat in contaminated soil. Therefore, RHB shows a promising potential for the reduction of Cd and Pb bioaccumulation in grains from wheat grown on heavy-metal-polluted soils.
The wide spread of Perfluoroalkyl substances (e.g., PFOA and PFOS) in soil can alter native soil geochemical properties and microbial communities through various approaches. Nonetheless, it is ...unclear that how PFOA and PFOS in soil affect the mineralization of soil organic carbon (SOC). A laboratory-scale culture experiment (180 d) was performed to explore the contribution of PFOA and PFOS to SOC dynamics and soil geochemical processes. Results showed that positive priming effect (PE) occurred in the short term (i.e., 30 days after PFOA and PFOS addition) and subsequently shifted to a slightly negative PE (i.e., 90 days) and remained in a significant negative PE thereafter (i.e., > 180 days). The PEs caused by PFOA and PFOS both accelerated the consumption of dissolved organic carbon (DOC), resulting in a significant increase in SOC mineralization (10.45%–127.36%) under the short-term incubation (30 d). As for long-term exposure (> 90 d), the organic carbon mineralization rate was significantly reduced (58.30%–65.24%) due to the excessive DOC consumption in the initial stage. High throughput analysis indicated that both PFOA and PFOS changed soil bacterial and fungal community structures, altered the relevant metabolic pathways and resulted in the enrichment of specific taxa.
Graphical Abstract
Fe
4
O
3
has shown great potential as an enhancer of batch anaerobic digestion performance. In this study, the effect of two types of Fe
3
O
4
additive utilization strategies (magnetic separation ...recycling strategy and replenishment without recycling strategy) on semi-continuous anaerobic co-digestion of sludge and corn straw were investigated. A maximum methane yield of 163.88 ± 12.18 mL/g·VS·d was obtained at the dosage of 10 g/kg Fe
3
O
4
with magnetic separation recycling strategy compared to the control without the addition of Fe
3
O
4
. As compared to the replenishment strategy, the recycling strategy improved specific daily methane yields by 38.45% and 45.75% for Fe
3
O
4
addition amounts of 5 g/kg and 10 g/kg, respectively. The results show that the recycling of Fe
3
O
4
additives can further optimize the composition of VFAs. Although the total VFAs were not elevated, the proportion of acetic acid increased and the proportion of propionic acid as well as butyric acid decreased. The present research supports the magnetic recycling of Fe
3
O
4
as a new strategy to solve the problem of additive loss in semi-continuous anaerobic digestion process.
Excessive existences of nutrients such as phosphate in the aqueous environment remain as a heavy concern although many researches have been reported for dealing with their removal. Based on the ...understanding toward the interactions of Fe compounds with phosphate and carbonate from many available researches, we designed a very simple and efficient approach for phosphate removal by using in situ generated fresh trivalent Fe composition through the interaction of Fe(II) as FeSO
on CaCO
. Addition and agitation of Fe(II) and CaCO
simultaneously to phosphate solution allowed an amorphous Fe(III)-P or Ca-Fe(III)-P precipitation, with a phosphate removal rate close to 100%, to reduce the residual phosphorus concentration less than 0.03 mg/L from 100 mg/L, reaching the discharge limit, even with the addition amounts of CaCO
as low as a stoichiometric ratio of CaCO
/PO
at 0.9 and ratio of Fe(II)/PO
at 1.5, and the percent of P
O
in the precipitate was as high as 19.4% enough as phosphate source for fertilizer production. Different from the alkaline process with enough OH
group, the slow hydrolysis of CaCO
resulting in low concentration of OH
group for the formation of Fe(OH)
, which was oxidized soon by air into trivalent Fe, achieved a continuous generation of fresh ferric composition for phosphate precipitation and could avoid its rapid formation and subsequent transformation into stable FeOOH of large particle size to lose the activity. These results based on the synergistic effect of using CaCO
and Fe(II) together may have applications in the treatment of eutrophic wastewater through a process with many advantages of easy operation and low-cost besides the high removal efficiency with phosphate percentage inside the precipitate high enough to serve for fertilizer production.
