Sustainable soil rehabilitation with multiple network structures of layered double hydroxide beads: Immobilization of heavy metals, fertilizer release, and water retention.

The remediation of heavy metal-contaminated soils necessitated a holistic approach that encompassed water and fertilizer conservation alongside soil property restoration. This study introduced the synthesis of (poly)acrylamide-layered double hydroxide gel spheres (PAM-LDH beads), which were designed to simultaneously immobilize heavy metals, control the release of fertilizers, and enhance soil water retention. Laboratory soil experiments under diverse conditions highlighted the superior performance of PAM-LDH beads in the immobilization of hexavalent chromium (Cr(VI)).

Iron coupled with hydroxylamine turns on the "switch" for free radical degradation of organic pollutants under high pH conditions.

Reducing iron by hydroxylamine (HA) can promote the generation of reactive oxygen species (ROS) in the Fenton reaction and play a crucial role in the degradation of organic pollutants. However, the performance of this system at wider environmental thresholds is still not sufficiently understood, especially in the highly alkaline environments resulting from human activities. Here, we assessed the impact of solution pH on organic pollutant degradation by goethite with the addition of HA and HO.

The coupling of sulfide and Fe-Mn mineral promotes the migration of lead and zinc in the redox cycle of high pH floodplain soils.

In this study, we investigated the impact of fluctuating water levels on the distribution of lead (Pb) and zinc (Zn) in soil and sediments at a historical Pb-Zn smelting site along the Xiangjiang River. Despite the high pH levels (7 to 11) in the study area, which generally inhibits heavy metal solubility, we found that regular changes in water levels still affect Pb-Zn movement. Soil analysis revealed distinct redox zones within the unconfined aquifer, as shown by the variable Fe/Mn and Ce/Ce* ratios.

Double-edged effect of frequent freeze-thaw on the stability of zero-valent iron after heavy metal remediation.

Freeze-thaw cycles (FTCs) cause dynamic microscale changes in ions and solvents. During freezing, heavy metals adsorbed on zero-valent iron (M-ZVI) and protons are excluded by ice crystals and concentrated in the liquid-like grain boundary region. The high proton concentration in this region leads to the dissolution of the passivation layer of ZVI.

Direct degradation of Bisphenol A from aqueous solution by active red mud in aerobic environment.

As industrial waste from aluminum production, red mud (RM) poses a severe threat to the local environment that needs to be appropriately utilized. The activation of iron oxide, which is abundant in RM, improves its effectiveness as a catalytic material for the degradation of organic pollutants. This study developed a novel activation approach by adding dithionite citrate bicarbonate (DCB) for Bisphenol A (BPA) degradation under aeration conditions.

The influence of various microplastics on PBDEs contaminated soil remediation by nZVI and sulfide-nZVI: Impedance, electron-accepting/-donating capacity and aging.

The microplastics (MPs) existed in the environment widely has resulted in novel thinking about in-situ remediation techniques, such as nano-zero-valent iron (nZVI) and sulfided nZVI (S-nZVI), which were often compromised by various environmental factors. In this study, three common MPs such as polyvinyl chloride (PVC), polystyrene (PS), and polypropylene (PP) in soil were found to inhibit the degradation rate of decabromodiphenyl ether (BDE209) by nZVI and S-nZVI to different degrees due to MPs inhibiting of electron transfer which is the main way to degrade BDE209. The inhibition strength was related to its impedance (Z) and electron-accepting (EAC)/-donating capacity (EDC).

New insight of Mn(III) in δ-MnO for peroxymonosulfate activation reaction: Via direct electron transfer or via free radical reactions.

Due to the increasing of industrial plastic waste and its refractory characteristics, it is extremely urgent to develop new degradation technology and environmentally friendly catalyst for industrial plastic waste. Manganese oxides are one of the most promising candidates for the catalytic degradation of plastic wastes. However, an improved understanding of the structural properties affecting their catalytic activity is required for high-efficient wastewater treatment.

Effect of calcination temperatures on the performance of rectorite for cadmium immobilization in soil: Freeze-thaw, plant growth, and microbial diversity.

The immobilization of cadmium (Cd(II)) in soil using calcined rectorite (REC) was investigated in this research. The results of immobilization show that a small amount of REC calcined at 700 °C (REC-700 °C) could effectively immobilize 90% of Cd(II) in soil, while the immobilization efficiency of REC only reached 42%. Moreover, the immobilization efficiency of REC calcined at 300 °C and 500 °C (REC-300 °C and REC-500 °C) were lower than REC.

Remediation of chromium-contaminated soil using delaminated layered double hydroxides with different divalent metals.

Soil is commonly polluted by chromium, and layered double hydroxides (LDHs) are widely used for chromium removal due to their strong adsorption capacity and the unique properties of their delaminated products. In this study, delaminated LDHs (S-Mg-LDH and S-Ca-LDH) and their original LDHs were used to remediate Cr(VI)-contaminated soil. A series of characterizations confirmed the successful synthesis of delaminated LDHs whose sheet structure was thinner with a greater surface energy than the original LDHs.

Metal-support interactions on Ru/CaAlO catalysts derived from structural reconstruction of Ca-Al layered double hydroxides for ammonia decomposition.

Strong metal-support interaction (SMSI) over Ru/CaAlOx was constructed by utilizing the surface structural reconstruction of Ca-Al layered double hydroxides (LDHs) in aqueous solution and their subsequent hydroxide-to-oxide transformations. Ru nanoparticles were found to uniformly embed with CaAlOx. The electronic interactions and changes in CO adsorption behavior confirmed the SMSI state between Ru and CaAlOx.

Degradation of bisphenol A by Fe-Al layered double hydroxides: A new synergy of homo- and heterogeneous Fenton systems.

Fe(II)-Al(III) layered double hydroxides (Fe-Al-LDHs) prepared by co-precipitation were used to degrade bisphenol A (BPA) in water. The LDH/HO system proved to be effective in degrading BPA, even under high pH conditions. Influencing factors on the removal of BPA, such as LDH dosage, initial BPA concentration and HO concentration, were studied.

Double-Edged Effect of Humic Acid on Multiple Sorption Modes of Calcined Layered Double Hydroxides: Inhibition and Promotion.

Layered double hydroxides (LDHs) are a typical class of anionic clay minerals whose structural memory effect has been widely used in pollutant adsorption. However, the influencing mechanism of humic acid (HA) on the structural memory effect in adsorption is not clear. In this study, HA was extracted from black soil and sediments, and its effect on the structural memory effect of LDHs with different divalent metals was evaluated in adsorption.

Enhanced surface Fenton degradation of BPA in soil with a high pH.

Although the heterogeneous Fenton process of iron-bearing minerals has been widely studied due to its potential use for the removal of organic pollutants, the transformation mediated by Fe species in soil particles remains poorly understood. Here, we compared the removal of bisphenol A (BPA) from soil using a Fenton system at low and high pH values. At low pH value, the BPA removal rate decreased with increasing pH value; this result was consistent with the amount of soluble Fe(II) and surface-bound Fe(II) observed in the soil systems.

Remediation of hexavalent chromium in contaminated soil by Fe(II)-Al layered double hydroxide.

In this study, high-efficiency and low-cost Fe(II) and Al(III) layered double hydroxide (Fe-Al-LDH) was synthesized and used for the remediation of Cr(VI) contaminated soil. The Fe-Al-LDH characteristics were analyzed with different techniques. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses revealed its highly crystalline structure with sheet morphology, and a Brunauer-Emmett-Teller (BET) surface area of 46.

Structural Memory Effect of Mg-Al and Zn-Al layered Double Hydroxides in the Presence of Different Natural Humic Acids: Process and Mechanism.

The structural memory effect of layered double hydroxides (LDHs) is one of the important reasons for their extensive use in environmental remediation. In this study, humic acid (HA) was extracted from black soil and sediments and characterized to determine their structures. The regeneration mechanisms of calcinated LDHs (CLDHs) including different divalent metals (Mg-CLDH and Zn-CLDH) in deionized water and different HA solutions were carefully elucidated, and the reasons for the behavior differences in the two materials were explained.

Ionothermal synthesis of FeO magnetic nanoparticles as efficient heterogeneous Fenton-like catalysts for degradation of organic pollutants with HO.

FeO magnetic nanoparticles (MNPs) are attractive heterogeneous Fenton-like catalysts for oxidative degradation of organic pollutants with HO. Herein highly efficient and stable FeO MNPs (FeO-op-DES, ca. 10nm) were successfully prepared via a novel oxidative precipitation-combined ionothermal synthesis, which comprised oxidative precipitation of FeSO·7HO in choline chloride:2urea deep eutectic solvent.

Transport of nano zero-valent iron supported by mesoporous silica microspheres in porous media.

Effective in situ remediation of groundwater requires the successful delivery of reactive iron particles through sand. However, the agglomeration of nano zero-valent iron (NZVI) particles limits the migration distance, which inhibits their usefulness. In the study described herein, NZVI supported by mesoporous silica microspheres covered with FeOOH (SiO2@FeOOH@Fe) was synthesized, and its mobility was demonstrated on the basis of transport in porous media.

Mechanism of boron uptake by hydrocalumite calcined at different temperatures.

Hydrocalumite (Ca-Al-layered double hydroxide (LDH)) was prepared and applied for the removal of borate. The properties of Ca-Al-LDH calcined at different temperatures were diverse, which affected the sorption density and mechanism of boron species. The sorption density increased with increase in calcined temperature and the sample calcined at 900°C (Ca-Al-LDH-900) showed the maximum sorption density in this work.

Sorption of H₃BO₃/B(OH)₄⁻ on calcined LDHs including different divalent metals.

LDHs with different divalent metals (Zn-LDH, Mg-LDH and Ca-LDH) have been synthesized and produced calcined LDHs (Zn-CLDH, Mg-CLDH and Ca-CLDH) for borate removal. Based on XRD, SEM, BET, (27)Al NMR, CO2-TPD, and (11)B NMR, detailed characterization of different CLDHs before and after reaction with the boron species was systematically performed. The surface area, basicity and the particle charge of the different CLDHs, which are related to the hydration and regeneration, were markably influenced by the nature of the divalent metals.

Comparisons of the reactivity, reusability and stability of four different zero-valent iron-based nanoparticles.

Our previous reports showed that nano zero-valent iron (nZVI), steel pickle liquor for the synthesis of nZVI (S-nZVI), nZVI immobilised in mesoporous silica microspheres (SiO2@FeOOH@Fe) and nano Ni/Fe bimetallic particles (Ni/Fe) have been proved to show good property for elimination of polybrominated diphenyl ethers (PBDEs). However, it is necessary to compare their reactivity, reusability and stability when applied to in situ remediation. In this study, the performances of different iron-based nanoparticles were compared through reusability, sedimentation and iron dissolution experiments.

Degradation of decabromodiphenyl ether by nano zero-valent iron immobilized in mesoporous silica microspheres.

The agglomeration of nanoparticles reduces the surface area and reactivity of nano zero-valent iron (NZVI). In this paper, highly dispersive and reactive NZVI immobilized in mesoporous silica microspheres covered with FeOOH was synthesized to form reactive mesoporous silica microspheres (SiO(2)@FeOOH@Fe). The characteristics of SiO(2)@FeOOH@Fe were analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy simultaneous thermal analysis, X-ray photoelectron spectroscopy, and Brunnaer-Emmett-Teller surface area analysis.

Debromination of polybrominated diphenyl ethers by Ni/Fe bimetallic nanoparticles: influencing factors, kinetics, and mechanism.

Polybrominated diphenyl ethers have been identified as a new class of organic pollutants with ecological risk due to their toxicity, bioaccumulation, and global distribution. Proper remediation technologies are needed to remove them from the environment. In this paper, Ni/Fe bimetallic nanoparticles were synthesized by chemical deposition and used to degrade decabromodiphenyl ether (BDE209).

[Discussion on reinforcing-reducing manipulations of acupuncture in Internal Classic].

To study and analyze the reinforcing-reducing manipulations of acupuncture in Internal Classic. The major methods of reinforcing-reducing manipulations of acupuncture in Internal Classic were reinforcing-reducing by manipulating the needle in cooperation with the patient's respiration, reinforcing-reducing effect induced by slow and quick manipulation of needle, and open-close reinforcing-reducing manipulation, these three methods were usually applied in combination. All of reinforcing-reducing manipulations should be based on the principle of puncturing along and against the flowing direction of the meridian qi.