Soil, Plant, and Microorganism Interactions Drive Secondary Succession in Alpine Grassland Restoration.

Plant secondary succession has been explored extensively in restoring degraded grasslands in semiarid or dry environments. However, the dynamics of soil microbial communities and their interactions with plant succession following restoration efforts remain understudied, particularly in alpine ecosystems. This study investigates the interplay between soil properties, plant communities, and microbial populations across a chronosequence of grassland restoration on the Qinghai-Tibet Plateau in China. We examined five succession stages representing artificial grasslands of varying recovery durations from 0 to 19. We characterized soil microbial compositions using high-throughput sequencing, enzymatic activity assessments, and biomass analyses. Our findings reveal distinct plant and microbial secondary succession patterns, marked by increased soil organic carbon, total phosphorus, and NH4+-N contents. Soil microbial biomass, enzymatic activities, and microbial community diversity increased as recovery time progressed, attributed to increased plant aboveground biomass, cover, and diversity. The observed patterns in biomass and diversity dynamics of plant, bacterial, and fungal communities suggest parallel plant and fungal succession occurrences. Indicators of bacterial and fungal communities, including biomass, enzymatic activities, and community composition, exhibited sensitivity to variations in plant biomass and diversity. Fungal succession, in particular, exhibited susceptibility to changes in the soil C: N ratio. Our results underscore the significant roles of plant biomass, cover, and diversity in shaping microbial community composition attributed to vegetation-induced alterations in soil nutrients and soil microclimates. This study contributes valuable insights into the intricate relationships driving secondary succession in alpine grassland restoration.

Insights into the mechanism involved by electric double layer on phosphate removal of metal-bearing environmental remediation agent: Taking tricalcium aluminate as representative.

Metal-bearing materials are known to be desirable environmental captures for phosphate removal, yet few studies focus on understanding the reaction process, especially formed a special phenomenon, i.e., electric double layer (EDL), which might influence the phosphate removal. To fill in this gap, we fabricated metal-bearing tricalcium aluminate (C3A, Ca3Al2O6) as representative, to remove phosphate and unveil the impact by electric double layer (EDL). Specifically, a preeminent removal capacity of 142.2 mg·g-1 was achieved at the initial phosphate concentration below 300 mg·L-1. Following thorough the characterizations, the process was that the released Ca2+ or Al3+ of C3A formed positive charged stern layer attracted phosphate to generate Ca or Al-precipitation. At high phosphate concentration (>300 mg·L-1), C3A exhibited inferior removal capability for phosphate (<45 mg·g-1), due to the aggregation of C3A particles with low water permeability under the EDL effect, obstructing Ca2+ and Al3+ to release for phosphate removal. In addition, the feasibility application of C3A was evaluated based on response surface methodology (RSM), highlighting its prospective phosphate treatment. This work not only provides a theoretical guidance for the application of C3A to remove phosphate, but also deepens the understand of phosphate removal mechanism by metal-bearing materials, shedding light on environmental remediation.

Engineering 3D graphene-like carbon-assembled layered double oxide for efficient microplastic removal in a wide pH range.

Microplastics (MPs) elimination is becoming an intractable environmental issue due to their nonbiodegradable nature and wide spreading，especially in the case of wastewater containing acid or alkaline effluent. To target the dilemma, this work rationally engineered a robust three-dimensional graphene-like carbon assembled layered double oxide material (defined as G@LDO) from hierarchical organic LDH (i.e., 3D OLDH) via a "precursor-calcination" strategy. In virtue of the mutually protection effect of graphene-like carbon (G) and LDO, the engineered G@LDO featured the preeminent acid and base resistance for polystyrene (PS, as representative of MPs) removal. Especially and importantly, the removal efficiency of PS was ≥ 80% at pH= 3-11, even nearly 60% PS was removed at pH= 1 and 13. The maximum adsorption ability of G@LDO for PS was estimated to be 209.39 mg/g by a Langmuir isotherm model, much superior to that of pure G, LDO, and 2D G@LDO. Furthermore, the removal pathway was analyzed by kinetic together with thermodynamic study, revealing that the PS removal on G@LDO was an exothermic reaction controlled by chemisorption. By systematical characterization and DFT calculation, the removal mechanism of PS was revealed to be hydrogen bond and complexation associated with LDH recovered from LDO and π-π conjunction from G. Notably, the existence of sulfure (S) in the carbon network was also identified as significant component in PS removal via p-π interaction. Overall, this work not only provides a effective candidate for microplastics removal in a wide applicable scope (especially acid/alkaline effluent), shedding light on environmental remediation, but also opens a new anvenue for the disposal of LDHs adsorbed organic in a high value-added manner.

The Joint Toxicity of Organic Three-dimensional Layered Double Hydroxide and Methyl Orange to Green Algae Chlorella Vulgaris.

Organic modified layered double hydroxides (O-LDHs), known as attractive adsorbents for organic pollutants, may pose severe toxicity to the aquatic organisms during their large-scale application. However, little information is available on the toxicity of O-LDHs and the joint toxicity with the coexisted organic pollutants. Herein, we employed organic three-dimensional layered double hydroxide (O3D-LDH) and methyl orange (MO) as representative to investigate the toxicity mechanisms of single substance and its binary mixture on green algae Chlorella vulgaris. Results showed that O3D-LDH and MO presented concentration-dependent toxicity, the binary mixture showed additive effect after exposed to low O3D-LDH concentration (≤ 50 mg/L), but antagonism was observed for the other. It revealed that the agglomeration of O3D-LDH and microalgae influenced chlorophyll content, eventually inhibiting the growth of algae. Overall, this toxicity investigation was critical for understanding the environmental risk of organic LDHs to provide theorical guidance for their practical application in the water purification.

High-efficiency water purification for methyl orange and lead(II) by eco-friendly magnetic sulfur-doped graphene-like carbon-supported layered double oxide.

Traditional disposal techniques for the spent layered adsorbents after capturing organics suffer from intractable obstacles, such as resource waste and secondary pollution. To address this diploma, we here developed the "resource-utilization" strategy, i.e., converting the organic layered double hydroxide (as representative) to magnetic sulfur (S)-doped graphene-like carbon-supported layered double oxide (MG/S-LDO) to be reutilized in water purification. The as-prepared MG/S-LDO exhibited outstanding remediation ability toward methyl orange (MO) and lead(II), with the adsorption capacity of 1456 and 656 mg g-1, respectively. Specifically, the residue concentration of Pb2+ was reduced to 0.15 mg L-1 within 1 h, which met the discharge limit of the secondary industrial wastewater. MG/S-LDO could also maintain the preeminent adsorption capability under various interferences (such as wide pH and co-existing ions), even in the authentic water matrices. The removal mechanisms were systematically investigated to unveil that MO removal was dominated by metal-complexation, "memory effect", and π-π electron donor-acceptor (EDA). While for Pb2+ removal, besides the released OH- from LDO as precipitate agent, the vacancy defect resulting from the S doping played a crucial role in electron interaction between Pb2+ and S-doped graphene. Additionally, the MG/S-LDO was further confirmed as an eco-friendly adsorbent with excellent reusability via the acute toxicity tests using green algae and multiple cycle experiments. This work provides a novel resource-utilization strategy for organic layered wastes to construct the functional eco-friendly materials in wastewater purification realm.

The tetracyclines removal by MgAl layered double oxide in the presence of phosphate or nitrate: Behaviors and mechanism exploration.

Pollution of tetracyclines (TCs) in swine wastewater has been a critical concern worldwide. Notably, multiple anions (e.g. PO43-, NO3-) coexist in the actual environments, which could significantly influence the TCs removal. In the current study, MgAl layered double oxide (MgAl-LDO) was adopted for investigating the TC removal performance with/without PO43- or NO3-. In all systems, the adsorption performance exhibited two different approaches between low and high TC concentrations. In the single system, pseudo-second-order and the Freundlich model fitted well to the equilibrium adsorption data when TC concentration was below 125 mg·L-1, while the pseudo-first-order and the linear model could describe the removal process at high TC concentration (>125 mg·L-1). The maximum adsorption capacity was 83.56 mg·g-1. In the co-existing system, the adsorption capacity was slightly enhanced when TC concentration below 150 mg·L-1 however was inhibited at high concentration (>150 mg·L-1). Combined with the characterization analyses, the interaction mechanism at low concentration was primarily surface adsorption on reconstructed LDH from LDO in the TC-alone system. It is worth mention that both PO43- and NO3- facilitated the formation of LDH via rehydration of LDO which enhanced surface adsorption in the co-existing system. At high TC concentration, the formation of tetracycline-metal complexes played a dominant role in TC removal in the single system, whereas diminished complexation in the binary system led to the decreased TC removal. This study provides a theoretical and practical guidance for MgAl-LDO on the efficient remediation of actual tetracyclines wastewater.

Novel Two-Dimensional Magnetic Titanium Carbide for Methylene Blue Removal over a Wide pH Range: Insight into Removal Performance and Mechanism.

Two-dimensional (2D) layer-structured titanium carbide MXenes (e.g., 2D Ti3C2 MXene) have received tremendous attention owing to their excellent properties and unique 2D planar topology. Nevertheless, there are still several challenges to be addressed for well dispersibility and easy separation from a heterogeneous system, hindering the practical applications. Herein, 2D Ti3C2 MXene, as the most typical member of 2D MXenes, is functionalized with magnetic Fe3O4 nanoparticles via an in situ growth approach (designated as MXene@Fe3O4), which exhibits the intriguing phenomenon on methylene blue (MB) adsorption in the environmental remediation realm. The maximum adsorption capacity of the MXene@Fe3O4 composites for MB is calculated to be 11.68 mg·g-1 by a Langmuir isotherm model. A thermodynamic study of the adsorption demonstrates that the reaction process is exothermic and entropy-driven. Attractively, the removal process is a pH-independent process, and the optimal MB adsorption capacity is achieved at pH = 3 or 11, which is ascribed to electrostatic interactions and the hydrogen bond effect. X-ray diffraction, Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculation results reveal that the adsorption process is based on a combination of Ti-OH···N bonding, electrostatic attraction, and reductivity. Furthermore, multiple cycle runs demonstrate an excellent stability and reusability of MXene@Fe3O4 composites. This study provides a promising approach for the alternative removal of MB and broadens the potential application of 2D MXene for the treatment of practical acidic or alkaline wastewater.

The enhancement roles of sulfate on the adsorption of sodium dodecylsulfate by calcium-based layered double hydroxide: microstructure and thermal behaviors.

As a commonly used surfactant, sodium dodecyl sulfate (SDS) usually coexists with inorganic anions in the industrial wastewater. These anions have a significant influence on SDS removal, indirectly threatening the environment. It is important to understand the relationship between the adsorption of SDS and inorganic anions. In this study, calcium-based layered double hydroxide (CaAl-LDH-Cl) as an efficient adsorbent was synthesized for investigating the effect of SO42- on SDS removal. The SDS adsorption capacities were enhanced to 3.21 and 4.21 mmol g-1 in the presence of SO42- with low/high SDS concentration, respectively. The phenomenon and mechanism were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM). Anionic exchange played a dominant role in the adsorption of SDS onto CaAl-LDH-Cl at DS-/SO42- < 2, while both anion exchange and precipitation occurred when DS-/SO42- exceeded 2. Moreover, the thermal analysis (TG-DTA) was employed to further reveal the interaction mechanism. The results showed the highest total mass loss and the lowest loss temperature of interlayer water in the sulfate coexist system, confirming the enhancement of SDS adsorption amount in the presence of SO42-.