Plant growth-promoting rhizobacteria (PGPR) are a specific category of microbes that improve plant growth and promote greater tolerance to metal stress through their interactions with plant roots. We ...evaluated the effects of phytoremediation combining the cadmium accumulator Solanum nigrum L. and two Cd- and Pb-resistant bacteria isolates. To understand the interaction between PGPR and their host plant, we conducted greenhouse experiments with inoculation treatments at Nanjing Agricultural University (Jiangsu Province, China), in June 2018. Two Cd- and Pb-resistant PGPR with various growth-promoting properties were isolated from heavy metal-contaminated soil. 16S rRNA analyses indicated that the two isolates were Bacillus genus, and they were named QX8 and QX13. Pot experiments demonstrated that inoculation may improve the rhizosphere soil environment and promote absorption of Fe and P by plants. Inoculation with QX8 and QX13 also enhanced the dry weight of shoots (1.36- and 1.7-fold, respectively) and roots (1.42- and 1.96-fold) of plants growing in Cd- and Pb-contaminated soil, and significantly increased total Cd (1.28–1.81 fold) and Pb (1.08–1.55 fold) content in aerial organs, compared to non-inoculated controls. We also detected increases of 23% and 22% in the acid phosphatase activity of rhizosphere soils inoculated with QX8 and QX13, respectively. However, we did not detect significant differences between inoculated and non-inoculated treatments in Cd and Pb concentrations in plants and available Cd and Pb content in rhizosphere soils. We demonstrated that PGPR-assisted phytoremediation is a promising technique for remediating heavy metal-contaminated soils, with the potential to enhance phytoremediation efficiency and improve soil quality.
•Two Cd- and Pb-resistant PGPR of Bacillus sp. QX8 and QX13 was isolated from heavy-metal-contaminated soil.•PGPR inoculation significantly promoted the growth of Solanum nigrum.•PGPR inoculation increased Cd and Pb phytoextraction by Solanum nigrum.
Activated siderite, endowed with excellent properties, was simply prepared by co-grinding with Fe sulfate to enhance its high reducing ability for Cr(VI). Batch experiments were conducted to ...investigate the main affecting parameters, such as material ratio, pH, temperature, etc. The removal of Cr(VI) by activated siderite was completed within 4 h of the reaction. The activated siderite maintained a high removal effect of Cr(VI) within a wide pH range (3–9). Various analytical methods, including XRD, SEM/EDS, XPS, etc., were employed to characterize the samples and discover variations before and after the reaction. The Fe (Ⅱ) in activated siderite becomes highly active, and it can even be released from the solid phase in the mildly acidic liquid phase to efficiently reduce Cr(VI) and mitigate its toxicity. These findings introduce an innovative approach for activating various minerals widely distributed in nature to promote the recovery of the ecological system.
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•Natural siderite was simply activated by co-grinding with Fe sulfate.•Activated siderite exhibited high reducing ability for Cr(VI) within a wide range of pH.•The highly active Fe (Ⅱ) can even be released from the solid phase in the mildly acidic solution.
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•Porous Ni, N-codoped C networks were prepared through an simple in-situ self-growth NaCl-templated strategy.•The as-synthesized Ni, N-codoped C networks exhibited abundant pores ...characterization with high specific surface area.•A novel non-enzymatic glucose sensor with excellent performance is developed basing the Ni, N-codoped C networks.•The strategy may provide guidance for the synthesis of other carbon-based materials.
Carbon materials have received intensive attention due to their unique property in the field of electrochemical analysis. As transition metallic heteroatom and nitrogen-codoped carbon (M-N-C) materials commonly exhibit enhanced electrochemical activity for the tuned electronic structure, therefore, fabricating a novel structure of M-N-C material for electrochemical analysis is highly pursued. Herein, an in-situ self-growth NaCl-templated strategy is proposed to fabricate three-dimensional porous Ni, N-codoped carbon material (3D Ni-N-C). The as-obtained 3D Ni-N-C demonstrates superior electrochemical performance toward glucose oxidation and sensing, and a highly sensitive and selective non-enzymatic glucose sensor is subsequently developed for human serums with a wide linear range of 0.001–1.20 mM, low detection limit of 0.15 μM, and high sensitivity of 1181.0 μA mM−1 cm-2. It is believed that the unique structural properties of 3D Ni-N-C (abundant N-doped and Ni-N coordinated active sites, large surface area, open micro-porous structure) are conducive to the formation and exposure of highly catalytic centers and improvement of electron-transfer rate.
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•Grinding leads to structural change in muscovite and final amorphization.•Ball milling increases citric acid-soluble potassium in muscovite.•Cogrinding with CaCl2 or MgSO4 increases ...water-soluble potassium.•Cogrinding with CaCl2 or MgSO4 increases citric acid-soluble silicon to 47.33% or 46.54%.
A novel mechanochemical method was proposed to transform muscovite, a silicate mineral, into citric acid-soluble composite fertilizers. With the increase of ball milling strength, the structure of muscovite was continuously changed from muscovite-2M1 to muscovite-1M at 300 rpm and then to amorphous at 600 rpm, which enhanced silicon dissolution from 0.23% to 16.05% and potassium dissolution from 2.62% to 81.39% in 2% citric acid solution. The addition of CaCl2 and MgSO4 increased citric acid-soluble silicon to 47.33% and 46.54%, respectively, demonstrating potential use as a controlled release fertilizer of silicon-potassium for the sustainable development of agriculture.
A mechanochemical (MC) method was employed for the remediation of soil contaminated with fluoranthene (C
16
H
10
, FL) a four-ringed polycyclic aromatic hydrocarbon (PAH) containing three benzene ...rings and a central five-membered heterocyclic ring, with the effects of soil inorganic components, milling conditions, and the degradation mechanism investigated. Results showed that the addition of SiO
2
and kaolin to soil resulted in a greater increase in the effectiveness of FL removal than other inorganic additives. After 3 hours of milling at 500 rpm, the FL removal rate from SiO
2
containing soil, reached 99.26%, with the removal efficiency increasing in accordance with an increase in milling duration and speed. The milled samples were characterized by FT-IR, Raman spectroscopy, and GC-MS analysis, revealing the mechanism of FL degradation, including destruction of the aromatic skeleton structure and the formation of amorphous carbon and graphite. The MC remediation method was applied to FL contaminated soil, showing that FL was efficiently degraded in soil without any soil additives, resulting in a significant reduction in the biotoxicity of the remediated soil. The organic matter, moisture content and pH of the actual soil changed slightly after mechanical ball milling. Thus, the MC method has high potential in the remediation of PAH-contaminated soils.
HIGHLIGHTS
A mechanochemical (MC) method for the degradation of fluoranthene was assessed.
The use of silica and kaolin as soil additives enhances fluoranthene remediation.
Fluoranthene can be efficiently removed from contaminated soil by milling alone.
The degradation mechanism was skeleton structure destruction and carbonization.
The biotoxicity of soil was significantly reduced by milling.
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•LDHs were used as carriers in (AO)n-SBBR systems.•Phosphate removal was due to the synergistic effects between LDHs and microorganisms.•LDHs accelerated biofilm formation and ...improved biodiversity.
Layered double hydroxides (LDHs) were used as carriers for the microbial consortium in sequencing biofilm batch reactor (SBBR) without inoculation to promote the removal of phosphate. The adsorption capacity of Zn-Al-LDH was significantly better than that of Mg-Al-LDH. The pollutants removal performance and behavior of microorganisms in LDH-SBBRs were also investigated. LDH-SBBRs showed improved removal efficiencies of COD, phosphate and TP with a low C/N ratio. Microscopic images show that biofilm formed rapidly in LDH-SBBRs. SEM-EDS detected abundant carbon and phosphorus, implying that biomass and phosphorus accumulate on LDH carriers. The microbial compositions of the three SBBRs indicate that the LDHs carriers improved the biodiversity of biofilm in the bioreactors. Synergistic effects of adsorption and biodegradation between well-structured LDHs and microorganisms led to an improved phosphate removal performance of LDH-SBBR. The results also demonstrate that Zn-Al-LDH carrier is the best for improving SBBR phosphate removal.
Food waste represents a valuable resource potential for the production of advanced biofuels, including biomethane. This study systematically assessed the impact of salt on biomethane production from ...different components of food waste. The highest biomethane yields of 258.89 ± 10.96, 337.52 ± 16.36, and 448.49 ± 23.375 mL/g volatile solids (equivalent to biodegradability indexes of 75.75%, 88.92% and 92.66%) were achieved from cellulose-rich, starch-rich and protein-rich components, respectively, at a salt concentration of 3 g NaCl/L. The biomethane yield was improved by 9.69–31.24% with low-concentration salt compared with no salt addition, but it was inhibited by high salinity. Inhibition induced by high salinity (15 g NaCl/L) on biomethane production followed the order of protein (15.50%) < starch (28.03%) < cellulose (42.92%). Co-digestion of different components effectively mitigated the inhibitory effect of salt on biomethane production. Microbial community analysis revealed that archaea were significantly affected by high salinity. With a high concentration of salt (15 g/L), acetoclastic methanogens (Methanosatea) predominated in the digestion of starch-rich components, whilst hydrogenotrophic methanogens (Methaonmassiliicoccus and Methanobacterium) predominated in the digestion of cellulose-rich and protein-rich components. Additionally, some salt-tolerant microorganisms (SC103, Thermovirga and Methanosarcina) were selectively enriched at high salinity.
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•Maximum CH4 yield was 448.5 mL/g VS from protein-rich components at 3 g/L NaCl.•Lowest salt inhibition threshold (5 g NaCl/L) was observed in starch-rich digestion.•Fermentative bacteria were more resistant to salinity compared to methanogens.•Acetoclastic Methanosatea was dominant under high-salinity starch-rich digestion.
Anaerobic ammonia-oxidizing bacteria (AAOB) have a long growth time and low activity at low temperatures. In suspended systems, sludge is easily lost, which limits the mainstream application of ...anaerobic ammonia oxidation (anammox).Entrapment provides effective ideas for solving these problems. In this study, polyvinyl‑sodium alginate (PVA-SA) and nano Fe2O3-PVA-SA entrapment beads were prepared to discuss the effectiveness of entrapment enhanced anammox sludge at low temperatures. The differences in the entrapped beads and granules were compared to analyze the strengthening mechanism. The results show that the nitrogen removal performance of granules, PVA-SA and nano Fe2O3-PVA-SA entrapped beads, first decreased and then increased during the cooling and low-temperature operation. Nano Fe2O3-PVA-SA entrapped beads showed the smallest decline and the highest degree of recovery. Reaction metering ratio (△NO2−-N/△NH4+-N and △NO3−-N/△NH4+-N) showed that entrapment could realize Nitrite oxidizing bacteria (NOB) inhibition and improve the activity of denitrifying bacteria (DNB) to promote the removal of total nitrogen by providing a strict anaerobic environment. The results demonstrate that entrapment is beneficial for maintaining the content of heme c, specifically, nano Fe2O3 can stimulate its production, and is beneficial for alleviating the reduction of hydrazine dehydrogenase (HDH) enzyme activity. The extracellular polymeric substances (EPS) content and analysis showed that entrapment does not change the composition of EPS, and can maintain the EPS content. Nano Fe2O3 can stimulate AAOB to secrete more EPS to maintain sludge stability. From a molecular perspective, entrapment can maintain the expression of functional genes, promote the enrichment of AAOB, thus improving the nitrogen removal performance from the dual perspectives of “quality” and “quantity”.
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•The performance of anammox entrapped beads at 10 °C was explored.•Nano Fe2O3-PVA-SA entrapped beads have excellent low-temperature resistance.•Nano Fe2O3 stimulate heme c synthesis and EPS secretion.•Entrapment can provide a good anaerobic environment for sludge to enrich the AAOB.
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