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•Amino-MIL-101(Al/Fe) MOFs was applied in high strength phosphate adsorption.•Fast kinetics, high sorption capacity and strong selectivity were demonstrated.•Electrostatic attraction ...and ligand exchange were identified as the main mechanisms.
Although adsorbents for phosphate removal from eutrophic water have been widely explored, it remains a critical challenge to develop robust and highly selective phosphate adsorbents featuring abundant binding sites and high affinity. In this work, two stable metal-organic frameworks (MOFs) of amine functionalized MIL-101 based on trivalent metal aluminum and iron were synthesized by simple solvothermal methods and applied as adsorbents to capture phosphate ions of high strength. Phosphate adsorption kinetics, isotherm behavior, and solution matrix effects (eg. solution pH, coexisting ions and ionic strength) were reported. Results showed that trivalent metal based NH2-MIL-101 MOFs outperformed most adsorbents ever reported, exhibiting fast kinetics and high maximal adsorption capacity above 79.414 mg P/g at 298 K, pH independence in the range from 3 to 11, less sensitivity to ion strength, strong selectivity for phosphate in presence of competing ions and could be easily regenerated and re-applied for phosphate removal. It was noticeable that phosphate adsorption performance varied on the two kinds of trivalent metals based MOFs due to their difference in morphology, surface and interface properties including zeta potential, chemical affinity toward target anion and the types of complexation formed with phosphate. NH2-MIL-101(Al) showed faster kinetics, while NH2-MIL-101(Fe) has higher affinity toward phosphate. Furthermore, based on Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) spectra and zeta potential analysis, electrostatic attraction and ligand exchange were identified as the main phosphate adsorption mechanisms by NH2-MIL-101(Al/Fe). Besides, the functionalized adsorbents with amine group further enhanced the phosphate removal capacities by providing extra surficial positive charges. These findings demonstrate that trivalent metal based NH2-MIL-101 is a promising candidate for phosphate adsorption from aqueous solution with high efficiency and selectivity.
•Exudates acted as endogenous carbon sources in micro-polluted CW.•Exudates and microorganisms varied significantly among plant species and seasons.•Denitrifier gene abundances were significantly ...affected by sucrose and glucose.•Microbial communities were significantly affected by sucrose and oxalic acid.
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In micro-polluted constructed wetland (CW), the low pollutant concentrations and the low COD/N ratios (chemical oxygen demand: total nitrogen in influent), make the biological treatment more difficult. It is expected that root exudates drive microbial-based transformations within plant rhizosphere. In this research, the roles of root exudates of three aquatic plants (Phragmites australis, Typha angustifolia and Cyperus alternifolius) in improving the growth of heterotrophic denitrifying bacteria were determined in a micro-polluted CW. In studied root rhizospheres, the total organic carbon (TOC) released from the plant roots varied significantly among plant species and seasons; the average TOC ranged from 0.1715 to 0.9221mgg−1rootDMd−1, which could fuel a denitrification rate of approximately 156–841kgNO3−-Nha−1year−1 if all were used by the denitrifying bacteria; the abundances of nirK- and nirS-encoding bacteria were significantly influenced by the concentration of sucrose and glucose (0.869≤r≤0.933, p<0.05), and microbial community richness and diversity had response to root exudates. The results revealed that root exudates can act as endogenous carbon sources for heterotrophic denitrifying bacteria and ultimately determine the microbe distribution patterns in micro-polluted CW.
► The preparation of ACF-NanoHFO using Sol–Gel method is investigated. ► Sol–Gel is quoted to be a simple and effective method for ACF-NanoHFO preparation. ► The performance and mechanisms of ...ACF-NanoHFO for phosphate removal are studied. ► Ligands exchange, electrostatic interactions become weaker with pH increasing.
Sol–Gel method is used to immobilize nano-particulates of hydrated ferric oxide (HFO) within macroporous activated carbon fibers (ACFs), and the phosphate removal behavior and its mechanisms of the new hybrid phosphate adsorbent named as ACF-NanoHFO are studied. The surface structure of ACF-NanoHFO is characterized by scanning electron microscopy (SEM), showing Sol–Gel method to be a reliable method for improving performances of depositing iron nano-particles on the ACF. The Freundlich and Langmuir models are used to simulate the sorption equilibrium, indicating that the Langmuir model is more suitable than the Freundlich model for well elucidation of the experimental data. The maximum adsorption capacity is calculated to be 12.86mg/g. The kinetic data from the adsorption of phosphate are discussed in a framework of the pseudo second-order model, indicating that the adsorption of phosphate is a chemisorption process. The phosphate adsorption is highly pH dependent. The coexistence of other anions in solutions has an adverse effect on phosphate adsorption. A decrease in adsorption capacity follows the order of exogenous anions, i.e., F->NO3->Cl->SO42-. The ligands exchange and electrostatic interactions are manifested to be two main mechanisms for phosphate adsorption of ACF-NanoHFO revealed by Fourier transform infrared (FT-IR) spectroscopy and change of pH values associated with the adsorption process. All the results indicate that the ACF-NanoHFO has a considerable potential for the phosphate removal from contaminated waters.
To enhance the reducing sugar yield in enzymatic hydrolysis, various factors (NaOH concentration, solid content and pre-treatment time) that affect the pre-treatment process were investigated and ...evaluated based on the reducing sugar yield of the subsequent enzymatic hydrolysis. The enzymatic hydrolysis was based on the cellulase from Trichoderma reesi ATCC 26921, the optimum NaOH pre-treatment conditions were an NaOH concentration of 1.0% (w/w), a solid content of 5.0% (w/v) and a pre-treatment time of 60 min. Various parameters that affect the enzymatic hydrolysis of wheat straw, including the solid content, enzyme loading, pH and hydrolysis time, were investigated and optimized through a Box-Behnken design and response surface methodology. The predicted optimum conditions for enzymatic hydrolysis were a solid content of 8.0% (w/v), an enzyme loading of 35 FPU/g substrate, a temperature of 50 °C, a pH of 5.3 and a hydrolysis time of 96 h. The experimental result showed that the maximum reducing sugar yield was 60.73% (53.35% higher than the wheat straw without NaOH pre-treatment), which is in accordance with the predicted conditions.
Contamination of water streams by dyes and heavy metals has become a major problem due to their persistence, accumulation, and toxicity. Therefore, it is essential to eliminate and/or reduce these ...contaminants before discharge into the natural environment. In recent years, 3D graphene has drawn intense research interests owing to its large surface area, superior charge conductivity, and thermal conductivity properties. Due to their unique surface and structural properties, 3D graphene-based materials (3D GBMs) are regarded as ideal adsorbents for decontamination and show great potential in wastewater or exhaust gas treatment. Here, this minireview summarizes the recent progress on 3D GBMs synthesis and their applications for adsorbing dyes and heavy metals from wastewater based on the structures and properties of 3D GBMs, which provides valuable insights into 3D GBMs’ application in the environmental field.
Phosphate removal from wastewater is very important for the prevention of eutrophication. Adsorption of phosphate from water was investigated using activated carbon fiber loaded with lanthanum oxide ...(ACF-La) as a novel adsorbent. The effects of variables (La/ACF mass ratio, impregnation time, activation time, and activation temperature) have been studied by the single-factor method. Response surface methodology (RSM), based on three-variable-three-level Box–Behnken design (BBD), was employed to assess the individual and collective effects of the main independent parameters on the phosphate removal. The optimal conditions within the range studied for preparing ACF-La were found as follows: La/ACF mass ratio of 11.78%, activation time of 2.5
h and activation temperature at 650
°C, respectively. The phosphate removal using the ACF-La prepared under the optimal conditions was up to 97.6% even when the phosphate concentration in water was 30
mg
P/L, indicating that ACF-La may be an effective adsorbent. The results from Fourier transform infrared (FT-IR) spectroscopy and change of pH values associated with the adsorption process revealed that the probable mechanism of phosphate ions onto ACF-La was not only ion exchange and coulomb interaction, but also a result of Lewis acid–base interaction due to La–O coordination bonding.
The problems of vibration and noise have seriously affected people’s production and life. Hydrogel can be used as damping material because of its good viscoelasticity, but the current damping ...material is difficult to meet the needs of actual production and life because of the lack of wide damping temperature and frequency range and high loss factor. In this work, ammonium persulfate was used as both initiator and oxidant to form a mixed double network hydrogel of polyacrylamide and oxidized sodium alginate. The double network hydrogel prepared by this method has good adhesion and mechanical properties. In addition, due to the adjustable viscoelasticity of the hydrogel, the hydrogel shows excellent damping properties. When the concentration of MBA is 0.02%, it can reach the temperature range of 0-125 ℃, and the damping factor is more than 0.3. The visualization experiment proves the practical application effect of the hydrogel, so it is expected to be used as a damping material in damping, noise reduction and other fields in the future.
With the goal of obtaining a high ethanol yield, wheat straw (WS) was pretreated with a 1.0% (w/w) NaOH solution. Further parameters, including temperature, enzyme loading, yeast concentration and pH ...that would affect the ethanol yield through simultaneous saccharification and fermentation (SSF), were optimised by means of Box-Behnken design (BBD), a response surface methodology (RSM). All of the experiments were carried out with an initial solid content of 16.0% (w/v) and fermentation time of 120h. A well fitted regression equation with an R2 value of 0.9603 was obtained. The predicted maximum response value (ethanol yield) was 69.49% under the optimised conditions for SSF: temperature of 37.5°C, enzyme loading of 30 FPU/g substrate, yeast concentration of 10g/L and pH of 4.6. The validation experimental result showed that the maximum ethanol yield was 70.76%, which was in accordance with the predicted value.
Hyperthermophilic microorganisms play a key role in the hyper-thermophilic composting (HTC) technique. However, little information is available about the hyperthermophilic microorganisms prevalent in ...HTC systems, except for the
Calditerricola satsumensis
,
Calditerricola yamamurae
, and
Thermaerobacter
. To obtain effective hyper-thermophilic microorganisms, a continuous thermo-acclimation of the suitable thermophilic microorganisms was demonstrated in this study.
Bacillus thermoamylovorans
with high-temperature endurance (70 °C) were newly isolated from sludge composting, and an adequate slow heating rate (2 °C per cycle) was applied to further improve its thermostability. Finally, a strain with a maximum growth temperature of 80 °C was obtained. Moreover, structural and hydrophobic changes in cell proteins, the special amino acid content ratio, and the membrane permeability of the thermophilic bacterium after thermo-acclimation were evaluated for improved thermostability. In addition, the acclimated hyperthermophilic bacterium was further inoculated into the HTC system, and an excellent performance with a maximum operating temperature of 82 °C was observed.
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On-site sampling analysis and laboratory-scale experiments were conducted to study the pollution status and release potential of EDCs in Erhai Lake. We found that nitrogen and phosphorus pollution in ...Erhai Lake sediment were both at a high level, as well as EDCs pollution. The concentrations of BPA, E2α, E1, E2β, EE2, and E3 were 36.84 ng/g(DW), 13.04 ng/g(DW), 128.97 ng/g(DW), 52.57 ng/g(DW), 18.48 ng/g(DW) and 5.36 ng/g(DW), respectively. The concentrations of E2α, E1, E2β and EE2 in the bottom water were higher than the surface water due to the impact of sediment release. The results of the 20 days release test indicated that BPA release from the sediment had a greater correlation with the original concentration and the particle size of sediment, while the steroid EDCs had no obvious correlation with these two factors, probably due to the difference in hydrophobicity between them. Under hydraulic disturbance and aerobic conditions, the release process of EDCs was accompanied by a large amount of microbial degradation, and degradation amount > released amount. BPA was released quickly, 9.56% was released in 20 days, but only 3.37% of steroid EDCs released. In comparison, the release process of steroids was longer and posed a greater threat to aquatic ecology.
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