Soil degradation, characterized by declines in nutrient status and simultaneous accumulation of pesticide residues, is a major problem affecting agricultural ecosystems. Previous studies indicate ...that biochar application to soil has promise as a practical method to alleviate these pressures: increasing crop yield and enhancing pesticide degradation. Here, we review the roles of biochar in both chemical and biological promotion of pesticide degradation and the potential benefits of biochar relating to the efficiency of fertilizer use, availability of nutrients, and nutrient exchange. Biochar typically has a high surface area featuring many functional groups, a high cation exchange capacity, and high stability. Major factors that impact on the nutrient retention characteristics of biochar (e.g., feedstock, pyrolysis temperature, and application rate) are also discussed herein. Nonetheless, more studies of the long-term impacts on soil properties from biochar addition are still required before it can be possible to accurately quantify the sustainability of this approach to sequester carbon and restore soil function.
Sulfamethoxazole (SMX), a representative sulfonamide antibiotic, has been identified as a new kind of persistent pollutant with property of hard biodegradation and hydrolyzation. Conventional methods ...cannot remove it well. In this study, the performances and mechanisms for SMX degradation were examined by persulfate (PS) activation with nanoscale zero-valent iron (nZVI) at various conditions including dosages of nZVI and PS, pH value, and initial SMX concentration. Results showed that about 88.4% SMX (10 mg/L) was removed by nZVI/PS system (0.10 g/L nZVI, 1.0 mM PS) within 120 min compared to 63.1% by nZVI alone system under room temperature. Lower initial SMX concentration and higher PS concentration were beneficial to the degradation of SMX, while pH (from 3.11 to 9.33) and nZVI dosage (from 0.05 to 0.30 g/L) had little effect. Radical quenching experiment and electron spin resonance test demonstrated that the degradation of SMX was attributed to sulfate radicals (SO
4
·−
) and hydroxyl radicals (·OH) produced in this system. SMX reduction reaction by nZVI in nZVI/PS process was proved by reductive-oxidative degradation experiment and HPLC test, and the reduction product could be oxidized by SO
4
·−
and ∙OH to other products even to H
2
O and CO
2
. Further, probable removal mechanisms have also been proposed. This study manifests that nZVI/PS system is effective for SMX removal and may provide some ideas for understanding the transformation process of antibiotic in iron-based advanced oxidation processes.
Immobilized
Saccharomyces cerevisiae on the surface of chitosan-coated magnetic nanoparticles (SICCM) was applied as a new magnetic adsorbent for the adsorption of Cu(II) from aqueous solution. The ...prepared magnetic adsorbent was characterized by TEM, XRD and FTIR. TEM images indicated that
S. cerevisiae was immobilized on the surface of chitosan-coated magnetic nanoparticles (CCM) successfully, and conglobation was not observed. The XRD pictures suggested that the Fe
3O
4 nanoparticles were pure Fe
3O
4 with a spinel structure and that the immobilizing process did not result in the phase change of Fe
3O
4. Factors that influence the adsorption of Cu(II) were investigated, which included the initial pH of Cu(II) solution, initial concentration of Cu(II) solution and contact time. The optimum pH for Cu(II) absorption was 4.5. The highest removal efficiency of 96.8% was reached when the initial Cu(II) concentration was 60
mg
L
−1, and the adsorption capacity was increased with the increase of initial concentration of Cu(II). In particular, SICCM was highly efficient for the fast adsorption of Cu(II) within the first 10
min, and adsorption equilibrium could be achieved in 1
h. Equilibrium studies show that the data of Cu(II) adsorption follow the Langmuir model. The maximum adsorption capacity for Cu(II) was estimated to be 144.9
mg
g
−1 with a Langmuir adsorption equilibrium constant of 0.0719
L
mg
−1 at 301
K.
Environment functional materials have been widely used, but whether their effects on the contaminated environment could facilitate phytoremediation is not yet well understood. In this study, starch ...stabilized nanoscale zerovalent iron (SN), multiwall carbon nanotubes (MW) and tea waste derived biochar (TB) were used to facilitate the phytoremediation of cadmium (Cd) contaminated sediments by Boehmeria nivea (L.) Gaudich. Results showed that 100 mg/kg SN, 500 mg/kg MW and 500 mg/kg TB facilitated phytoremediation, as evidenced by increasing Cd accumulation and/or promoting plant growth. These concentrations of materials increased the reducible fraction of Cd by 9–10% and decreased the oxidizable proportion of Cd by 48–52%, indicating the improvement of Cd bioavailability through converting the oxidizable Cd into reducible form. The activities of urease, phosphatase and catalase, which related to nutrient utilization and oxidative stress alleviation, increased by 20–24%, 25–26%, and 8–9% in the sediments treated with 500 mg/kg MW and 500 mg/kg TB, respectively. In addition, the 16S rRNA gene sequence results showed that these concentrations of materials changed the bacterial diversity. The abundance of Acidobacteria, Actinobacteria, Nitrospirae and Firmicutes were increased by some of the applied materials, which could promote plant growth, change Cd bioavailability and reduce Cd toxicity. These findings indicated that the applied environment functional materials could facilitate the phytoremediation of Cd contaminated environment by changing Cd fractions, sediments properties and bacterial community structure.
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•SN100, MW500 and TB500 promoted the uptake of Cd in ramie seedlings.•The addition of materials improved the bioavailability of Cd in the sediments.•The applied materials altered the bacterial community structure in the sediments.•Materials induced sediments environment change could facilitate phytoremediation.
Metal sulfide precipitation by sulfate-reducing bacteria (SRB) is considered to be a promising method for antimony (Sb) removal from wastewater. Moreover, the addition of ferrous ions (Fe(II)) to the ...SRB system is expected to increase the metabolic activity of SRB. In this study, batch microcosms of SRB, with 0–600 mg/L Fe(II), are used to assess the effect of Fe(II) on enzyme activity, Sb bioremediation process, and antioxidant capacity of precipitates. Especially, the presence of 100–200 mg/L of Fe(II) enhanced the hydrogenase activity of the microcosms and accelerated the consumption of sulfate and bioprecipitation of Sb(III), thereby increasing the efficiency of total Sb removal. In the first three days, the SRB system with 200 mg/L Fe(II) displayed the highest Sb(V) removal ratio, whereas, the SRB system with 100 mg/L Fe(II) displayed the highest Sb(V) removal ratio (98.3%) after 9-days of incubation. Characterisation of the precipitate revealed that the soluble Sb(V) was mainly converted to Sb2S3 and Sb2O3, and the presence of Fe(II) prevented Sb2S3 from being oxidized by air.
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•The adaptive phase of SRB could effectively be shorten by Fe(II).•Adding Fe(II) can increase the hydrogenase activity of SRB, thereby accelerating the Sb bioprecipitation.•Adding Fe(II) could quickly stabilize the pH of the SRB system.•Sb(V) removed by SRB was mainly converted to Sb2S3 and Sb2O3.•The presence of Fe(II) could prevent the Sb2S3 from being oxidized by air.
The isotherms, kinetics and thermodynamics of Cd(II), Zn(II) and Pb(II) biosorption by
Penicillium simplicissimum were investigated in a batch system. The effects of pH, initial metal ions ...concentration, biomass dose, contact time, temperature and co-ions on the biosorption were studied. Adsorption data were well described by both the Redlich–Peterson and Langmuir model. Chemical ion-exchange was found to be an important process based on free energy value from Dubini–Radushkevich isotherm for all metal ions. The results of the kinetic studies of all metal ions at different temperature showed that the rate of adsorption followed the pseudo second-order kinetics well. The thermodynamics constants Δ
G°, Δ
H° and Δ
S° of the adsorption process showed that biosorption of Cd(II), Zn(II) and Pb(II) ions on
Penicillium simplicissimum were endothermic and spontaneous.
Filamentous fungi are important cell factories for the production of high-value enzymes and chemicals for the food, chemical, and pharmaceutical industries. Under submerged fermentation, filamentous ...fungi exhibit diverse fungal morphologies that are influenced by environmental factors, which in turn affect the rheological properties and mass transfer of the fermentation system, and ultimately the synthesis of products. In this review, we first summarize the mechanisms of mycelial morphogenesis and then provide an overview of current developments in methods and strategies for morphological regulation, including physicochemical and metabolic engineering approaches. We also anticipate that rapid developments in synthetic biology and genetic manipulation tools will accelerate morphological engineering in the future. KCI Citation Count: 0
Abstract
Humic acids (HAs) widely exist in water environment, and has an important impact on the adsorption of pollutants. Herein, HAs (both dissolved and coated) was employed to assess the effect on ...the removal of the organic contaminant tetracycline (TC) by K
2
CO
3
modified magnetic biochar (KMBC). Results showed that low concentration of dissolved HAs promoted TC removal, likely due to a bridging effect, while higher concentration of dissolved HAs inhibited TC adsorption because of the competition of adsorption sites on KMBC. By characterization analysis, coated HAs changed the surface and pore characteristics of KMBC, which suppressed the TC removal. In a sequential adsorption experiment involving dissolved HAs and TC, the addition of HAs at the end of the experiment led to the formation of HAs-TC ligands with free TC, which improved the adsorption capacity of TC. TC adsorption by KMBC in the presence of dissolved HAs and coated HAs showed a downward trend with increasing pH from 5.0 to 10.0. The TC adsorption process was favorable and endothermic, and could be better simulated by pseudo-second-order kinetics and Freundlich isotherm model. Hydrogen bonds and
π
–
π
interactions were hypothesized to be the underlying influencing mechanisms.
Bechmeria nivea (L.) Gaud. (Ramie) is a promising species for Cd phytoextraction with large biomass and fast growth rate. Nevertheless, little information is available on its tolerance mechanisms ...towards Cd. Determination of Cd distribution and chemical speciation in ramie is essential for understanding the mechanisms involved in Cd accumulation, transportation and detoxification. In the present study, ramie plants were grown in hydroponics with increasing Cd concentrations (0, 1, 3, 7
mg
l
−1). The subcellular distribution and chemical forms of Cd in different tissues were determined after 20 days exposure to this metal. To assess the effect of Cd uptake on plant performance, nitrate reductase activity in leaves and root activity were analyzed during the entire experimental period. Increased Cd level in the medium caused a proportional increase in Cd uptake, and the highest Cd concentration occurred in roots, followed by stems and leaves. Subcellular fractionation of Cd-containing tissues indicated that about 48.2–61.9% of the element was localized in cell walls and 30.2–38.1% in soluble fraction, and the lowest in cellular organelles. Cd taken up by ramie rapidly equilibrated among different chemical forms. Results showed that the greatest amount of Cd was found in the extraction of 1
M NaCl and 2% HAC, and the least in residues in all test tissues. In roots, the subdominant amount of Cd was extracted by d-H
2O and 80% ethanol, followed by 0.6
M HCl. While in stems and leaves, the amount of 0.6
M HCl-extractable Cd was comparable with that extracted by 80% ethanol or d-H
2O. 1
mg
l
−1
Cd stimulated nitrate reductase activity in leaves and root activity, while a concentration-dependent inhibitory effect was observed with increasing Cd concentration, particularly at 7
mg
l
−1
Cd. It could be suggested that the protective mechanisms evolved by ramie play an important role in Cd detoxification at relatively low Cd concentrations (below 3
mg
l
−1
Cd) but become restricted to maintain internal homeostasis with higher Cd stress.
The removal of Cr(VI) from aqueous solution by rice straw, a surplus agricultural byproduct was investigated. The optimal pH was 2.0 and Cr(VI) removal rate increased with decreased Cr(VI) ...concentration and with increased temperature. Decrease in straw particle size led to an increase in Cr(VI) removal. Equilibrium was achieved in about 48
h under standard conditions, and Cr(III), which appeared in the solution and remained stable thereafter, indicating that both reduction and adsorption played a part in the Cr(VI) removal. The increase of the solution pH suggested that protons were needed for the Cr(VI) removal. A relatively high level of NO
3
− notably restrained the reduction of Cr(VI) to Cr(III), while high level of SO
4
2− supported it. The promotion of the tartaric acid modified rice straw (TARS) and the slight inhibition of the esterified rice straw (ERS) on Cr(VI) removal indicated that carboxyl groups present on the biomass played an important role in chromium remediation even though were not fully responsible for it. Isotherm tests showed that equilibrium sorption data were better represented by Langmuir model and the sorption capacity of rice straw was found to be 3.15
mg/g.
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