Search

Cardiac surgery-associated acute kidney injury (CS-AKI) is common and is associated with increased risk for postoperative morbidity and mortality. Our recent survey of the Society of Cardiovascular Anesthesiologists (SCA) membership showed 6 potentially renoprotective strategies for which clinicians would most value an evidence-based review (ie, intraoperative target blood pressure, choice of specific vasopressor agent, erythrocyte transfusion threshold, use of alpha-2 agonists, goal-directed oxygen delivery on cardiopulmonary bypass [CPB], and the "Kidney Disease Improving Global Outcomes [KDIGO] bundle of care"). Thus, the SCA's Continuing Practice Improvement Acute Kidney Injury Working Group aimed to provide a practice update for each of these strategies in cardiac surgical patients based on the evidence from randomized controlled trials (RCTs). PubMed, EMBASE, and Cochrane library databases were comprehensively searched for eligible studies from inception through February 2021, with search results updated in August 2021. A total of 15 RCTs investigating the effects of the above-mentioned strategies on CS-AKI were included for meta-analysis. For each strategy, the level of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) methodology. Across the 6 potentially renoprotective strategies evaluated, current evidence for their use was rated as "moderate," "low," or "very low." Based on eligible RCTs, our analysis suggested using goal-directed oxygen delivery on CPB and the "KDIGO bundle of care" in high-risk patients to prevent CS-AKI (moderate level of GRADE evidence). Our results suggested considering the use of vasopressin in vasoplegic shock patients to reduce CS-AKI (low level of GRADE evidence). The decision to use a restrictive versus liberal strategy for perioperative red cell transfusion should not be based on concerns for renal protection (a moderate level of GRADE evidence). In addition, targeting a higher mean arterial pressure during CPB, perioperative use of dopamine, and use of dexmedetomidine did not reduce CS-AKI (a low or very low level of GRADE evidence). This review will help clinicians provide evidence-based care, targeting improved renal outcomes in adult patients undergoing cardiac surgery.

Microbially derived extracellular polymeric substances (EPSs) occupy a large portion of dissolved organic matter (DOM) in surface waters, but the understanding of the photochemical behaviors of EPS is still very limited. In this study, the photochemical characteristics of EPS from different microbial sources (Shewanella oneidensis, Escherichia coli, and sewage sludge flocs) were investigated in terms of the production of reactive species (RS), such as triplet intermediates (3EPS*), hydroxyl radicals (•OH), and singlet oxygen (1O2). The steady-state concentrations of •OH, 3EPS*, and 1O2 varied in the ranges of 2.55–8.73 × 10–17, 3.01–4.56 × 10–15, and 2.08–2.66 × 10–13 M, respectively, which were within the range reported for DOM from other sources. The steady-state concentrations of RS varied among different EPS isolates due to the diversity of their composition. A strong photochemical degradation of the protein-like components in EPS isolates was identified by excitation emission matrix fluorescence with parallel factor analysis, but relatively, humic-like components remained stable. Fourier-transform ion cyclotron resonance mass spectrometry further revealed that the aliphatic portion of EPS was resistant to irradiation, while other portions with lower H/C ratios and higher O/C ratios were more susceptible to photolysis, leading to the phototransformation of EPS to higher saturation and lower aromaticity. With the phototransformation of EPS, the RS derived from EPS could effectively promote the degradation of antibiotic tetracycline. The findings of this study provide new insights into the photoinduced self-evolution of EPS and the interrelated photochemical fate of contaminants in the aquatic environment.

The biological treatments are promising for nitric oxide (NO) reduction, however, the biotechnology has long suffered from high demands of NO-complexing agents (i.e., Fe(II)EDTA), leading to extra operation costs. In this study, novel complexing agents-free bioelectrochemical systems have been developed for direct NO reduction. The electricity-driven bioelectrochemical trickling system (ED-BTS, a denitrifying biocathode driven by the external electricity and an acetate-consuming bioanode) achieved approximately 68% NO removal without any NO-complexing agents, superior to the bioanode-driven BTS and open-circuit BTS. The extracellular polymeric substances from the biofilms of ED-BTS contained more polysaccharides, humic substrates, and hydrophobic tryptophan that were beneficial for NO reduction. Additionally, the external electricity altered the microbial community toward more denitrifying bacteria and a higher abundance of NO reduction genes (nosZ and cnorB). This study provides a comprehensive understanding of microbial behaviors on the adsorption and reduction of NO and proposes a promising strategy for mesothermal NO biotreatment.

Phenolic resin modified by common physical methods cannot be applied directly in the military and aerospace fields due to its brittleness, poor heat resistance, and poor friction and wear resistance. Here, a strategy to significantly reinforce these properties was proposed by constructing self-assembled hybrid particles of graphite oxide (GO) and zirconia (ZrO2) nanoparticles to modify phenolic resin. The bending and impact test results showed that the bending strength, bending modulus, and impact strength maximumly increased by 73.6%, 52.3%, and 115.3%, respectively. The thermogravimetric analysis showed that the residual carbon rate increased by 19.7%, and the temperature Td, max at the fastest thermal decomposition rate increased by 18 °C. The friction and wear tests showed that the friction coefficient and wear rate reduced by 27.7% and 64.8%, respectively. The modified phenolic resin has met the applicable standards in military and aerospace fields. This strategy is also applicable to the performance reinforcement of other polymers. Strategy to significantly achieve multifunctional collaborative enhancement for phenolic resin by constructing self-assembled hybrid particles of graphite oxide as nano-fillers

An efficient adsorbent for the treatment of Cr(VI) was simply fabricated by combining graphene oxide with MoS2 nanosheets via in situ hydrothermal process with CTAB as the surfactant. The experimental results indicated that the agglomeration of the MoS2 nanosheets are reduced and uniformly grown on the graphene sheet during the in situ hydrothermal process, and the introduction of graphene oxide provided higher specific surface area and abundant oxygenic groups. Based on this, the removal efficiency of Cr(VI) onto MoS2/rGO was 75.9% at pH 2.0, which was higher than that of bulk MoS2 (61.0%). On account of Sips adsorption isotherm model, the highest uptake capacity of MoS2/rGO toward Cr(VI) reached 80.8 mg g−1. The adsorption kinetic consequences showed that the chemisorption process was the control step, and the removal mechanism for Cr(VI) is redox and adsorption; in this way, the adsorbed Cr(VI) was partially reduced to Cr(III). Furthermore, this as-prepared adsorbent also presented satisfying reusability for removal of Cr(VI) and can be used for the selective removal of Cr(VI) in the presence of NO3−. In short, it may provide a potential route to enhance the adsorption property of MoS2 toward heavy metals through incorporating with GO, which would expand the applications of MoS2 in the field of treatment of the heavy metal wastewater.

This study reports a novel carboxylated nanodiamond (CND)-enhanced self-cleaning antifouling catalytic membrane. Four poly(vinylidene fluoride) (PVDF)-based membranes (PVDF, P-CND, P-TiO2, and P-CN...

This study for the first time proposed an efficient microbial electrolyte/UV system for Methyl Orange decomposition. With an external applied voltage of 0.2 V and cathode aeration of 20 mL/min, H2O2 could be in-situ generated from two-electron reduction of oxygen in cathode, reaching to 8.1 mg/L in 2 hr and continued to increase. The pollutant removal efficiency of approximate 94.7% was achieved at initial neutral pH, with the activation of •OH in the presence of UV illumination. Although the nature of its guiding principles remain on the vista of practical exploration, this proof-of-concept study provides an alternative operation pattern of solar–microbial hybrid technology for future wastewater treatment from a basic but multidisciplinary view.

Extracellular polymeric substances (EPS) extracted from electroactive bacteria show promising redox activity, but the electron transfer (ET) mechanism of the EPS has been rarely elucidated because of their structural complexity and lack of efficient methodologies. In this study, the charge transfer theory of surface-enhanced Raman spectroscopy (SERS) was applied to evaluate the redox properties of EPS adsorbed on Ni and Ag nanoparticles (NPs). These metal NPs were used to simultaneously magnify Raman signals and reduce/oxidize the redox moieties in EPS. As a result, the ET between EPS and metal NPs was evaluated through the changes in Raman signals. In this regard, we compared the redox activity of EPS extracted from two typical electroactive bacteria ( Shewanella oneidensis and Geobacter sulfurreducens ) and another two nonelectroactive strains ( Escherichia coli and Bacillus subtilis ). Electrochemical measurements show that the electroactive strains have higher redox capabilities than nonelectroactive strains. The SERS analysis shows that the porphyrin present in cytochrome c is the dominating redox moiety in the EPS of electroactive bacteria. The results of this study show that SERS with active metal substrates is a sensitive tool to probe the redox response of EPS, offering an opportunity to better understand the redox nature of biomolecules.

ZrO2 nanoparticles were electrostatic self-assembled on the surface of graphene oxide (GO) for enhancing the mechanical and tribological properties of phenolic resin. Zeta potential analysis and structural characterization confirmed that ZrO2 nanoparticles had been successfully adhered onto the surface of GO, and the as-prepared ZrO2@GO nanohybrid possessed good dispersity. The results showed that filling 1.5 wt% ZrO2@GO nanohybrid could improve the flexural strength, flexural modulus and impact strength of phenolic resin (PF) by 38.6%, 10.7% and 8.3%, respectively. When 0.5 wt% ZrO2@GO was added, the initial decomposition temperature and the residual content at 800 °C of PF increased by 20.0% and 16.9%, respectively. The ZrO2@GO nanohybrid also exhibited synergistic effect for improving the tribological performance of PF effectively, that when adding 0.5 wt% ZrO2@GO nanohybrid, the average friction coefficient and wear rate of the composites reduced by 21.8% and 30.6%, respectively. SEM observation and 3D non-contact surface topography analysis showed the wear surface of ZrO2@GO nanohybrid filling PF composite was smooth, low spalling and shallowly grooved with the typical characteristic of abrasive wear. It was explained that the ZrO2@GO nanohybrid could play the role of rolling bearings, form stable and smooth friction transfer film and enhance the interfacial interaction, thus indicated the synergistic wear-resisting performance for PF matrix. It provides a green, convenient and fast method for preparing ZrO2 nanoparticles-attached GO nanohybrid that can enhance the mechanical and tribological performance of resin-based materials effectively.

The “trash to treasure” process has been extensively demonstrated for various energy and environmental issues in the past few decades. Abundant biomass is well accepted as a carbon-rich, sustainable, and renewable precursor, offering us a plethora of possibilities for advanced materials for energy conversion and storage as well as environmental treatments; spatial modification of biomass facilitates the formation of a unique three-dimensional (3D) structure with micro- to macropores, yielding higher surface area and enhanced physicochemical properties. This novel concept provides sufficient reaction sites, excellent adsorption capability, more activated sites for catalyst doping, and fascinating electrochemical performance. Basically, the 3D cadre of biomass-derived carbon strengthens the economic competitiveness of these materials and broadens their applications in fields such as in supercapacitors, chemical batteries, bioenergy harvest, adsorbents for organic pollutants and greenhouse gases, and efficient (photo)catalysts. The scope of this review mainly focuses on the most popular synthesis methodology of three-dimensional carbon materials derived from biomass and their critical applications in the fields of energy and environment.

Bioelectrochemical systems (BESs) with integrated photoactive components have been shown to be a promising strategy for enhancing the performance for bioenergy generation and pollutant removal. This study revealed an efficient photo-BES with an enhanced pollutant degradation rate by utilizing self-produced biomolecules as photosensitizers in situ. Results showed that the BES could increase the coulombic efficiency from 60.8% to 73.0% and the degradation rate of bisphenol A (BPA) from 0.030 to 0.189 h

This study aimed to investigate the degradation efficiency of 2,4,6-trichlorophenol through a batch of potentiostatic experiments (0.2 V vs. Ag/AgCl). Efficiencies in the presence and absence of acetate and glucose were compared through open-circuit reference experiments. Significant differences in degradation efficiency were observed in six reactors. The highest and lowest degradation efficiencies were observed in the closed-circuit reactor fed with glucose and in the open-circuit reactor, respectively. This finding was due to the enhanced bacterial metabolism caused by the application of micro-electrical field and degradable organics as co-substrates. The different treatment efficiencies were also caused by the distinct bacterial communities. The composition of bacterial community was affected by adding different organics as co-substrates. At the phylum level, the most dominant bacteria in the reactor with the added acetate and glucose were Proteobacteria and Firmicutes, respectively.

To obtain strong interfacial adhesion between basalt fiber (BF) and polyamide 6 (PA6) matrix, a multiscale graphene-basalt fiber reinforcement was introduced by directly coating graphene (GR) onto the surface of individual basalt fiber via polyurethane sizing agent. The GR on the surface of BF was homogeneous, and the microstructure of the interfacial region between BF and matrix could be adjusted by varying the content of GR in the sizing agent. Owing to the bridge effect of GR, a mechanical meshing nanoscale interfacial area was generated, which could enhance the interfacial adhesive between BF and PA6 matrix, and the stress transfer of the corresponding composites was improved. The uniform coating of GR on the surface of BF increased the storage modulus and Tg for the BF/PA6 composites and 18.2% and 34% improvement for their tensile and flexural strength. Compared with BF/PA6, the GR-BF/PA6 composites obtained a fairly low friction coefficient and highly wear-resisting property, which was explained by the improved interfacial adhesion, effective stress transfer and the highly unfolded feature and flexibility of the introduced GR. This work presents a suitable approach for industrial production that can improve the comprehensive performance of fiber-reinforced composites effectively.

This study presents an innovative microbial fuel cell-based biosensor for carbon monoxide (CO) monitoring. The hypothesis for the function of the biosensor is that CO inhibits bacterial activity in the anode and thereby reduces electricity production. A mature electrochemically active biofilm on the anode was exposed to CO gas at varied concentrations. A proportional linear relationship (R2 = 0.987) between CO concentration and voltage drop (0.8 to 24 mV) in the range of 10% and 70% of CO concentration was observed. Notably, no further decrease of voltage output was observed by with further increasing CO concentration over 70%. Besides, the response time of the biosensor was 1 h. The compact design and simple operation of the biosensor makes it easy to be integrated in existing CO-based industrial facilities either as a forewarning sensor for CO toxicity or even as an individual on-line monitoring device.

Water quality deterioration caused by a wide variety of recalcitrant organics and pathogenic microorganisms has become a serious concern worldwide. Bio-electro-Fenton systems have been considered as cost-effective and highly efficient water treatment platform technology. While it has been extensively studied for recalcitrant organics removal, its application potential towards water disinfection (e.g., inactivation of pathogens) is still unknown. This study investigated the inactivation of Escherichia coli in a microbial electrolysis cell based bio-electro-Fenton system (renamed as microbial electrolytic-Fenton cell) with the aim to broad the application of microbial electrochemistry. Results showed that a 4-log reduction of Escherichia coli (107 to hundreds CFU/mL) was achieved with an external applied voltage of 0.2 V, 0.3 mM Fe2+ and cathodic pH of 3.0. However, non-notable inactivation was observed in the control experiments without external voltage or Fe2+ dose. The disinfection effect was enhanced when cathode air flow rate increased from 7 to 41 mL/min and was also in proportion to the increase of Fe2+ concentration from 0.15 to 0.45 mmol/mL. Fatal cell membrane destruction by [rad]OH was identified as one potential mechanism for disinfection. This study successfully demonstrated the feasibility of bio-electro-Fenton process for pathogens inactivation, which offers insight for the future development of sustainable, efficient, and cost-effective biological water treatment technology.

Polyvinylidene fluoride (PVDF) is a popular membrane material, but it has the drawback of relatively high fouling potential. In this study, we prepared carboxylated nanodiamonds (CNDs) by thermal oxidation, and then incorporated CNDs into PVDF membranes during phase inversion. Transmission electron microscopy (TEM) showed that the CNDs had minimized aggregation and better dispersity compared with the raw nanodiamonds. The prepared membranes were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM) and water contact angle analysis. The bulk porosities and pore sizes of the membranes were evaluated by the gravimetric method and the filtration method, respectively; surface pores were evaluated based SEM images. Compared with the pristine PVDF membrane, CNDs blended membranes had larger porosities and surface pore sizes, higher water permeabilities and hydrophilicities, smoother surfaces, and improved antifouling and cleaning performance due to the incorporation of hydrophilic carboxyl groups. In particular, the irreversible fouling ratio to the total fouling ratio (Rir/Rt) dropped from 85% for the pure PVDF membrane to 21% for the CNDs blended membrane. Our study demonstrates that CNDs are excellent pore-forming fillers in developing antifouling membranes, and they may open up a new avenue to the next generation of high performance membranes.

In order to seek for high performance electrochemical sensing materials toward heavy metal ions with excellent electrical conductivity, high adsorption capacity and good electrocatalytic activity, in this study, graphene oxide was incorporated with mesoporous MnFe2O4 (MnFe2O4/GO) to fabricate an electrochemical platform for sensing Pb(II). The as-prepared mesoporous MnFe2O4/GO nanocomposites contained uniformly MnFe2O4 particles with the diameter about 400 nm. The maximal pore diameter of MnFe2O4/GO was 4.5 nm and its specific surface area was obviously increased from 167.0 m2 g−1 to 285.7 m2 g−1 with the incorporation of GO. The CV, EIS and SWASV response toward Pb(II) showed the incorporation of GO would enhance the electrochemical activity of MnFe2O4 due to the improvement of specific surface area, electrocatalytic activity and conductivity supported by GO sheets. It provided the sensitivity of 33.9 μA/μM and LOD of 0.0883 μM for electrochemical detection toward Pb(II), and it was even suitable for the selective detection of Pb(II) in the presence of Zn(II). This MnFe2O4/GO modified electrode also presented satisfying reproducibility, stability, repeatability and applicability for detection of Pb(II). In short, it provides a simple and promising platform to develop novel electrochemical sensor for detecting heavy metal ions with high performance.

In order to improve the electrochemical sensing performance toward heavy metal ions, this work presents a novel L-cysteine functionalized mesoporous MnFe2O4 hybrid nanospheres (MnFe2O4@Cys) applied as electrochemical sensor for determination of Pb(II), Hg(II), Cu(II) and Cd(II) based on square wave anodic stripping voltammetry (SWASV) technique. Combined the excellent adsorption capacity toward heavy metal ions of mesoporous MnFe2O4 nanocluster with Lewis acid-base interaction supported by L-cysteine, the MnFe2O4@Cys modified glass carbon electrode (GCE) successfully realized individual and simultaneous detection toward four target ions. In particular, the L-cysteine modified Mn and Fe bimetal oxides nanoparticles displayed good selectivity toward Pb(II) with high sensitivity of 57.0 μA/μM and 35.3 μA/μM under the individual and simultaneous determination conditions, respectively. Meanwhile, this fabricated sensor showed satisfying anti-interference, reproducibility, stability, repeatability and applicability for detecting heavy metal ions. It provides a promising platform for developing new and high performance electrochemical sensors applied in individual and simultaneous determination of various of heavy metal ions.

Aerobic denitrification is a novel strategy for nitrogen removal in wastewater treatment. As an important functional component, extracellular polymeric substances (EPS) secreted by aerobic denitrifiers during the denitrification process are poorly understood. This paper presents the characteristics of EPS production by thermophilic bacterium Chelatococcus daeguensis TAD1 during aerobic denitrification in liquid cultures. Results indicated that strain TAD1 was capable of simultaneously accumulating EPS and reducing nitrate, with 245.1 mg g−1 EPS obtained after aerobic denitrification. Polysaccharide and protein were determined to be the major components of EPS. Further single factor experiments showed that the EPS production was significantly affected by the carbon source, C/N ratio and pH value, rather than the incubation temperature. Moreover, good positive correlation (R2 = 0.86) was observed between the EPS production and the nitrate removal efficiency, which implied that aerobic denitrification might prompt EPS production by strain TAD1.

Extracellular polymeric substances (EPS) have been considered as a barrier for toxic species penetration into the cells, but their function in protecting electroactive biofilms (EABs) had been rarely revealed. In this study, the anode potential was used to regulate the EPS quantity and components in mixed-culture EABs, where their resistance to Ag+ shock was assessed. The results showed that the EAB grown at 0 V showed the highest anti-shock capability by the Ag+ exposure compared to those grown at −0.2, 0.2, and 0.4 V. The EAB produced at 0 V had both of the highest amounts of loosely bound EPS (LB-EPS; 61.9 mg-EPS/g-VSS) and tightly bound EPS (TB-EPS; 74.8 mg-EPS/g-VSS) than those grown under other potentials, where proteins and humic acid were the predominated components. The abundance of genes associated with EPS biosynthesis were also confirmed to be related with the applied anode potentials, based on the metagenomic analysis. Considering proteins and humic acid in LB-EPS showed positive linearity with the current recovery and viability of the EABs, these two main components might play important roles in reducing the Ag+ toxicity. Synchronous fourier transform infrared (FTIR) spectroscopy integrated two-dimensional correlation spectroscopy (2D-COS) analyses further confirmed that the oxygen and nitrogen moieties (i.e. amide, carbonyl C O, phenolic, and C–O–C) in proteins and humic acid of the LB-EPS were response for the binding with the Ag+ to prevent the penetration into the cells. The underlying molecular mechanisms of EPS in protecting EABs from the Ag+ shock explored in this study can provide implications for developing new methods to construct highly stable EABs.

An efficient adsorbent for the treatment of Cr(VI) was simply fabricated by combining graphene oxide with MoS

Spread of pathogens in pig farms not only causes transfection of diseases to other pigs or even farmers working in the farms, but also induces pollution to the living atmospheric environment of the residents around the farm. Therefore, it is necessary to establish a rapid and simple monitoring method. In this study, full genome sequences of common viruses were analyzed in pig farms, in combination with the design of primers, optimization of the reaction parameters, so as to establish a multiplex RT-PCR assay for the identification of classical swine fever virus (CSFV), Japanese encephalitis virus (JEV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus Type 2 (PCV-2), porcine pseudorabies virus (PRV) and porcine parvovirus virus (PPV), which are common in pig farms. This method has a minimal detectable concentration of 10−3 ng/μL, which is highly specific. Furthermore, multiplex RT-PCR was applied to examine air samples from 4 pig farms located in different cities of China. The results were in line with those obtained by single PCR. Therefore, this study can be expected to provide essential technique support for the early warning mechanism as well as disease prevention and control system against the major viruses.

Three-dimensional (3D) nano-structure materials with a large bacterial accessible specific area have emerged as promising electrode materials for bioelectrochemical systems (BESs), achieving high bioelectricity outputs. However, it remains a challenge that biofilms with increased thickness inhibit substrate diffusion into the 3D nano-structure during long-term operation of BESs, causing a reduction in bioenergy output. Herein, an innovative ordered 3D nano-structure electrode was fabricated by growing self-supported N-doped C/Fe3O4-nanotube composite arrays onto carbon fiber cloth (CC@N-C/Fe3O4), using template-based deposition coupled with thermal reduction/carbonization methods. The fabricated CC@N-C/Fe3O4 electrode was applied as a bioelectrode in a conventional three-electrode BES and as an anode in microbial fuel cell (MFC), while their capacity to improve bioelectricity generation was assessed. Results indicate that the hierarchical N-doped C-coated nanotube arrays not only significantly enhanced conductivity and areal capacitance of the electrode, but also reduced its charge transfer resistance and provided the 3D open nano-structure with excellent biocompatibility for microbial colonization and internal diffusion of the culture substrate. Consequently, a high maximum current density (4.11 mA/cm2) and coulombic efficiency (~89%) was obtained from the CC@N-C/Fe3O4 electrode after about 3 months of BES operation, exhibiting higher biocatalytic performance and extracellular electron transfer efficiency than the original carbon fiber cloth (CC, 1.89 mA/cm2). Moreover, MFC equipped with CC@N-C/Fe3O4 anode produced a maximum power density of 1.21 ± 0.04 W/m2, which was 2.1 times higher than CC (0.58 ± 0.03 W/m2). This study demonstrates the outstanding advantages of CC@N-C/Fe3O4 nanotube composite arrays assembled on CC, making it a potential alternative to existing 3D electrodes for high-performance BES applications.

The extraction and quantitative analysis of extracellular polymeric substances (EPS) have been frequently reported in studies of activated sludge. However, little is currently known about the EPS in the biofilms of biofilter systems. This study investigates the EPS in biofilms of Chelatococcus daeguensis TAD1 established in a suspended biofilter for nitric oxide (NO) removal under thermophilic conditions. Polysaccharide was the main EPS component under all experimental operation conditions of the aerobic biofilter, although the EPS contents and components varied under different operating conditions. As the concentration of the inlet NO varied from 200 to 2000 mg/m3, the EPS and protein contents generally increased. At the highest inlet concentration (2000 mg/m3), the EPS and protein contents reached 0.118 and 0.055 mg/g, respectively (representing increases of 7.3 and 35 %, respectively, over the inlet concentration of 200 mg/m3). In contrast, the polysaccharide content was quite stable against inlet NO concentration. Decreasing the empty bed residence time increased the EPS and polysaccharide contents, but exerted little effect on the protein content. Varying the pH of the circulating fluid from 4 to 8 changed the EPS and its components in complex ways. We also found a strong correlation between the total EPS content and the NO removal efficiency. Therefore, it is possible to take EPS into consideration for biofilter control.

This study was conducted to investigate the nitrogen removal efficiency and N2O emission characteristics of a novel thermophilic aerobic denitrifying bacterium, Chelatococcus daeguensis TAD1, under different C/N ratios and pH values in a batch reactor. Nitrogen removal efficiency and N2O emissions were dramatically influenced by C/N ratio and pH. Moreover, multifactor analysis of variance suggested that these two factors also had significant interaction effects on N2O emissions. The optimum C/N ratio was determined to be 8 (where pH was set to 7), at which a very high nitrogen removal efficiency (>99%) was achieved. Under these conditions, N2O emissions were only 34.43 μg/L and the N2O emission factor was 0.046%, which could offer a promising new microbial resource for N removal and reduction of greenhouse gas emissions during wastewater treatment.

Nanoscale zero-valent iron (nZVI) is easy to agglomerate and be oxidized by surrounding media, and even can't be prepared continuously, which have seriously restricted its application in environmental restoration. Herein, we report a facile technique for the continuous preparation of nZVI with excellent dispersion and stability on a large scale using impinging stream-rotating packed bed (IS-RPB) as the reactor and chitosan as the stabilizer. The effects of high-gravity factor, liquid flow and the additive amount of chitosan on the removal capacity of the chitosan-stabilized nZVI (CS-nZVI) were investigated. It was discovered that the removal capacity toward Cr(VI) was firstly increased and then reduced with each operating parameter increasing. The reactivity of CS-nZVI prepared via different reactors (traditional stirred tank reactor (STR) and IS-RPB) was studied through the removal of Cr(VI). With enhancement mass transfer and rapid micromixing capacities of IS-RPB reactor, CS-nZVI prepared in IS-RPB (CS-nZVI-R) had higher reaction rate constant (0.0836 min−1) and adsorption capacity (101.837 mg g−1) than that prepared in STR. CS-nZVI-R was shown higher stability and reusability, and it could be reused more than four times. Furthermore, this as-prepared CS-nZVI-R can be used for the selective removal of Cr(VI) in the presence of NO3–. In short, it provides an effective route for the controllable continuous preparation of high reactive nZVI, which would expand the application of nZVI in the field of heavy metal pollution remediation.

The performance of microbial electrochemical system for hexavalent chromium (Cr(VI)) contaminant has been a severe challenge remaining active for further development. In this study, we developed a novel biochar material from industrial paper sludge for microbial fuel cell cathode fabrication to reduce aquatic Cr(VI) to non-toxic Cr(III). With additive melamine as nitrogen source and self-containing small portion of Fe as catalyst, the sludge evolved into electroactive biochar (BC-M) rendering a unique N-doped carbon nanotubes/activated carbon (N-CNT/AC) frame after pyrolyzed at 900 °C for 2 h. Electrochemical analysis revealed enhanced electron transference capacity of this composite material, such effectiveness was attributed to the increased surface area and superior electroconductivity of N-doped CNTs. For performance of Cr(VI) reduction, a 55.1% reduction efficiency was achieved in an microbial fuel cell equipped with BC-M cathode while it reduced to about 41.8% when the cathode was replaced by electrode modified with no-melamine-involved biochar. The strategy of biochar upgrading from industrial paper sludge proposed in this work is expected to not only bring technical solution for low-cost CNT materials preparation for Cr(VI) reduction, but also put forward further research on value-added chemical synthesis from waste in various fields of energy and environment.

The aim of this study is to explore facile and large-scale method for the preparation of magnetic adsorbent materials with high-efficient heavy metal removal performance. Here, based on the process intensification of high-gravity technology, the carboxymethyl cellulose-immobilized Fe