Recovery of biochar particles laden with lead in saturated porous media by DC electric field.

The co-transport behavior of environmental pollutants with biochar particles has aroused great interests from researchers due to the concerns about pollutant diffusion and environmental exposure after biochar is applied to soil. In this work, the recovery and co-transport behavior of biochar micron-/nano-particles (BCMP and BCNP) and lead (Pb2+) in saturated porous media were investigated under different ionic strength conditions (IS = 1, 5 and 10 mM) under a direct current electric field. The results showed that the electric field could significantly enhance the mobility of Pb adsorbed biochar particles, particularly BCNP. The recovery of Pb laden biochar particles was improved by 1.8 folds, reaching 78.8% at maximum under favorable condition at +0.5 V cm-1. According to the CDE (Convection-Dispersion-Equation) model and DLVO (Derjaguin-Landau-Verwey-Overbeek) theory analysis, the electric field facilitated the transport of Pb carried biochar mainly by increasing the negative charges on biochar surface and improving the repulsive force between biochar and porous media. High IS was favorable for biochar transport under the electric field, but inhibited desorbing Pb2+ from biochar (18% by maximum at IS = 10 mM). By switching the electric field power, a two-stage strategy was established to maximize the recovery of both biochar particles and Pb, where BCNP and Pb recovery were higher than electric field free case by 90% and 35%, respectively. The findings of this study can help build a biochar recovery approach to prevent potential risks from biochar application in heavy metal contaminated soil remediation.

Transport behaviors of biochar particles in saturated porous media under DC electric field.

The mobility of biochar in saturated quartz sand under a direct current (DC) electric field was investigated by column transport test. The effects of biochar preparation temperature (350 and 550 °C), solution chemistry (pH of 4, 7, and 10, and ion strength of 1, 10, 100 mM) and voltage gradient (0, 0.5 and 1.0 V cm-1) on the mobility of biochar were explored. It was found that DC electric field could significantly promote the migration of biochar, and the recovery rate of particles could be improved by 0.5-6.1 folds under 0.5 V cm-1. Higher voltage potential, solution pH and ionic strength were more favorable for biochar migration. The transport of biochar could be well interpreted by deterministic nonequilibrium convection-dispersion equation model. The enhanced mobility caused by DC electric field was attributed to the following reasons: enhanced electromigration following electrostatic attraction from the anode; increasing surface negative charges and functional groups on biochar surface as a result of electrochemical oxidization; reducing size blocking of biochar particles by decreasing particle size. Moreover, the interaction between biochar particles and electrode could alter solution chemistry, in particular, increasing solution pH, which in turn facilitated the transport of biochar. This study provided a perspective to modulate the transport behavior of biochar particle in the soil for the remediation of polluted sites.

Role of the surface characteristics of hyper-crosslinked polymers on the transformation of adsorbed trichlorophenol: Implications for understanding the surface reactivity of biochar derived from waste biomass.

The surface reactivity of biochar derived from waste biomass has not been well understood due to its complex composition and heterogeneity. Therefore, this study synthesized a series of biochar-like hyper-crosslinked polymers (HCPs) with different amounts of phenolic hydroxyl groups on the surface as an indicative tool to investigate the roles of key surface properties of biochar on transforming pollutants being adsorbed. Characterization of HCPs suggested that electron donating capacity (EDC) of different HCPs was positively correlated with increasing amounts of phenol hydroxyl groups, whereas specific surface area, degree of aromatization and graphitization were negatively correlated. It was found that greater amounts of hydroxyl radicals were produced with increasing amounts of hydroxyl groups on the synthesized HCPs. Batch degradation experiments with trichlorophenols (TCPs) suggested that all HCPs could decompose TCP molecules upon contact. The degree of TCP degradation (~45 %) was highest for HCP made from benzene monomer with the lowest amounts of hydroxyl groups, which was likely driven by its greater specific surface area and reactive sites for TCP degradation. Conversely, the degree of TCP degradation (~25 %) by HCPs with the highest hydroxyl group abundance was the lowest, probably because the lower surface area of HCPs had limited TCP adsorption, which led to lower interaction between HCP surface and TCP molecules. The results concluded from the contact of HCPs and TCP suggested both EDC and adsorption capacity of biochar played critical roles in transforming organic pollutants.

PtNi alloy nanoparticles grown in situ on nitrogen doped carbon for the efficient oxygen reduction reaction.

Currently, Pt based materials are still the most efficient oxygen reduction reaction (ORR) catalysts. However, their poor stability obstructs the commercial viability of fuel cells. To lower the reaction potential barrier and enhance the stability, we constructed alloy PtNi nanoparticles (NPs) with a Pt-rich surface supported on nitrogen-doped carbon (NC) via a simple one-step solvothermal method using easily accessible reagents. The synthesized PtNi/NC exhibits enhanced mass activity (MA), specific activity (SA), and positive onset potential compared with commercial Pt/C catalysts. Meanwhile, the half-wave potential shifted negatively to only 18 mV after 5000 cycles for PtNi/NC, indicating excellent stability. The enhanced ORR performance can be ascribed to the introduction of Ni into Pt optimizing the adsorption energy of Pt towards oxygen by adjusting the d band center of the Pt atom and stronger interaction between the metal NPs and support. Our work provides a potential synthesis strategy for developing a Pt-based catalyst with a low Pt loading and high ORR performance.

Microwave-Assisted Metal-Organic Frameworks Derived Synthesis of Zn2GeO4 Nanowire Bundles for Lithium-Ion Batteries.

Germanium-based multi-metallic-oxide materials have advantages of low activation energy, tunable output voltage, and high theoretical capacity. However, they also exhibit unsatisfactory electronic conductivity, sluggish cation kinetics, and severe volume change, resulting in inferior long-cycle stability and rate performance in lithium-ion batteries (LIBs). To solve these problems, we synthesize metal-organic frameworks derived from rice-like Zn2GeO4 nanowire bundles as the anode of LIBs via a microwave-assisted hydrothermal method, minimizing the particle size and enlarging the cation's transmission channels, as well as, enhancing the electronic conductivity of the materials. The obtained Zn2GeO4 anode exhibits superior electrochemical performance. A high initial charge capacity of 730 mAhg-1 is obtained and maintained at 661 mAhg-1 after 500 cycles at 100 mA g-1 with a small capacity degradation ratio of ~0.02% for each cycle. Moreover, Zn2GeO4 exhibits a good rate performance, delivering a high capacity of 503 mA h g-1 at 5000 mA g-1. The good electrochemical performance of the rice-like Zn2GeO4 electrode can be attributed to its unique wire-bundle structure, the buffering effect of the bimetallic reaction at different potentials, good electrical conductivity, and fast kinetic rate.

Recent Advances in TiO2 -based Photoanodes for Photoelectrochemical Water Splitting.

Photoelectrochemical (PEC) water splitting has attracted great attention in the past several decades as it holds great promise to address global energy and environmental issues by converting solar energy into hydrogen. However, its low solar-to-hydrogen (STH) conversion efficiency remains a bottleneck for practical application. Developing efficient photoelectrocatalysts with high stability and high STH conversion efficiency is one of the key challenges. As a typical n-type semiconductor, titanium dioxide (TiO2 ) exhibits high PEC water splitting performance, especially high chemical and photo stability. But, TiO2 has also disadvantages such as wide band gap and fast electron-hole recombination rate, which seriously hinder its PEC performance. This review focuses on recent development in TiO2 -based photoanodes as well as some key fundamentals. The corresponding mechanisms and key factors for high STH, and controllable synthesis and modification strategies are highlighted in this review. We conclude finally with an outlook providing a critical perspective on future trends on TiO2 -based photoanodes for PEC water splitting.

A process-based model for describing redox kinetics of Cr(VI) in natural sediments containing variable reactive Fe(II) species.

Sediment-associated Fe(II) is a critical reductant for immobilizing groundwater contaminants, such as Cr(VI). The reduction reactivity of sediment-associated Fe(II) is dependent on its binding environment and influenced by the biogeochemical transformation of other elements (i.e., C, N and Mn), challenging the description and prediction of the reactivity of Fe(II) in natural sediments. Here, anaerobic batch experiments were conducted to study the variation in sediment-associated Fe(II) reactivity toward Cr(VI) in natural sediments collected from an intensive agricultural area located in Guangxi, China, where nitrate is a common surface water and groundwater contaminant. Then, a process-based model was developed to describe the coupled biogeochemical processes of C, N, Mn, Fe, and Cr. In the process-based model, Cr(VI) reduction by sediment-associated Fe(II) was described using a previously developed multirate model, which categorized the reactive Fe(II) into three fractions based on their extractabilities in sodium acetate and HCl solutions. The experimental results showed that Fe(II) generation was inhibited by NO3- and/or NO2-. After NO3- and NO2- were exhausted, the Fe(II) content and its reduction rate toward Cr(VI) increased rapidly. As the Fe(II) content increased, the three reactive Fe(II) fractions exhibited approximately linear correlations with aqueous Fe(II) concentrations ( [Formula: see text] ), which was probably driven by sorptive equilibrium and redox equilibrium between aqueous and solid phases. The model results indicated that the reaction rate constants of the three Fe(II) fractions (kn) significantly increased with incubation time, and log(kn) correlated well with [Formula: see text] [ [Formula: see text] , [Formula: see text] and [Formula: see text] ]. The numerical model developed in this study provides an applicable method to describe and predict Cr(VI) removal from groundwater under dynamic redox conditions.

Role of the biochar modified with ZnCl2 and FeCl3 on the electrochemical degradation of nitrobenzene.

The Zn/Fe-modified biochar on nitrobenzene (NB) removal during the electrolysis was investigated in this study. Both the Fe and Zn-modified biochar enhanced the NB adsorption compared with the un-modified biochar due to their greater specific surface area and more abundant surface function groups, respectively. The electrolysis under 2-11 V with the assist of both Fe/Zn-modified biochar achieved effective NB removal (>93%). The removal rate under 2 V using Zn/Fe-modified biochar (∼94%) was higher than that of the un-modified biochar (∼80%), whereas the removal was similar for those under 5, 8 and 11 V. The NB removal under 2 and 5 V was attributed to both adsorption and electrochemical decomposition of NB molecules. Electrolysis under 5 V by Fe-modified biochar had a higher degree of NB mineralisation than that using un-modified and Zn-modified biochar. This was likely that the Fe-modified biochar exhibited higher electrocatalytic properties, facilitating the further NB mineralisation. The ∙OH played significant roles in the degradation of NB by Fe-modified and un-modified biochar but did not significantly participated for the test using Zn-modified biochar. This was possibly because the Zn-modified biochar could adsorb greater amounts of ∙OH into the inner pores of Zn-modified biochar via its greater porosity and specific surface area, which may prevent the contact between ∙OH and NB molecules.

Behavior of fast and slow phosphorus release from sewage sludge-derived biochar amended with CaO.

The pyrolyzation of sewage sludge (SS) could efficiently transform inherent phosphorus (P) into bioavailable phosphate forms, which endows SS-derived biochar (SSB) the potential as a soil fertilizer. However, the details about the release behavior of P in SSB have not been systematically investigated. This study evaluated the fast and slow P releasing behaviors from SSB and CaO-amended SSB prepared under different pyrolysis temperature. The higher pyrolysis temperature and CaO addition could enhance the conversion of non-apatite inorganic phosphorus (NAIP) into more bioavailable apatite inorganic phosphorous (AP). Acidic and alkaline conditions were favorable for the fast release of P from SSB. Higher ionic strength condition gave greater releasing amounts of TP and the SO42- facilitating a rapid release of TP than those for Cl- and NO3-. SSBs with CaO addition showed a much slower TP release than those without CaO both in fast release (24 h, with CaO: 0.05~0.4 mg TP g-1 SSB, e.g., without CaO 0.5~5 mg TP g-1 SSB) and slow release tests (21 days, with CaO: 1.2~4.1 mg TP g-1 SSB, e.g., without CaO 1.8~5.7 mg TP g-1 SSB). Ortho-P release was more remarkable for the SSB amended with CaO (~54% of TP), which was likely due to the formation of orthophosphate. The results of this study suggested that SSB prepared by high pyrolysis temperature and CaO addition had high potential as a slow P-releasing fertilizer for the soil.

Regeneration of Fe II /Fe III complex from NO chelating absorption by microbial fuel cell.

Ferrous chelates (FeIIEDTA) can effectively absorb NO, but the regeneration of them usually consumes large amounts of organic matter or energy. In this study, a new approach to regenerate NO absorbed ferrous chelates with simultaneous electricity generation was investigated by a microbial fuel cell (MFC). The performance and mechanisms of FeIIEDTA regeneration were evaluated in the cathode of MFC reactor with and without the presence of microorganisms (referring to biocathode and abiotic cathode), respectively. It was found that FeIIEDTA-NO and FeIIIEDTA could be used as the cathode electron acceptors in MFC. Low pH (pH = 5) was beneficial to electricity generation and FeIIIEDTA/FeIIEDTA-NO reduction by the abiotic cathode. The biocathode performed better in electricity generation and FeIIEDTA regeneration, and achieved a FeIIIEDTA reducing rate of 0.34 h-1 and a FeIIEDTA-NO reducing rate of 0.97 L mmol-1 h-1, which are much higher that than those for the abiotic cathode (0.23 h-1 for FeIIIEDTA, 0.44 L mmol-1 h-1 for FeIIEDTA-NO). This was likely because the activation polarization loss and over cathode potential were reduced as a result of the catalytic activity of NO and iron reducing bacteria.

Phosphorus speciation and bioavailability of sewage sludge derived biochar amended with CaO.

In this study, biochar samples were prepared from the co-pyrolysis of sewage sludge (SS) and CaO to explore the transformation of P speciation in sample. The potential of these biochar as a fertilizer to promote the growth of the plant was also evaluated. The result indicated that CaO addition can greatly facilitate the conversion of non-apatite inorganic phosphorus (NAIP) to apatite inorganic phosphorus (AP, mainly Ca3(PO4)2 and Ca3Mg3(PO4)4). The addition of 10% CaO in feedstock is sufficient to convert SS inherent P into more bioavailable AP. Under such a dosage, AP content in biochar increased by 21.2-33.6% in contrast to CaO free sample at pyrolysis temperature of 500-800 °C, and water-soluble phosphorus (WSP) content decreased to less than 1% of TP. The addition of CaO can also apparently reduce Zn, Mn leaching from biochar. Additionally, hydroponics assay showed that CaO amended SS biochar can promote the growth of rice seedling. The results of this study indicate that preparing CaO amended SS biochar is a technically feasible strategy to utilize P resource in SS.

Identification of the first case of SFTSV infection in the Hunan Province of China and epidemiological surveillance in the locality.

This study reports the etiological identification, clinical diagnosis, and the results of the local epidemiological surveillance of the first case of severe fever with thrombocytopenia syndrome virus (SFTSV) infection in 2014 in Hunan Province, China. The infected patient was isolated and closely monitored. The virus is a member of the Bunyaviridae sandfly family and is characterized by real-time PCR, electron microscopy, immunofluorescence, and whole-genome sequencing. We also detected IgG and IgM antibodies against SFTSV among the local human population and domestic animals in a serological surveillance. Prevalence of SFTSV-specific antibodies was monitored in the local population for two years after the identification of the first SFTS case. Approximately 5% (4/77) of the people who had direct contact with the patient were seropositive, which is significantly higher than the seropositivity of the general local population [1.57% (44/2800), P < 0.05]. Furthermore, the percentage of the general population who were seropositive was higher in 2015 than in 2014 (χ2 = 7.481, P = 0.006). The epidemiological investigation found that the SFTSV is epidemic in goats, cattle, and chickens in Hunan Province. The risk of infection of domestic animals can be minimized by feeding in pens rather than allowing foraging.

The QRAR model study of beta-lactam antibiotics by capillary coated with cell membrane.

With the accelerating development of new drugs, there is a great need for rapid and simple screening technologies. In this paper, a new in vitro method, capillary coated with cell membrane, was presented for drug screening based on the real biomembrane-drugs interaction, in which the cell membrane was applied to chromatography as pseudo-stationary phase directly. As the cell membrane was coated on the bare-fused capillary via sol-gel technology in our present work, it will be shown to be superior to other pseudo-stationary phases mimicking biological environment. Meanwhile, the quantitative retention-activity relationships (QRAR) model of beta-lactam antibiotics was studied through investigating the effect of the membrane coating amount and pH of running buffer on the retention behaviors of the drugs and the logarithm of octanol-water partition coefficient (logP) at pH 7.4 and pH 6.5 were also obtained for comparison. The results showed that the capillary coated with cell membrane could suit the study of QRAR model.

Improving Cu(II) sorption by biochar via pyrolyzation under CO2: the importance of inherent inorganic species.

Biochar from Spartina alterniflora (SA) and rice straw (RS) under N2/CO2 were evaluated for Cu(II) removal from aqueous solution. The result indicates SA biochar prepared at 700 °C under CO2 can achieve a Cu(II) sorption capacity of 89.12 ± 2.77 mg/g, which is higher than that from N2 by about 50%. CO2 can promote the development of multi-porous structure, enhance specific surface area, and increase the amounts of hydroxyl and carboxyl groups on biochar. In addition, CO2 can inhibit the thermal decomposition of inorganic carbonate, such as MgCO3 and CaCO3 in biochar. These matters facilitate Cu(II) removal via the formation of chemical precipitation of Cu2(OH)2CO3. The dissolution of inherent inorganic matter makes Cu(II) transformed into hydrolyzed species or amorphous precipitation, which contributes to about 75% (w/w) of Cu(II) removal. Metal exchange with complexed cations and the formation of basic cupric carbonate are time-consuming and responsible for about 24% (w/w) of Cu(II) removal. Graphical abstract ᅟ.

Identifying the reducing capacity of biomass derived hydrochar with different post-treatment methods.

In this study, hydrochar was prepared from wheat straw (WS) and Spartina alterniflora (SA) biomass by hydrothermal carbonization, and further treated with HCl and NaOH washing, HNO3 oxidization and low temperature thermal heating. The reducing capacity (RC) of sample was quantified by I2 titration to explore how these modification methods affected the redox properties of hydrochar. The results indicated HNO3 and thermal oxidization increased the RC of hydrochar by 2-5 folds while NaOH washing had the negative effect on samples' RC. By analyzing the excitation-emission matrix (EEM) fluorescence of alkaline extraction solution of sample, humic acid like substances generated from various methods were identified as one of the major sources for electron donating. HNO3 oxidization could significantly increase the RC in hydrochar, which was likely resulting from the generation of alkali-soluble small molecule organic compounds. However, excessive oxidation by nitric acid with prolonged duration led to the gradual decrease in hydrochar's RC. Heating treatment caused a significant increase in the content of redox-active oxygen-containing functional groups and persistent free radicals (PFRs) in hydrochar. Even though both could donate electrons in the redox reaction with I2, the former was considered a greater contributor for the RC of hydrochar. From this study, the origin of RC of hydrochar can be identified as: oxygen-containing functionality, humic-like matter and PFRs. By employing different modification methods, the RC of hydrochar could be tuned by regulating the above sources. This study provided fundamental knowledges and simple routes to manipulate the redox properties of hydrochar for different environmental applications.

Degradation of refractory organics in biotreated landfill leachate using high voltage pulsed discharge combined with TiO2.

The effect of high voltage pulsed discharge (HVPD) combined with TiO2 on the degradation of refractory organic compounds in actual biotreated landfill leachate was investigated. The optimal chemical oxygen demand (COD) removal efficiency could achieve to 58.9% using HVPD+TiO2 within 30min at 40kV, 400Hz, and the conductivity of 4.05mscm-1 in gas-liquid pulsed discharge. The aromatic compounds decreased by 33.6% compared with HVPD alone according to the UV absorbance at 254nm. Moreover, the fluorescence intensity of humic and fulvic substances was greatly decreased. Active species such as OH radical and H2O2 were enhanced in the presence of TiO2, resulting in more high molecular weight organic matter into small molecules or mineralized. In addition, possible degradation pathways was proposed based on acetophenone, which is effective for the degradation of organic matter in biotreated landfill leachate as long as the active species increased.

Molecularly imprinted polymers combination with deep eutectic solvents for solid-phase extraction of caffeic acid from hawthorn.

Molecularly imprinted polymers (MIPs) with caffeic acid as template and non-imprinted polymers (NIPs) materials were prepared in the same procedure. Field emission scanning electron microscopy (FE-SEM) and adsorption capacity test were used to evaluate characteristic of the new materials. MIPs, NIPs and C18 were used for rapid purification of caffeic acid from hawthorn with solid-phase extraction ( SPE) , and extract yields of caffeic acid with the proposed materials were 3.46 µg/g, 1.01 µg/g and 1.17 µg/g, respectively. To optimize the MIPs-SPE procedures, different kinds of elution solutions were studied. Deep eutectic solvents (DESs) were prepared by choline chloride (ChCl)-glycerol (1/2, n/n) and choline chloride-urea (1/ 2, n/n). Methanol was mixed with the two kinds of DESs (glycerol-based DESs, urea-based DESs) in different ratios (0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, v/v), and they were used to investigated as elution solutions in the above MIPs-SPE procedures. The results showed that MIPs were potential SPE materials, and methanol/ glycerol-based DESs (3 :1, v/v) had the best elution capability with the recovery of 82.32%.

[Monitoring report of Oncomelania hupensis snail distribution and diffusion in main drainages of Hexi Reservoir].

OBJECTIVE: To understand the status of Oncomelania hupensis snail distribution and diffusion in main drainages of Hexi Reservoir and evaluate the snail control effect of the schistosomiasis control engineering of Hexi Reservoir. METHODS: The O. hupensis snails were investigated by using the straw curtain method and fishing net method in different areas of the main drainages of Hexi Reservoir, and the results were analyzed. RESULTS: A total of 1 800 straw curtains were used and 37 snails were found in Naxi stream. Totally 5 870 kg floats were salved and no snails were found. CONCLUSION: The schistosomiasis control engineering of Hexi Reservoir is effective in the prevention of the snail diffusion, but there are still snails in the upstream. rherefore, the snail surveillance and control need to be strengthened.

[Preparation of interferon-alpha-loaded poly-L-lactic acid lamellar particles].

Lamellar particles(lamellae) were prepared by non-solvent precipitation from crystalic poly-L-lactic acid (PLLA). The PLLA lamellae exhibite a diamond or stepped irregular shape with a size range between 3-5 microns. Prepared without any surfactants and dispersing agents, the lamellar particles have clean surface, which is advantageous for the adsorption of proteins. The PLLA lamellar particles adsorbed protein cytokine interferon-alpha (IFN-alpha) with an adsorption efficiency of > or = 95%. The release of loaded IFN could continue for more than 10 days. The cell incubation experiments showed that the PLLA lamellar particles were easy to be phagocytosed by macrophages. The immunological experiments showed that the biological activity of IFN-alpha loaded on the PLLA lamellar particle was effectively retained.

[Effect of schistosomiasis control projects in Hexi Reservoir on Oncomelania snail control].

OBJECTIVE: To evaluate the effect of schistosomiasis control projects in Hexi Reservoir on Oncomelania hupensis snail control. METHODS: The canal hardening + main water system widening + the overflow dam project, the concrete slope protection, the banking and reclamation + concrete slope protection project, the environment reform project, and the comprehensive treatment were implemented in the tail area, the hydro-fluctuation belt, the rainwater harvesting zoon of the upstream area, the dam area, and the downstream area of the reservoir, respectively. The changes of the snail situation were investigated before and after the construction of the reservoir, and the snail control effects of the schistosomiasis control projects in different parts of the reservoir were analyzed. RESULTS: There were no Oncomelania snails found 3 years in the bottom area, dam area, hydro-fluctuation belt, tail region and downstream of the dam after the construction and storage of the reservoir and the implementation of the schistosomiasis control projects. In the rainwater harvesting zoon of the upstream area, the density of living snails decreased from 0.620 4 snails/0.1 m2 in 2009 to 0.113 2 snails/0.1 m2 in 2013, but the snail area still remained. CONCLUSIONS: The schistosomiasis control projects in Hexi Reservoir have effectively prevented the diffusion of Oncomelania snails from the rainwater harvesting zone of the upstream area to the dam area, and they are effective in the snail control.