Degradation of benzene derivatives in the CuMgFe-LDO/persulfate system: The role of the interaction between the catalyst and target pollutants.

A novel insight on the role of interactions between target pollutants and the catalyst in the copper-containing layered double oxide (LDO)-catalyzed persulfate (PS) system was elucidated in the present study. 4-Chlorophenol (4-CP), as a representative benzene derivative with a hydroxyl group, was completely removed within 5 min, which was much faster than the reaction of monochlorobenzene (MCB) without a hydroxyl group, with the degradation efficiency of 31.7% in 240 min. Through the use of radical quenching and surface inhibition experiments, it could be concluded that the interaction between 4-CP and CuMgFe-LDO, rather than free radicals, played a key role in the decomposition of 4-CP, while only the free radicals participated in the MCB degradation process. According to electron paramagnetic resonance and X-ray photoelectron spectroscopy data, the formation of a Cu(II)-complex between phenolic hydroxyl groups and surface Cu(II) was primarily responsible for the degradation of phenolic compounds, in which PS accepted one electron from the complex and generated sulfate radicals and chelated radical cations. The chelated radical cations transferred one electron to Cu(II) followed by Cu(I) generation and pollutant degradation successively.

Multifunctional Pd/Fe-biochar composites for the complete removal of trichlorobenzene and its degradation products.

To elucidate the effect of structure and property of biochar on the structure-activity relationship among the composites of biochar supported Pd/Fe and 1,2,4-trichlorobenzene (1,2,4-TCB) and its dechlorination products, biochar supported Pd/Fe nanoparticles with different mass ratios were investigated for the enhanced removal of 1,2,4-TCB (52 µmol/L) and its dechlorination products. 1,2,4-TCB was removed through the electrochemical dechlorination by Pd/Fe and adsorption by biochar simultaneously. As the mass ratio of CS700 to Pd/Fe was 0.1:1, biochar within the Pd/Fe-CS7000.1 system played a significant role in the adsorption of 1,2,4-TCB. However, there is little adsorption to biochar for dechlorination products due to strong competition by 1,2,4-TCB. As the mass ratio of CS700 to Pd/Fe was increased to 5:1, 1,2,4-TCB was completely removed from the solution by the composites within 0.5 h. The dechlorination products (1,2-DCB, MCB, benzene and trace 1,3-DCB) were completely sequestered on solid phase but absent in aqueous solution. However, the excessive biochar increased the inaccessibility of 1,2,4-TCB or decreased the reactive sites of Pd/Fe leading to the less dechlorination of 1,2,4-TCB. The alkaline biochar did not influence the chemical reactivity of Pd/Fe in the composites and buffered the acid and alkaline solutions with pH being maintained at neutral conditions under initial pH ranging from 3.07 to 10.03. The highly hydrophobicity of biochar could maintain the affinity of the composite for the chlorinated compounds even if the concentration of 1,2,4-TCB was up to 80.9% of its aqueous solubility. This study provides efficient synergistic removal support for the treatment of TCB affected groundwater.

Performance of field demonstration nanoscale zero-valent iron in groundwater remediation: A review.

Nanoscale zero-valent iron (nZVI) has gained widespread usage in groundwater remediation due to its exceptional reactivity. Since its initial deployment in field demonstrations in 2001, nZVI has proven to be an effective nanomaterial for addressing groundwater contaminants. Subsequent research has highlighted the versatility of nZVI, showcasing its potential to overcome critical limitations associated with conventional remediation technologies. The effectiveness of nZVI in remediation varies, contingent on factors such as the type of nZVI, contaminant nature, site conditions, and injection methodologies employed. This review aims to present a comprehensive progress report on the field application of nZVI spanning 22 years across eight countries. Drawing from a database encompassing 32 pilot or full-scale remediation sites, the study delineates the various types of nZVI, modification methods, demonstration sites, and primary contaminants targeted in field tests. Specific attention is given to the application effects and mechanisms of unmodified nZVI, Pd, surfactants, and carbon-modified nZVI in diverse field demonstrations. An analysis of the key factors influencing their performance is provided, and potential future applications of nZVI in groundwater remediation are discussed.

Dual role of biochars as adsorbents for aluminum: the effects of oxygen-containing organic components and the scattering of silicate particles.

The adsorption of aluminum by biochars produced at different temperatures from rice straw (RS) and cattle manure (CM) was studied to determine the dual roles of biochar for aluminum adsorption. The compositional structures and surface charges of the biochars and ashes with and without Al loading were analyzed by Fourier-transform infrared spectroscopy, ζ-potential, scanning electron microscopy, and X-ray diffraction. The Al adsorption isotherms were fit well by the Langmuir model. The adsorption of Al to the biochars produced at 400 and 700 °C was much greater than the adsorption to the precursory materials and ashes. We found that the organic components and silicate particles within the biochars served as dual adsorptive sites for Al. The complexation of Al with organic hydroxyl and carboxyl groups and the surface adsorption and coprecipitation of Al with silicate particles (as KAlSi3O8) both contributed to the Al adsorption of the biochars. After the biochars were loaded with Al, the ζ-potentials of the biochars and ashes increased as a function of pH. The positive charge was maximized at pH 4.5, which is similar to the pH at which the maximum positive charge occurs for silica. The charge reversal was caused by the Stern-layer adsorption of hydrolyzed aluminum species (i.e., Al(OH)(2+) and Al(OH)2(+)) on the silicate surfaces via hydrogen bonds.

Effective alleviation of aluminum phytotoxicity by manure-derived biochar.

The alleviation of aluminum phytotoxicity to wheat plants in a hydroponic system through the amendment of biochar is investigated to explore the possibility of applying biochar in acidic soil amelioration. Biochar derived from cattle manure pyrolyzed at 400 °C (CM400) and the CM400 biochar washed with distilled-deionized water to remove alkalinity (WCM400) were prepared to determine the roles of the liming effect and adsorption during the alleviation of Al toxicity. Upon addition of 0.02% (W/V) CM400 to the exposure solution, the inhibition of plant growth by Al was significantly reduced while the toxic threshold was extended from 3 to 95 µmol/L Al(3+). Due to the biochar liming effect, the aluminum species were converted to Al(OH)(2+) and Al(OH)2(+) monomers, which were strongly adsorbed by biochar; furthermore, the highly toxic Al(3+) evolved to less toxic Al(OH)3 and Al(OH)4(-) species. Adsorption of Al by the biochar is dominated by surface complexation of the carboxyl groups with Al(OH)(2+)/Al(OH)2(+) rather than through electrostatic attraction of Al(3+) with negatively charged sites. Compared to the liming effect, the adsorption by biochar exhibited a sustainable effect on the alleviation of Al toxicity. Therefore, the biochar amendment appears to be a novel approach for aluminum detoxification in acidic soils.

New insight into the activation mechanism of hydrogen peroxide by greigite (Fe3S4) for benzene removal: The combined action of dissolved and surface bounded ferrous iron.

Iron sulfides have attracted growing concern in heterogeneous Fenton reaction. However, the structure of iron sulfides is different from that of iron oxides and how the structures affect the activation property of hydrogen peroxide (H2O2) remains unclear. This study investigated benzene removal through the activation of H2O2 by the synthesized magnetite (Fe3O4) and greigite (Fe3S4). The structures of Fe3O4 and Fe3S4 were characterized by XRD and EPR, the electron transfer properties of Fe3O4 and Fe3S4 were analyzed by electrochemical workstation, XPS and DFT. It is revealed that the effective benzene removal rate of 88.86％ in the Fe3S4/H2O2 was achieved, which compared to 15.58％ obtainable from the Fe3O4/H2O2, with the apparent rate constant in the Fe3S4/H2O2 being approximately 65 times over that in the Fe3O4/H2O2. The better H2O2 activation by Fe3S4 was attributed to the significant roles of S (-II) and S vacancies in regulating the dissolution of ferrous iron ions, thus generating abundant free •OH radical. In addition, surface bounded ferrous iron of Fe3S4 could transfer more electrons to H2O2 and O2 to generate more surface bounded •OH and •O2-. This study revealed the combined action of dissolved and surface bounded ferrous iron of greigite on H2O2 activation, and provides an efficient heterogeneous H2O2 activator for the remediation of organic contaminants in groundwater.

Enhanced removal of cis-1,2-dichloroethene and vinyl chloride in groundwater using ball-milled sulfur- and biochar-modified zero-valent iron: From the laboratory to the field.

Sulfidated zero-valent iron (ZVI) and biochar-supported ZVI have received increasing attention for their potential to dechlorinate trichloroethylene. However, minimal data are available regarding the combined effect of sulfur and biochar ZVI on trichloroethylene byproducts. The primary aim of the current study is to determine whether sulfur- and biochar-modified ZVI (ZVI-BC-S) enhances the removal of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) from groundwater. Results show that biochar and sulfur facilitated the milling of ZVI-BC-S into micro- and nanoscale particles and increased FeS formation. Moreover, the rates of cDCE and VC removal by ZVI-S increased by 30.1% and 30.2%, respectively, compared to those obtained with ZVI, owing to enhanced dechlorination via ß-elimination by sulfur. Meanwhile, treatment with ZVI-BC-S harnessed the benefits of biochar and sulfur to enhance the cDCE and VC removal rates by 62.0% and 67.7%, respectively. Mechanistically, biochar enhanced the corrosion of ZVI-S to increase FeS production and enhance the electron transfer, ß-elimination, and hydrogenolysis involved in cDCE and VC dechlorination. The effectiveness of ZVI-BC-S was confirmed in a field demonstration, during which cDCE and VC concentrations significantly decreased within 10 days following injection. The findings of this study can help inform the rational design of ZVI for in-situ remediation of chlorinated hydrocarbons in groundwater.

Unveiling the role of biochar in simultaneous removal of hexavalent chromium and trichloroethylene by biochar supported nanoscale zero-valent iron.

The simultaneous removal of hexavalent chromium (Cr(VI)) and Trichloroethylene (TCE) is facing great challenges, and the influences of the biochar on their removal by nanoscale zero-valent iron (nZVI) are poorly understood and seldom addressed in the literature. The rice straw pyrolysis at 700 °C (RS700) and their supported nZVI composites were investigated on the removal of Cr(VI) and TCE by batch experiments. The surface area and chromium bonding state of biochar supported nZVI with and without Cr(VI)-TCE loading were analyzed by Brunauer-Emmett-Teller analysis and X-ray photoelectron spectroscopy. In single pollutants system, the highest removal amounts of Cr(VI) and TCE were observed in RS700-HF-nZVI (76.36 mg/g) and RS700-HF (32.32 mg/g), respectively. The Cr(VI) removal was attributed to the reduction by Fe(II) with the adsorption by biochar primarily controlling the TCE removal. The mutual inhibition was revealed in simultaneous removal of Cr(VI) and TCE, in which the reduction of Cr(VI) was decreased due to the adsorption of Fe(II) by biochar, while the TCE adsorption was primarily inhibited owing to the blockage of surface pores of biochar supported nZVI by chromium­iron oxides. Therefore, biochar supported nZVI could be potentially used for the combined contaminated groundwater remediation, but the mutual inhibition should be evaluated.

Efficient Remediation of p-chloroaniline Contaminated Soil by Activated Persulfate Using Ball Milling Nanosized Zero Valent Iron/Biochar Composite: Performance and Mechanisms.

In this study, efficient remediation of p-chloroaniline (PCA)-contaminated soil by activated persulfate (PS) using nanosized zero-valent iron/biochar (B-nZVI/BC) through the ball milling method was conducted. Under the conditions of 4.8 g kg-1 B-nZVI/BC and 42.0 mmol L-1 PS with pH 7.49, the concentration of PCA in soil was dramatically decreased from 3.64 mg kg-1 to 1.33 mg kg-1, which was much lower than the remediation target value of 1.96 mg kg-1. Further increasing B-nZVI/BC dosage and PS concentration to 14.4 g kg-1 and 126.0 mmol L-1, the concentration of PCA was as low as 0.15 mg kg-1, corresponding to a degradation efficiency of 95.9%. Electron paramagnetic resonance (EPR) signals indicated SO4•-, •OH, and O2•- radicals were generated and accounted for PCA degradation with the effect of low-valence iron and through the electron transfer process of the sp2 hybridized carbon structure of biochar. 1-chlorobutane and glycine were formed and subsequently decomposed into butanol, butyric acid, ethylene glycol, and glycolic acid, and the degradation pathway of PCA in the B-nZVI/BC-PS system was proposed accordingly. The findings provide a significant implication for cost-effective and environmentally friendly remediation of PCA-contaminated soil using a facile ball milling preparation of B-nZVI/BC and PS.

Significant roles of surface functional groups and Fe/Co redox reactions on peroxymonosulfate activation by hydrochar-supported cobalt ferrite for simultaneous degradation of monochlorobenzene and p-chloroaniline.

CoFe2O4/hydrochar composites (FeCo@HC) were synthesized via a facile one-step hydrothermal method and utilized to activate peroxymonosulfate (PMS) for simultaneous degradation of monochlorobenzene (MCB) and p-chloroaniline (PCA). Additionally, the effects of humic acid, Cl-, HCO3-, H2PO4-, HPO42- and water matrices were investigated and degradation pathways of MCB and PCA were proposed. The removal efficiencies of MCB and PCA were higher in FeCo@HC140-10/PMS system obtained under hydrothermal temperature of 140 °C than FeCo@HC180-10/PMS and FeCo@HC220-10/PMS systems obtained under higher temperatures. Radical species (i.e., SO4•-, •OH) and nonradical pathways (i.e., 1O2, Fe (IV)/Co (IV) and electron transfer through surface FeCo@HC140-10/PMS* complex) co-occurred in the FeCo@HC140-10/PMS system, while radical and nonradical pathways were dominant in degrading MCB and PCA respectively. The surface functional groups (i.e., C-OH and CO) and Fe/Co redox cycles played crucial roles in the PMS activation. MCB degradation was significantly inhibited in the mixed MCB/PCA solution over that in the single MCB solution, whereas PCA degradation was slightly promoted in the mixed MCB/PCA solution. These findings are significant for the provision of a low-cost and environmentally-benign synthesis of bimetal-hydrochar composites and more detailed understanding of the related mechanisms on PMS activation for simultaneous removal of the mixed contaminants in groundwater.

Enhanced oxidation of benzo[a]pyrene by crude enzyme extracts produced during interspecific fungal interaction of Trametes versicolor and Phanerochaete chrysosporium.

The effects of interspecific fungal interactions between Trametes versicolor and Phanerochaete chrysosporium on laccase activity and enzymatic oxidation of polycyclic aromatic hydrocarbons (PAHs) were investigated. A deadlock between the two mycelia rather than replacement of one fungus by another was observed on an agar medium. The laccase activity in crude enzyme extracts from interaction zones reached a maximum after a 5-day incubation, which was significantly higher than that from regions of T. versicolor or P. chrysosporium alone. The enhanced induction of laccase activity lasted longer in half nutrition than in normal nutrition. A higher potential to oxidize benzo[a]pyrene by a crude enzyme preparation extracted from the interaction zones was demonstrated. After a 48 hr incubation period, the oxidation of benzo[a]pyrene by crude enzyme extracts from interaction zones reached 26.2%, while only 9.5% of benzo[a]pyrene was oxidized by crude extracts from T. versicolor. The oxidation was promoted by the co-oxidant 2,2'-azinobis-3-ethylbenzthiazoline-6-sulphonate diammonium salt (ABTS). These findings indicate that the application of co-culturing of white-rot fungi in bioremediation is a potential ameliorating technique for the restoration of PAH-contaminated soil.

Electron induced efficient dechlorination of trichlorethylene with S doped Fe2B: The enhancement mechanism of S.

In this work, S doped Fe2B (Fe2B-S) was synthesized by sintering method and applied for the enhanced dechlorination of trichlorethylene (TCE). The degradation ratio (D) of TCE was 99.8% with reaction rate constant (kobs) of 0.956 h-1 by 10.0at% S doped Fe2B (corresponding to Fe2B-S10.0), compared to D and kobs values 37.3% and 0.067 h-1 by Fe2B, respectively. The major dechlorination products of acetylene, ethene, ethane and C3-C6 hydrocarbon compounds were observed from a reductive ß-elimination pathway. S doped and undoped Fe2B could form the first-level in-situ galvanic cell, and the returned S provided a second-level galvanic cell to further enhance electron transfer. The doped S worked as electron donor to increase the density of localized unpaired electrons, and the electron enriched Fe atoms leading to stronger reducibility were verified by the density functional theory (DFT) calculation. This work provides a complete insight into the enhancement mechanism of S doped Fe2B and guides the potential design of zero-valent iron (ZVI) with properties tailored for chlorinated hydrocarbons dechlorination.

Hydrothermally assisted synthesis of nano zero-valent iron encapsulated in biomass-derived carbon for peroxymonosulfate activation: The performance and mechanisms for efficient degradation of monochlorobenzene.

A facile, green and easily-scalable method of synthesizing stable and effective nano zero-valent iron (nZVI)­carbon composites for peroxymonosulfate (PMS) activation was highly desirable for in-situ groundwater remediation. This study developed a two-step hydrothermally assisted carbothermal reduction method to prepare nZVI-encapsulated carbon composite (Fe@C) using rice straw and ferric nitrate as precursors. The hydrothermal reactions were conducive to iron loading, and carbothermal temperature was crucial for the aromatization and graphitization of hydrothermal carbonaceous products, the reductive transformation of iron oxides into nZVI and the development of porous structure in composites. At carbothermal temperature of 800 °C following hydrothermal reactions, the stable Fe@C800 with nZVI encapsulated in the spherical carbon shell was obtained and exhibited the best catalytic performance for PMS activation and the degradation of monochlorobenzene (MCB) in a wide range of pH values (3-11) with removal efficiency after 120 min reaction and first-order kinetic rate constant (k1) of 98.7% and 0.087 min-1 respectively under the optimum conditions of 10 mM PMS and 0.2 g·L-1 Fe@C800. The inhibiting effects of common co-existed anions (i.e., Cl-, HCO3- and H2PO4-) and humic acid in groundwater on the removal of MCB in Fe@C800/PMS system was also investigated. Both OH-dominated radical processes and nonradical pathways involving 1O2 and surface electron transfers were accounted for PMS activation and MCB removal. The inner nZVI was protected by the carbon shell, endowing Fe@C800 with high reactivity and good reusability. Additionally, 81.2% and 73.5% of MCB removal rates were achieved in tap water and actual contaminated groundwater respectively. This study not only provided a novel strategy to synthesize highly effective and stable nZVI­carbon composites using the agricultural biomass waste for PMS induced oxidation of organic contaminants in groundwater, but also enhanced the understanding on the activation mechanism of iron­carbon based catalysts towards PMS.

Nanoscale zero-valent iron supported by attapulgite produced at different acid modification: Synthesis mechanism and the role of silicon on Cr(VI) removal.

The attapulgite of different morphologies and mineral compositions were successfully obtained following the treatment by HCl and HF with different concentrations. Variations of morphologies, elemental and mineral components of the pristine and modified attapulgite were investigated and assessed in detail by a series of characterization methods. The SEM-EDS results indicated significant variations on the contents and morphologies of silicon after acid modification. The Cr(VI) removal efficiencies under pristine and modified attapulgite-supported nZVI composites were evaluated with the removal rate in case of 0.5HAT-nZVI being 69.2% more superior than that of 6FAT-nZVI. The reaction kinetic is well fitted with pseudo second order kinetics model. The correlation analysis indicated that Cr(VI) removal efficiency was positively correlated with the content of active silicon in the attapulgite-nZVI composites (R2 = 0.979∗∗). Additionally, the reduction of Cr(VI) is more likely to occur in silicon-rich composites based on the analysis of XPS spectra and Cr concentration changes, which were mainly attributed to the enhanced Si-O-Fe coupling mediated by silicon. Attapulgite with more exposure sites of silicon enhanced the Cr(VI) reduction process and promoted crystallization of the reaction products. Simultaneously, the nZVI consumption caused by oxidation and aggregation were improved by silicon in attapulgite. It is concluded that silicon played a significant role on Cr(VI) removal through the reductive precipitation by Si-O-Fe coupling.

Trichloroethylene dechlorination rates, pathways, and efficiencies of ZVMg/C in aqueous solution.

The removal mechanism from the reductive dechlorination of trichloroethylene (TCE) by zero valent magnesium (ZVMg) in aqueous solution is systematically studied. Following the preparation and characterization of ball-milled micro ZVMg with graphite (ZVMg/C) particles, this paper evaluated the TCE reaction rates, pathways, utilization rates and aging effects of ZVMg/C particles in aqueous solution under uncontrolled pH conditions. Overall, 38 µM of TCE was transformed by 10 g/L of ZVMg/C to methane (62.51%) and n-hexane (11.86%) and ethane (7.40%) and other alkene and alkyne products through the catalytic hydrogenation pathway. The measured surface area normalized pseudo-first order rate constants (KSA) were up to 9.31 × 10-2 L/m2/h and the utilization rate of Mg0 accounted for around 60%. The KSA were decreased to 1.90 × 10-2 L/m2/h in case of ZVMg/C being exposed in the atmosphere for 6 days due to 7.3% reduction in the utilization rate of Mg0 from the initial 85.2%, and 5.11 × 10-2 L/m2 h in case of ZVMg/C aged in water for one day. The removal efficiencies of approximately 56%, 58% and 87% by 10 g/L of ZVMg/C were achieved in the contaminated groundwater comprising 38 µM of TCE, 43 µM of 1,2-dichlorobenzene and 8.12 µM of trichlormethane. Therefore, it is concluded that ZVMg/C is viewed as a potential and effective remediation reagent for the groundwater remediation.

Nano-magnetite supported by biochar pyrolyzed at different temperatures as hydrogen peroxide activator: Synthesis mechanism and the effects on ethylbenzene removal.

Nano-magnetite supported by biochar (nFe3O4/BC) pyrolyzed at temperatures of 300 °C-600 °C was developed to activate hydrogen peroxide (H2O2) for the efficient degradation of ethylbenzene in aqueous solution. It was revealed that the degradation efficiency of ethylbenzene and TOC removal were 96.9% and 36.2% respectively after the reaction for 40 min in the presence of initial concentration of 0.1 mmol L-1 ethylbenzene, 2.76 g L-1 nFe3O4/BC500 with the mass ratio of nFe3O4 to BC500 of 4:1 and 2.0 mmol L-1 H2O2 at pH 7.0. Based on electron paramagnetic resonance (EPR), quenching experiment and X-ray photoelectron spectroscopy (XPS) data, both OH and O2- radicals were generated in the nFe3O4/BC500 activated H2O2 system, and the OH radicals were the predominant species for the degradation of ethylbenzene. Through electron transfer process, mechanisms of Fe(II), phenolic hydroxyl group and persistent free radicals (PFRs) on BC surfaces accounted for the generation of OH radicals, and Fe(III) in nFe3O4 and formed from Fe(II) oxidation responsible for the generation of O2- radicals in the nFe3O4/BC activated H2O2 system were proposed.

Enhanced removal of 1,2,4-trichlorobenzene by modified biochar supported nanoscale zero-valent iron and palladium.

Biochar pyrolysed at 300 °C, 500 °C, 700 °C was modified by hydrochloric acid (HCl), hydrofluoric acid (HF), sodium hydroxide (NaOH), hydrogen peroxide (H2O2), nitric acid (HNO3) and potassium permanganate (KMnO4), and subsequently evaluated for removal efficiency of 1,2,4-trichlorobenzene (1,2,4-TCB) by biochar supported nanoscale zero-valent iron (nZVI) and palladium (Pd) composites. Under the initial 1,2,4-TCB concentration of 10 mg L-1 and the solid-liquid ratio of 0.16 g L-1, the synthesized composites of nZVI-Pd with BC700 modified by HF (FBC700-nZVI-Pd) and nZVI-Pd with BC300 modified by NaOH (SBC300-nZVI-Pd) demonstrated significantly enhanced removal efficiencies for 1,2,4-TCB achieving 98.8% and 94.7% after 48 h, respectively. The physicochemical properties of biochar including specific surface area, aromaticity and hydrophobicity after the modification by HF and NaOH were improved. Increased the supporting sites for Fe/Pd nanoparticles and the contact between composites and 1,2,4-TCB were mainly responsible for enhanced removal efficiency for 1,2,4-TCB. Both the adsorption by biochar and reduction by Fe/Pd nanoparticles effectively contributed to the removal of 1,2,4-TCB. It is estimated that the proportion of reduction was about twice that of adsorption in the first 12 h, which produced 1,2-DCB, benzene and other degradation products. Therefore, biochar treated with HF and NaOH and supported Fe/Pd nanoparticles could be effective functional materials for remediation of groundwater contaminated by 1,2,4-TCB.

Field demonstration of enhanced removal of chlorinated solvents in groundwater using biochar-supported nanoscale zero-valent iron.

The application of biochar-supported nanoscale zero-valent iron (biochar-nZVI) was successfully implemented in a field demonstration for the first time. To overcome the significant shortcomings of nZVI agglomeration for in-situ groundwater remediation, biochar-nZVI was injected into groundwater using direct-push and water pressure driven packer techniques for a site impacted by chlorinated solvents in the North China Plain. The field demonstration comprising two-step injections was implemented to demonstrate the effectiveness of nZVI and biochar-nZVI respectively. The outcome of the demonstration revealed a sharp reduction of contaminant concentrations of chlorinated solvents in 24 h following the first injection of nZVI, but the rebound of the concentrations of these contaminants in groundwater has occurred within the next two weeks. However, application of biochar-nZVI greatly enhanced the removal of chlorinated solvents in groundwater over the longer period of 42 days. The enhanced removal of chlorinated solvents in groundwater by biochar-nZVI is mainly attributed to the synergistic effects of adsorption and reduction. The adsorption by biochar significantly reduced the level of chlorinated solvents in groundwater. Overall increases in ferrous iron and chloride concentrations after the injections indicated that the reduction has occurred during the removal of chlorinated solvents in groundwater. In summary, biochar-supported nZVI could be potentially used for the effective remediation of chlorinated solvents in groundwater.

[Antiarrhythmic effect of ethyl acetate extract from Chrysanthemum Morifolium Ramat on rats].

OBJECTIVE: To investigate the effect of ethyl acetate extract from Chrysanthemum Morifolium Ramat (CME) on experimental arrhythmia induced by ischemia/reperfusion or aconitine in rats and to explore its underlying mechanisms. METHODS: Arrhythmia model in intact rat was induced by aconitine (30 microg/kg body weight, i.v.). In isolated Langendorff perfused rat hearts, regional ischemia and reperfusion was induced by ligation and release of left anterior descending artery. The ventricular fibrillation threshold (VFT), effective refractory period (ERP), and diastolic excitation threshold (DET) in the isolated heart were measured. The action potentials of papillary muscle in rat right ventricle were recorded by conventional glass microelectrode technique. RESULTS: Compared with control group CME significantly decreased the number and duration of ventricular tachycardia (VT); delayed the occurrence of ventricular premature beats (VPB) and VT induced by aconitine. Arrhythmia score of the CME group was lower than that in aconitine-treated group. CME markedly prolonged the ERP and increased the VFT in the isolated perfused rat hearts during ischemia and reperfusion. CME prolonged action potential duration at 50% and 90% repolarization of the right ventricular papillary muscles and decreased the maximal rate of rise of the action potential upstroke, but did not affect the resting potential, amplitude of action potential. CONCLUSION: CME can reduce myocardial vulnerability and exerts its antiarrhythmic effects induced by aconitine or ischemia/reperfusion, which may be related to its prolongation of action potential duration and effective refractory period that enhance the electrophysiological stability of myocardiaium.

Catalysis of hydrogen peroxide with Cu layered double hydrotalcite for the degradation of ethylbenzene.

A high catalytic system using Cu layered double hydrotalcite (Cu(II)-Mg(II)-Fe(III)LDHs) and hydrogen peroxide (H2O2) was developed for the degradation of ethylbenzene. It was identified that the degradation efficiency of ethylbenzene (0.08 mmol L-1) and TOC removal were 96.1% and 39.7% respectively in the presence of 0.1 g L-1 Cu(II)-Mg(II)-Fe(III)LDHs with (Cu2+ + Mg2+)/Fe3+ molar ratio of 5.0 and 0.16 mmol L-1 H2O2 in 6.0 h. Based on ESR and XPS data, hydroxyl radicals (•OH) were the predominant free radical specials generated from the catalytic decomposition of H2O2 for the degradation of ethylbenzene. The redox of Cu(II)/Cu(III) on the layered Cu(II)-Mg(II)-Fe(III)LDHs surface active sites accounted for the formation of •OH radicals and the cycle of Cu(II) in the Cu(II)-Mg(II)-Fe(III)LDHs/H2O2 system were proposed.