pH-neutral Condition Research Articles

Cu1-Fe Dual Sites for Superior Neutral Ammonia Electrosynthesis from Nitrate.

The electrochemical nitrate reduction reaction (NO3RR) is able to convert nitrate (NO3 -) into reusable ammonia (NH3), offering a green treatment and resource utilization strategy of nitrate wastewater and ammonia synthesis. The conversion of NO3 - to NH3 undergoes water dissociation to generate active hydrogen atoms and nitrogen-containing intermediates hydrogenation tandemly. The two relay processes compete for the same active sites, especially under pH-neutral condition, resulting in the suboptimal efficiency and selectivity in the electrosynthesis of NH3 from NO3 -. Herein, we constructed a Cu1-Fe dual-site catalyst by anchoring Cu single atoms on amorphous iron oxide shell of nanoscale zero-valent iron (nZVI) for the electrochemical NO3RR, achieving an impressive NO3 - removal efficiency of 94.8 % and NH3 selectivity of 99.2 % under neutral pH and nitrate concentration of 50 mg L-1 NO3 --N conditions, greatly surpassing the performance of nZVI counterpart. This superior performance can be attributed to the synergistic effect of enhanced NO3 - adsorption on Fe sites and strengthened water activation on single-atom Cu sites, decreasing the energy barrier for the rate-determining step of *NO-to-*NOH. This work develops a novel strategy of fabricating dual-site catalysts to enhance the electrosynthesis of NH3 from NO3 -, and presents an environmentally sustainable approach for neutral nitrate wastewater treatment.

Total Synthesis of 6-Deoxy-l-talose Containing a Pentasaccharide Repeating Unit of Acinetobacter baumannii K11 Capsular Polysaccharides.

Herein, we report a concise synthetic approach for the first total synthesis of a pentasaccharide repeating unit of Acinetobacter baumannii K11 capsular polysaccharides containing a rare sugar 6-deoxy-l-talose. The pentasaccharide was synthesized in a convergent manner using a [3 + 2] block glycosylation strategy. During this synthetic strive, we used a 2,2,2-trichloroethoxycarbonyl (Troc)-protected monosaccharide unit to achieve a high yield during the glycosylation to synthesize a trisaccharide, and chemoselective deprotection of the Troc group from the trisaccharide was carried out under a mild, pH-neutral condition, keeping the O-glycosidic bond, azido, and acid/base sensitive group intact. A thiotolylglycoside disaccharide donor containing 6-deoxy-l-talose was synthesized for the first time by the armed-disarmed glycosylation method between two thiotolylglycosides.

Development of Unique Technology Using Plasma on a Liquid Surface, and Its Application to Novel Cosmetic Materials

Titanium dioxide (TiO2) nanoparticles have been used as ultraviolet light scattering agents in sunscreen cosmetics. However, they tend to self-aggregate due to their high surface energies and strong interparticle attraction in water. In this research, we focused on liquid surface plasma (LSP), and studied the water dispersion technology of fine-particle TiO2. The plasma formed is considered to generate shock waves and species such as O radicals, which have high oxidation potential, around the liquid surface. The LSP treatment enabled preparation of the aqueous dispersions with 10% (wt) TiO2 nanoparticles that have approximately 100 nm particle size and long-term stability. In addition, from the chemical analyses of the dispersions, Al compounds derived from the underwater Al electrode were formed on the TiO2 surface. It was clear that TiO2 nanoparticles had high positive charge under pH neutral condition due to Al compounds on the surface, so that the dispersions were stabilized by electrostatic repulsion between the particles. Furthermore, from the X-ray absorption fine structure (XAFS) measurements, it was found that the chemical state and molecular structure of Ti were not altered by the LSP treatment, and amorphous aluminum hydroxide (Al(OH)3) was detected on the surface. These findings suggest that the TiO2 aqueous dispersion obtained by the LSP treatment can be safely applied to cosmetics. Finally, a composite powder (PLD-TiB), which is BaSO4 covered with TiO2, was obtained by electrostatic combination in aqueous dispersion. From the SEM image, it was observed that the BaSO4 surface was uniformly coated with TiO2. Due to the uniform coating without aggregation, PLD-TiB had a great UV protecting effect and a smooth feeling on the skin.

Degradation of QPPO-based anion polymer electrolyte membrane at neutral pH.

The chemical stability of anion polymer electrolyte membranes (AEMs) determines the durability of an AEM water electrolyzer (AEMWE). The alkaline stability of AEMs has been widely investigated in the literature. However, the degradation of AEM at neutral pH closer to the practical AEMWE operating condition is neglected, and the degradation mechanism remains unclear. This paper investigated the stability of quaternized poly(p-phenylene oxide) (QPPO)-based AEMs under different conditions, including Fenton solution, H2O2 solution and DI water. The pristine PPO and chloromethylated PPO (ClPPO) showed good chemical stability in the Fenton solution, and only limited weight loss was observed, 2.8% and 1.6%, respectively. QPPO suffered a high mass loss (29%). Besides, QPPO with higher IEC showed a higher mass loss. QPPO-1 (1.7 mmol g-1) lost nearly twice as much mass as QPPO-2 (1.3 mmol g-1). A strong correlation between the degradation rate of IEC and H2O2 concentration was obtained, which implied that the reaction order is above 1. A long-term oxidative stability test at pH neutral condition was also conducted by immersing the membrane in DI at 60 °C water for 10 months. The membrane breaks into pieces after the degradation test. The possible degradation mechanism is that oxygen or OH˙ radicals attack the methyl group on the rearranged ylide, forming aldehyde or carboxyl attached to the CH2 group.

RETRACTED: Super-hydrophilic MgO/NiCo2S4 heterostructure for high-efficient oxygen evolution reaction in neutral electrolytes

Oxygen evolution reaction (OER) in pH-neutral electrolyte is considered more difficult for the additional adsorption and the dissociation process of H 2 O. Herein, by in-suit construction of the heterostructure between MgO and NiCo 2 S 4 on carbon cloth (CC), a novel MgO/NiCo 2 S 4 heterostructure on CC (MgO/NCS-CC) is successfully fabricated. Benefitting from the optimized electronic structure attributed to the construction of hetero-interface, and the intense adsorption of H 2 O on the surface of catalysts owing to the introduction of hydration-effect-promoting (HEP) element Mg, the MgO/NCS-CC exhibits outstanding OER activity with overpotential of 145 mV at the current density of 10 mA·cm −2 in pH-neutral electrolyte and can maintain stability over 40 h. Density-functional theory (DFT) also demonstrates that the MgO/NiCo 2 S 4 heterostructure can effectively adjust the electronic structure and enhance the adsorption of reactant, thus further optimizing Gibbs free energies and improving the activity for OER in pH-neutral electrolyte. A novel heterostructure between MgO and NiCo 2 S 4 on carbon cloth (MgO/NCS-CC) was successfully constructed. Benefiting from the enhancement of H 2 O adsorption by the introduction of hydration-effect-promoting (HEP) element Mg and the construction of the heterostructure, MgO/NCS-CC exhibits outstanding OER performance in pH-neutral electrolyte, which the overpotential of 145 mV at the current density of 10 mA·cm −2 is the lowest among the reported OER electrocatalysts in pH-neutral electrolyte. • The hydration-enhancing-effect element Mg effectively enhanced the adsorption of H 2 O on the surface of catalyst. • The unique electronic structure of the heterostructure is the intrinsic reason for the super OER performance. • The catalyst shows outstanding OER performances and excellent stability in pH-neutral condition. • DFT calculation further reveals the change of electronic structure and the enhancement of water adsorption of the catalyst.

Simultaneous determination of 46 semi-volatile organic compounds in water by liquid-liquid extraction-gas chromatography-mass spectrometry

半挥发性有机物主要包括多环芳烃类(PAHs)、邻苯二甲酸酯类(PAEs)、有机氯农药类(OCPs)和硝基苯类(NBs)等化合物,这些物质多具有致癌、致畸、致突变作用,以及内分泌干扰效应。因此,快速准确测定水中半挥发性有机物非常重要,目前国内尚无水中半挥发性有机物的检测标准。该研究从氮吹温度、水样pH值和萃取时间3个方面进行了优化,旨在建立一种液液萃取-气相色谱-质谱(LLE-GC-MS)同时测定水中46种半挥发性有机物的方法。结果表明:氮吹温度对46种半挥发性有机物的回收率影响不大,考虑回收率及浓缩效率,将氮吹温度设定为35 ℃;水样在中性环境下萃取效果好于碱性环境下的效果;萃取时间由7 min增加至10 min时,回收率也随之提高,但时间增加至15 min时,17种(占比37%)化合物回收率有所增加,29种(占比63%)化合物回收率则呈降低趋势。因此,将萃取时间设定为每次10 min。采用气相色谱-质谱仪进行检测,内标法定量。该方法在20.0~2000 μg/L范围内线性良好,相关系数(r 2)≥0.9916, 46种SVOCs检出限为0.28~16.55 ng/L,定量限为0.92~55.16 ng/L;在0.02、0.2、0.4 μg/L 3个加标水平下的平均回收率为63.6%~125%,相对标准偏差(n=6)为1.03%~17.0%。采用该方法检测了黄河流域济南段的27个地表水样品,检出的物质以PAEs和PAHs为主,2种OCPs在部分点位有检出,NBs均未检出。该方法操作简单,通用性强,准确度及精密度良好,检出限低,适用于地表水及地下水中46种半挥发性有机物的同时检测。

Ligand-to-metal charge transfer (LMCT) complex: New approach to non-enzymatic glucose sensors based on TiO2

Titanium metal covered with titanium dioxide (Ti/TiO2) was used as a promising non-enzymatic glucose sensor demonstrating a new approach to electrochemical glucose determination. A Ti/TiO2 nanotubes-glucose complex formation on an electrode surface was demonstrated by infrared, Raman, and X-ray photoelectron spectroscopy. The main electrochemical method used for glucose detection was electrochemical impedance spectroscopy as a promising method for an easy electrochemical determination. To the best of our knowledge, this kind of sensor has never been studied especially in case of non-enzymatic glucose detection. Ti/TiO2 glucose sensor displays a wide practical linear range (1–15 mM) in a pH neutral condition, which cover the typical range in diabetic patients. The selectivity and the limit of detection were 8.3 kΩ·mM−1 and 1.2 mM, respectively. Therefore this kind of a system is very promising candidate for blood glucose sensing which should be able to replace enzymatic glucose sensors. Based on the properties of the prepared sensors, TiO2 is an unrivalled material for glucose sensing comparable with the enzymatic sensors.

Turning thiophene contaminant into polymers from wastewater by persulfate and CuO

Turning heterocyclic contaminants into polymers from industrial wastewater is a promising method that opens a new door for feasible and cost-effective treatment for aromatic wastewater. In this study, CuO shows the high reactivity in the catalytic oxidation of thiophene by persulfate (PS) under pH-neutral condition, and the observed rate constant (kobs) in the PS-CuO system is about 10 times of that in the PS-alone system at pH 7.0. The linear relationship between the consumed PS and the removed thiophene reveals that a complete removal of 1.0 mM thiophene from solution requires 1.11 mM PS in the PS-CuO system, indicating that thiophene has not been completely mineralized into CO2 and H2O. Quenching experiments and EPR analysis rule out contributions of O2•− and 1O2 to thiophene oxidation, and suggest that although both SO4•− and •OH contribute to thiophene oxidation to some extent, they are not the primary oxidants in the PS-CuO system at pH 7.0. Meanwhile, the presence of thiophene radical cation indicates that electron abstraction from thiophene is an important pathway in the oxidation. The produced thiophene radical cations are then polymerized into polymers. Solid characterizations further confirm that polythiophene S,S-dioxide is the primary oxidation product. The electrochemical analysis indicates that the produced polythiophene S,S-dioxide polymers show pseudocapacitive characteristics and can be used for capacitors.

Conjugated donor-acceptor (D-A) supramolecule catalyst for visible-light-driven photocatalytic removal of bromate in water

To guarantee drinking water security, removal of bromate (BrO3−) has garnered plenty of attention in water treatment. In current study, we have developed a novel conjugated donor-acceptor (D-A) photocatalyst (4,4′'-bis(diphenylamino)-[1,1′:4′,1′'-terphenyl]-2′,5′-dicarbaldehyde, BDTD) with supramolecule architecture assembling via intermolecular CH···O hydrogen bonds and CH···π interactions. Both diffuse reflectance spectrum (DRS) and density functional theoretical (DFT) calculations gave the bandgap of Eg = 2.21 eV, clearly indicating the visible-light response of BDTD supramolecule. The calculations showed that BDTD supramolecule could induce nearly 100% removal of BrO3− stably at pH-neutral condition driven by visible light, accounting for a first-order kinetic constant being one order of magnitude higher than most of the photocatalysts previous reported. As demonstrated by our electron scavenger experiment and DFT calculations, the BDTD supramolecule should undergo the photocatalytic reduction of BrO3− through direct reduced by the lowest unoccupied molecular orbital of conduction band (potential of −1.705 V versus standard hydrogen electrode) electron. The BDTD supramolecule may serve as an attractive photocatalyst by virtue of response to visible light, efficient charge transfer and separation as well as high photocatalytic activity, which will make the removal of BrO3− in water much easier, more economical and more sustainable.

Grasping periodic trend and rate-determining step for S-modified metals of metal sulfides deployable to produce [rad]OH via H2O2 cleavage

Iron sulfides are fascinating catalytic phases because these include S-modified Feδ+ (δ ≤ 2) species functioning as H2O2 activators to form OH used for oxidatively degrading aqueous contaminants (e.g., phenol). As an initial step for locating S-modified metal species (Mδ+) that outperform Feδ+ in catalytic H2O2 cleavage, hexagonal metal sulfides (MS) were synthesized using Mn, Fe, Co, Ni, and Cu to understand electric potential-assisted H2O2 scission kinetics on Mδ+ species. Niδ+ species were found to show the greatest OH productivity among all Mδ+ species studied, mainly resulting from the Lewis acidic nature of Niδ+ species adequate to expedite the liberation of OH species. This was partially evidenced by H2O2 activation/phenol degradation runs on Mδ+ species, wherein initial H2O2 activation rate (-rH2O2,0) or initial phenol degradation rate (-rPHENOL,0) of Niδ+ species was 3–9 times those of the other Mδ+ species. Niδ+ species, therefore, were located in the middle of the volcano-shaped curve plotting -rH2O2,0 (or -rPHENOL,0) versus the type of Mδ+. Kinetic assessment of Mδ+ species under fine-tuned reaction environments also showed that regardless of varying H2O2 concentrations, Mδ+ species were found to retain their -rH2O2,0 values in the absence of electric potentials. Conversely, Mδ+ species could enhance -rPHENOL,0 values at larger electric potentials, where greater energies were likely exerted on Mδ+ species. This indeed corroborated that OH desorption from Mδ+ species was the rate-determining step to direct catalytic H2O2 scission. In addition to heterogeneous catalytic nature of Niδ+ species in fragmenting H2O2, outstanding H2O2 scission ability provided by Niδ+ species could also compensate for their moderate catalytic stability at pH-neutral condition.

Electrochemical degradation of perfluorooctanoic acid by macro-porous titanium suboxide anode in the presence of sulfate

The present study investigated the electrochemical degradation of perfluorooctanoic acid (PFOA) by macro-porous titanium suboxide (p-TiSO) anode in the presence of sulfate at pH-neutral condition (pH 6.9 ± 0.3). Based on initial PFOA concentration of 0.1 mmol L−1, current density of 10 mA cm−2 and electrolysis of 2 h, the removal efficiencies of PFOA were 97.1% and 90.8% for Na2SO4 electrolyte (kapp = 2.1 h−1) and NaNO3 electrolyte (k = 0.84 h−1), corresponding to defluorination efficiency of 61.4% and 54.2%, respectively. The 2.3-fold enhancement of oxidation rate should be originated from the production of sulfate radicals (SO4−) by activation of sulfate via direct electron transfer with anode and indirect OH-mediated oxidation under the potential of 3.01–3.41 V versus standard hydrogen electrode (SHE). The production of OH and SO4− could be verified on a qualitative basis by using electron spin resonance (ESR) technology. Localized pH measurement achieved with a Pt/IrOx ultra-micro electrode revealed significantly lower pH inside the pores of p-TiSO anode (pH 2.6) compared to that in bulk electrolyte (pH 6.1). The formation of pH gradient should be attributed to surface interaction and diffusion restriction in the porous structure, and the resulting low pH was favorable for enhancing oxidizability of OH toward activation of bisulfate and oxidation of PFOA pollutant. This study offers a proof-in-concept demonstration of electrochemical activation of sulfate and PFOA degradation without need for chemical addition and pH adjustment, which can be realized by simply creating macro-porous structure of anode materials in electrochemical advanced oxidation process.

Stabilizing the isolated Sn2Bi nanosheet and tailoring its electronic structure by chemical functionalization: A computational study

Very recently, a two-dimensional nanomaterial, the Sn2Bi nanosheet, has been synthesized on a silicon wafer. Here, utilizing first-principles calculations, we explore the structural stability and electronic property of the free-standing Sn2Bi nanosheet. Different from the experimentally supported one, we find that the isolated Sn2Bi nanosheet is a metal and suffers from dynamical instability. Its structural stability can be greatly enhanced by surface hydrogenation, which can completely eliminate the soft modes from the high-buckled tricoordinate Sn atoms. Both the single-side and double-side hydrogenated Sn2Bi (s-/d-H-Sn2Bi) nanosheets possess robust energetic, dynamical, and thermal stabilities and exhibit a semiconducting behavior akin to the supported Sn2Bi system. In particular, the band edge of the s-H-Sn2Bi nanosheet can saddle the redox potential of water under a strong alkaline condition, and its analogue by the iodization (s-I-Sn2Bi) is even suitable for photocatalytic water splitting under the pH neutral condition. Moreover, these functionalized systems exhibit high solar-to-hydrogen efficiencies, which reach up to 18% and 36% in the s-H-Sn2Bi and s-I-Sn2Bi nanosheets, respectively. Our study demonstrates that the functionalized Sn2Bi nanosheets have robust structural stabilities and promising electronic properties for potential applications in nano-energy and nano-electrics.

Visible-light-driven photocatalytic activation of peroxymonosulfate by Cu2(OH)PO4 for effective decontamination

The advanced oxidation process (AOP) based on SO4- radicals draws an increasing interest in water and wastewater treatment. Producing SO4- radicals from the activation of peroxymonosulfate (PMS) by transition metal ions or oxides may be problematic due to high operational cost and potential secondary pollution caused by metal leaching. To address this challenge, the present study reports the efficient production of SO4- radicals through visible-light-driven photocatalytic activation (VL-PCA) of PMS by using Cu2(OH)PO4 single crystal for enhanced degradation of a typical recalcitrant organic pollutant, i.e., 2,4-dichlorophenol (2,4-DCP). It took only 7 min to achieve almost 100% removal of 2,4-DCP in the Cu2(OH)PO4/PMS system under visible-light irradiation and pH-neutral condition. The 2,4-DCP degradation was positively correlated to the amount of Cu2(OH)PO4 and PMS. Both OH and SO4- radicals were responsible for enhanced degradation performance, indicated by radical scavenger experiments and electron spin resonance (ESR) measurements. The Cu2(OH)PO4 single crystal exhibited good cyclic stability and negligible metal leaching. According to density functional theory (DFT) calculations, the visible-light-driven transformation of two copper states between trigonal bipyramidal sites and octahedral sites in the crystal structure of Cu2(OH)PO4 facilitates the generation of OH and SO4- radicals from the activation of PMS and cleavage of O-O bonds. This study provides the proof-in-concept demonstration of activation of PMS driven by visible light, making the SO4- radicals-based AOPs much easier, more economical and more sustainable in engineering applications for water and wastewater treatment.

In Situ Photochemical Activation of Sulfate for Enhanced Degradation of Organic Pollutants in Water

The advanced oxidation process (AOP) based on SO4•- radicals has been receiving growing attention in water and wastewater treatment. Producing SO4•- radicals by activation of peroxymonosulfate or persulfate faces the challenges of high operational cost and potential secondary pollution. In this study, we report the in situ photochemical activation of sulfate (i-PCAS) to produce SO4•- radicals with bismuth phosphate (BPO) serving as photocatalyst. The prepared BPO rod-like material could achieve remarkably enhanced degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of sulfate, indicated by the first-order kinetic constant (k = 0.0402 min-1) being approximately 2.1 times that in the absence (k = 0.019 min-1) at pH-neutral condition. This presented a marked contrast with commercial TiO2 (P25), the performance of which was always inhibited by sulfate. The impact of radical scavenger and electrolyte, combined with electron spin resonance (ESR) measurement, verified the formation of •OH and SO4•- radicals during i-PCAS process. According to theoretical calculations, BPO has a sufficiently high valence band potential making it thermodynamically favorable for sulfate oxidation, and weaker interaction with SO4•- radicals resulting in higher reactivity toward target organic pollutant. The concept of i-PCAS appears to be attractive for creating new photochemical systems where in situ production of SO4•- radicals can be realized by using sulfate originally existing in aqueous environment. This eliminates the need for extrinsic chemicals and pH adjustment, which makes water treatment much easier, more economical, and more sustainable.

Removal of Nitrate by Photocatalytic Denitrification Using Nonlinear Optical Material

Removal of nitrate from water has been receiving growing attention in water treatment. In this study, we report the photocatalytic denitrification (PCDN) by nonlinear optical (NLO) material, i.e. lithium niobate (LiNbO3). The hydrothermally synthesized LiNbO3 powder could achieve efficient denitrification in water, evidenced by 98.4% nitrate removal and 95.8% nitrogen selectivity at reaction time of 120 min and pH-neutral condition. Based on the first-order kinetics of PCDN, the kinetic constant for LiNbO3 is almost three times as that of conventional TiO2 (P25) under the same conditions. As suggested by the hole scavenger experiments, the LiNbO3 should proceed with photocatalytic reduction of nitrate through direct heterogeneous interaction with electrons at the conduction band of LiNbO3. This may represent a different mechanism from P25, where nitrate is mainly reduced by CO2•- radicals generated by the holes at the valence band. The unique second harmonic generation (SHG) effects of NLO materials enable them to produce more electrons and minimize the electron-hole recombination, which improves the efficiency and stability of the PCDN process. The current study provides a proof-of-concept demonstration of NLO photocatalytic material for more effective nitrate removal in water treatment.

Graphene-Supported Silver Nanoparticles for pH-Neutral Electrocatalytic Oxygen Reduction

Developing an electrocatalyst with desired activity and affordable cost for oxygen reduction reaction (ORR) of microbial fuel cell (MFC) remains a key challenge for practical application of MFC in wastewater treatment. In order to find an economic replacement of Pt-based catalysts while maintaining comparable catalytic efficiency, an electrocatalyst of graphene-supported silver nanoparticles (AgNPs/rGO) was prepared via a facile coreduction and its activity toward ORR in pH-neutral MFC was examined. It has been demonstrated that one-pot aqueous coreduction yielded high-quality AgNPs/rGO catalyst, as revealed by X-ray diffraction and transmission electron microscope. Interestingly, the XPS profiles also indicated the presence of oxygen-containing groups on graphene surface, which provided nuclei to form AgNPs. The resultant AgNPs/rGO catalyst displayed good ORR catalytic activity under pH-neutral condition in cyclic voltammogram and its selectivity of four-electron reduction was verified by rotating disk electrode (RDE) measurement. Moreover, AgNPs/rGO could deliver power generation and sustainability comparable to those of commercial Pt/C in a double-chamber MFC. Thus, we have demonstrated, for the first time, that graphene sheets may provide an alternative way for preparation of Ag nanocomposite catalyst and AgNPs when loaded onto graphene surface can function as a promising replacement of Pt-based catalysts under pH-neutral condition. Since Ag is less expensive and more resistant to poisons than Pt, AgNPs/rGO has better potential to be applied to MFC for recovering energy during wastewater treatment.

Nitrification potentials of Chinese tea orchard soils and their adjacent wasteland and forest soils

To investigate the nitrifying activities of different soil types, soil samples collected from 8-, 50- and 90-year old tea orchards, the adjacent wasteland, and 90-year old forest were measured for their nitrification potentials using the conventional soil incubation and the liquid incubation method. Among different soil types, the nitrification potential of soil in tea orchards was higher than that of wasteland and forest soils. The slurry shaken liquid incubation method was confirmed to be more accurate and have reliable results than the soil incubation. Interestingly, experimental result revealed that the generally applied pH value of 7.2 for the liquid media was not the optimal pH for these acid soils with a strong buffer capacity. This suggested that tea orchard soils may have nitrifiers requiring pH-neutral condition for the best activity. Our data also showed that treatment with the commonly used nitrogen fertilizer urea significantly improved nitrification potential of the soils; such enhancement effect was stronger on all of three tea orchard soils than on wasteland and forest soils, and also stronger on the younger (8- and 50-year old) tea orchard soils than on the older one (90-year old).

Chemical extraction of organic carbon to reduce the leaching potential risk from MSWI bottom ash

The performance of extraction solvents, including organic and inorganic solvents, for organic carbon extraction from municipal solid waste incinerator (MSWI) bottom ash was evaluated. The total carbon (TC) extracted was used to ascertain the efficiency of extraction solvents and the reduction of dissolved organic carbon (DOC) leaching potential was used to evaluate the capacity of solvents to minimize environmental impacts of MSWI bottom ash over short- and long-term considerations in landfill sites. Extract final pH value was a prominent parameter affecting TC extraction. The higher efficiency was obtained at the lower extract final pH and acid or neutral condition was necessary to achieve approximately 30% of TC extraction from bottom ash. On the basis of the results of TC extraction, the efficiency of organic carbon reduction was evaluated using organic carbon leaching potential. Hydrochloric acid was the best solvent to extract organic carbon in controlled pH conditions. Hydrochloric acid reduced the organic carbon leaching potential of MSWI bottom ash by about 68% at neutral leaching pH.

Ｅｓｃｈｅｒｉｃｈｉａ ｃｏｌｉ Ｏ１５７：Ｈ７に対するケフィールの抗菌作用

Kefir, which is a fermented milk product that was recently introduced in Japan is becaming available for widespread consumption.Because there is the effect of controlling the growth of food poisoning bacteria in acid milk, it is expected that the growth of E. coli O157: H7 in kefir can be similarly controlled. When E. coli ATCC or E. coli O157: H7 was cultivated in a pH-neutral condition, the growth of the bacterium was not influenced at all regardless of the presence of kefir. On the other hand, when E. coil ATCC or E. coli O157: H7 was cultivated in pH-acid condition, the growth of these was markedly inhibited. The growth of E. coli ATCC of 109 cfu/ml or E. coli O157: H7 of 107 cfu/ml to which kefir of pH 4 was added was especially completely inhibited in a short time.These results suggested that an antibacterial substance to the growth of E. coli ATCC or E. coli O157: H7 was existed in kefir.