以甲醇为碳源生物反硝化过程释放一氧化二氮的试验研究

污水生物反硝化脱氮过程是一氧化二氮(N2O)的重要释放源之一.试验采用序批式反应器以甲醇为碳源(电子供体),硝酸盐(NO3--N)为电子受体驯化反硝化菌,并采用批处理试验研究不同电子受体、不同碳氮(C/N)比和不同初始亚硝酸盐(NO2--N)质量浓度条件下N2O释放情况.在典型周期试验和批处理试验中均能检测到N2O的释放.以NO2--N为电子受体时会释放较多的N2O,而以NO3--N为电子受体时释放的N2O相对较少.不同C/N比通过影响反硝化菌的活性进而影响N2O的释放,反硝化菌的活性和N2O的释放量均随着C/N比的降低而降低.N2O的释放量随着初始NO2--N质量浓度的增加而增加,一定浓度范围内的NO2--N会增强反硝化菌的活性.初始NO2--N质量浓度与N2O的释放量具有较好的指数相关性.     

猫跳河流域梯级水库夏季N2O的产生与释放机理

为了研究河流筑坝对河流氮生物地球化学循环的影响，在夏季水体分层期间对猫跳河梯级水库坝前分层采集水样进行了相关地球化学分析。结果显示，在上游的两座水库存在2个明显的温度分层现象，并影响到了水体N2O的产生和分布。红枫水库整个剖面的氮分布主要受硝化作用控制，而百花湖、修文及红岩水库则表现为上层水体为硝化作用，中层为硝化反硝化共同作用。所有水库表层水和下泄水高饱和度的N2O含量表明这些水体为大气N2O的源。百花湖底层反硝化作用强烈，中间产物N2O大量消耗。底层泄水的方式对于温室气体释放影响重大，因此不同水库下泄水的N2O含量在时间和空间上的变化与水库运行和调蓄模式有关。研究结果表明，梯级水库过程对N2O的排放影响很大，在水电开发的环境保护中应当引起重视。     

Oxidation of antimony (III) in soil by manganese (IV) oxide using X-ray absorption fine structure

The oxidation of antimony (III) in soils was studied using X-ray absorption fine structure (XAFS) spectra. An andosol soil sample and artificial soil samples (SiO₂ blended with iron (III) hydroxide and manganese (IV) oxide) were used herein. After adding antimony (III) oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe K-edge, and Mn K-edge. The results indicated that manganese (IV) oxide played an important role in the oxidation of Sb(III); however iron (III) hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure (XANES) measurement with an interval of 1 min of one of the artificial soil samples (SiO₂ + MnO₂ + Sb₂O₃), a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ± 0.04 hr^? 1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn(IV) in natural soils, the oxidation process of Sb(III) might be relatively slow and require more time to convert Sb(III) to Sb(V).     

ZnO-NPs对好氧反硝化细菌Zobellella sp. B307的致毒机制

本文以一株筛自胶州湾沉积物中的好氧反硝化细菌Zobellella sp.B307为研究对象，在短期暴露条件下，通过细菌的生长、脱氮能力，相关酶活以及代谢途径等指标的变化，研究纳米氧化锌（ZnO-NPs）对该菌株的毒性效应；结合锌离子溶出试验、CAT和ROS等氧化应激水平测定，探讨ZnO-NPs对该菌株的致毒机制.结果表明，200mg/L的ZnO-NPs会使菌株硝酸盐氮去除率降至57.53%，LDH升高至对照组的378%，ROS水平高达对照组的5.34倍，SOD活性比对照组升高了60.32%，NIR活性仅为对照组的14.46%；ZnO-NPs主要通过诱导菌株活性氧的生成使其膜通透性改变、相关酶活性下降，并使相关蛋白质、氨基酸的合成及基因表达等代谢通路受到影响，进而抑制该菌株的反硝化能力；游离锌离子的产生可能不是ZnO-NPs对菌株的主要致毒途径.     

改性环氧有机涂层的电偶腐蚀行为模拟分析

目的 实现二氧化钛-还原氧化石墨烯改性环氧防腐涂层在海洋工程应用下的电偶腐蚀行为分析。方法 以还原氧化石墨烯、二氧化钛为纳米填料,制备改性环氧防腐涂层,并以此涂层为模型,利用有限元计算软件,研究改性环氧涂层存在微观缺陷情况下,涂层抑制金属电偶腐蚀的作用规律。结果 改性环氧涂层可以有效抑制金属电偶腐蚀问题。计算研究了缺陷涂层在不同孔洞宽度和分布状态下,涂层对电偶腐蚀的抑制程度。当缺陷涂层孔洞宽度为500 μm,阴阳面积比为2︰1时,电位差最小为1.05×10^–6 V,可以有效抑制电偶腐蚀。结论 二氧化钛-还原氧化石墨烯的添加,可以填补涂层空隙,阻碍水渗透,有效提高环氧涂层的防腐性能。利用有限元模拟计算可得,涂层破损时会发生局部严重腐蚀,最终造成工程结构的失效。     

Effect of precipitation pH and coexisting magnesium ion on phosphate adsorption onto hydrous zirconium oxide

To understand the effect of precipitation pH and coexisting Mg~(2+) on phosphate adsorption onto zirconium oxide(ZrO_2), ZrO_2 particles precipitated at pH 5.3, 7.1 and 10.5, i.e., ZrO_2(5.3), ZrO_2(7.1)and ZrO_2(10.5), respectively were prepared and characterized, then their adsorption performance and mechanism in the absence and presence of Mg~(2+) were comparatively investigated in this study. The results showed that the Elovich, pseudo-second-order and Langmuir isotherm models correlated with the experimental data well. The adsorption mechanism involved the complexation between phosphate and zirconium. Coexisting Mg~(2+) slightly inhibited the adsorption of phosphate on ZrO_2(5.3), including the adsorption capacity and rate, but coexisting Mg~(2+) greatly increased the adsorption capacity and rate for ZrO_2(7.1)and ZrO_2(10.5). The enhanced adsorption of phosphate on ZrO_2(7.1) and ZrO_2(10.5) in the presence of Mg~(2+) was mainly due to the formation of Mg~(2+)-HPO_4~(2-) ion pair(MgHPO_4~0) in the solution and then the adsorption of MgHPO_4~0 on the adsorbent surface, forming the phosphatebridged ternary complex Zr(OPO_3H)Mg. In the absence of Mg~(2+) , the maximum phosphate adsorption capacity at pH 7 calculated from the Langmuir isotherm model decreased in the order of ZrO 2(7.1)(67.3 mg/g) ZrO_2(5.3)(53.6 mg/g) ≈ ZrO_2(10.5)(53.1 mg/g), but it followed the order of Zr O2(7.1)(97.0 mg/g) ZrO_2(10.5)(79.7 mg/g) ZrO_2(5.3)(51.3 mg/g) in the presence of Mg~(2+) . The results of this work suggest that ZrO_2(7.1) is more suitable for use as an adsorbent for the effective removal of phosphate from municipal wastewater than ZrO_2(5.3) and ZrO_2(10.5),because Mg~(2+) is generally present in this wastewater.     

Nano CuO/g-C3N4 sheets-based ultrafiltration membrane with enhanced interfacial affinity, antifouling and protein separation performances for water treatment application

To improve the interfacial affinity and antifouling properties of polyphenylsulfone(PPSU)membrane, nano CuO/g-C3 N4(g-CN) sheets were synthesized via facile calcination route as one pot synthesis method. The uniformly assembled nanohybrid fillers, CuO on g-CN sheets were confirmed by using XRD, TEM, EDX and FTIR analysis. The non-solvent induced phase inversion technique was used to fabricate the nanohybrid ultrafiltration(UF)membranes by doping different concentration(0.5–1 wt.%) of nano CuO/g-C_3 N_4(g-CN)sheets within the PPSU matrix. The results of contact angle, atomic force microscopy,energy-dispersive X-ray spectroscopy reveal that surface structure and physico-chemical properties of nanohybrid membrane plays lead role in solute interaction and rejection compared to bare membrane, M0. Furthermore, the interfacial affinity of membrane was explored in detail via surface free energy, spreading coefficient, wetting tension and reversible work of adhesion analysis. Nanohybrid UF membrane, with 0.5% of the filler(M1)displayed remarkable permeation flux of 202, 131 L/m2/hr for pure water and protein solution, respectively while maintaining a high protein rejection(96%). Moreover, the exceptional dispersion of the nanosheets in the polymer matrix enhanced FRR(79%) and decreased the overall resistance of M1 compared to the pristine membrane(M0). Overall results suggest that the incorporation of nano sheets is a facile modification technique which improves the comprehensive membrane performance and holds a great potential to be further explored for water treatment.     

Microwave mediated synthesis and characterization of CeO2-GO hybrid composite for removal of chromium ions and its antibacterial efficiency

A facile fabrication and processing of cerium oxide-graphene oxide(CeO_2-GO) hybrid nanocomposites without the use of any surfactant or any organic solvents using chemical method and treatment with microwave irradiation technique are reported. In-situ hexagonal nano cerium oxide particles embedded on the layered surface of GO sheets were investigated for the photodegradation of dyes, removal of chromium Cr(VI) ions and against antibacterial studies. The results imply that hybrid nanocomposites shows enhanced 5-folds of photocatalytic activities in UV(ultraviolet) light irradiation and exhibited rapid efficiency in the elimination of chromium ion better than the pure GO and CeO_2, which are inhibited by competent photosensitive electron inoculation and controlling the electron–hole recombination. The synergetic effect of CeO_2-GO composites played a vital role in showing better results against model bacterium than GO and CeO_2 are due to higher physical interaction endorsed to the stress of membranes acute by piercing edges,large surface area, and higher adsorptive conditions of graphene oxide sheets tailored with ceria particles. The amount of charge transferred at the interface increases with the concentration of O atoms, demonstrating the interaction between CeO_2 and GO is much stronger than CeO_2 and GO are due to the decrease of the average equilibrium distance between the interfaces. The CeO_2-GO interface staggered band alignments existing between the CeO_2 surfaces and GO which shows an excellent synergism. The structure and morphology of composites were tested by X-ray diffraction(XRD), Fourier transform infrared(FTIR), Raman, X-ray photoelectron spectroscopy(XPS), and high-resolution transmission electron microscope(HR-TEM).     

活性污泥中一氧化氮还原酶的提取和测定优化

通过正交实验,研究了超声破碎法和低温高压破碎法提取一氧化氮还原酶（nitric oxide reductase,nor）的活性,分析了超声强度和次数,破碎压力和次数,裂解液的添加量等因素对于胞内可溶性蛋白和核酸（DNA）的释放与提取nor活性的影响.根据活性污泥中酶的催化特性以及其他实验条件,完善了nor催化活性的测定方法.结果表明超声法提取nor的参数应设定为,超声次数为100次,超声强度为500W,裂解液的添加量为0.1mL.低温高压破碎法提取nor的参数应设定为破碎次数为4次,破碎压力为50MPa,裂解液的添加量为0.1mL.低温高压破碎法下的胞内可溶性蛋白和DNA的释放量与nor的最大催化活性要高于超声破碎法.此外,在nor催化活性的测定方法中,nor活性测定终点时间应为15min.