铜锰基整体式催化剂对烧结烟气CO净化特性

基于改性铜锰氧化物作为CO催化活性组分,分别制备了催化剂原粉、以泡沫金属、堇青石为载体的两种整体式催化剂,在实验室配气条件下对比了3种样品的CO催化效率及稳定性,优选了堇青石整体式催化剂,并在某钢厂实际烧结烟气条件下测试了其在不同催化剂负载量、空速、温度下的CO催化效率、稳定性以及衰减后样品催化特性;最后批量制备了2m³优选整体式催化剂并开展了6000m³/h烧结烟气CO净化中试实验.结果表明,烟气高浓水蒸气显著抑制CO催化反应,经240h催化后T₉₀最大提升38℃;催化剂负载量越高,T₉₀越低,催化效率衰减时间越短,稳定后的效率越高,但随着空速增加,该优势减小;1440h(2个月)中试实验中,进气温度185~195℃下,CO催化效率大于85%(平均90%),出口CO浓度低于1000×10^-6,出口平均烟温达220℃,具有节能减排双重效益.     

The combined toxicity and mechanism of multi-walled carbon nanotubes and nano copper oxide toward freshwater algae: Tetradesmus obliquus

Nanoparticles(NPs) are widely used for their special physical properties and released into the natural environment. When two types of NPs exist in the same environment, the presence of one type of NP may affect the properties of the other type of NP. This study investigated the toxic effects of multi-walled carbon nanotubes(MWCNTs) and copper oxide nanoparticles(Cu O NPs) on Tetradesmus obliquus. Both NPs had toxic effects on algae, and the toxic effects of MWCNTs were significantly stronger tha...     

Effects of cobalt doping on the reactivity of hausmannite for As(III) oxidation and As(V) adsorption

Hausmannite is a common low valence Mn oxide mineral, with a distorted spinel structure, in surficial sediments. Although natural Mn oxides often contain various impurities of transitional metals (TMs), few studies have addressed the effect and related mechanism of TM doping on the reactivity of hausmannite with metal pollutants. Here, the reactivity of cobalt (Co) doped hausmannite with aqueous As(III) and As(V) was studied. Co doping decreased the point of zero charge of hausmannite and its adsorption capacity for As(V). Despite a reduction of the initial As(III) oxidation rate, Co-doped hausmannite could effectively oxidize As(III) to As(V), followed by the adsorption and fixation of a large amount of As(V) on the mineral surface. Arsenic K-edge EXAFS analysis of the samples after As(V) adsorption and As(III) oxidation revealed that only As(V) was adsorbed on the mineral surface, with an average As-Mn distance of 3.25–3.30 Å, indicating the formation of bidentate binuclear complexes. These results provide new insights into the interaction mechanism between TMs and low valence Mn oxides and their effect on the geochemical behaviors of metal pollutants.     

基于神经网络模型绿色合成纳米氧化锰及其性能研究

近年来,基于对纳米材料生物毒性和合成成本的考虑,纳米材料的绿色合成和应用在环境领域受到了广泛关注,但迄今仍面临纳米材料的绿色合成机制尚未明确及去除效率不理想两个问题.本研究选择As（III）和As（V）作为目标污染物,通过神经网络模型对纳米氧化锰（MONPs）的合成条件进行优化,发现当污染物浓度和材料投加量分别为0.1 mg?L^-1和5 mg?L^-1时,优化后的MONPs对As（III）和As（V）的去除 效率分别从43.9%、80.0%提高到90.2%、92.2%.从SEM的结果中发现优化后的材料粒径更小,根据EDS和FTIR结果,可以证明优化后材料中的Mn元素比例显著增加.另外,XRD和XPS结果则证明优化后材料从原来的Mn（II）变为Mn（IV）,提高了材料的氧化能力.Zeta电位结果表明优化后材料表面的负电荷减少,进而循环伏安法结果证实了材料电子转移能力的提高,均有利于As的去除.最后,优化后MONPs在经过5次重复利用后仍具高的性能,同时对多种重金属具有一定的吸附能力.显然,基于神经网络模型绿色合成氧化锰纳米材料对砷污染修复具有 较强的针对性和实用性.     

铁锰基整体式催化剂催化燃烧甲苯和氯苯性能

对比了3种不同合成方法(等体积浸渍法、超声辅助浸渍法、氧化还原沉淀法)制备的铁锰复合过渡金属氧化物负载堇青石整体式催化剂,通过BET、SEM、XRD、H₂-TPR、XPS等表征手段分析了催化剂物理结构和化学性质.结果表明,氧化还原沉淀法负载的铁锰氧化物具有独特的片层状结构,暴露出较大的比表面积和较多的活性位点,其表面氧物种还原温度更低、Mn⁴⁺含量更高,增强了其催化燃烧性能.该催化剂对甲苯和氯苯表现出优异的催化性能,T₅₀分别为200℃和261℃,T₉₀分别为270℃和320℃,其热稳定性及耐久性也表现良好.     

Preparation of a metal-phosphate/chromium oxide nanocomposite from Cr(III)-containing electroplating sludge and its optical properties as a nanopigment

A nanocomposite composed of metal-phosphates and chromium oxide was prepared from a Cr(III)-containing electroplating sludge (CES) by a facile three-step (extraction–precipitation–calcination) process. Optimal process parameters were determined, and the structure of the metal-phosphate/chromium oxide nanocomposite (MPCON) was investigated by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results show that the optimal extraction pH is 2.0. The MPCON presents a polyhedral morphology with average particle size of around 100 nm. The components of MPCON vary from AlPO₄/Cr₂O₃ to Mg₃(PO₄)₂/AlPO₄/Cr₂O₃ at different solution pH during precipitation. Meanwhile, the optical performance of the nanocomposite as a pigment is discussed. The reflectance of MPCON-6.5 in the near-infrared range is around 56%, making it a strong prospect to be used as a functional pigment in energy-efficient buildings. This study proposes a novel recycling process for the conversion of CES into high-value products, which is beneficial for the treatment of waste.     

Differences in the Spatial Variability Among CO2, CH4, and N2O Gas Fluxes from an Urban Forest Soil in Japan

The spatial variability of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) fluxes from forest soil with high nitrogen (N) deposition was investigated at a rolling hill region in Japan. Gas fluxes were measured on July 25th and December 5th, 2008 at 100 points within a 100 × 100 m grid. Slope direction and position influenced soil characteristics and site-specific emissions were found. The CO₂ flux showed no topological difference in July, but was significantly lower in December for north-slope with coniferous trees. Spatial dependency of CH₄ fluxes was stronger than that of CO₂ or N₂O and showed a significantly higher uptake in hill top, and emissions in the valley indicating strong influence of water status. N₂O fluxes showed no spatial dependency and exhibited high hot spots at different topology in July and December. The high N deposition led to high N₂O fluxes and emphasized the spatial variability.     

Instream Large Wood: Denitrification Hotspots with Low N2O Production

We examined the effect of instream large wood on denitrification capacity in two contrasting, lower order streams — one that drains an agricultural watershed with no riparian forest and minimal stores of instream large wood and another that drains a forested watershed with an extensive riparian forest and abundant instream large wood. We incubated two types of wood substrates (fresh wood blocks and extant streambed wood) and an artificial stone substrate for nine weeks in each stream. After in situ incubation, we collected the substrates and their attached biofilms and established laboratory‐based mesocosm assays with stream water amended with ¹⁵N‐labeled nitrate‐N. Wood substrates at the forested site had significantly higher denitrification than wood substrates from the agricultural site and artificial stone substrates from either site. Nitrate‐N removal rates were markedly higher on woody substrates compared to artificial stones at both sites. Nitrate‐N removal rates were significantly correlated with biofilm biomass. Denitrification capacity accounted for only a portion of nitrate‐N removal observed within the mesocosms in both the wood controls and instream substrates. N₂ accounted for 99.7% of total denitrification. Restoration practices that generate large wood in streams should be encouraged for N removal and do not appear to generate high risks of instream N₂O generation.     

Ce-promoted Mn/ZSM-5 catalysts for highly efficient decomposition of ozone

Manganese oxides supported by ZSM-5 zeolite (Mn/ZSM-5) as well as their further modified by Ce promoter were achieved by simple impregnation method for ozone catalytic decomposition. The yCe20Mn/ZSM-5–81 catalyst with 8% Ce loading showed the highest catalytic activity at relative humidity of 50% and a space velocity of 360 L/(g × hr), giving 93% conversion of 600 ppm O₃ after 5 hr. Moreover, this sample still maintained highly activity and stability in humid air with 50%–70% relative humidity. Series of physicochemical characterization including X-ray diffraction, temperature-programmed technology (NH₃-TPD and H₂-TPR), X-ray photoelectron spectroscopy and oxygen isotopic exchange were introduced to disclose the structure-performance relationship. The results indicated that moderate Si/Al ratio (81) of zeolite support was beneficial for ozone decomposition owing to the synergies of acidity and hydrophobicity. Furthermore, compared with 20Mn/ZSM-5-81, Ce doping could enhance the amount of low valance manganese (such as Mn²⁺ and Mn³⁺). Besides, the Ce³⁺/Ce⁴⁺ ratio of 8Ce20Mn/ZSM-5-81 sample was higher than that of 4Ce20Mn/ZSM-5-81. Additionally, the synergy between the MnO_x and CeO₂ could easily transfer electron via the redox cycle, thus resulting in an increased reducibility at low temperatures and high concentration of surface oxygen. This study provides important insights to the utilization of porous zeolite with high surface area to disperse active component of manganese for ozone decomposition.     

化学还原氧化石墨烯修饰PbO2电极及催化降解酸性红G

为了提高Ti/PbO₂电极的稳定性与催化氧化能力,将化学还原氧化石墨烯（RGO）以共沉积的方法修饰于β-PbO₂层.通过扫描电镜（SEM）,X射线衍射仪（XRD）,循环伏安法（CV）,电化学交流阻抗（EIS）,产羟基自由基（·OH）能力,强化寿命等测试方法对电极性能进行表征,并以酸性红G（ARG）为目标降解物,评估PbO₂-RGO电极的催化效果.结果表明,电极经RGO改性后晶型仍为β-PbO₂,析氧过电位由1.60V升至1.83V,膜阻抗由144 Ω/cm²降至16.2 Ω/cm²,强化寿命提升了43.6%.通过ARG降解实验表明,改性后的PbO₂-RGO电极催化性能均有所提高,其中PbO₂-RGO（0.05）电极具有最优的催化能力,120min内对ARG的脱色率可达到98.5%,同时对COD的去除率可达76.89%.