汞污染农田土壤的化学稳定化修复

土壤重金属污染问题已经成为环境污染的热点问题。以FeS、Na_2S、黄铁矿、CaO、黄铁矿+CaO作为稳定剂,应用化学稳定化修复技术对贵州万山地区的2种汞污染程度不同的农田土壤(1号土、2号土)进行修复,并研究稳定剂用量、稳定时间等因素对稳定效率的影响,确定最佳稳定条件。结果显示:在FeS、Na_2S、黄铁矿、CaO、黄铁矿+CaO这5种稳定剂中Aa_2S的稳定效果最好,对2种土的稳定效率均高达90%左右;对于1号土,最佳稳定条件为:稳定剂Na_2S,稳定时间7d,稳定剂用量S:Hg=1。对于2号土,最佳稳定条件为:稳定剂Na_2S,稳定时间7 d,稳定剂用量S:Hg=5。Na_2S作为稳定剂通过改变汞在土壤中的形态分布降低污染土壤中汞的浸出毒性。

淬火合金钢中的奥氏体稳定化

研究了马氏体(M)和贝氏体(B)两相温度区等温淬火组织中的奥氏体稳定化.在一定等温时间内,奥氏体稳定化程度,即残余奥氏体量与等温温度间的关系呈马鞍型曲线.在实验钢中,其谷底值低于用同冷却介质淬火组织中的AR,表明在一定条件下等温停留并不引起残余奥氏体量增多.可利用马鞍型曲线调整AR与M及B的含量配比,获得无变形或强韧性配合最佳的准贝氏体等温淬火工艺.奥氏体稳定化为热稳定化、化学稳定化、相致稳定化和宏观热应力稳定化诸机制的综合作用.马氏体临界点Mc点无特殊物理意义.

CO_2对飞灰稳定化效果的影响

用CO2 作为化学稳定剂或辅助稳定剂处理三种不同的来自实际垃圾焚烧厂的飞灰 ,并对处理后的飞样进行浸滤实验来衡量稳定效果。结果表明二氧化碳对飞灰中所含的重金属Pb和Cd具有稳定效果 ,对飞灰中的Cr有促进溶出的效果。当以磷酸盐和绿矾为稳定剂稳定飞灰中的重金属时 ,先采用CO2 进行预处理基本不影响对Pb和Cd的稳定效果 。

垃圾焚烧飞灰双重稳定资源化的研究

为实现垃圾焚烧飞灰的无害化和资源化,先将绿矾溶液与飞灰混合后氧化稳定飞灰中的重金属,然后将处理后的飞灰与水泥混合、养护,使焚烧飞灰在双重稳定化的同时,得到的水泥砌块浸出浓度低,具有相当的强度,可以在特殊场合安全利用。还以Pb、Cd和Cr为代表,检验双重稳定化过程中一些反应条件的选用对重金属的稳定效果,并对比了双重稳定化所获得的砌块与直接水泥固化所得砌块的强度。研究结果表明,自然淡水可为化学处理介质,洗去盐分有利于重金属固化,化学稳定化后再与水泥混合获得的砌块试件强度明显提高。

新标准下垃圾焚烧飞灰化学稳定技术的比选和研究

研究了新的生活垃圾填埋场污染控制标准(GB16889-2008)实施后,飞灰要进入生活垃圾卫生填埋场时传统的重金属稳定方法可行性,并在此基础上提出了新的复合药剂稳定法.研究结果表明,已经报道的化学药剂稳定法均有必要重新检验其对重金属的稳定效果是否满足新的填埋标准的要求.绿矾与TMT-18配合使用、绿矾用量为25%(质量分数)以下、TMT-18的用量为8‰左右时完全可以使飞灰中所有重金属浸出浓度满足新的填埋标准要求,是处理二噁英含量不高于3ng.g-1(以TEQ计)飞灰的一种经济处理技术.对二噁英含量高于3ng.g-1(TEQ)的飞灰,采用绿矾辅助水热处理的方法可以稳定包括Pb、Cd在内的所有重金属和降解二噁英使之符合新填埋标准对飞灰填埋的要求.

基于AHP的飞灰处理技术综合评价

城市生活垃圾焚烧飞灰因其含有重金属、二噁英等污染物而被定义为危险固体废物,需进行特别的处理处置。目前国际上对于垃圾焚烧飞灰的处理主要采用固化与稳定化处理。采用层次分析法(AHP)建立了综合评价体系,并对四种飞灰固化与稳定化处理工艺进行比较。结果表明化学药剂稳定化优于其他三种技术,值得向相关行业推广。

城市垃圾焚烧飞灰处理方法及探讨

本文阐述了中国城市垃圾焚烧处理现状,从重金属飞灰稳定化的需求方面介绍了化学稳定化、水泥固化和熔融固化三种飞灰稳定技术。通过已有实验和应用分析了三种技术的优缺点,得出我国未来垃圾焚烧飞灰处理的发展趋势。

浅谈国内生活垃圾焚烧飞灰的处置技术

我国生活垃圾焚烧正处在快速发展时期,生活垃圾焚烧飞灰的产生量快速增长,飞灰的处置问题成为制约生活垃圾焚烧厂稳定运营的因素之一。固化稳定化填埋是目前应用较为广泛的飞灰处置技术,资源化处置尚处于工程化的早期,相关法律法规亟待出台,规范行业发展。

A Comparative Study of the Performance of Symmetric and Asymmetric Mixed-conducting Membranes

According to the configuration,mixed-conducting membranes are classified as symmetric membranes and asymmetric membranes consisting of a thin dense layer and a porous support.In this study,these two kinds of SrCo0.4Fe0.5Zr0.1O3-δ oxide-based membranes were systematically compared in terms of oxygen permeability and chemical stability,and their differences were elucidated by means of the theoretical calculation.For the oxygen permeability,the asymmetric membrane was greater than the symmetric membrane due to the significant decrease of bulk diffusion resistance in the thin dense layer of the asymmetric membrane.In regard to the chemical stability,the increase of oxygen partial pressure on the asymmetric membrane surface at CH4 side produced the stable time of over 1032h in partial oxidation of methane at 1123K,while the symmetric membrane was only of 528h.This study demonstrated that the asymmetric membrane was a promising geometrical configuration for the practical application.

Thermal properties of glass-ceramic bonded thermal barrier coating system

The thermal properties of a thermal barrier coating （TBC） system comprised of BaO-MgO-SiO_2 based glass-ceramic bond coating, 8% （mass fraction） yttria stabilized zirconia （8YSZ） top coating and nimonic alloy substrate were evaluated. The thermal diffusivity and thermal conductivity of the TBC coated substrate were lower than those of bare substrate and glass-ceramic coated substrate under identical conditions. The specific heat capacity, thermal diffusivity and thermal conductivity of the TBC coated substrate increase with the increase of the temperature. Further, it is observed that the thermal conductivity of the TBC system decreases with the increase in the top coating thickness.

Magneli phase titanium sub-oxide conductive ceramic Ti_nO_(2n-1) as support for electrocatalyst toward oxygen reduction reaction with high activity and stability

Magneli phase titanium sub-oxide conductive ceramic Tin O2n-1 was used as the support for Pt due to its excellent resistance to electrochemical oxidation, and Pt/Tin O2n-1 composites were prepared by the impregnation-reduction method. The electrochemical stability of Tin O2n-1 was investigated and the results show almost no change in the redox region after oxidation for 20 h at 1.2 V(vs NHE) in 0.5 mol/L H2SO4 aqueous solution. The catalytic activity and stability of the Pt/Tin O2n-1 toward the oxygen reduction reaction(ORR) in 0.5 mol/L H2SO4 solution were investigated through the accelerated aging tests(AAT), and the morphology of the catalysts before and after the AAT was observed by transmission electron microscopy. At the potential of 0.55 V(vs SCE), the specific kinetic current density of the ORR on the Pt/Tin O2n-1 is about 1.5 times that of the Pt/C. The LSV curves for the Pt/C shift negatively obviously with the half-wave potential shifting about 0.02 V after 8000 cycles AAT, while no obvious change takes place for the LSV curves for the Pt/Tin O2n-1. The Pt particles supported on the carbon aggregate obviously, while the morphology of the Pt supported on Tin O2n-1 remains almost unchanged, which contributes to the electrochemical surface area loss of Pt/C being about 2times that of the Pt/Tin O2n-1. The superior catalytic stability of Pt/Tin O2n-1 toward the ORR could be attributed to the excellent stability of the Tin O2n-1 and the electronic interaction between the metals and the support.

Physicochemical Features of Phosphorus-Modified ZSM-5 Zeolite and Its Performance on Catalytic Pyrolysis to Produce Ethylene

The physicochemical features of phosphorus-modified ZSM-5 zeolites (SiO2/Al2O3 molar ratio is 25) were characterized by XRD(X-ray diffraction), BET(Brunauer, Emmett and Teller spcific surface area measurement), NH3-TPD(ammonia temperature-programmed desorption) and MASNMR(magic angle spinning nuclear magnetic resonance), and the performance on catalytic pyrolysis to produce ethylene was investigated with a light hydrocarbon fixed bed micro-reactor with n-octane as feed. The results show that the acid site density, acid intensity and hydrothermal stability of ZSM-5 zeolite were improved by phosphorus modification. When P2O5 content in ZSM-5 zeolite is higher than 2.5%, phosphorus modification can prevent ZSM-5 zeolite crystal structure transformation from orthorhombic to monoclinic. In addition, the dealumination of ZSM-5 zeolite framework was moderated by phosphorus modification under high temperature hydrothermal treatment. The results of n-octane pyrolysis on phosphorus-modified ZSM-5 zeolites show that ethylene yields of zeolites with different phosphorus content are almost the same under the same n-octane conversion. However, the modified zeolites with higher pyrolysis activity give lower yield of propene, butene and total olefin than lower pyrolysis activity under the same n-octane conversion.

Synthesis of Cu nanoparticles by chemical reduction method

Cu nanoparticles (CuNPs) have been synthesized through an easy route by chemical reduction at room temperature. The Cu^2+ ions were reduced and stabilized with sodium borohydride and polyvinylpyrrolidone, respectively. The effect of the variation of the reducing agent/precursor-salt (RA/PS) ratio on the size and morphology of the CuNPs was evaluated. The synthesized material was studied by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The UV-Vis spectra showed a CuNPs plasmon peak at 569 nm and another peak belonging to Cu2O at 485 nm. XRD analysis showed the fcc-Cu phase with a small amount of fcc-Cu2O compound. SEM and TEM studies displayed that small semispherical CuNPs of approximately 7 nm were obtained at the RA/PS ratio of 2.6. The excess of polyvinylpyrrolidone stabilizer played an essential role in preventing CuNPs oxidation. On the other side, Cu2O polyhedral particles with larger sizes up to 150 nm were identified in the RA/PS ratio range of 2.0-1.84. In addition, Cu2O particles having star morphologies with quantum confinement at their tips were obtained at the RA/PS ratio of 1.66.

Insight into the degradation mechanism of cefixime under crystallization condition

The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives. The degradation process follows the first-order kinetics. A pH-rate profile exhibits the U-shape and shows the maximum stability of cefixime at pH = 6. The stability in different pure solvents is ranked as acetone 〉 ethanol 〉 methanol 〉 water, while the degradation rate of cefixime exists a maximum at the ratio of 0.6 in water ＋ methanol mixtures. In addition, the degradation rate increases with the temperature increasing and the activation energy of degradation was found to be 27.078 kJ. mol- 1 in acetone ＋ water mixed solvents. The addition of different additives was proven to either inhibit or accelerate the degradation. The degradation products were analyzed using HPLC, LC-MS and infrared spectroscopy, and the possible degradation pathways in acid as well as alkaline environment were proposed to help us understand the degradation behavior of cefixime.

Estimation of Formation Enthalpies of Organic Pollutants from a New Structural Group Contribution Method

Chemical stability and reactivity of organic pollutants is dependent to their formation enthalpies. The main objective of this study is to provide simple straightforward strategy for prediction of the formation enthalpies of wide range organic pollutants only from their structural functional groups. Using such an extended dataset cornprising 1694 organic chemicals from 77 diverse material classes benefits the generalizability and reliability of the study. The new suggested collection of 12 functional groups and a simple linear regression lead to promising statis- tics of R2= 0.958, Q2 =0.956, and AEE= 57 kJ.mo1-1 for the whole dataset. Moreover, unknown experimental formation enthalpies for 27 organic pollutants are estimated by the presented approach. The resultant model needs no technical software/calculations, and thus can be easily applied by a non-specialist user.

Overcoming coke formation in high-temperature CO_(2)electrolysis

High-temperature CO_(2)reduction reaction(HT-CO_(2)RR)in solid oxide electrochemical cells(SOECs)features near-unity selectivity,high energy efficiency,and industrial relevant current density for the production of CO,a widely-utilized“building block”in today’s chemical industry.Thus,it offers an intriguing and promising means to radically change the way of chemical manufacturing and achieve carbon neutrality using renewable energy sources,CO_(2),and water.Albeit with the great potential of HT-CO_(2)RR,this carbon utilization approach,unfortunately,has been suffering coke formation that is seriously detrimental to its energy efficiency and operating lifetime.In recent years,much effort has been added to understanding the mechanism of coke formation,managing reaction conditions to mitigate coke formation,and devising coke-formation-free electrode materials.These investigations have substantially advanced the HT-CO_(2)RR toward a practical industrial technology,but the resulting coke formation prevention strategies compromise activity and energy efficiency.Future research may target exploiting the control over both catalyst design and system design to gain selectivity,energy efficiency,and stability synchronously.Therefore,this perspective overviews the progress of research on coke formation in HT-CO_(2)RR,and elaborates on possible future directions that may accelerate its practical implementation at a large scale.

Synthesis and ionic conductivity of Li_6La_3BiSnO_(12) with cubic garnet-type structure via solid-state reaction

The synthesis and transport properties of the Li6La3BiSnO1212 solid electrolyte by a solid-state reaction were reported. The condition to synthesize the Li6La3BiSnO1212 is 785 °C for 36 h in air. The refined lattice constant of Li6La3 BiSnO1212 is 13.007A. Qualitative phase analysis by X-ray powder diffraction patterns combined with the Rietveld method reveals garnet type compounds as major phases. The Li-ion conductivity of the prepared Li6La3BiSnO12 is 0.85×10^-4 S/cm at 22 °C, which is comparable with that of the Li5La3Bi2O12. The Li6La3BiSnO1212 compounds are chemically stable against Li CoO2 which is widely used as cathode material up to 700 °C but not against the Li Mn2O4 if the temperature is higher than 550 °C. The Li6La3 BiSnO1212 exhibits higher chemical stability than Li5La3Bi2O12, which is due to Sn substitution for Bi.

Green Synthesis of RuO2 Electrode for Electrochemical Water Treatment

Nowadays, the electrochemical water treatments are very important methods used for the removal of organic and inorganic impurities from fresh, drinking water and wastewater. The method consists of carrying out the oxidation reaction at the anode where pollutants are transferred into non-toxic substances, by decomposing into simpler compounds or transferring into oxidation form. RuO2-based Dimensional Stable Anode （DSA） is a technologically good and important electrode for water treatment because of its unique characteristics such as high thermal and chemical stability, low resistivity and low overpotential. This paper reviews the methods for fabricating RuO2-based electrodes that can be used in electrochemical water treatment. Depending on the different fabrication routes, RuO2 electrodes will possess the different electro-catalytic property and stability.

六安市某六价铬污染场地修复工程实践

以污染地块修复项目为依托,综合场地特性和污染特征,进行修复技术筛选,确定以“化学还原稳定化+固化技术”对Cr(Ⅵ)污染土壤进行修复,对总铬污染土壤进行风险管控;通过小试和中试试验,获得最佳修复药剂组成和添加比例。结果表明:六价铬污染土壤经化学还原稳定化+固化技术处理,土壤样品中Cr(Ⅵ)的浸出浓度低于修复目标值,达到修复方案要求,为污染土壤修复工程的有效实施提供参考。

Microaerobic iron oxidation and carbon assimilation and associated microbial community in paddy soil

Iron oxidation is a prevalent and important biogeochemical process in paddy soil,but little is known about whether and how microbially mediated iron oxidation is coupled with carbon assimilation,particularly under microaerobic conditions.Here,we investigated kinetics of CO_2 assimilation and Fe(Ⅱ)oxidation in an incubation experiment with paddy soil under suboxic conditions,and profiled the associated microbial community using DNA-stable isotope probing and 16S r RNA gene-based sequencing.The results showed that CO_2 assimilation and Fe(II)oxidation in the gradient tubes were predominantly mediated by the microbes enriched in the paddy soil,primarily Azospirillum and Magnetospirillum,as their relative abundances were higher in the^( 13)C heavy fractions compared to^( 12)C heavy fractions.This study provided direct evidence of chemoautotrophic microaerophiles linking iron oxidation and carbon assimilation at the oxic–anoxic interface in the paddy soil ecosystem.