焦化厂SCR脱硝催化剂积碳失活研究

以焦化厂烟气脱硫前脱硝中失活的板式选择性催化还原(selective catalytic reduction,SCR)催化剂为研究对象,采用比表面及孔径分布分析仪、元素分析仪、热重∕差示扫描量热分析(TG∕DSC)、X射线光电子能谱(XPS)对失活催化剂进行表征,并对未经焙烧和经焙烧处理的失活催化剂的脱硝性能进行测试。结果表明:相较新鲜催化剂,失活催化剂比表面积和孔容大幅下降;失活催化剂表层吸附了大量的硫酸氢铵(NH₄HSO₄)∕硫酸铵〔(NH₄)₂SO₄〕和积碳,其中积碳以单质碳(C)形式存在,C浓度达0.87%;350 ℃焙烧可清除失活催化剂表面附着的NH₄HSO₄,使催化剂活性得到小幅度的恢复,400~500 ℃焙烧使积碳氧化生成二氧化碳从催化剂表面脱离,从而使催化剂活性得到大幅度的恢复;积碳是导致SCR脱硝催化剂失活的主要原因,可在脱硝前设置布袋除尘器,捕集烟气中的焦油积碳等有害物质,以降低积碳对SCR脱硝催化剂的有害作用。     

Folding and association of oligomeric enzymes

The spontaneous structure formation of oligomeric enzymes consists of the consecutive ‘folding’ and association of the constituent polypeptide chains. Whether catalytic function is an intrinsic property of the folded monomers may be determined using kinetic reconstitution experiments. It is shown that full activity requires association; the correct assembly of subunits depends on their proper folding. The native structure is determined as the kinetically accessible state of lowest free energy.     

1000MW燃煤电厂商业SCR脱硝催化剂的失活

以浙江某燃煤电厂1000MW商业SCR脱硝催化剂为研究对象,通过催化表征和活性评价综合分析该电厂1000MW商业SCR脱硝催化剂的失活原因.研究表明,催化剂的失活是多种因素共同作用的结果,（1） Fe,S,K和As元素中毒,其元素含量较新鲜催化剂分别增加了318.0%,233.3%,199.3%和99.8%;（2）催化剂表面孔道的飞灰堵塞,硫酸盐类沉积以及长时间高温反应造成催化剂的烧结和颗粒物的团聚,导致失活SCR脱硝催化剂比表面积较新鲜催化剂下降了20.3%;（3）活性组分V的价态变化造成V⁴⁺/V⁵⁺的比值由6.46下降至1.35,以及Lewis酸位点减少了34.2%,从而导致催化剂的失活.     

Performance and microbial response during the fast reactivation of Anammox system by hydrodynamic stress control

Anaerobic ammonium oxidation （Anammox） has become a promising method for biological nitrogen removal. However, this biotechnology application is always limited due to the low growth rate and biomass yield of Anammox bacteria. This study investigated the process of fast reactivation of an Anammox consortium idled for 2 years uia hydrodynamic stress control. The results showed that the Anammox system was efficiently and quickly reactivated by shortening of the hydraulic retention time （I-IRT） of the reactor from 12 to 6 hr within 68 days of operation. Moreover, at a 4-hr HRT with an influent total nitrogen loading rate of 1.2 kg N/（m3.day）, the reactor maintained high biological performance with an ammonium removal loading rate of 0.52 kg N/（m3.day） and a nitrite removal rate of 0.59 kg N/（m3.day）. In the reactivated Anammox reaction, the stoichiometric coefficients of NH4-N to NOE-N and NH4-N to NO4-N were 1：1.04± 0.08 and 1：0.31 ± 0.03, respectively. The specific Anammox activity and hydrazine oxidoreductase activity, both of which represent the degree of Anammox bacteria present, increased as the hydrodynamic stress increased and were maximally （125.38 ± 3.01 mg N/（g VSS.day） and 339.42 ± 6.83 μmol/（min.g VSS）, respectively） at 4-hr HRT. Microbial response analysis showed that the dominant microbial community was obviously shifted and the dominance of Anammox bacteria was enhanced durinR the hydrodynamic selection.     

Evaluation of maternal serum dimeric inhibin a as a first-trimester marker of down's syndrome

While second-trimester prenatal screening programmes for Down's syndrome have become established in prenatal care, it would be advantageous to be able to offer screening in earlier preganancy. To this end, we have evaluated a new potential maternal serum marker, dimeric inhibin A, as a possible first-trimester marker. Dimeric inhibin A was measured in propsectively collected maternal serum from 23 cases of Down's syndrome and matched chromosomally normal controls, at 11–13 weeks' gestation. Levels of this protein were significantly elevated in the Down's pregnancies compared with the control pregnancies. The median multiple of the normal median (MOM) for the Down's samples was 2.46 (95 per cent confidence interval: 2.11–3.26, P<0.0001 vs. controls). These results suggest that dimeric inhibin A is a useful discriminator of Down's-affected pregnancies from normal pregnancies in the first trimester and that sensitive screening in combination with maternal age and other possible markers may be practicable in the first trimester.     

Variations in surface functional groups, carbon chemical state and graphitization degree during thermal deactivation of diesel soot particles

The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters (DPFs). This work focused on the changes in the surface functional groups, carbon chemical state, and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600°C, 800°C, and 1000°C and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer (TGA-GC/MS). The surface functional groups and carbon chemical state were characterized using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The graphitization degree was evaluated by means of Raman spectroscopy (RS). The concentrations of aliphatic C–H, C–OH, C=O, and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature, while the sp²/sp³ hybridized ratio and graphitization degree enhance. These results provide comprehensive evidence of the decreased reactivity of soot samples. Among oxygenated functional groups, the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability. TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000°C thermal treatment of diesel soot.     

UV light tolerance and reactivation potential of tetracycline-resistant bacteria from secondary effluents of a wastewater treatment plant

Tetracycline-resistant bacteria (TRB) are of concern as emerging microbial contaminants in reclaimed water. To understand the effects of UV disinfection on TRB, both inactivation and reactivation profiles of TRB, as well as 16 tetracycline-resistant isolates from secondary effluent, were characterized in this study. The inactivation ratio of TRB was significantly lower (3.0-log) than that of heterotrophic bacteria (> 4.0-log) in the secondary effluent. Additionally, the proportion of TRB significantly increased from 1.65% to 15.51% under 20 mJ/cm² ultraviolet (UV) exposure. The inactivation rates of tetracycline-resistant isolates ranged from 0.57/s to 1.04/s, of which tetracycline-resistant Enterobacter-1 was the most tolerant to UV light. The reactivation of TRB, tetracycline-resistant isolated strains, as well as heterotrophic bacteria commonly occurred in the secondary effluent even after 20 mJ/cm² UV exposure. The colony forming ability of TRB and heterotrophic bacteria reached 3.2-log and 3.0-log under 20 mJ/cm² UV exposure after 22 hr incubation. The final inactivation ratio of tetracycline-resistant Enterobacter-1 was 1.18-log under 20 mJ/cm² UV exposure after 22 hr incubation, which is similar to those of TRB (1.18-log) and heterotrophic bacteria (1.19-log). The increased proportion of TRB and the reactivation of tetracycline-resistant enterobacteria in reclaimed water could induce a microbial health risk during wastewater reuse.     

Influence of reactivation on the electrochemical performances of activated carbon based on coconut shell

Coconut shell-based activated carbon (AC) were prepared by CO₂ activation, and then the ACs with higher mesopore ratio were obtained by steam activation and by impregnating iron catalyst followed by steam activation, respectively. The AC with the highest mesopore ratio (AC_hmr) shows superior capacitive behavior, power output and high-frequency performance in supercapacitors. The results should attribute to the connection of its wide micropores and mesopores larger than 3 nm, which is more favorable for fast ionic transportation. The pore size distribution exhibits that the mesopore ratios of the ACs are significantly increased by reactivation of steam or catalyst up to 75% and 78%, respectively. As evidenced by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic measurements, the AC_hmr shows superior capacitive behaviors, conductivity and performance of electrolytic ionic transportation. The response current densities are evidently enhanced through the cyclic voltammery test at 50 mV/sec scan rate. The electrochemical impedance spectroscopy demonstrates that the conductivity and ion transport performance of the ACs are improved. The specific capacitances of the ACs were increased from 140 to 240 F/g at 500 mA/g current density. The AC_hmr can provide much higher power density while still maintaining good energy density, and demonstrate excellent high-frequency performances. The pore structure and conductivity of the AC_hmr also improve the cycleability and self-discharge of supercapacitors. Such AC_hmr exhibits a great potential in supercapacitors, particularly for applications where high power output and good high-frequency capacitive performances are required.     

Influence of reactivation on the electrochemical performances of activated carbon based on coconut shell

Coconut shell-based activated carbon (AC) were prepared by CO₂ activation, and then the ACs with higher mesopore ratio were obtained by steam activation and by impregnating iron catalyst followed by steam activation, respectively. The AC with the highest mesopore ratio (AC_hmr) shows superior capacitive behavior, power output and high-frequency performance in supercapacitors. The results should attribute to the connection of its wide micropores and mesopores larger than 3 nm, which is more favorable for fast ionic transportation. The pore size distribution exhibits that the mesopore ratios of the ACs are significantly increased by reactivation of steam or catalyst up to 75% and 78%, respectively. As evidenced by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic measurements, the AC_hmr shows superior capacitive behaviors, conductivity and performance of electrolytic ionic transportation. The response current densities are evidently enhanced through the cyclic voltammery test at 50 mV/sec scan rate. The electrochemical impedance spectroscopy demonstrates that the conductivity and ion transport performance of the ACs are improved. The specific capacitances of the ACs were increased from 140 to 240 F/g at 500 mA/g current density. The AC_hmr can provide much higher power density while still maintaining good energy density, and demonstrate excellent high-frequency performances. The pore structure and conductivity of the AC_hmr also improve the cycleability and self-discharge of supercapacitors. Such AC_hmr exhibits a great potential in supercapacitors, particularly for applications where high power output and good high-frequency capacitive performances are required.     

磺胺甲噁唑对猪粪堆肥过程中堆料性质与酶活性的影响

以猪粪、小麦秸秆为材料,研究了磺胺甲噁唑（SMZ）对高温堆肥过程中理化性质（温度、pH值、E₄/E₆）和酶活性（纤维素酶、磷酸酶、脲酶、多酚氧化酶）的影响.结果表明：SMZ对堆肥理化性质的影响与其浓度有关.高浓度（95 mg·kg^-1）SMZ会对微生物活性产生显著抑制作用,表现出堆肥温度难以达到无害化标准,堆料pH值较低（<9.0）.但高浓度（95 mg·kg^-1）SMZ能激活多酚氧化酶活性,且水提浸液E₄/E₆值较低.在堆肥过程中,SMZ对纤维素酶和脲酶活性呈现出“抑制-激活-抑制”的作用,50 mg·kg^-1的SMZ对纤维素酶产生不同程度的激活作用.相比之下,脲酶活性对SMZ的敏感性比纤维素酶更敏感,5 mg·kg^-1的SMZ即能显著抑制脲酶活性,中浓度（50 mg·kg^-1）的SMZ对碱性磷酸酶活性产生了显著的抑制作用.综上,SMZ通过影响酶活性而影响堆肥过程的物质转化.此外,SMZ浓度越大,种子发芽指数越低.当SMZ≥50 mg·kg^-1时,堆肥难以腐熟而对植物毒性较大.     

Inactivation and subsequent reactivation of Aspergillus species by the combination of UV and monochloramine: Comparisons with UV/chlorine

Ultraviolet (UV)/monochloramine (NH₂Cl) as an advanced oxidation process was firstly applied for Aspergillus spores inactivation. This study aims to: i) clarify the inactivation and photoreactivation characteristics of UV/NH₂Cl process, ii) compared with UV/Cl₂ in inactivation efficiency, photoreactivation and energy consumption. The results illustrated that UV/NH₂Cl showed better inactivation efficiency than that of UV alone and UV/Cl₂, and could effectively control the photoreactivation. For instance, the inactivation rates for Aspergillus flavus, Aspergillus niger and Aspergillus fumigatus in the processes of UV/NH₂Cl (2.0 mg/L) was 0.034, 0.030 and 0.061 cm²/mJ, respectively, which were higher than that of UV alone (0.027, 0.026 and 0.024 cm²/mJ) and UV/Cl₂ (0.023, 0.026 and 0.031 cm²/mJ). However, there was no synergistic effect for Aspergillus flavus and Aspergillus fumigatus. As for Aspergillus niger, the best synergistic effect can reach 1.86-log₁₀. This may be due to their different resistance to disinfectants, which were related to the size, an outer layer of rodlets (hydrophobins) and pigments. After UV/NH₂Cl inactivation, the degree of cell membrane damage and intracellular reactive oxygen species were higher than that of UV alone. UV/NH₂Cl had the advantages of high inactivation efficiency and inhibition of photoreactivation, which provides a new entry point for the disinfection of waterborne fungi.     

二月桂酸二丁基锡对大鼠睾酮及合成关键酶的影响

用玉米油或二月桂酸二丁基锡[DBTD0.01,0.1,1mg/(kg·d)体重]对新生雄性Wistar大鼠连续5d注射染毒.至大鼠出生后第49d,检测其血清睾酮,细胞色素胆固醇侧链裂解酶(P450scc)、3β-羟基类固醇脱氢酶(3β-HSD)和细胞色素P450 17-α脱羟基酶(Cyp17)这3种睾酮合成关键酶mRNA表达及脏器系数.结果表明,大鼠血清睾酮随DBTD剂量升高呈上升趋势,1mg/(kg·d)组与对照组比较有显著性差异;P450scc和3β-HSD mRNA相对表达无显著性变化,Cyp17在0.1mg/(kg·d)组的相对表达有显著性升高;1mg/(kg·d)组大鼠睾丸脏器系数有显著性升高,而各DBTD处理组附睾和肝脏脏器系数与对照组比较无显著性变化.     

土壤酶对外源有机硒和无机硒的动态响应

通过室内非作物连续培养,研究了不同剂量、不同形态外源硒(亚硒酸钠、硒代蛋氨酸)对土壤脲酶、蔗糖酶、中性磷酸酶活性影响的动态变化过程.结果表明,低剂量(10 mg·kg~(-1))无机硒(亚硒酸钠)对土壤脲酶和蔗糖酶活性有先激活后抑制作用,对土壤中性磷酸酶活性有激活作用.而相同剂量有机硒(硒代蛋氨酸)处理时,3种酶均表现为不同程度的激活状态.高剂量(30 mg·kg~(-1))无机硒(亚硒酸钠)处理时,3种酶活性均表现先激活后抑制,其中对脲酶影响最大,对蔗糖酶影响次之,对中性磷酸酶影响最小.而施入高剂量(30 mg·kg~(-1))有机硒(硒代蛋氨酸)后,对土壤中脲酶、蔗糖酶的激活作用明显大于无机硒的影响,但对磷酸酶的影响不明显.试验充分说明施入不同剂量、不同形态的外源硒,土壤酶活性表现出不同的动态响应,并且有机硒比无机硒更有利于土壤微生物的生长,能提高土壤酶活性,促进N、P、C养分在土壤生态系统的循环.用有机硒替代无机硒作为外源硒源,有望成为未来发展方向.     

Maternal serum levels of dimeric inhibin A in pregnancies affected by trisomy 21 in the first trimester

Dimeric inhibin A was measured in maternal serum samples from 45 pregnancies affected by trisomy 21 and 493 samples from unaffected pregnancies at 10–14 weeks of gestation. Inhibin A levels in affected pregnancies were compared with levels of free β-hCG and PAPP-A in the same series. In the trisomy 21 group, the median multiple of the median (MoM) inhibin A was not significantly elevated (1.28 vs 1.00) with only 15.5% being above the 95th centile. In contrast, the median MoM free β-hCG was significantly increased (2.05 vs 1.00) with 36% above the 95th centile and PAPP-A was significantly reduced (0.49 vs 1.00) with 42% below the 5th centile. Inhibin A levels in the trisomy 21 group were significantly correlated with gestational age such that median levels rose from 1.04 at 11 weeks to 1.30 at 12 weeks and 1.67 at 13 weeks. These findings suggest that first trimester biochemical screening for trisomy 21, which is currently optimised using maternal serum free β-hCG and PAPP-A and fetal nuchal translucency, will not benefit from the inclusion of inhibin A. Copyright © 2001 John Wiley & Sons, Ltd.     

Inactivation, reactivation and regrowth of indigenous bacteria in reclaimed water after chlorine disinfection of a municipal wastewater treatment plant

Disinfection of reclaimed water prior to reuse is important to prevent the transmission of pathogens. Chlorine is a widely utilized disinfectant and as such is a leading contender for disinfection of reclaimed water. To understand the risks of chlorination resulting from the potential selection of pathogenic bacteria, the inactivation, reactivation and regrowth rates of indigenous bacteria were investigated in reclaimed water after chlorine disinfection. Inactivation of total coliforms, Enterococcus and Salmonella showed linear correlations, with constants of 0.1384, 0.1624 and 0.057 L/(mg·min) and R² of 0.7617, 0.8316 and 0.845, respectively. However, inactivation of total viable cells by measurement of metabolic activity typically showed a linear correlation at lower chlorine dose (0-22 (mg·min)/L), and a trailing region with chlorine dose increasing from 22 to 69 (mg·min)/L. Reactivation and regrowth of bacteria were most likely to occur after exposure to lower chlorine doses, and extents of reactivation decreased gradually with increasing chlorine dose. In contrast to total coliforms and Enterococcus, Salmonella had a high level of regrowth and reactivation, and still had 2% regrowth even after chlorination of 69 (mg·min)/L and 24 hr storage. The bacterial compositions were also significantly altered by chlorination and storage of reclaimed water, and the ratio of Salmonella was significantly increased from 0.001% to 0.045% after chlorination of 69 (mg·min)/L and 24 hr storage. These trends indicated that chlorination contributes to the selection of chlorine-resistant pathogenic bacteria, and regrowth of pathogenic bacteria after chlorination in reclaimed water with a long retention time could threaten public health security during wastewater reuse.     

Control of intestinal proteolytic enzymes in a cockroach

The Science of Nature -