Study on Screening of Fungi with High-resistance against Chromium and on Related Characteristics

[Objective] The aim was to separate chromium-resistant microorganism from soil contaminated by chromium.[Method] Separation and purification technique was used as follows：different concentrations of Cr^6＋ were added into medium,and chromium-resistant fungi were screened after separations and domestications.The selected fungi were under preliminary identification according to its morphological and colony characteristics.Then,related biological characteristics were studied,including measurement of growth curve,growing effects by temperature,pH value and osmotic pressure.[Result] The Cr（VI） with concentration of 1 000 mg/L was separated and selected from soils in ten different places contaminated seriously by heavy metal in adjacent region of Yulin City.Considering its morphological and colony characteristics,it was preliminarily identified as saccharomycetes,which can well grow within 15-37 ℃,and whose most suitable temperature was 28℃.Bacterial strain can grow well with pH of 4-10,and the optimum pH was 7.2;besides,it can grow well with NaCl concentration of 0.5%-5.0%.Through the experiment,the bacteria was found with resistance not only to chromium,but also to heavy metals such as Pb＋Cu,Cu＋Fe,Pb＋Fe,and Pb＋Cu＋Fe.[Conclusion] The fungi selected from the experiment were of good adaptability to natural environment,and it also had resistance to other heavy metals.

螯合剂与低分子有机酸复配淋洗修复Cr(Ⅵ)污染土壤

为探究可生物降解螯合剂氨三乙酸(NTA)替代乙二胺四乙酸二钠(EDTA)在复配淋洗剂中的作用,本文研究了NTA和EDTA与草酸和酒石酸所配制的复配淋洗剂在不同浓度、固液比、pH值和淋洗时间下对Cr(Ⅵ)污染土壤淋洗效果的影响及淋洗动力学,此外还使用顺序提取方案(BCR)分析了淋洗前后土壤中重金属的形态、迁移率和稳定性变化。结果表明:混合等体积的0.25 mol·L^(-1)NTA和0.3 mol·L^(-1)草酸在固液比为1∶9、pH为3、淋洗时长为240 min条件下达到最大Cr(Ⅵ)去除效率82.94%,这与使用EDTA淋洗时的效率相近;该复配淋洗剂淋洗Cr(Ⅵ)污染土壤时的动力学符合拟二级动力学方程;BCR实验结果表明,NTA和草酸复配淋洗后土壤中Cr的弱酸可提取态、可氧化态和残渣态组分含量分别从6346.67、4280.00、2387.67 mg·kg^(-1)下降至1161.67、433.35、741.00 mg·kg^(-1),可还原态组分从2746.67 mg·kg^(-1)上升至6016.67 mg·kg^(-1),污染土壤重金属迁移率下降。淋洗后土壤有机质含量从13.47%上升至30.56%,脲酶和脱氢酶活性分别从46.32、329.09μg·d^(-1)·g^(-1)降低至29.36、131.98μg·d^(-1)·g^(-1),土壤结构基本与原土一致。因此,NTA与草酸复配淋洗剂是一种高效且对土壤影响较小的淋洗剂。

Influence of vanadium and chromium additions on the wear resistance of a gray cast iron

A low-alloy gray cast iron containing hard carbide-forming elements, such as vanadium and chromium, was cast by sand mould casting. Its wear resistance was compared with that of an untreated gray cast iron. Three different loading conditions were tested under a con- stant speed. It was observed that this alloy could reduce the wear loss of standard gray cast iron by up to 89%, which was much greater than what was achieved in previous reports. Scanning electron microscopy （SEM） was used to determine the predominant wear mechanism of both the alloys. In a mild wear regime, the oxidative mechanism was predominant; however, in a severe wear regime, this mechanism was not predominant and the adhesive mechanism was involved. EDX analysis was conducted to evaluate the quantitative amounts of elements in the tribochemical films formed on the wear tracks.

Microstructure and wear resistance of highchromium cast iron containing niobium

In the paper, the effect of niobium addition on the microstructure, mechanical properties and wear resistance of high chromium cast iron has been studied. The results show that the microstructure of the heattreated alloys is composed of M7C3 and M23C6 types primary carbide, eutectic carbide, secondary carbide and a matrix of martensite and retained austenite. NbC particles appear both inside and on the edge of the primary carbides. The hardness of the studied alloys maintains around 66 HRC, not significantly affected by the Nb content within the selected range of 0.48%-0.74%. The impact toughness of the alloys increases with increasing niobium content. The wear resistance of the specimens presents little variation in spite of the increase of Nb content under a light load of 40 N. However, when heavier loads of 70 and 100 N are applied, the wear resistance increases with increasing Nb content.

一株耐铬细菌的分离鉴定及其对Cr(Ⅵ)的抗性

从山东省某含铬农田土壤取样进行宏基因测序、16SrDNA以及构建系统树等方法分离、鉴定耐铬细菌,并通过扫描电子显微镜等研究其对Cr(Ⅵ)的抗性。某含铬农田土壤中的优势菌为Enterobacter cloacae(阴沟肠杆菌),将其命名为Enterobacter cloacae SD。SD的Cr(Ⅵ)耐受质量浓度可达3 200 mg/L;在150 mg/L Cr(Ⅵ)中培养时,菌落较不加Cr(Ⅵ)时少且分散,但单菌落较大;SD细胞表面粗糙,似有沉淀物产生。以酵母浸粉为碳源,pH值为7,培养温度为30℃时菌株SD可较好生长。在150 mg/L Cr(Ⅵ)下,SD对Cr(Ⅵ)的去除率为39.67%。研究表明Enterobacter cloacae SD可耐受高质量浓度Cr(Ⅵ)的同时,对Cr(Ⅵ)有一定的去除能力,这为Cr(Ⅵ)污染的微生物修复提供了可能的菌种资源。

Microstructures and wear resistance of chromium coatings on P110 steel fabricated by pack cementation

In order to obtain a high-performance surface on P110 steel that can meet the requirements in oil/gas field environment, the chromium coatings were fabricated by pack cementation. The chromium coatings differed in with/without the addition of La2O3. Scanning electron microscope （SEM）, energy dispersive X-ray spectrometer （EDS）, X-ray diffractometer （XRD） and microhardness tester were employed to investigate the surface morphologies, surface element distributions, microstructures, phase constitutions and microhardness of the coatings. Friction-wear tests of the P110 steel substrate and the coatings were conducted in air at ambient temperature and humidity. The results show that ＇uniform and continuous coatings are formed on P110 steel regardless of adding La2O3 or not. The chromium coatings consist of Cr23C6, Cr7C3, and （Cr, Fe）7C3. The La2O3-added chromium coating is more beneficial in terms of surface morphology, microstructure, thickness and microharduess as compared with the coating without adding La2O3. Chromizing treatment significantly improves the surface hardness and wear resistance of the P110 steel. The wear resistance of the tested samples can be sorted in the following sequence： La2O3-coating 〉 no RE-coating 〉bare P110 steel.

Severe insulin resistance treatment with intravenous chromium in septic shock patient

Insulin resistance has been well documented in critically ill patients.Adequate blood sugar control has been associated with better wound healing,and better outcomes in selected patient populations.Chromium is an essential component of human diet.It is believed to affect changes in glucose uptake.Several studies have shown beneficial effects of oral chromium in diabetic patients with insulin resistance,but role of intravenous chromium infusion has not been completely evaluated.We present a case of extreme insulin resistance in a 62-year-old woman with history of diabetes who suffered a cardiac arrest and respiratory failure,leading to aspiration pneumonia and septic shock requiring greater than 7000 units of insulin over a period of 12 h which was successfully treated with intravenous chromium replacement.

Effect of surface Cr/C infiltration on microstructure,mechanical properties and wear resistance of high chromium cast iron

A new type of high chromium cast iron(HCCI)was prepared,and its microstructure,mechanical properties,and abrasion resistance were investigated systematically.Results showed that after surface carburizing and chromizing,the microstructure of HCCI mainly consists of martensite,boride(M_(2)B),and carbide(M_(7)C_(3)),accompanied with a large amount of secondary precipitations M_(23)C_(6).Moreover,the morphology and hardness of the carbide and boride in HCCI change little,while the volume fraction of carbide and boride increases from 16.23%to 23.16%.This effectively increases the surface hardness of HCCI from 64.53±0.50 HRC to 66.58±0.50 HRC,with the result that the surface of HCCI possesses a better abrasion resistance compared to the center position.Furthermore,the wear mechanism of HCCI changes from micro-plowing to micro-cutting with the increase of surface hardness.

预氧化法制备棉花秸秆活性炭去除印染废水中的铬(Ⅵ)

以新疆南疆棉花秸秆为原料,采用H_(2)SO_(4)预氧化和KOH活化制备活性炭,其Langmuir比表面积达到1 580.94 cm^(2)/g。采用静态吸附试验研究活性炭对印染废水中铬(Ⅵ)的吸附性能。结果表明:p H为2,Cr(Ⅵ)的初始质量浓度为0.5 mg/L,活性炭投加量为0.1 g,吸附时间为150 min时,Cr(Ⅵ)的吸附量为28 mg/g。Langmuir吸附等温线能更好地描述棉花秸秆活性炭吸附Cr(Ⅵ)的过程,R^(2)为0.988 24,说明棉花秸秆活性炭的表面Cr(Ⅵ)主要以单分子层形态吸附。活性炭对铬(Ⅵ)的吸附符合准二级动力学模型,R^(2)为0.950 25。

Characterization of Cr(Ⅵ) resistance and reduction by Pseudomonas aeruginosa

The experiments were conducted to evaluate the Cr(Ⅵ)resistance and reduction by Pseudomonas aeruginosa.After this bacterium tolerated 40 mg/L Cr(Ⅵ),the growth of cells was observed.The bacterial growth was obviously lower than the controls over 24 h and the binary cell fission was observed in cell morphology by scanning electron microscope.P.aeruginosa was found to be able to reduce Cr(Ⅵ)although Cr(Ⅵ)had toxic effects on the cells.The results demonstrate that Cr(Ⅵ)is reduced from 40 mg/L to about 18 mg/L in 72 h.The value of pH drops from 7.02 to around 5.65 after 72 h.A significant increase in the value of redox potential occurs during Cr(Ⅵ)reduction and Cr(Ⅵ)reduction can be observed over a range of redox potential from+3 mV to+91 mV.Both of SO4 2-and NO3 -have no effect on Cr(Ⅵ)reduction.The presence of Zn 2+has a notable inhibitory effect on Cr(Ⅵ) reduction while Cu 2+ substantially stimulates Cr(Ⅵ)reduction.In the presence of Zn 2+ ,Cr(Ⅵ)decreases from 40 mg/L to only 26-27 mg/L,whereas Cr(Ⅵ)drops to 1-2 mg/L after 48 h in the presence of Cu2 +.

改性球形二氧化硅吸附重金属Cr(Ⅵ)离子实验研究

采用水热法制备球形二氧化硅,并利用3-氨丙基三甲氧基硅烷(APTMS)对制备得到的球形二氧化硅进行了氨基改性。采用傅里叶红外光谱(FTIR)和透射电镜(TEM)等技术手段对氨基改性球形二氧化硅进行表征分析。考察了溶液pH、吸附时间、初始浓度等因素对铬离子(Ⅵ)吸附量的影响,获得系统吸附规律。研究结果表明:氨基改性球形二氧化硅比未改性二氧化硅具有更优异的铬离子(Ⅵ)吸附性能。

Oligomannuronate-Chromium (Ⅲ) Complex Ameliorates Insulin Resistance in C57BL/KsJ-db/db Mice

Diabetes mellitus is the most common metabolic disease and its prevalence is increasing in many countries year by year.More than 90% of diabetes patients are type 2 diabetes,which is caused by insulin resistance and beta-cell dysfunction.In this paper,the oligomannuronate-chromium(III)complex(OM2)was prepared and its effect and mechanism on attenuating insulin resistance in diabetic C57BL/KsJ-db/db mice were studied.The results indicated that oral intake of OM2(50 mg kg-1d-1)for 42 d decreased blood glucose and lipid concentration,which was associated with the reduced serum insulin concentration and insulin resistance.According to western blot assay,OM2 could activate AMPK pathway to regulate glycogen synthesis,gluconeogenesis and lipid metabolism in the liver,and attenuate the hyperglycemic symptom in db/db mice.The effects of OM2 on attenuating insulin resistance were com-parable to that of the established antidiabetic drug metformin,and OM2 showed less adverse effect than metformin in vivo.Based on the effectiveness and low toxicity,OM2 may potentially be used for prevention and treatment of type 2 diabetes mellitus.

Microstructure and corrosion resistance of high-chromium iron-base coating by plasma cladding

A new type of high-chromium iron-base coating was fabricated on substrate of hardened and tempered grade C steel by plasma cladding with Fe-Cr-C alloy powders. The coating has fine microstructure and is metallurgically bonded to the grade C steel substrate. The corrosion resistance of the coating in solutions of 0. 5 mol/L H2SO4 , 3.5 % NaCl and seawater was evaluated utilizing the electrochemical polarization corrosion-test method. Because of the inherent excellent corrosion- resisting properties of the constituting phase and the fine microstucture, the plasma clad coating exhibits excellent corrosion resistance in the water solutions of 0. 5 mol/L H2S04, 3.5% NaCl and seawater.

Low-Energy Multi-Impact Fracture Resistance of Cross Rolled Low Chromium Cast Semi-Steel Containing Rare Earth Grinding Ball

The low-energy multi-impact fracture resistance of the cross rolled low chromium cast semi-steel containing RE grinding balls was studied. Moreover, its damage mode was analyzed by means of metallographic examination, scanning electron microscopic examination and drop ball test. The results show that it can obtain extractive impact fracture resistance after proper heat treatment. More advantages were obtained for the ball worked in the condition of low-imp ductility act. The main reasons are the function of RE and the change in morphology of eutectic carbide network.

RESEARCH AND APPLICATION OF AS-CAST WEAR RESISTANCE HIGH CHROMIUM CAST IRON

The influence of alloy elements, such as boron and silicon, on the microstructure and properties of as cast high chromium cast iron is studied. The results show that boron and silicon have a great effect on the mechanical properties and the wear resistance. Through proper addition of boron and silicon, the properties of as cast high chromium cast iron can be improved effectively. Through analyzing the distribution of elements by scanning electron microscope, it has been shown that the addition of boron and silicon lowers the mass fraction of chromium saturated in as cast austenite, and makes it unstable and liable to be transformed into martensite. The as cast high chromium cast iron with proper content of boron and silicon is suitable for the manufacture of lining for asphalt concrete mixer and its wear resistance is 14 times that of lining made of low alloy white cast iron.

浅析水泥中的水溶性铬(Ⅵ)

鉴于国家监督抽查结果,本文测定了配制生料常用原材料中的总铬含量、水泥粉磨常用原材料中的水溶性铬(Ⅵ)含量,提出了水泥中水溶性铬(Ⅵ)测定的注意事项,并总结了水泥中水溶性铬(Ⅵ)的控制措施,希望对水泥生产企业控制产品中水溶性铬(Ⅵ)含量提供参考。

水浴磁力搅拌碱消解-火焰原子吸收分光光度法测定土壤中铬(Ⅵ)

建立水浴磁力搅拌碱消解火焰原子吸收分光光度法测定土壤中铬(Ⅵ)。称取5.00 g土壤样品置于250 mL聚乙烯瓶中,以20 g/L氢氧化钠和30 g/L碳酸钠碱性提取液提取,提取温度为93℃,提取时间为75 min;加入400 mg氯化镁,调节滤液pH值为7.0~8.0。铬(Ⅵ)质量浓度在0.0~2.0 mg/L范围内线性相关系数为0.9995,检出限为0.4 mg/kg。该方法应用于低、中、高3种铬(Ⅵ)土壤国家标准物质的分析,测定值与认定值相符,测定值的相对标准偏差为5.0%~7.7%(n=12)。

电化学修饰电极在检测Cr(Ⅵ)中的研究进展

随着对六价铬离子检测需求的不断增加,电化学检测因其高效、经济等优点而受到广泛关注。本文介绍了不同电活性层修饰电极在六价铬检测方面的应用,比较了不同修饰电极材料对六价铬的检测效果和各自的优缺点,包含无机纳米材料(纳米碳材料、纳米金属及金属氧化物)和有机聚合物、有机分子复合材料,并总结了不同修饰电极在检测六价铬过程中的行为机理,主要分为四类检测机制:包括木质素-聚(环氧丙烷)共聚物的静电吸附机理、氮杂冠与HCrO_(4)^(-)形成络合物阻碍电子转移、Cr^(6+)诱导二硫键形成引起rGO通道电阻变化以及pp结界面势垒作为驱动因素的检测机理。最后对修饰电极的优化设计、改善其选择性、稳定性及抗干扰能力,以及提升裸玻碳电极检测能力提出了展望。

Effect of Hot Deformation on Formation and Growth of Thermal Fatigue Crackin Chromium Wear Resistant Cast Iron

The formation and growth of thermal fatigue crack in chromium wear resistant cast iron was investigated, and the effect of hot deformation on the crack was analyzed by means of optical microscope and scanning electron microscope and high frequency induction thermal fatigue tester. The results show that eutectic carbide is the main location and passage for initiation and extension of thermal fatigue cracks, hot deformation can improve the eutectic carbiders morphology and distribution, inhibit the generation and propagation of thermal fatigue cracks. In the experiment, the propagation rate of thermal fatigue crack reduces with the quantity of hot deformation increasing, which was analyzed in the point view of the activation energy of crack propagation.

Influence of secondary carbide precipitation and transformation on abrasion resistance of a 3Cr15Mo1V1.5 white iron

The relationship between the secondary carbide precipitation and transformation of the 3Cr15Mo1V1.5 white iron and abrasion resistance was investigated by using optical microscope （OM）, transmission electron microscopy （TEM） and X-ray diffrac- tion （XRD）. The results show that the properties of secondary carbides precipitated at holding stage play an important role in the abrasion resistance. After certain holding time at 833 K subcritical treatment, the grainy （Fe, Cr）23C6 carbide precipitated and the fresh martensite transformed at the holding stage for 3Cr15Mo1V1.5 white iron improve the bulk hardness and abrasion resistance of the alloy. Prolonging holding time, MoC and （Cr, V）2C precipitations cause the secondary hardening peak and the corresponding better abrasion resistance. Finally, granular （Fe, Cr）23C6 carbide in situ transforms into laminar M3C carbide and the matrix structure transforms into pearlitic matrix. These changes weaken hardness and abrasion resistance of the alloy sharply.