Fe^(2+)/Mn^(2+)活化亚硫酸盐降解盐酸土霉素的机理研究

盐酸土霉素常被用于治疗畜禽疾病,但是它不能被畜禽完全代谢,残留的盐酸土霉素进入水体危害水环境的健康。铁锰作为常见的过渡金属,通常以二价态活化亚硫酸盐来降解有机污染物,反应条件温和、操作简单,但是单独的二价铁与二价锰氧化还原电势低,活化亚硫酸盐效果较差。本研究采用Fe^(2+)/Mn^(2+)共活化Na_(2)SO_(3)降解水中的盐酸土霉素,考察药剂用量、pH、溶解氧、氯离子、碳酸根及腐殖酸对Fe^(2+)/Mn^(2+)/Na_(2)SO_(3)体系降解盐酸土霉素的影响;通过焦磷酸盐实验、自由基淬灭实验和EPR实验分析Fe^(2+)/Mn^(2+)/Na_(2)SO_(3)体系中的活性物种;利用紫外可见光谱、傅里叶红外光谱、气相色谱-质谱联用仪识别盐酸土霉素的官能团及其降解中间产物的变化,推断盐酸土霉素的降解途径。结果表明:当Fe^(2+)/Mn^(2+)/Na_(2)SO_(3)浓度比为1∶4∶20(浓度分别为0.1、0.4和2 mmol/L)时,在反应45 min、pH为9.0条件下,盐酸土霉素的去除率和矿化率最高,分别达到94%和49%。随着溶解氧从9 mg/L下降至1.89 mg/L,盐酸土霉素去除率从94%下降至17%;氯离子、腐殖酸和碳酸根均对盐酸土霉素的降解产生抑制作用。Mn(Ⅲ)和SO_(4)·^(-)是降解盐酸土霉素的主要活性氧化剂,盐酸土霉素的降解经过电子转移、开环与酰基化等过程。

Fe-Mn/TiO_(2)的制备及其催化臭氧氧化双酚A的性能研究

采用浸渍法制备Fe-Mn/TiO_(2)双金属催化材料,以双酚A(BPA)为目标降解物,探究了Fe-Mn/TiO_(2)对其的降解效果及降解机制。结果表明,Fe-Mn/TiO_(2)催化臭氧氧化降解BPA的去除率相较于单独TiO_(2)处理提升了83.4%;Fe、Mn成功负载且催化剂孔洞较丰富;相较于TiO_(2),Fe-Mn/TiO_(2)中锐钛矿质量分数增加能产生更多的羟基自由基。同时,Fe、Mn在TiO_(2)表面能发生价态转化,可作为活性位点促进臭氧分解为·OH等活性物质,增强催化反应活性。

Mn-Fe-Ce-O催化剂对助燃脱硝性能的影响

采用改进的柠檬酸络合法制备了Mn-Fe-Ce-O复合氧化物,采用XRD,H_(2)-TPR,XPS,SEM,EDS等方法分析了试样的结构与物性,并对其氧化和催化CO还原NO的性能进行了评价。实验结果表明,Mn-Fe-Ce-O复合氧化物中主要为Mn_(3)O_(4)和CeO_(2)物相,Fe和Ce的加入可增大复合氧化物的比表面积,且表面元素分布均匀,无明显集聚状态,加入Ce后复合氧化物颗粒变得细小,Mn^(3+)+Mn^(4+)含量和表面吸附氧含量增大,H_(2)-TPR还原峰向低温区偏移。Mn_(9)Fe_(1)O_(z)具有良好的氧化CO能力,400℃下CO转化率为99.56%,Mn-Fe-Ce-O复合氧化物催化CO还原NO的活性高于Mn-Fe-O复合氧化物,其中,(Mn_(9)Fe_(1))_(7)Ce_(3)O_(z)活性最高,在350℃下NO转化率为85.75%。

不同Mn/Fe比例天然含铁锰矿的As(Ⅲ)吸附性能与机制

水体中的砷主要以亚砷酸(As(Ⅲ))形态存在.金属氧化物常用于水体砷的去除,但其对As(Ⅲ)的亲和力较弱,导致水体砷很难去除,因此,寻求高效、廉价、绿色的除As(Ⅲ)材料具有显著的环境意义.天然含铁锰矿是一种高效的砷吸附剂,由于自然形成条件复杂,其不同含铁锰矿对As(Ⅲ)的去除性能存在较大差异.本研究以两种不同Mn/Fe比例的天然含铁锰矿(NFM-L、NFM-H)为研究对象,评估其对As(Ⅲ)的吸附性能,并结合XPS、XRD等光谱学表征手段探究其砷的去除机制.实验结果表明,NFM-L的Fe含量是NFM-H的5.61倍,其As(Ⅲ)的最大吸附量(24.82 mg·g^(−1))与吸附速率亦显著高于NFM-H(18.94 mg·g^(−1)),NFM-L和NFM-H对As(Ⅲ)的等温吸附曲线更符合Freundlich模型.影响因子实验表明,溶液pH值对NFM-L的影响更大,共存离子H_(2)PO_(4)^(−)能够显著抑制两种材料对As(Ⅲ)的吸附,但是材料粒径对As(Ⅲ)去除的影响较小.光谱学表征发现,两种矿物吸附砷后结构并未发生明显变化,但锰氧化物能将As(Ⅲ)氧化为As(V),从而显著提高了铁锰矿对砷的吸附能力.

Removal of tungsten from molybdate solution by Fe-Mn binary oxide adsorbent

Considering the different geochemical enrichment behaviors of W and Mo,Fe?Mn binary oxide(FMBO),ferric hydroxide(Fe(OH)3)and manganese dioxide(MnO2)were studied to separate W from molybdate solution,respectively.The experimental results demonstrated that Fe?Mn binary oxide(FMBO)was the most suitable adsorbent for the separation.Under a wide pH(6.9?11.3)region,more than80%W removal efficiency and less than3%Mo loss could be obtained.In addition,the Fe?Mn binary oxide adsorbent can be regenerated by treating with3mol/L NaOH,and the W adsorption efficiency was retained after five adsorption?desorption?regeneration cycles.All these indicate that the Fe?Mn binary oxides have the potential for the separation of W from molybdate solution.

Artificial Neural Network and Full Factorial Design Assisted AT-MRAM on Fe Oxides, Organic Materials, and Fe/Mn Oxides in Surficial Sediments

Artificial neural network（ANN） and full factorial design assisted atrazine（AT） multiple regression adsorption model（AT-MRAM） were developed to analyze the adsorption capability of the main components in the surficial sediments（SSs）. Artificial neural network was used to build a model（the determination coefficient square r2 is 0.9977） to describe the process of atrazine adsorption onto SSs, and then to predict responses of the full factorial design. Based on the results of the full factorial design, the interactions of the main components in SSs on AT adsorption were investigated through the analysis of variance（ANOVA）, F-test and t-test. The adsorption capability of the main components in SSs for AT was calculated via a multiple regression adsorption model（MRAM）. The results show that the greatest contribution to the adsorption of AT on a molar basis was attributed to Fe/Mn（–1.993 μmol/mol）. Organic materials（OMs） and Fe oxides in SSs are the important adsorption sites for AT, and the adsorption capabilities are 1.944 and 0.418 μmol/mol, respectively. The interaction among the non-residual components（Fe, Mn oxides and OMs） in SSs interferes in the adsorption of AT that shouldn’t be neglected, revealing the significant contribution of the interaction among non-residual components to controlling the behavior of AT in aquatic environments.

Enhanced selective catalytic reduction of NO with NH3 via porous micro-spherical aggregates of Mn–Ce–Fe–Ti mixed oxide nanoparticles

We rationally designed a high performance denitration(De-NOx) catalyst based on a micrometer-sized spherical Mn–Ce–Fe–Ti(CP-SD)catalyst for selective catalytic reduction(SCR). This was prepared by a co-precipitation and spray drying(CP-SD) method. The catalyst was systematically characterized, and its morphological structure and surface properties were identified. Compare with conventional Mn–Ce–Fe–Ti(CP) catalysts, the Mn–Ce–Fe–Ti(CP-SD) catalyst had superior surface-adsorbed oxygen leading to enhanced 'fast NH3-SCR' reaction. The asobtained Mn–Ce–Fe–Ti(CP-SD) catalyst offered excellent NO conversion and N2 selectivity of 100.0% and 84.8% at 250℃, respectively, with a gas hourly space velocity(GHSV) of 40,000 h-1. The porous micro-spherical structure provides a larger surface area and more active sites to adsorb and activate the reaction gases. In addition, the uniform distribution and strong interaction of manganese, iron, cerium, and titanium oxide species improved H2O and SO2 resistance. The results showed that the Mn–Ce–Fe–Ti(CP-SD) catalyst could be used prospectively as a denitration(De-NOx) catalyst.

Measurement of Atrazine Adsorption onto Surficial Sediments(Natural Surface Coatings)——New Evidence for the Importance of Fe Oxides

To reveal the relative contribution of the components, Fe, Mn oxides or organic materials（OMs） in the surficial sediments（SSs）, and the natural surface coating samples（NSCSs） to adsorbing atrazine（AT）, a selective chemical extraction technique was employed, to remove the different components, and the adsorption characteristics of AT on the SSs and the NSCSs were investigated. The observed adsorptions of AT on the original and extracted SSs and NSCSs were analyzed by nonlinear least squares fitting（NLSF） to estimate the relative contribution of the components. The results showed that the maximum adsorption of AT on the NSCSs was greater than that in the SSs, before and after extraction treatments, implying that the NSCSs were more dominant than the SSs for organic pollutant adsorption. It was also found that the Fe oxides, OMs, and residues in SSs（NSCSs） facilitated the adsorption of AT, but Mn oxides directly or indirectly restrained the interaction of AT with SSs（NSCSs） particles. The contribution of the Fe oxides to AT adsorption was more than that of OMs; the greatest contribution to AT adsorption on a molar basis was from the Fe oxides in the nonresidual fractions, indicating that the Fe oxides played an important role in controlling the environmental behavior of AT in an aquatic environment.

The Effect of Oxidation/Reduction Disposing on Optical Properties of Mg:Fe:Mn:LiNbO_3 Crystals

The congruent tri-doped Mg:Mn:Fe:LiNbO 3 crystal has been grown by Czochralski method. Some crystal samples are reduced in Li 2CO 3 powder at 500 ℃ for 24 hours or oxidized for 10 hours at 1100 ℃ in Nb 2O 5 powder. Compared with As-grown Mg:Mn:Fe:LiNbO 3, the absorption edge in UV-Vis. absorption spectrum of the oxidized sample and the reduced shifts to the violet and the red, respectively. Reduction increases the absorption of crystals in visible light region. In two-wave coupling experiments, the writing time, maximum diffraction efficiency and the erasure time of crystal samples in the same conditions are determined. The results indicate that oxidation and reduction disposing has great effect on the holographic recording properties of these crystals. The reduced crystal exhibits the fastest response time of 160 s among the crystal series. The mechanism of post-disposing effect on the holographic recording properties of Mg:Mn:Fe:LiNbO 3 crystals are investigated.

Fe^(2+)和Mn^(2+)对水稻根表铁膜及镉吸收转运的影响

采用水培实验,研究外源添加Fe^(2+)和Mn^(2+)对水稻幼苗根表铁膜形成、抗氧化酶活性及镉吸收转运的影响。结果表明:(1)添加Fe^(2+)使水稻幼苗根表铁膜中铁元素显著增加114.9%(质量分数,下同),锰和镉元素则分别显著降低了55.2%和42.3%(P<0.05);添加Mn^(2+)使铁膜中锰元素显著增加180.1%,镉元素则显著降低了18.0%。(2)添加Fe^(2+)能显著降低水稻幼苗叶片中活性氧(ROS),缓解ROS对水稻幼苗的毒害;添加Mn^(2+)使得叶片中ROS、超氧化物歧化酶和谷胱甘肽转移酶增加,Mn^(2+)处理引起的ROS升高可能起到诱导水稻胁迫应答,缓解镉毒害作用。

非均相UV/Fe-Cu-Mn-Y/H_2O_2反应催化降解4BS染料废水

制备了负载在Na Y分子筛上的Fe Cu Mn Y复合催化剂,并对其在非均相UV Fe Cu Mn Y H2O2体系中催化氧化4BS染料废水进行了研究.结果表明,非均相UV Fe Cu Mn Y H2O2体系对4BS染料废水的处理具有很高的效率.在基准条件下,反应时间为20min时,废水中4BS的去除率达到了93 7%.与均相UV Fenton体系不同,非均相UV Fe Cu Mn Y H2O2体系在碱性条件下(pH=10 5)仍可高效去除CODCr.动力学研究得到催化氧化4BS废水的模型方程,该模型可以为非均相UV Fe Cu Mn Y H2O2体系处理高色度的实际染料废水提供指导.

Fe-30Mn-9Al奥氏体钢高温循环氧化特征

研究了Fe - 30Mn - 9Al奥氏体钢在 70 0℃、80 0℃和 95 0℃空气中循环氧化 16 0h表面形成的氧化膜形貌、成分和组织结构 .Fe - 30Mn - 9Al奥氏体钢在 70 0℃和 80 0℃氧化时 ,初期增重较快 ,随着循环次数增加 ,氧化增重减小 ,氧化 16 0h分别增重 1 0 0和 4 0 8mg/cm2 .氧化层主要由Mn2 O3 ,Al2 O3 和 (Mn ,Fe) 2 O3 等相组成 .在 95 0℃ ,钢的氧化增重显著上升 ,16 0h增重 4 3 5 0mg/cm2 ,表面形成了Fe2 O3 、MnO2 以及MnAl2 O4、Al2 Fe2 O6等复合氧化物 .80 0℃下循环氧化后形成了多层氧化物膜 ,外层以Mn2 O3 型氧化物为主 ,内层以Al2 O3 为主 ;钢基体表面为富Fe。

Fe掺杂Mn/TiO_2低温脱硝催化剂的催化性能研究

采用氧化沉淀-浸渍法制备了不同含量Fe掺杂的Fe-Mn/TiO_2低温脱硝催化剂,考察了催化剂在80~180℃范围内的脱硝能力并通过XRD、BET、TG、H_2-TPR、NH_3-TPD等测试手段,对催化剂的物理化学性质进行了表征。实验结果表明,Fe的加入并没有改变Mn/TiO_2的主要晶相,仍是锐钛矿型的TiO_2,Mn Ox和FeO_x均以非晶态结构高度分散于载体表面,而且Fe的加入可以有效地改善催化剂的微观形貌、比表面积及表面酸性位点,从而提高其低温脱硝性能。Fe掺量在Fe/Ti为0.10时催化剂具有最佳性能,在120℃时脱硝率可达90%以上。

钙钛矿氧化物La_(0.65)(Ca,Ba)_(0.35)Mn_(1-x)Fe_xO_y的磁电阻效应

本工作制备了La065(Ca,Ba)035Mn1-xFexOy(x=0～02)氧化物系列样品。发现在常温附近,含Ba样品的磁阻变化率远比相应含Ca样品的高。在x=0时,样品电阻随温度的变化曲线存在金属—半导体转换峰,随着Fe对Mn的部分替代,该转换峰向低温区移动,当替代量x达到一定程度时,在实验温区观察不到金属—半导体转换峰。磁阻效应在高铁含量时只能在低温观察到。Fe替代Mn对大磁阻效应的影响,可能主要因为:随着Mn3+被Fe3+所替代,样品La065(Ca,Ba)035Mn1-xFexOy中的铁磁相互作用受到抑制,反铁磁相互作用得到加强。

CeO2修饰Mn-Fe-O复合材料及其NH3-SCR脱硝催化性能

氨选择性催化还原(NH3-SCR)技术需要进一步研发在相对较低温度(<300℃)下具有良好催化活性、高稳定性及环境友好的脱硝催化材料。本工作采用草酸共沉淀法制备Mn-Fe-O催化材料,并对其进行不同含量CeO2修饰,用于低温NH3-SCR脱硝催化反应。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、氮气吸附-脱附、X射线光电子能谱(XPS)、程序升温还原或脱附(H2-TPR、NH3-TPD)等手段对催化剂进行了表征。催化结果表明,在相同反应条件下适量CeO2修饰后的Mn-Fe-O样品比纯Mn-Fe-O表现出更优异的NH3-SCR脱硝催化性能,在80℃时NO转化率在95%以上,且具有较高的N2选择性。CeO2修饰提高了Mn-Fe-O氧化物表面的Fe^3+、Mn^3+和Mn4+含量及表面酸性位点数量,从而有助于NH3的吸附及催化反应的进行,并且Fe^2+/Fe^3+、Mn^2+/Mn^3+/Mn^4+以及Ce^3+/Ce^4+电子对之间的相互氧化还原反应提高了催化剂的氧化还原能力及稳定性。

Al_2O_3负载Mn-Fe-K金属氧化物催化臭氧氧化去除水中三种内分泌干扰物的研究

采用Al2O3负载Mn-Fe-K金属氧化物催化臭氧化技术研究了水中2,4-D、甲草胺和对硝基甲苯三种内分泌干扰物的去除效能。探讨了溶液pH值、不同臭氧投加量、催化剂用量、叔丁醇以及混合体系对有机物去除效能的影响。在同等实验条件下,催化臭氧氧化对2,4-D、甲草胺和对硝基甲苯的去除率分别为48.9%、64.0%和80.8%。随着温度、pH值(<9)、催化剂量的增加,2,4-D、甲草胺和对硝基甲苯的去除率均随着增大,但当pH值>9时,去除率随着pH值升高而有所减小。加入自由基抑制剂叔丁醇后各去除率均降低,表明其催化臭氧氧化过程均遵循羟基自由基机理。混合体系有利于有机污染物的去除率增加。

PACMANUS热液区Si-Fe-Mn氧化物的显微结构特征及意义

用显微镜、电子探针和扫描电镜等分析技术,对2008年"KX08-973"航次中国首次在东马努斯海盆PACMANUS热液区用拖网取得的少量Si-Fe-Mn氧化物海底热液产物样品进行显微结构特征研究。研究表明,显微镜下,样品呈隐晶质结构;扫描电镜下可见已石化的硅藻;电子探针分析结果显示,Fe和Mn的分布具有明显的分带性,呈现出Si-Mn质层被Si-Fe质层包裹的特征,反应了Si-Fe-Mn氧化物的形成具有多期多阶段性特征。样品是富Si,Fe和Mn的低温热液流体直接沉淀产物。本研究结果对该区热液氧化物的进一步研究,如Si-Mn质层和Si-Fe质层中Si与Mn和Fe的化合方式、微生物在热液氧化物形成过程中的作用具有指导意义。

Fe-Mn-Al-C合金的高温氧化行为

为了考察Fe-Mn-Al-C合金在高温空气介质中的抗氧化性能,本文利用热分析天平连续称重法,测定了三种合金在700～900℃下的氧化动力学曲线,计算了其抛物线速度常数及氧化激活能。并利用X射线结构分析、扫描电镜观察、能谱分析等手段对氧化层的特征及合金元素在氧化层中的分布进行了分析。结果表明,由脱碳所控制的氧化第一阶段,导致了氧化膜的多孔性,显示出第一阶段高的抛物线速度常数。氧化第二阶段为合金元素所控制,锰的选择性氧化在氧化过程中起主要作用。稀土元素的加入,可使氧化第二阶段的激活能升高,且可减轻或抑制内氧化区的出现。

SiO_3^(2-)浓度对KMnO_4/FeSO_4工艺除磷过程的影响

考察了天然水体中常见的SiO_3^(2-)对KMnO_4/FeSO_4工艺混凝除磷的影响。SiO_3^(2-)存在时KMnO_4/FeSO_4工艺混凝除磷的效能随着溶液pH的升高呈现先增加后降低的趋势。SiO_3^(2-)浓度为1.0 mmol/L,溶液pH值为4～6时,SiO_3^(2-)可促进KMnO_4/FeSO_4工艺除磷的效能,KMnO_4/FeSO_4工艺对磷的去除效果分别增加了6.0%,9.9%和6.3%;溶液pH值为7～9时,SiO_3^(2-)可显著抑制KMnO_4/FeSO_4工艺除磷的效能,KMnO_4/FeSO_4工艺对磷的去除效果分别降低了14.76%,32.6%和17.3%。KMnO_4/FeSO_4工艺形成的絮体颗粒物表面ζ电位显著降低,溶液中残余铁的量明显提高。另外,水中SiO_3^(2-)对KMnO_4/FeSO_4工艺形成的絮体颗粒物的组成和表面特征均有一定影响。该研究为KMnO_4/FeSO_4工艺混凝除磷技术的推广提供了必要的理论基础。

FeMnMg氧化物Fenton催化降解有机废水

采用高温煅烧硝化法制备Fe Mn Mg氧化物纳米晶,并采用扫描电镜(SEM)对Fe Mn Mg氧化物进行表征。结果表明,高温煅烧硝化法制备的Fe Mn Mg氧化物粒径为纳米范围,具有均匀的粒子尺寸和晶体尺寸。采用不同配比的Fe Mn Mg氧化物纳米晶催化剂对亚甲基蓝模拟的有机废水进行Fenton催化降解实验,对实验结果进行分析讨论。Fe Mn Mg的摩尔比为2∶3∶1的氧化物对亚甲基蓝的降解效果最好。当p H值为7左右,反应温度为25℃时,降解速率最快。Fe Mn Mg氧化物催化剂的投加量为0.012 g,保证了亚甲基蓝较好的降解率。在反应体系中采用选取30%H2O20.5 m L(即2 mmol/L),能达到较好的氧化降解效果。