Functional groups assisted-photoinduced electron transfer-mediated highly fluorescent metal-organic framework quantum dot composite for selective detection of mercury (II) in water

The presence of toxic mercury (II) in water is an ever-growing problem on earth that has various harmful effect on human health and aquatic living organisms. Therefore, detection of mercury (II) in water is very much crucial and several researches are going on in this topic. Metal-organic frameworks (MOFs) are considered as an effective device for sensing of toxic heavy metal ions in water. The tunable functionalities with large surface area of highly semiconducting MOFs enhance its activity towards fluorescence sensing. In this study, we are reporting one highly selective and sensitive luminescent sensor for the detection of mercury (II) in water. A series of binary MOF composites were synthesized using in-situ solvothermal synthetic technique for fluorescence sensing of Hg²⁺ in water. The well-distributed graphitic carbon nitride quantum dots on porous zirconium-based MOF improve Hg²⁺ sensing activity in water owing to their great electronic and optical properties. The binary MOF composite (2) i.e., the sensor exhibited excellent limit of detection (LOD) value of 2.4 nmol/L for Hg²⁺. The sensor also exhibited excellent performance for mercury (II) detection in real water samples. The characterizations of the synthesized materials were done using various spectroscopic techniques and the fluorescence sensing mechanism was studied.     

污泥与煤在循环流化床混烧过程中的汞排放特性

在密相床截面积为0.23m×0.23m、高度为7 00m的循环流化床燃烧试验装置上进行了含汞污泥与煤的混烧试验.测试并分析讨论了污泥与煤混烧过程中汞的分布,探讨了Ca/S摩尔比、脱硫剂种类、过量空气系数等运行参数以及烟气成分对汞在烟气、飞灰和炉渣中形态分布的影响规律.结果表明,大部分汞进入烟气,且元素汞是混烧烟气中的主要存在形态.钙基脱硫剂对烟气中氧化态汞有较强的吸附脱除作用,CaO对汞的脱除效果要好于CaCO3.随着烟气中SO2、NOx浓度的增大,烟气中二价汞所占份额呈上升趋势.过量空气系数对烟气和灰渣中汞的浓度和形态分布有较大的影响.     

降水中汞的赋存形态

在北京市不同地点和不同时期采集降水样品 36个 .分析结果表明 ,汞易形成相对稳定的络合态汞 ,除 Hg⁰_(w) 外各形态汞含量均表现为采暖期大于非采暖期 .降水中各形态汞的含量和百分比按大小排序 ,经统计检验 ,在非采暖期水相中为 Hg^re_(w)>[Hg⁰_(w),Hg²⁺_(w)],颗粒态汞为 Hg^re_(p)>Hg²⁺_(p)>Hg⁰_(p);在采暖期水相中均为 Hg^re_(w)>Hg²⁺_(w)>Hg⁰_(w),颗粒态汞为 Hg^re_(p)>[Hg²⁺_(p),Hg⁰_(p)].在非采暖期颗粒态汞含量及百分比 Hg^T_(p)>溶解态汞 Hg^T_(w),在采暖期颗粒态汞和溶解态汞没有明显差异 .小于 0.45μm颗粒吸附的汞 Hg⁰相对较多 ,Hg²⁺形态汞较少 ,水溶液中 Hg⁰ 形态汞少 ,Hg²⁺形态汞多 ,表明 Hg⁰ 形态汞更易在微小颗粒物上吸附 ,而 Hg²⁺形态汞相当部分可以保留在水溶液中 .     

金属有机框架ZIF-8/聚二乙烯基苯纳米复合材料的合成及其吸附VOCs的性能

在常温常压下的甲醇溶液体系中,将COOH功能化的介孔材料聚二乙烯基苯(PDVB)与微孔材料金属有机框架(MOFs)ZIF-8进行复合,获得了一种新型的多孔纳米复合材料ZIF-8/PDVB,采用XRD、FTIR、SEM和氮气吸附-脱附等方法对ZIF-8/PDVB进行表征,并考察了其吸附甲苯、乙酸乙酯的性能.XRD谱图表明,所合成的ZIF-8以晶体形式存在;FTIR和XRD的结果表明,ZIF-8与PDVB的复合是通过Zn2+与PDVB上的COOH形成配位,未配位饱和的Zn~(2+)再与2-甲基咪唑进行配位,从而形成纳米复合材料ZIF-8/PDVB;SEM结果显示,ZIF-8晶体分散在PDVB的表面上;氮气吸附-脱附表征结果显示,ZIF-8/PDVB的比表面积达到1301 m~2·g~(-1),材料同时具有介孔与微孔结构.吸附性能评价结果表明,ZIF-8/PDVB对甲苯、乙酸乙酯均具有优良的吸附性能,ZIF-8/PDVB在吸附VOCs性能上显示出潜在的巨大优势.     

不同波长和强度光照对水体汞还原的影响

采用室内模拟实验,探讨不同光波长、强度对HgCl2还原反应的影响,根据载气中Hg0的实时浓度跟踪HgCl2还原反应的过程,计算Hg0释放通量来进行汞光还原程度定性分析、动力学定量分析,并运用积分法和微分法确定反应级数.结果表明,Hg2+的还原量与光波长呈负相关、与光强度呈正相关,说明光子提供的能量对汞的光还原反应起关键性作用,汞还原率由光波长和强度共同决定,并且受溶液体积和载气流速影响;在各组实验中,载气中的Hg0浓度均表现为先上升再下降后趋于平稳的规律,Hg0浓度上升阶段的主要反应是Hg2+的还原反应和Hg0的释放,而下降阶段的主要反应是Hg0的释放;本研究中可见光下的汞还原反应为一级反应,UVA、UVB光照下的汞还原反应为二级反应,这与汞的配合物具有特定的光谱吸收带和实验用灯提供的光波范围有关.     

Absorption characteristics of elemental mercury in mercury chloride solutions

Elemental mercury （Hg^0） in flue gases can be efficiently captured by mercury chloride （HgCl2） solution. However, the absorption behaviors and the influencing effects are still poorly understood. The mechanism of Hg^0 absorption by HgCl2 and the factors that control the removal were studied in this paper. It was found that when the mole ratio of Cl^- to HgCl2 is 10：1, the Hg^0 removal efficiency is the highest. Among the main mercury chloride species, HgCl3^- is the most efficient ion for Hg^0 removal in the HgCl2 absorption system when moderate concentrations of chloride ions exist. The Hg^0 absorption reactions in the aqueous phase were investigated computationaIIy using Moller-Plesset perturbation theory. The calculated Gibbs free energies and energy barriers are in excellent agreement with the results obtained from experiments. In the presence of SO3^2- and SO2, Hg^2＋ reduction occurred and Hg^0 removal efficiency decreased. The reduced Hg^0 removal can be controlled through increased chloride concentration to some degree. Low pH value in HgCla solution enhanced the Hg^0 removal efficiency, and the effect was more significant in dilute HgCl2 solutions. The presence of SO4^2- and NO3^- did not affect Hg^0 removal by HgCl2.     

Hg2+对固定化小球藻污水净化及生理特征的影响

利用褐藻酸钙凝胶包埋固定普通小球藻,对人工配制的含汞污水进行静态净化实验,研究了不同浓度Ｈｇ＾２＋对固定化小球藻净化污水中氨氮,正磷酸盐的效率及其４个生理指标（叶绿素α,光合强度,生长和过氧化物酶）的影响,并与悬浮藻对照比较。结果表明,由于小球藻的固定化增加了对Ｈｇ＾２＋毒性的抗性,０．２×１０＾－６浓度的Ｈｇ＾２＋对其净化效率无多大影响,而悬浮藻的净化明显下降。随着Ｈｇ＾２＋浓度的增加,固定藻的     

Mercury removal from coal combustion flue gas by modified fly ash

Fly ash is a potential alternative to activated carbon for mercury adsorption. The effects of physicochemical properties on the mercury adsorption performance of three fly ash samples were investigated. X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, and other methods were used to characterize the samples. Results indicate that mercury adsorption on fly ash is primarily physisorption and chemisorption. High specific surface areas and small pore diameters are beneficial to efficient mercury removal. Incompletely burned carbon is also an important factor for the improvement of mercury removal efficiency, in particular. The C-M bond, which is formed by the reaction of C and Ti, Si and other elements, may improve mercury oxidation. The samples modified with CuBr2 , CuCl 2 and FeCl3 showed excellent performance for Hg removal, because the chlorine in metal chlorides acts as an oxidant that promotes the conversion of elemental mercury (Hg0) into its oxidized form (Hg2+). Cu2+ and Fe3+ can also promote Hg 0 oxidation as catalysts. HCl and O2 promote the adsorption of Hg by modified fly ash, whereas SO2 inhibits the Hg adsorption because of competitive adsorption for active sites. Fly ash samples modified with CuBr2 , CuCl2 and FeCl3 are therefore promising materials for controlling mercury emissions.     

Influence of dissolved organic matter character on mercury incorporation by planktonic organisms：An experimental study using oligotrophic water from Patagonian lakes

Ligands present in dissolved organic matter （DOM） form complexes with inorganic divalent mercury （Hg^2＋） affecting its bioavailability in pelagic food webs. This investigation addresses the influence of a natural gradient of DOM present in Patagonian lakes on the bioaccumulation of Hg^2＋ （the prevailing mercury species in the water column of these lakes） by the algae Cryptomonas erosa and the zooplankters Brachionus calyciflorus and Boeckella antiqua. Hg^2＋ accumulation was studied through laboratory experiments using natural water of four oligotrophic Patagonian lakes amended with^197Hg^2＋. The bioavailability of Hg^2＋ was affected by the concentration and character of DOM. The entrance of Hg^2＋ into pelagic food webs occurs mostly through passive and active accumulation. The incorporation of Hg^2＋ by Cryptomonas, up to 27% of the Hg^2＋ amended, was found to be rapid and dominated by passive adsorption, and was greatest when low molecular weight compounds with protein-like or small phenolic signatures prevailed in the DOM. Conversely, high molecular weight compounds with a humic or fulvic signature kept Hg^2＋ in the dissolved phase, resulting in the lowest Hg^2＋ accumulation in this algae. In Brachionus and Boeckella the direct incorporation of Hg from the aqueous phase was up to 3% of the Hg^2＋ amended. The dietary incorporation of Hg^2＋ by Boeckella exceeded the direct absorption of this metal in natural water, and was remarkably similar to the Hg^2＋ adsorbed in their prey. Overall, DOM concentration and character affected the adsorption of Hg^2＋ by algae through competitive binding, while the incorporation of Hg^2＋ into the zooplankton was dominated by trophic or dietary transfer.     

低分子有机酸对汞氧化还原反应的影响

为探究植被根系分泌物的主要成分低分子有机酸对汞氧化还原反应的影响,采用室内模拟试验,探讨了酒石酸、柠檬酸及琥珀酸对汞的还原、氧化反应的影响,并分析了其相应的作用机制.结果表明,酒石酸对汞还原反应有明显的促进作用,柠檬酸有抑制作用.低浓度琥珀酸对汞还原反应有促进作用,高浓度为抑制作用.酒石酸还原Hg2+的反应为二级动力学反应,速率常数为0.0014~0.0056 L·(ng·min)-1.3种有机酸在反应初期对Hg0表现出一定的氧化作用,但随后被氧化的Hg0又被重新还原.3种有机酸对Hg0的氧化能力顺序为:柠檬酸>酒石酸>琥珀酸.     

Hg0 removal from flue gas over different zeolites modified by FeCl3

The elemental mercury removal abilities of three different zeolites (NaA, NaX, HZSM-5) impregnated with iron (III) chloride were studied on alab-scale fixed-bed reactor. X-ray diffraction, nitrogen adsorption porosimetry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption (TPD) analy-ses were used to investigate the physicochemical properties. Results indicated that the pore structure and active chloride species on the surface of the samples are the key factors for physisorption and oxidation of Hg⁰, respectively. Relatively high surface area and micropore volume are beneficial to efficient mercury adsorption. The active Cl species generated on the surface of the samples were effective oxidants able to convert elemental mercury (Hg⁰) into oxidized mercury (Hg²⁺). The crystallization of NaCl due to the ion exchange effect during the impregnation of NaA and NaX reduced the number of active Cl species on the surface, and restricted the physisorption of Hg⁰. Therefore, the Hg⁰ removal efficiencies of the samples were inhibited. The TPD analysis revealed that the species of mercury on the surface of FeCl₃-HZSM-5 was mainly in the form of mercuric chloride(HgCl₂), while on FeCl₃-NaX and FeCl₃-NaA it was mainly mercuri coxide(HgO).     

TiO2/膨润土复合材料对Hg2+的吸附性能研究

利用纳米TiO_2对膨润土进行复合改性,制备TiO_2/膨润土复合材料.采用电镜扫描、X-射线衍射表征改性前后膨润土的结构和形貌.通过室内模拟实验,以膨润土为对照,研究不同添加量、pH、吸附时间及初始Hg~(2+)浓度等条件下,TiO_2/膨润土复合材料对Hg~(2+)的吸附特性与性能,同时通过正交试验,探究TiO_2/膨润土复合材料吸附Hg~(2+)的最优条件.结果表明,改性后的膨润土颗粒明显变小,且颗粒疏松多空孔,层间距增大.相比于膨润土,TiO_2/膨润土复合材料吸附性能得到极大提高.TiO_2/膨润土复合材料对Hg~(2+)的吸附率均随着添加量、pH、吸附时间的增大而增大,添加量为1.5 g·L~(-1)、pH为7.0、吸附时间为120 min时,吸附率达98.0%以上.但TiO_2/膨润土复合材料对Hg~(2+)的吸附率随着初始Hg~(2+)浓度的增大而减小.通过4种动力学模型拟合发现,吸附过程符合假二级动力学方程,吸附以化学吸附为主.吸附等温线更符合Langmuir等温方程,属于典型的单分子层吸附,最大吸附量为20.66 mg·g-1.吸附Hg~(2+)的最优实验条件:添加量为2.0 g·L~(-1),pH为8.0,初始Hg~(2+)浓度为45 mg·L~(-1),吸附时间为16 h,此时吸附率99.9%,平衡浓度为0.034 mg·L~(-1).     

Comparative proteomic study and functional analysis of translationally controlled tumor protein in rice roots under Hg2+ stress

So far, very little is known about mercury stress-induced intercellular metabolic changes in rice roots at the proteome level. To investigate the response of rice roots to mercury stress, changes in protein expression in rice roots were analyzed using a comparative proteomics approach. Six-leaf stage rice seedlings were treated with 50 μmol/L HgCl₂ for 3 hr; 29 protein spots showed a significant changes in abundance under stress when compared with the Hg²⁺-tolerant rice mutant and wild type (Zhonghua 11). Furthermore, all these protein spots were identified by mass spectrometry to match 27 diverse protein species. The identified proteins were involved in several processes, including stress response, redox homeostasis, signal transduction, regulation and metabolism; some were found to be cellular structure proteins and a few were unknown. Among the up-regulated proteins, OsTCTP (translationally controlled tumor protein) was chosen to perform hetereologous expression in yeast which was presumed to participate in the Hg²⁺ tolerance of rice, providing evidence for its role in alleviating Hg²⁺ damage. Among the many tests, we found that OsTCTP-overexpressed yeast strains were more resistant to Hg²⁺ than wild-type yeast. Thus, we propose that OsTCTP contributes to Hg²⁺ resistance. Here we present, for the first time, the functional characterization of OsTCTP in connection with Hg²⁺ stress in plants.     

Mercury oxidation and adsorption characteristics of potassium permanganate modified lignite semi-coke

The adsorption characteristics of virgin and potassium permanganate modified lignite semi-coke (SC) for gaseous Hg⁰ were investigated in an attempt to produce more effective and lower price adsorbents for the control of elemental mercury emission. Brunauer-Emmett-Teller (BET) measurements, X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to analyze the surface physical and chemical properties of SC, Mn-SC and Mn-H-SC before and after mercury adsorption. The results indicated that potassium permanganate modification had significant influence on the properties of semi-coke, such as the specific surface area, pore structure and surface chemical functional groups. The mercury adsorption efficiency of modified semi-coke was lower than that of SC at low temperature, but much higher at high temperature. Amorphous Mn⁷⁺, Mn⁶⁺ and Mn⁴⁺ on the surface of Mn-SC and Mn-H-SC were the active sites for oxidation and adsorption of gaseous Hg⁰, which oxidized the elemental mercury into Hg²⁺ and captured it. Thermal treatment reduced the average oxidation degree of Mn^x+ on the surface of Mn-SC from 3.80 to 3.46. However, due to the formation of amorphous MnO_x, the surface oxidation active sites for gaseous Hg⁰ increased, which gave Mn-H-SC higher mercury adsorption efficiency than that of Mn-SC at high temperature.     

Release characteristics of mercury in chemical looping combustion of bituminous coal

This study evaluated the release characteristics of mercury from bituminous coal in chemical looping combustion (CLC) using Australian iron ore as the oxygen carrier in a fixed bed reactor. The effects of several parameters, such as temperature in the fuel reactor (FR) and air reactor (AR), gasification medium in the FR, and reaction atmosphere in the AR, on mercury release characteristics, were investigated. The mercury speciation and release amount in the FR and AR under different conditions were further explored. The results indicate that most of the mercury in coal was released in the FR, while the rest of it was released in the AR. Hg⁰ was found to be the major species in the released mercury. The results also indicate that a higher temperature in the FR led to an increase in the total mercury release amount and a decrease in Hg⁰ proportion. However, a higher temperature in the AR resulted in a decrease in the total mercury release amount and Hg⁰ proportion. The increase in the H₂O/CO₂ ratio of gasification mediums in the FR was beneficial for the increase in the total mercury release amount and Hg⁰ proportion. A higher O₂ concentration in reaction atmosphere in AR had a negligible effect on the total mercury release amount, but a positive effect on Hg⁰ oxidization.     

Some aqueous reactions of potential importance in the atmospheric chemistry of mercury

Reactions of Hg(I) and Hg(II) with oxidizing and reducing agents have been investigated using stopped-flow and spectroscopic techniques. Hg₂²⁺ was found to be oxidized by HClO and radicals produced by Fentons reagent (Fe²⁺ + H₂O₂). The rate determining step in the reaction of Hg₂²⁺ and HClO is probably a relatively rapid reaction of Hg⁰ and HClO. A photochemically induced reduction of Hg(OH)₂(aq) to Hg⁰ was observed when irradiating with simulated sunlight (λ>290 nm), which may be a process of environmental importance. Aqueous Hg(CN)₂ and HgCl₂ were found to be stable. The rate of reduction of Hg(SO₃)₂²⁻ is not affected by irradiation. No oxidation of Hg₂²⁺ was found when mixing solutions containing H₂O₂ or Fe³⁺ or a mixture of the two which suggests that H₂O₂ is not an important oxidant for mercury under environmental conditions.     

MOFs材料在废水污染物吸附治理中的应用研究进展

介绍了国内外MOFs材料吸附去除废水中各种污染物的研究进展,主要针对重金属离子(Hg²⁺、U⁶⁺、Cr⁶⁺、Cd²⁺、Pb²⁺、Co²⁺、Sb⁵⁺、Sr²⁺)及类金属离子(As³⁺、As⁵⁺)、有机污染物(染料分子、芳香化合物)等的去除,分析了MOFs及改性MOFs材料对废水中污染物的吸附性能;展望了MOFs材料在废水污染物吸附治理中的应用前景,提出高稳定性及具有催化性质的MOFs材料是用于废水中污染物吸附治理的理想材料。     

生物毒性测试微孔板MTOXPlate的分析性能研究

采用以11种微生物为指示生物的毒性测试微孔板MTOXPlate,以污染物对微生物细胞的脱氢酶活性抑制为测试终点,对重金属Hg2+、Cd2+、Cr6+、Pb2+,酚类化合物2,4-二氯酚(2,4-DCP)、邻氯苯酚(2-CP)、对氯苯酚(4-CP)、邻硝基酚(2-NP)、对硝基酚(4-NP)及地表水、生活污水、印染废水的生物毒性进行分析.结果表明,MTOXPlate生物毒性测试微孔板具有良好的毒性分析性能,Hg2+、Cd2+、Cr6+和Pb2+的EC50值分别为0.617、21.05、35.21和11.22 mg·L-1,2,4-DCP、2-CP、4-CP、2-NP和4-NP的EC50值分别为27.26、64.29、44.19、85.89和33.84 mg·L-1.MTOXPlate分析得到地表水原水的抑制率均小于20%,生活污水的EC50值为62.19%,印染废水的EC50值为16.42%,表明生物毒性测试微孔板MTOXPlate能真实地反映地表水、生活污水和印染废水的毒性情况.     

耐汞好氧反硝化菌的鉴定及适应汞离子的特性研究

从实验室保存的高效好氧反硝化菌种中筛选得到一株抗汞细菌并命名为X1,经生理生化特性和16SrRNA基因序列分析,初步鉴定该菌为恶臭假单胞菌(Pseudomonasputida).对菌株X1进行Hg2适应特性研究,结果表明,对于Hg2浓度为2、67++4、、mg·L-1的实验组,菌体分别需要被延滞12、284018、、h后进入对数期,而8mg·L-1实验组则不能进入对数期;在好氧反硝化过程中,Hg2浓度在7mg·L+-1范围内各实验组的好氧反硝化过程中NO3-N浓度变化速率、NO2-N累积峰值、pH特征点出现时刻随着Hg2浓度的增大而增大(延迟),而Hg2浓度呈现出同硝氮一致的下降趋势,并且在对数期内除汞率能达到100%.研究表明,菌株X1对Hg2最大适宜耐受浓度为7mg·L+-1,相应适应时间约为40h.在最大耐受浓度范围内,菌株X1的生长和好氧反硝化过程呈现出"被抑制-适应-受刺激"的变化规律,其中,被抑制的时间和受刺激的程度都随着Hg2浓度的增大而增大,主要表现为延滞期的延长和对数期的缩短.此外,在对数期,菌株X1的生长速率、达到稳定期的浓度和好+氧反硝化速率也都随着Hg2浓度的增大而增大,且大于无Hg2菌组.++     

中国燃煤汞排放清单的初步建立

建立中国分省燃煤汞排放清单,对于研究汞的大气化学转化、迁移和沉降,制定中国汞污染控制对策具有重要意义.本研究按经济部门、燃料类型、燃烧方式和污染控制技术将排放源划分为65种不同类型,根据各类型的煤炭消费量、燃料汞含量和汞排放因子计算汞排放量,最终建立了分省燃煤汞排放清单.用2组原煤汞含量数据资料计算的2000年中国燃煤大气汞排放量分别为161.6 t和219.5 t,其中绝大部分汞排放来自工业、电力和生活消费,分别占46%、35%和14%.Hg⁰、Hg²⁺和Hg_p在中国燃煤大气汞排放中所占的比例分别为16%、61%和23%.中国燃煤汞排放在各地区间有较大差异,排放量较大的省份有河南、山西、河北、辽宁和江苏,均超过10t/a.