乌达-乌斯太工业园大气颗粒物中汞的形态及空间分布特征

利用碳质分析（OC/EC）、离子色谱分析（IC）、程序升温脱附分析（TPD）、成像分析等综合分析手段,对内蒙古乌达-乌斯太工业园大气细颗粒物中汞的具体存在形态和空间分布特征进行了研究.结果表明,乌达-乌斯太工业园PM_2.5中Hg含量与有机碳（OC）、元素碳（EC）、Cl^-和NO₃^-含量的相关性系数r分别为<0.1、<0.1、0.854和0.745.PM_2.5中的汞以无机态为主,且可能以HgCl₂、HgS、HgO和Hg（NO₃）₂·H₂O为主要存在形态.PM_2.5中汞含量相对富集区多分布在高Hg⁰浓度,高氯和高酸（硝酸）区域,表明排氯、排酸等工业活动与PM_2.5中汞的形成具有重要的内在联系.     

云贵川交界区晚二叠世煤中汞形态分析

通过RA-915测汞仪与程序升温热解仪联用,分析了云贵川交界区晚二叠世煤在氩气、氮气和氧气3种不同气氛下的汞释放规律及煤中汞的存在形态.研究表明,煤在还原环境下热解时,汞的释放范围较广,且由于煤中汞的存在形态不唯一而呈现出明显的阶段性释放特征,在氮气和氩气气氛下煤中汞的释放行为接近一致.在氧气气氛下热解时,HgS和HgSO₄可能以HgSO₄·HgO和HgSO₄·2HgO这种过渡形式而使汞的释放温度范围趋于集中.云贵川交界区晚二叠世煤中的汞以HgS和HgSO₄为主要存在形态,部分煤样中含有一定量的HgO.     

添加CaCl2对烟气净化装置联合脱汞的规律分析

煤炭燃烧向大气中排放了大量汞。为了探究经济有效的汞排放控制方法,在管式炉中进行了CaCl₂晶体的水解实验,CaCl₂在一定温度和气氛下会水解产生HCl,HCl有利于烟气中Hg0的氧化。且随着反应温度的增加,水解率呈上升趋势。在流化床炉中进行了CaCl₂溶液蒸发协同脱汞实验。CaCl₂溶液喷洒在燃煤中可显著提高SCR脱销装置对Hg0的氧化率;煤中喷洒CaCl₂溶液可提高烟气中Hg2+的浓度和占比,从而提高湿法烟气脱硫装置（WFGD）对气态Hg的脱除效果。相比于喷洒在原煤中,将CaCl₂溶液喷洒在布袋除尘器（FF）前的蒸发干燥塔中,可显著提高FF脱除Hg的效果。整体上看,当温度越高,氯添加比越高时,烟气净化装置协同脱汞的效率也越高。     

化学氧化法和化学混凝法用于染料废水的脱色研究

研究了化学氧化法和化学混凝法处理染料废水的脱色效果,考查了氧化剂及混凝剂种类、投加量和pH值对脱色效果的影响。结果发现,光激发产生的复合氧化气体较纯ClO₂具有更好的脱色效果,且二者对活性染料废水的脱色效果优于对分散染料废水的脱色效果,都是在pH<10的条件下取得良好的脱色效果;化学混凝法对分散染料废水的脱色效果优于对活性染料废水的脱色效果,MgCl₂。6H₂O的脱色效果最好,PAC次之,Al₂(SO₄)₃。18H₂O最差;pH值对MgCl₂。6H₂O的脱色效果影响较大,在pH≥12的条件下,MgCl₂。6H₂O的脱色效果达最佳。      

烟气单质汞氧化去除过程络合反应机理

湿法氧化去除烟气Hg⁰过程中产物Hg²⁺易发生络合反应,络合产物可能改变氧化体系形成新反应机制,这一现象尚未被认识研究.为获得Hg²⁺络合物生成及其对烟气脱汞影响机理,研究了配体阳离子、配体浓度、反应pH值、反应温度和摩尔比等对Hg²⁺络合反应的影响和氧化去除烟气Hg⁰的络合反应机理.结果表明MgCl₂、KCl、NiCl₂和BaCl₂配体均能与HgCl₂形成络合物,而CuCl₂和SnCl₄则不能生成络合物.络合物生成量随配体浓度的增加先升高然后趋于平衡;络合反应在酸性环境下发生且不受pH值变化影响;碱性环境下络合反应不能进行;反应温度基本不影响络合反应效应;增加配体浓度可提高络合物产量,不同配体络合效应不同,但最大吸光度基本相同,为（4.20±0.03）A.配体对络合反应有响应区间,低于区间下限值时不能形成络合物,高于上限制值时络合物产量不随配体浓度而变化.HgCl₂络合反应累积稳定常数β₄=10^15.07;[HgCl₄]^2-可螯合Hg（aq）和O₂（aq）使其与ClO^-和Hg₂Cl₂反应,形成氧化-络合氧化反应新机理.     

汞污染土壤治理修复技术研究进展

总结了国内外土壤Hg环境质量标准限值,比较了中国和美国对汞污染土壤处理技术规定;在此基础上对热脱附、固化/稳定化、化学萃取和植物修复等Hg污染土壤治理修复进行了综述,总结了各技术的特点、优势和局限,可为我国汞污染土壤治理修复技术研究和工程实践提供参考。     

Ce-Mn/TiO2吸附剂的脱汞性能及抗SO2特性

采用浸渍法制备Mn/TiO₂（MT）、Ce/TiO₂（CT）和Ce-Mn/TiO₂（CMT）脱汞吸附剂,在固定床脱汞实验台上研究吸附剂的脱汞性能.结果表明,吸附温度为100~200℃时,3种吸附剂的脱汞性能均随温度的升高而增强;而在200~300℃范围内,脱汞效率均出现不同程度的降低.MT、CT及CMT吸附剂的脱汞效率在200℃时达到最高,分别为91%、58%和95%.MT和CT吸附剂的抗SO₂性能较弱,在N₂+6% O₂+1000×10^-6SO₂烟气条件下,30min内脱汞效率均下降到50%,而CMT吸附剂在2h内仍能保持80%以上的脱汞效率,表明在MT中掺杂Ce不仅可以提高吸附剂的脱汞性能,还可以增强抗SO₂性能.利用N₂吸附/脱附、X射线衍射（XRD）、H₂-程序升温还原（H₂-TPR）和X射线光电子能谱（XPS）等方法对吸附剂的物理化学性质进行表征,并对吸附产物进行热重分析（TG）和程序升温脱附实验（TPD）,阐明了CMT脱汞吸附剂的抗SO₂特性机理.Ce的掺杂,提高了活性组分在吸附剂表面的分散度及Mn⁴⁺的比例;相比于MnO₂,CeO₂可优先与SO₂反应,抑制了SO₂对Mn⁴⁺的毒害作用,从而提高了抗硫性能.     

武汉市高校大气降尘中水溶性离子污染特征及来源解析

于2017年11月采集武汉高校大气降尘样品106个,采用离子色谱仪分析样品中9种水溶性离子（F-、Cl-、NO₃-、SO₄2-、Na+、NH₄+、K+、Mg2+、Ca2+）的含量,用相关性分析和比值分析法解析其污染特征,用PCA-MLR模型初步探讨其来源及贡献率。结果表明:武汉高校降尘中主要水溶性离子为Ca2+、SO₄2-、NO₃-,平均浓度顺序为Ca2+>SO₄2->NO₃->K+>Na+>Cl->Mg2+>NH₄+>F-,且F-、Cl-、NO₃-、SO₄2-、Na+、K+、Mg2+、Ca2+分布存在明显的空间质异性。m（NO₃-）/m（SO₄2-）为0.28,以固定源污染为主;降尘样品总体呈碱性。9种可溶性离子主要以NaCl、KCl、MgCl₂、Mg（NO₃）₂、MgSO₄、Ca（NO₃）₂、CaSO₄等形式存在,主要来源于土壤/交通混合源、燃烧源、工业源,三者贡献率分别为8%、12%、80%。     

Mn活化铁盐絮凝污泥制备磁性吸附剂脱除烟气中Hg0

采用Mn(NO₃)₂活化铁盐絮凝污泥制备磁性吸附剂用于烟气中Hg⁰的脱除。结果表明：1)Mn(NO₃)₂热分解产生的O₂促进了污泥一次热解过程中产生的FeC_x分解,并有利于Mn⁴⁺与Fe³⁺等高价态金属氧化物的生成;Mn(NO₃)₂分解产生的气体有扩孔作用,在其掺杂量为10%时,吸附剂比表面积达到最大(88.5 m²/g),但Mn(NO₃)₂的掺杂量过高时会产生较多的晶相物质,并导致吸附剂的比表面积降低。2)当Mn掺杂量为10%(记为Mn₁₀-SFS),反应温度为150℃时,吸附剂脱汞效率最高(92.7%)。3)烟气中的O₂可对吸附剂中的活性氧进行有效补充,促进Hg⁰的脱除;NO以及低浓度的SO₂...     

污灌区盐分累积对污染土壤汞释放通量的影响

采用优化设计的动态通量箱,对不同盐分（NaCl和Na₂SO₄）和盐度（0~5%）的盐渍化土壤土-气界面的汞交换通量进行动态监测,研究盐渍化对污灌区土壤汞和大气释放的影响.结果表明：（1）两种盐分类型对土壤Hg释放的影响呈相反趋势.与未发生盐渍化的对照土壤相比,随着NaCl盐度梯度的上升,土壤Hg释放通量呈现上升趋势,5%盐度处理下,Hg通量均值与对照相比提高了48.94%;而随着Na₂SO₄盐度梯度的上升,土壤Hg释放通量呈现下降趋势,5%盐度处理下,Hg通量均值与对照相比降低了20.62%.（2）土壤盐分含量与土壤汞释放通量均值之间呈线性关系.对于NaCl,含量x（g/kg）与汞通量y [ng/（m²·h）]之间的模型为y=0.8258x+86.709（R²=0.9734）,对于Na₂SO₄,模型为y=-0.3354x+85.997（R²=0.9581）.从研究结果来看,高浓度的NaCl环境对土壤汞释放通量有显著影响,土壤的盐渍化趋势会使汞释放及作物吸收风险更趋严重.     

氯元素对烟气中汞的形态和分布的影响

采用化学热力平衡分析方法研究了在煤燃烧在气化过程中产生的瀵气里痕量元素汞的形态及分布，在一个大气压下，400K－2000K温度范围里，研究了汞－煤系统和汞－煤－氯系统中汞在还原性气氛和氧化性气氛的烟气中的化学形态和分布，着重探讨了煤中的氯元素对汞在烟气中的形态和分布的影响，化学热力平衡分析结果表明，在煤燃烧和气化的最高温度区域里，单质汞是示是主要形式，少量的氯元素可以大大地增强汞元素的蒸发;在气化的还原性气氛烟气中，汞的主要形式是单质汞，在氧化性气氛的燃煤烟气中随着在烟气中温度的降低，单质汞将发生化学反应而生成氯化汞；烟气中氯元素的含量越大，氯化汞作为稳定相的温度范围越宽。     

FeCl3强化汞污染土壤热解吸修复

目前采用的热解吸技术修复汞污染土壤所需热解吸温度(600~800 ℃)较高,导致修复成本很高,也造成土壤本身结构的破坏. 采用在土壤中加入添加剂的方式来降低土壤修复的热解吸温度和热解吸时间, 分析了热解吸修复汞污染土壤时FeCl₃的最佳投加量、热解吸时间和热解吸温度,并且对试验条件进行优化. 结果表明:在土壤中添加FeCl₃能够有效提高汞的去除率,可降低热解吸所需的温度和时间. 当热解吸温度为400 ℃、热解吸时间为30 min时,随着c(FeCl₃)/c(Hg)的增加,汞的去除率逐渐提高. c(FeCl₃)/c(Hg)、热解吸温度、热解吸时间分别为150、450 ℃、20 min下,是汞污染土壤热解吸修复的最佳条件. 在热解吸过程中添加FeCl₃,可以使土壤中的w(Hg)在较低热解吸温度、较短的热解吸时间下降至GB 15618—1995《土壤环境质量标准》三级标准限值(1.5 mg/kg)以下.      

施加盐基离子调控水稻Cd的吸收与累积

盐基离子含量是土壤肥力的重要指标,也是决定土壤Cd生物有效性的重要因素.为探明盐基离子对稻田系统中Cd迁移、转运与累积的影响,本研究通过水稻盆栽试验,按照土壤中盐基离子的物质的量比施加不同浓度梯度KCl、CaCl_2、NaCl和MgCl_2到模拟制备的轻度(0.5 mg·kg~(-1))和中度(1.5 mg·kg~(-1))Cd污染土壤,分析盐基离子对土壤CaCl_2提取态Cd含量和水稻吸收累积Cd的影响.结果表明:施加盐基离子能够增加土壤阳离子交换量(CEC),在轻度和中度Cd污染土壤中,土壤CaCl_2提取态Cd含量分别下降了24.6%～56.1%和17.0%～71.1%,糙米Cd含量分别降低了9.1%～60.5%和7.2%～36.0%.在轻度和中度Cd污染土壤中,糙米Cd含量与土壤CaCl_2提取态Cd含量之间存在线性正相关关系,根、茎、叶Cd含量与Ca含量均呈线性负相关.     

粉煤灰综合利用过程中汞的二次释放规律研究

我国粉煤灰年产生量4亿t左右,近年来利用率稳定在65%～68%,主要利用方式包括建材生产、道路施工、建筑工程和农业利用.建材生产包括高温工序,可能存在粉煤灰中汞的二次释放.本研究设计实验模拟了水泥生产、蒸养砖生产的主要环境因素,利用程序升温脱附的方法研究粉煤灰利用过程中的汞迁移转化规律,并对全国范围内粉煤灰利用过程汞的二次释放量做出估算.研究发现,粉煤灰中的汞以HgCl2(Hg2Cl2)、HgS和HgO的形式存在;水泥生产过程中,粉煤灰中98%以上的汞会释放;蒸养砖生产过程中,粉煤灰中汞的平均释放率为28%,释放率主要受到粉煤灰中的HgCl2(Hg2Cl2)比例的影响.我国粉煤灰利用过程中的汞二次排放量由2002年的4.07 t.a-1增至2008年的9.18 t.a-1,其中水泥行业的贡献率占到96.6%.     

Potential bioavailability of mercury in humus-coated clay minerals

It is well-known that both clay and organic matter in soils play a key role in mercury biogeochemistry, while their combined effect is less studied. In this study, kaolinite, vermiculite, and montmorillonite were coated or not with humus, and spiked with inorganic mercury (IHg) or methylmercury (MeHg). The potential bioavailability of mercury to plants or deposit-feeders was assessed by CaCl₂ or bovine serum albumin (BSA) extraction. For uncoated clay, IHg or MeHg extraction was generally lower in montmorillonite, due to its greater number of functional groups. Humus coating increased partitioning of IHg (0.5%–13.7%) and MeHg (0.8%–52.9%) in clay, because clay-sorbed humus provided more strong binding sites for mercury. Furthermore, humus coating led to a decrease in IHg (3.0%–59.8% for CaCl₂ and 2.1%–5.0% for BSA) and MeHg (8.9%–74.6% for CaCl₂ and 0.5%–8.2% for BSA) extraction, due to strong binding between mercury and clay-sorbed humus. Among various humus-coated clay particles, mercury extraction by CaCl₂ (mainly through cation exchange) was lowest in humus-coated vermiculite, explained by the strong binding between humus and vermiculite. The inhibitory effect of humus on mercury bioavailability was also evidenced by the negative relationship between mercury extraction by CaCl₂ and mercury in the organo-complexed fraction. In contrast, extraction of mercury by BSA (principally through complexation) was lowest in humus-coated montmorillonite. This was because BSA itself could be extensively sorbed onto montmorillonite. Results suggested that humus-coated clay could substantially decrease the potential bioavailability of mercury in soils, which should be considered when assessing risk in mercury-contaminated soils.     

Hg 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 a lab-scale fixed-bed reactor. X-ray diffraction, nitrogen adsorption porosimetry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption (TPD) analyses 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 (Hg^2 +). 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 mercuric oxide (HgO).     

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).     

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.     

Removing and recycling mercury from scrubbing solution produced in wet nonferrous metal smelting flue gas purification process

Wet purification technology for nonferrous metal smelting flue gas is important for mercury removal; however, this technology produces a large amounts of spent scrubbing solution that contain mercury. The mercury in these scrubbing solutions pose a great threat to the environment. Therefore, this research provides a novel strategy for removing and recycling mercury from the scrubbing solution, which is significant for decreasing mercury pollution while also allowing for the safe disposal of wastewater and a stable supply of mercury resources. Some critical parameters for the electrochemical reduction of mercury were studied in detail. Additionally, the electrodeposition dynamics and electroreduction mechanism for mercury were evaluated. Results suggested that over 92.4% of mercury could be removed from the scrubbing solution in the form of a Hg-Cu alloy under optimal conditions within 150 min and with a current efficiency of approximately 75%. Additionally, mercury electrodeposition was a quasi-reversible process, and the controlled step was the mass transport of the reactant. A pre-conversion step from Hg(Tu)₄²⁺ to Hg(Tu)₃²⁺ before mercury electroreduction was necessary. Then, the formed Hg(Tu)₃²⁺ on the cathode surface gained electrons step by step. After electrodeposition, the mercury in the spent cathode could be recycled by thermal desorption. The results of the electrochemical reduction of mercury and subsequent recycling provides a practical and easy-to-adopt alternative for recycling mercury resources and decreasing mercury contamination.     

胡敏酸对汞还原能力的测定和表征

还原容量(RC)是表征胡敏酸(HA)氧化还原特性的重要指标.采用饱和H2振荡法和土壤溶液法对HA分别进行化学和微生物预处理,结合对照(未经任何还原前处理),在Fe3+还原法测定RC基础上,以柠檬酸铁(FeCit)为参照,分别以氯化汞(HgCl2)及硝酸汞[Hg(NO3)3]作电子受体,测定了3种HA(上海巨枫SH、天津光复TJ、缙云山JY)对汞的化学还原容量(CRC)、微生物还原容量(MRC)、本底还原容量(NRC),以了解HA对Hg2+的还原能力.结果表明,①不同电子受体对HA还原汞能力影响显著,FeCit条件下测得RC值远高于Hg(NO3)2和HgCl2(1～2个数量级),因此采用Fe3+还原法会过高估计HA对Hg2+的实际还原能力;②受自身结构和基团的影响,3种胡敏酸对汞的还原能力差异明显,以JY最高,分别(以C计)为(0.95±0.03)mmolc.mol-1(NRC)、(5.95±0.63)mmolc.mol-1(CRC)和(6.26±0.51)mmolc.mol-1(MRC);③溶液态HA还原Hg能力明显高于固态HA,增幅在100%～691.67%之间.同时,通过对比3个还原容量指标发现,CRC和MRC均显著大于NRC,而CRC和MRC之间无明确大小关系,因此,CRC并不能完全代表HA在微生物还原条件下对Hg的真实还原容量.