锰基水滑石固定修复U(Ⅵ)污染土壤的研究

以水热法制备了二元水滑石(MnAl-LDH)和三元水滑石(MnMgAl-LDH),将其作为固定剂对U(Ⅵ)污染的土壤进行修复。利用毒性浸出实验(TCLP)和Tessier逐级化学提取法研究了固定前后铀的浸出特性与形态变化。结果表明,当含铀土壤不添加固定剂时,铀的浸出质量分数为147.20 mg/kg;当土壤中添加MnAl-LDH为固定剂培养28 d后,土壤中铀的浸出质量分数为44.16 mg/kg,浸出率为30.00%;投加MnMgAl-LDH培养28 d后,土壤中铀的浸出质量分数仅为31.90 mg/kg,浸出率降低至21.67%。     

功能化四乙烯五胺对镉铅污染土壤的钝化修复效应

通过美国毒性浸出实验(TCLP)和连续浸提实验(SEP),对比传统的土壤无机钝化修复剂:九水硫化钠和磷酸二氢钾,评价了二硫代氨基甲酸基团封端的四乙烯五胺对镉、铅污染土壤的钝化修复效果。研究结果表明:功能化的四乙烯五胺自身具有良好的生物降解性能,能够显著降低土壤中镉、铅的浸出毒性,将土壤中可交换态与碳酸盐结合态的镉、铅转化为有机结合态,对镉、铅的钝化效果明显优于传统的磷酸二氢钾和九水硫化钠。     

不同固定剂对铬污染土壤的原位修复

以某中度铬污染土壤为研究对象,通过室内模拟固定原位修复实验,探究石灰、天然沸石、钙镁磷肥、硫酸亚铁、氧化镁5种固定剂对铬各形态的影响并对生物可利用性进行评价。结果表明:固定剂的添加使Cr残渣态比例增加,易于被植物利用的弱酸提取态减少,从而使铬的生物利用性降低。5种固定剂中氧化镁固定化后的土样中铬的残渣态转化率为19.72%,生物可利用系数为0.048,极大地降低了土壤重金属进入生物链的几率。     

土壤电荷特性对NH4-D树脂修复铀污染土壤的研究

为解决铀尾矿库中铀元素迁移污染周围环境的问题,采用氨基磷酸螯合树脂D418制备出NH₄-D材料,通过表面电荷特性实验、毒性浸出实验和形态分析实验,考察了铀污染土壤固化效果与土壤电荷变化之间的关系。结果表明,土壤中铀的固定效率和电荷变化受土壤pH、固定剂投加量(n)的影响。随pH和投加量(n)的增加,固化后土壤表面负电荷数增大,电荷密度增强,在pH=5和n=6%时,出现铀最佳固定效率83.67%、最大负电位(φ)=-17.345 mV和最大负电荷密度(SCN)=1.142 cmol/kg;与CK组对比,NH₄-D增强了土壤中铀由不稳定的可交换态向稳定的残渣态转换。NH₄-D表现出对污染土壤中U(Ⅵ)有较好的固定和富集效果。     

化肥的施加对土壤中外源性Cd、Pb赋存形态的影响

采用盆栽培育土壤的方式,通过修正的Tessier连续提取法(七步法)研究了N、P和K肥对外源Cd、Pb污染土壤重金属赋存形态的影响。结果表明,无论是原土还是添加外源性Cd、Pb的污染土壤,Pb基本被固定在残渣态和铁锰氧化物结合态,在外源Cd、Pb污染土壤中添加肥料可降低Pb的铁锰氧化物结合态等较稳定形态的赋存比例,提高生物可利用态的百分比,促进Pb向植物体系的迁移。原土中的Cd大部分处于生物可利用态,当外源性Cd污染进入土壤,离子交换态进一步增加,且土壤中Cd的浓度越大离子交换态所占的百分比越高。向中低浓度的Cd污染土加入肥料可增加离子交换态的赋存比例,提高土壤中Cd的活性;对更高浓度的Cd污染土,离子交换态已基本饱和,加入肥料对Cd的形态分布未有显著影响。添加肥料可促进土壤中外源性重金属Cd和Pb向植物体系迁移,为植物修复重金属污染土壤提供技术支持。     

钝化剂对废弃石煤矿山铀污染土壤修复效果研究

本文采集江西省内某废弃石煤矿区周边实际铀（U）污染土壤为研究对象，选用泥炭和玉米秸秆炭作为有机钝化剂，以及将沸石和蛭石作为无机钝化剂对污染土壤进行钝化处理，以此考察不同钝化剂对污染土壤理化性质和U形态分布的影响。结果表明，四种钝化剂对污染土壤pH值影响不显著，沸石处理的土壤pH值虽有增加，但对U的钝化效果最不理想；泥炭对污染土壤中U的钝化效果最显著，与污染土壤混合培养5周后，铁锰氧化物结合态U占比降低了15.15%，硫化物及有机物结合态U占比增加了22.22%，与原始土壤中U形态分布对比，残余态U和硫化物及有机物结合态U总占比加和明显增加；蛭石对污染土壤中U也具有一定的钝化效果，与污染土壤混合培养3周后，U形态分布基本趋于稳定，铁锰氧化物结合态含量占比出现了较为明显的降低。     

磷酸亚铁铵对铅污染土壤的修复研究

利用磷酸亚铁铵对5倍铅(GB 15618—1995三级标准)污染土壤进行固化,并通过TCLP和Tessier连续提取法对固化效果进行分析。结果表明,磷酸亚铁铵的加入使可交换态和碳酸盐结合态铅显著减少,降低了重金属Pb的有效性,可有效固化土壤中的重金属Pb。磷酸亚铁铵质量分数为1.5%时能达到固化要求,且加入的固化剂量越大,稳定效率越高。利用XRD和SEM对土壤进行结构表征,结果表明,经固化处理后形成的磷酸铅盐(PbH_2PO_4、Pb_3(PO_4)_2)、类磷氯铅矿(Pb-PO_4-Cl/OH)及混合重金属沉淀物(Fe-PO_4-Pb-OH)结构稳定,使得重金属离子难以浸出。     

不同浸提方法对固体废物中重金属浸出含量的影响

比较了4种浸提方法[水提法、毒性特征浸出程序(TCLP)、pH控制的改良TCLP和连续化学浸提法(SCE)]在不同的液固比(L/S)、pH和浸提剂类型下，对城市固体废弃物(MSW)焚烧炉空气污染控制(APC)残留物中重金属浸出质量浓度的影响。结果表明：用蒸馏水浸提时，当L/S在2～100 mL·g^-1范围内，所有重金属的浸出质量浓度均随着L/S的增加而降低，多数重金属的释放量随着L/S的增加而增加，且当浸出时间大于30 min后，浸出时间对于重金属浸出质量浓度和释放量的影响较小。在TCLP和改良的TCLP试验中，浸出质量浓度和重金属释放量(AHMR)都极依赖于浸提过程中的pH。在SCE实验中，碳酸盐结合态(CB)和Fe-Mn氧化态(OX)(易溶于酸的部分)在浸出的重金属中占比最高。此外，SCE和改良的TCLP试验中浸出的目标重金属量均远高于常规TCLP和水提法浸提的量。     

腐植酸矿粉钝化红沙泥中镉的效应与作用机理研究

正通过室内培养实验,研究45%WHC(饱和田间持水量)和110%WHC两种水分条件下,施用腐植酸矿粉钝化红沙泥中外源镉(10 mg/kg)的效应及其作用机理。结果表明:红沙泥中外源镉经陈化后约80%以交换态镉形态存在,施用腐植酸矿粉,能有效降低红沙泥中DTPA提取镉的含量,其降幅为4.8%~25.8%,并促使土壤中对植物有效性高的交换态镉向有效性低的碳酸盐结合态镉     

固化稳定化技术修复化工厂污染土壤中的实验研究

目的:探究固化稳定化技术对化工厂污染土壤修复时的固化效果和稳定化效果。方法：选择以某地区金属冶炼化工厂为依托，获取化工厂场地中污染土壤作为实验样本，在改变固化稳定化技术中稳定剂、固化剂添加量的条件下，对土壤本身pH值变化和污染物浸出质量浓度变化进行分析。结果：稳定剂添加量越大，土壤pH值越高，土壤中污染物浸出质量浓度逐渐降低，在15%前变化幅度较大，随后逐渐减缓；固化剂添加比例增加，土壤中污染物浸出质量浓度逐渐降低；添加的固化剂会发生水化反应，提高了土壤对污染物的吸附能力。结论：在应用固化稳定化技术对污染土壤进行修复时，应将稳定剂配比控制在5%～15%，将固化剂配比控制在15%～25%，以此能够达到最佳的土壤修复效果。     

黑曲霉产有机酸浸出铀矿石的影响因素

为了解培养基种类、培养温度和pH值等因素对黑曲霉产生的混合有机酸浸出铀矿石的影响,从铀矿山水样中分离、纯化得到了一株真菌--黑曲霉,应用马铃薯-蔗糖培养基（potato sucrose agar,PSA）和葡萄糖-玉米浆培养基(dextrose corn syrup,PCS)进行黑曲霉培养,获得了不同培养温度下产生的pH值不同的黑曲霉产混合有机酸,并将之作为浸出剂用于浸铀实验研究。研究表明,黑曲霉产生的有机酸的主要组分为草酸和柠檬酸等有机酸,培养基种类的不同会影响黑曲霉所产有机酸的浸铀效果,采用PSA培养基培养的黑曲霉产生的有机酸浸铀效果更好（p<0.05）。培养温度和混合有机酸的pH值也会对黑曲霉代谢产物的铀浸出率有显著性影响（p<0.05）,且二者具有交互效应,pH值对铀浸出率的影响相对较大。应用PSA培养基时,最佳培养温度为25℃,最佳代谢产物pH值为2.3;应用PCS培养基时,最佳培养温度为30℃,最佳混合有机酸pH值为2.0。培养基种类、温度和pH值主要通过改变黑曲霉产生的有机酸的成分和含量对铀浸出率产生影响。     

Flotation of uranium from uranium ores in canada: Part I-flotation results with elliot lake uranium ores using chelating agents as collectors

About 150 flotation tests were done on Elliot Lake ore with 15 reagents as collectors in order to screen and choose an attractive collector for uranium flotation. Several variables were studied including pH, conditioning time and mode of collector addition. The tests were done in a Denver or Agitair subacration cell. The particle size of the ore was kept at 85% below-325 mesh. Three reagents (Kelex 100, TOPO, and cupferron) were identified as having the most promise. The best results were obtained with cupferron, where 93-95% of the uranium was recovered in 25-30% of the mass of original ore. Radium in the tails varied between 15 and 30 pCi/g depending on the mass of uranium floated. Radium was recovered in proportion to uranium in the tests done at neutral pH. The preconcentration results obtained by flotation alone were comparable to those obtained by Raicevic of CANMET using pyrite flotation and wet high intensity magnetic separation of uranium. The consumption of cupferron was 4 kg/Mg ore for each flotation stage. This was 10-15 times larger than the collector usage in conventional oxide flotation. This scheme did not require other reagents as depressants, activators or modifiers. Reproducibility was good and similar recoveries were obtained with fresh or old ores, and with distilled or mine water. The selectivity of cupferron for uranium in the ore studied was outstanding.     

攀枝花钛渣氧化改性酸浸和微波消解工艺对比

为获得攀枝花钛渣制备高品质富钛料的适宜方法,对比研究了氧化改性酸浸工艺和微波消解工艺,并利用X射线衍射（XRD）、扫描电镜（SEM）对产物进行表征。结果表明：钛渣氧化改性后在常压酸浸工艺中反应活性差,难以有效除杂;微波消解工艺有利于破坏钛渣的致密固溶体,其效果比氧化改性常压酸浸工艺好。在盐酸质量分数为25%、液固比为4 mL/g、压力0.2 MPa条件下,采用微波消解工艺制得了二氧化钛质量分数为88%、铁质量分数为2%~3%、氧化镁+氧化钙质量分数<1.5%的富钛料。该富钛料符合沸腾氯化工艺生产钛白粉对原料的要求。     

镁渣固化/稳定污酸渣中重金属铜和镉

利用镁渣固化/稳定污酸渣中重金属铜和镉。向污酸渣与镁渣的混合渣料中掺杂不同浓度的铜和镉,做毒性浸出实验,用ICP检测铜和镉的含量,XRD研究渣料的物相变化。研究表明：用体积分数为1%~5%的硝酸溶液为浸提剂时浸取液中铜和镉的最高质量浓度分别为0.52、0.32 mg/L;用体积分数为1%~3%的硫酸溶液为浸提剂时浸取液中铜和镉的最高质量浓度分别为3.06、2.9 mg/L;镁渣固化/稳定污酸渣中重金属铜和镉的效果显著;污酸渣中掺杂镁渣后并没有引起渣料的物相变化,只是衍射峰的强弱发生了变化。     

Immobilization of heavy metals in a contaminated soil using organic sludge char and other binders

The applicability of tannery (TSC) and dye sludge char (DSC) as a binder to immobilize heavy metals (Zn, Cu and Ni) in soil was investigated. The toxicity characteristic leaching procedure (TCLP) was used to estimate the immobilization efficiency for single-binders (TSC and DSC) and binary-binders (TSC or DSC combined with tripostassium phosphate (K₃PO₄) diammonium phosphate (DAP), lime or ladle slag). The immobilization efficiencies of Zn, Cu and Ni by TSC amendment were 84.2, 100.0 and 40.0%, respectively, which were higher than 28.5, 100.0 and 54.9% by DSC amendment for a binder dose of 0.80 g char/g soil. The binary-binder enhanced Zn immobilization to 56.3 and 97.2% at 0.6 g-DSC/0.06 g-Ca(OH)₂ and 0.4 g-TSC/0.08 g-Ca(OH)₂, respectively per 1 g dried soil. The immobilization efficiencies of heavy metals increased with aging for the DSC-binary binders, but not for TSC-binary binders.     

Glass-ceramics with internally crystallized pyrochlore for the immobilization of uranium wastes

In this work, pyrochlore glass-ceramics (GCs)for uranium immobilization were synthesized by a pretreatment and melting-heat treatment method. The effects of different uranium contents on the phase composition, microstructure, uranium valence and chemical durability of the glass-ceramics were systematically investigated. With increasing uranium content, pyrochlore was always the dominant phase internally crystallized in the glass. CaAl₂Si₂O₈, UTi₂O₆ and U₃O₈were gradually observed as minor phases in the glass-ceramics. The growth of pyrochlore enriched with uranium at different uranium contents and the overall distribution of uranium in the glass-ceramics were revealed by SEM. The uranium valence states in the samples were confirmed by XPS to be a mixture of tetravalent and hexavalent states. In addition, the GC3 sample with a high uranium waste content of 16.96 wt% exhibited a low uranium leaching rate.     

Sono-chemical leaching of uranium

A fundamental study on the mechanism of uranium leaching in nitric acid and sulphuric acid media has been carried out to understand the effect of the ultrasound on leaching. The use of ultrasound clearly improves the leaching rate within the studied leach acid media. The enhancement in the leaching rate in the presence of ultrasound is higher with low leach acid concentration of nitric acid (HNO₃), and it is high at high leach acid concentration in the case of sulphuric acid (H₂SO₄) being used as a leachant, when compared to conventional mechanical agitation. The basic reason behind this observed variation is explained on the basis of the reaction mechanism involving the oxidative conversion of acid insoluble tetravalent uranium form to the soluble hexavalent form of uranium in the presence of ultrasound at a faster rate.     

土壤中铀污染修复技术研究进展

铀及其衰变产物引起的土壤污染是全球关注的重大环境问题,不仅会引起生态风险,还会对人体健康造成威胁。因此,如何有效地解决铀污染、完善铀污染土壤修复技术体系,是实现铀矿冶行业可持续发展的关键。目前,铀污染土壤的修复技术主要有物理-化学修复、生物修复以及联合修复3种方式。本文首先介绍了铀在土壤中的赋存形态及其危害,然后对各种修复技术的研究现状及优缺点进行了详细综述,阐述了铀污染修复的影响因素,最后总结了目前铀污染土壤修复技术存在的挑战,并展望了该领域修复技术未来的发展方向,以期在实际应用中充分结合环境因素和各种修复方法的适用性,选择合适的修复技术实现污染土壤中铀的高效去除。     

Characterization of glassy materials for immobilization of radioactive waste with a high iron oxide content

The influence of the content of oxides in the simulated high-level wastes on the phase composition, the structure, and the water resistance of borosilicate-based glassy materials for immobilization is investigated. An increase in the waste oxide content from 45 to 65 wt % leads to an increase in the fraction of the crystalline phase of the magnetite-type spinel from 3–5 to 20–22 vol %. The glassy materials are characterized by a low leaching rate of the main waste components in water. A considerable increase in the leaching rate of sodium ions and, to a lesser extent, aluminum and uranium ions is observed for the glassy materials containing waste oxides at a content of 55 wt % and more due to the depolymerization of the structural glass network. Under the same conditions, the leaching rate of iron does not increase noticeably because of the high resistance of the iron-containing spinel to water.     

硅藻土的可控沸石化及其对铅离子的吸附固定

铅离子已造成严重的环境污染,所以开发高效的处理材料势在必行。以硅藻土作为基材和原料,采用水热合成的方法对硅藻土进行沸石化改性,制备出硅藻土/沸石复合吸附剂。将这一吸附剂用于水相以及多相体系（如土壤）中铅离子的吸附、固定,室温下水溶液中铅（Ⅱ）的最高吸附量可达448.20 mg/g。土壤连续浸提（BCR）实验结果表明,500 mg/kg铅污染土壤中加入质量分数为1%至10%的复合吸附剂,固定钝化7 d后易迁移的可交换态（EX）铅质量分数从9.25%降至1.97%,转化为稳定的组分,且随着时间延长至60 d,可交换态铅含量仍维持在较低水平。上述结果证实了合成的硅藻土/沸石复合材料具有良好的铅离子吸附和固定性能,在环境净化领域表现出经济、绿色、便捷的特点,因此具有较大的推广应用潜力。