Simulating experiment on the enrichment of precious metals in Lower Cambrian black shale series of Hunan and Guizhou provinces

Adsorption experiments were made at room temperature and neutral pH value on different types of min-erals associated with the Lower Cambrian black shale series polymetallic layers in Hunan and Guizhou provinces on nanometer-sized Pt colloids and PtCl42--bearing ionic solutions with an attempt to constrain the relationship between the different types of minerals in the polymetallic layers and the enrichment of platinum group elements (PGEs). Experimental results showed that the different types of minerals show strong selectivity to the adsorption of nano-meter-sized Pt colloids and PtCl42--bearing ionic solutions. Metallic sulfides, organic matter and clay minerals are the strong adsorbents of PGEs, while quartz, albite, muscovite and other silicate minerals show a week adsorbility to both of them. This phenomenon is well consistent with the geological fact that metallic sulfides, organic matter and clay minerals in the polymetallic layers of the black shale series are the major carrier minerals of PGEs, giving a thorough explanation to the mechanism of enrichment of previous metal elements. Adsorption may be a principal mechanism of enrichment of precious metal elements under lower temperature conditions. The presence of the aforementioned strong adsorbents is the good geochemical barriers for the enrichment of PGEs.

Trace Metal Levels in Lichen Samples From Roadsides in East Black Sea Region,Turkey

Objective To determine the metal contents of lichen species from East Black Sea region of Turkey for investigation of trace metal pollution sourced traffic. Methods The levels of copper, cadmium, lead, zinc, manganese, iron, chromium, nickel, cobalt, palladium in lichen samples collected from East Black Sea region of Turkey were determined by flame and graphite furnace atomic absorption spectrometry after microwave digestion method. The accuracy of the method was corrected by standard reference material （NIST SRM IAEA-336 Lichen）. Results The contents of invest!gated trace metals in lichen samples were 7.19-22.4 μg/g for copper, 0.10-0.64 μg/g for cadmium, 4.03-44.6 μg/g for lead, 14.5-41.8 μg/g for zinc, 25.8-208 μg/g for manganese, 331-436 μg/g for iron, 1.20-3.01 μg/g for chromium, 1.48-3.90 μg/g for nickel, 0.20-3.55 μg/g for cobalt, 0.11-0.64 μg/g for palladium. The results were compared with the literature values. Conclusion Some lichen species such as Xanthoparmelia conspersa, Xanthoria calcicola, Peltigera membranacea, and Physcia adscendens are accumulated trace metals at a high ratio.

黑龙江省黑土区土壤重金属污染及风险评价

为探究黑龙江省黑土区土壤重金属污染现状和生态风险,该文采集黑土区农田表层土壤(0~15 cm)样品(N=303),测定土壤重金属含量及p H值。结合地累积指数法、潜在生态风险指数法与地统计学法对研究区土壤重金属污染水平和生态风险进行评价,利用绝对主成分-多元线性回归(APCS-MLR)模型和正定矩阵因子分解(PMF)模型进行溯源分析。结果表明:研究区土壤以弱酸性为主,Cr、Ni、Cu、Zn、As、Pb、Cd的浓度分别为(50.60±9.16)、(18.35±5.25)、(26.49±6.35)、(55.71±12.26)、(11.73±3.75)、(20.47±5.12)、(0.13±0.077)mg/kg,有3%点位的Cd超过农用地土壤污染风险筛选值,其他重金属均未超标。地累积指数结果表明,研究区以Cd污染为主,污染率达41%;潜在生态风险指数法表明Cd为主要风险因子,RI均值为77.10,属于低风险。APCS-MLR和PMF模型分析结果一致,均解析出3种相同的污染源,分别为自然与交通混合源、农业源、工业源,APCS-MLR模型中3种污染源贡献率分别为42.02%、15.70%、14.82%,而在PMF模型中分别为37.64%、28.82%、33.54%。综上,黑龙江省黑土区土壤环境质量良好,但要注重Cd的潜在污染。

典型黑色页岩地区土壤风化速率及潜在生态效应研究

风化条件作用下,黑色页岩富含的重金属元素释放到周围环境中,会造成土壤重金属的超标富集,从而形成重金属地质高背景区。为了了解黑色页岩地质高背景区重金属风化富集过程和特征,本研究以浙西地区典型寒武系黑色页岩区土壤为研究对象,运用PROFILE模型定量计算土壤剖面化学风化速率,并以此评估重金属释放速率,同时对该地区的土壤重金属潜在生态效应进行了评估。研究结果表明,土壤的化学风化速率为62.95~412.62 mmol/(m^(2)·a),盐基阳离子(Ca^(2+)、Mg^(2+)、Na^(+)和K^(+))的释放速率为97.47~806.16 mmol/(m^(2)·a)。黑色页岩土壤中碳酸盐含量的大小对风化速率强弱的影响比较大。研究区土壤As、Cd、Cr、Cu、Hg、Pb、Zn的平均释放速率分别为31.25、18.79、135.65、65.14、0.15、28.02和367.35 mmol/(m^(2)·a)。土壤的重金属浓度和盐基阳离子浓度(CBCt)对重金属释放速率的影响较大,盐基阳离子释放速率(RBC)对重金属释放速率的影响较小。研究区重金属综合潜在生态风险指数平均值为961.89,Cd的潜在生态风险指数最高,贡献率在53.44%~99.70%之间。

我国南方桉树人工林区水体泛黑物质分子组成及形成机理

我国南方桉树人工林区水库在秋冬季频繁出现黑水现象。现有研究指出,桉树叶中单宁酸等物质与金属离子(如铁离子)反应产生的金属-有机质络合物是导致这一现象的主要原因。然而,目前对于桉树叶中能形成金属-有机质络合物的潜在有机质前体物认识仍然有限,基于分子组成层面的桉树人工林区水库水体泛黑形成机理也尚不清楚。为此,本研究利用傅立叶变换离子回旋共振质谱(FT-ICR MS)等手段,对桉树叶浸泡液与典型桉树林区水库(金窝水库和天雹水库)水体中可溶性有机物进行了分子组成的分析。研究结果显示,桉树叶浸泡液主要由以苯三酚、没食子酸为母体的多酚类化合物及其多聚衍生物构成,其中最典型的化合物是鞣花酸(C_(14)H_(6)O_(8))。冬季水库水中鞣花酸强度远高于夏季,且表层水体高于底层水体,这表明秋冬季大量凋落的桉树叶释放出的这些芳香多酚类物质会显著促进水库黑水的形成。进一步的实验证明,鞣花酸、苯三酚和没食子酸都会与铁离子发生络合反应,生成黑色沉淀。这些结果均表明,桉树叶溶解出的芳香多酚类物质是导致水库变黑的核心因素。本研究基于分子组成层面提出了桉树人工林区水库水体泛黑形成机理,对于桉树人工林区的黑水治理和保障水库饮用水安全具有十分重要的意义。

黑磷中基于热驱动金属扩散诱导的相变

二维(2D)材料具有原子级平整、可范德华堆叠集成的性质,同时蕴含了丰富的物理现象与优异的电学性质,对其相变行为的研究一直是凝聚态物理与材料科学领域的前沿。本研究中,我们在黑磷(BP)中首次实现了基于热驱动金属扩散诱导的阶段式可控相变。通过对BP-In界面的热退火处理,我们观察到了从BP纯相到BP/InP混合相,再到InP纯相的阶段式相变现象。利用透射电子显微与拉曼光谱等表征技术,我们对诱导相变产生的机制进行了深入剖析,揭示了BP-In中热驱动的金属扩散行为是诱导相变发生的主要原因。通过对热驱动中影响能量供给的两个自由度(温度与时间)的精准调控,得到了阶段式相变过程中两个关键的阈值温度(相变启动与实现纯相转变)分别为300与350℃。本研究为2D材料体系中相变工程相关的研究提供了新的思路,也为拓展BP在电子学与光电子学器件中的应用提供了更多的可能性。

造纸黑液源类黄腐酸对水体中铅的吸附作用研究

造纸黑液占整个造纸业污染的90%以上,对环境造成严重影响,造纸黑液中大量的有机质可以作为黄腐酸的合成前体,黄腐酸对重金属有良好的吸附作用。根据国际腐植酸协会推荐方法,自两种不同造纸工艺的黑液中成功提取出了碱法类黄腐酸(JFLA)和铵法类黄腐酸(AFLA);通过平衡络合试验,在不同Pb^(2+)浓度和pH的重金属水溶液中,研究了两种类黄腐酸对铅的吸附效果与规律,AFLA在低Pb^(2+)浓度、高pH条件下具有更好的吸附能力,且AFLA比JFLA的吸附能力更强。研究结果表明了黑液类黄腐酸有修复Pb^(2+)污染水体的可能性,为相关研究开展奠定了理论基础。

Long-term impact of municipal sewage irrigation on treated soil and black locust trees in a semi-arid suburban area of Iran

The effects of municipal sewage irrigation on the soil and black locust （Robinia pseudoacacia L.） tree were studied. For this purpose, two artificial black locust stands under irrigation of municipal sewage and well water were selected in south of Tehran, Iran. Data were collected using technique of systematic random sampling with 4 replicates in each stand. It was found that the growth of black locust tree, as indicated by diameter at breast height, total height, crown length, average crown diameter, basal area and volume, in sewage irrigation stand was much higher than that of well water irrigation stand （P 〈 0.01）. Plant analysis indicated that concentrations of leaf nutrients （N, E K, Ca, Mg, Na, Fe, Mn, Cu and Zn） were greater in sewage-irrigated trees, without toxicity to the minerals of tree leaf, than those of well waterirrigated trees, and positively correlated with their respective value in soil. Ni, Cr and Pb were not detected in leaf samples. Application of sewage resulted in a 1.5-fold increase in the concentrations of soil nutrients, Ni, Cr and Pb. Among these minerals only Pb and Ni in some soil samples exceeded the toxicity limit. The increase in pH, electrical conductivity （EC） and organic carbon of soil was also observed in sewage irrigation. Results confirm that besides the use as irrigation water, municipal sewages are also a potential source of plant nutrients. However, significant accumulation of heavy metals such as Pb and Ni in soil needs to be monitored.

Formation of Black Patina on Bronze Mirrors Caused by Multiphenol

Hot solution of hydroquinone is oxidized by air forming quinone and quinhydrone, both of which have weak oxidizeability, enabling to oxidize metals on the surface of bronze mirror samples forming black and brilliant patina. SEM and electron micro probe analysis show that Cu content is lower than that of the original alloy due to Cu loss; Sn content is higher than the original alloy in patina. This indicates that humic acid is not the substance resulting in making black patina on the bronze mirror surface, but the black patina which produced from hydroquinone solution absence of Si, Al and Mg.

Development of the N-Doped Cu-Carbon Composite as a Novel Catalyst for the Removal Reactive Black 5

In this study, two Cu-based catalysts with and without N doped carbon matrix, named N-Cu/CuO/C and Cu/CuO were synthesized via calcination of melamine-cupper acetate complex and cupper acetate at 500°C under an inert atmosphere. The catalysts were characterized by X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and CHNS elemental analyzer. The catalytic activity of both catalysts was evaluated through the NaBH4 associated reduction of commercial textile dye named reactive black 5 (RB5). The kinetics of the reduction of reactive black 5 was also described by the pseudo-first-order kinetic equation. For the studied reduction, N-Cu/CuO/C exhibited enhanced catalytic activity both in conversion and kinetics (97% conv. in 315 sec) compared to that of by Cu/CuO/C (25% conv. in 1500 sec). Besides, N-Cu/CuO/C also demonstrated good reusability up to four consecutive cycles.

电化学参数对硫化黑染色废水絮凝效果的影响

为解决硫化染料染色废水的处理难题,选择六种不同金属作为阳极、石墨作为阴极,通过电絮凝技术对硫化黑染色废水进行处理,观察废水色度、电絮凝效果和电极表面腐蚀情况,确定适宜的阳极材料。在直流稳压电源体系中,以施加电压、电解时间、极板间距、初始pH为影响因子设计正交试验,探究絮凝物质量、上清液化学需氧量(COD)、色度及反应过程中电极损失率等影响因子的显著性,综合评价废水处理效果。结果表明:镁阳极可使处理后上清液色度降低,絮凝时间和极板间距对电絮凝效果影响较大。最佳电絮凝条件为:施加电压8 V,电解时间20 min,初始p H为9,极板间距为2 cm,此时废水的COD去除率为44%,色度降为90倍,电极损失率为12.23%,絮凝物质量达1.124 6 g。

下寒武统黑色页岩金属富集机理与小行星撞击

扬子地台寒武系下统存在富含V、Ni、Mo和铂族元素(platinum group element, PGE)等的黑色页岩,局部地区有U或者Ba、Hg、As等的富集,研究这些元素富集机理有利于寻找相关矿产或者探究地质事件。6 500万年前的小行星撞击地球产生了高PGE含量的地层或者化石,依据这一事实和陨石的特征及其他地质地球化学证据,推断下寒武统黑色页岩中Ni-Mo-PGE富集是陨石撞击结果,PGE中的Ir、Os富集最明显是因为二者最抗淋滤。U在康滇地轴东侧黑色页岩中最高可达480×10^(-6),因康滇地轴本身就存在混合型铀矿,推测黑色页岩中U来自它的风化。据V和Ba-Hg-As等的地化特性,认为V富集是受生物活动影响,但因V易于在热泉水中富集,故寒武纪早期泛非运动的构造-热事件可导致V富集成矿,Ba、Hg、As也因该事件产生构造裂隙后,它们优先随热液沿裂隙上升富集,并在海底局部成矿。此外,5.65亿年前的埃迪卡拉动物群发生地基本上就是5.8亿年前小行星撞击地点,提出此次行星撞击可能与埃迪卡拉生物群出现存在因果关系。由于在中国存在寒武纪澄江生物群大爆发事件,推测该次生物大爆发之前存在的下寒武统黑色页岩也存在陨石撞击痕迹。寒武系下统的含岩屑细砂岩夹黑色页岩甚至砾岩,反映了黑色页岩沉积时存在的突变沉积环境,加上其他地球化学特征也支持小行星撞击说。

Comparative Study of Gold Concentration by Elutriation from Different Precious Metal Bearing Ores

Conventional methods for precious metals gravimetric concentration involve equipment such as shaking tables, centrifuging concentrators, jigs, trommels, or a combination of those. A less commonly used technique is elutriation, which represents an efficient, safe and low-cost method of separation. The goal of the present investigation was to make a comparative study of gold concentration by elutriation from different precious metal bearing ores: an oxide ore, a mineral consisting of a sulfide matrix, a mineral in which the precious metals are free and disseminated and a slimy and clayey black sand material. The best recoveries of precious metals by elutriation were attained for the free disseminated ore and for the black sands, obtaining gold recoveries of 70% and 96% respectively, with appreciable ratios of concentration as well.

土壤重金属健康风险时空预测及管控目标研究

以土壤重金属Cr、Pb、Cd、As和Hg调查数据为基础,利用黑箱理论、健康风险评估模型和反距离权重插值法,预测分析了南京市六合区土壤重金属健康风险的时空变化特征,并基于健康风险视角探究了土壤重金属管控目标。结果表明:研究区重金属Cr、Pb、Cd、As和Hg在2007—2017年的平均累积速率分别为–0.711、0.558、0.006、–0.086和0.013 mg/(kg·a),且Pb、Cd、As和Hg在2007年和2017年均处于中度或高度变异状态。Cr和As的儿童致癌风险在2017年的最小值分别为13.307×10^(-6)和4.548×10^(-6),Pb儿童非致癌风险的最大值为1.366,且该风险值高于1的点位占所有调查点位的11.58%,Cr、Pb和As是六合区土壤重金属健康风险特征因子。2017—2030年,Pb儿童非致癌风险呈上升趋势,该风险值高于1的区域主要分布在大厂街道、长芦街道等六合区南部区域和以金牛湖街道为核心的六合区北部区域;Cr和As儿童致癌风险总体呈下降趋势,但对应的平均值分别高于8.670×10^(-6)和9.564×10^(-6),其中Cr儿童致癌风险值高于20×10^(-6)的区域逐渐集中在以六合开发区和化工园区为核心的周边区域,As儿童致癌风险值高于10×10^(-6)的区域逐渐集中在以马鞍街道为核心的六合区北部区域。基于2030年健康风险管控目标,Cr和As的含量分别需降低到37.500mg/kg和4.167mg/kg,对应的年均降低速率分别处于0.978~8.122mg/(kg·a)和0.305~0.747mg/(kg·a),且均值分别为3.176mg/(kg·a)和0.381mg/(kg·a);Cr降低速率高值区域主要分布在六合开发区周边的区域以及冶山镇南部区域,As则主要分布在以竹镇镇西部、冶山镇北部以及马鞍街道北部为核心的六合区北部区域。

利用Mo-U等多指标判别黑色岩系中硅质岩形成氧化-还原环境的可行性分析及意义

硅质岩作为一种重要的沉积岩类型,是研究前新生代古海洋环境的重要手段,但其缺乏在氧化-还原环境方面的应用;同时硅质岩是黑色岩系的重要组成部分,拓展硅质岩在该方面的应用,有利于加深对黑色岩系形成机理的认识。本文综述了硅质岩的现有研究方法、黑色岩系中黑色页岩和硅质岩研究的局限性和互补性,并论述了将Mo-U等氧化-还原敏感金属多指标判别方法应用于硅质岩,用来判断其形成的氧化-还原环境和盆地局限性等方面的理论可行性。在分析扬子地块及其周缘黑色岩系及硅质岩研究现状的基础上,认为将在黑色页岩使用成熟的氧化-还原环境研究方法应用于互层的(热水沉积)硅质岩,理论上具有可行性,并在扬子地块西北缘若尔盖地区奥陶-志留纪黑色岩系中互层的黑色页岩和热水沉积硅质岩岩性组合中得到进一步验证。该方法的应用可深化对扬子地块西北缘黑色岩系沉积环境特殊性及其中U-Au-Ni-Mo-V多金属矿源层形成机理的认识。

碳黑金属酞菁原位生高价铁氧降解有机污染物

为高效去除复杂水体环境中的有机污染物,制备过氧化物模拟酶催化剂,以双氧水为氧化剂,构建环境友好型的仿生催化体系,来催化降解水体中的地塞米松有机污染物。研究催化剂的形貌及结构特征,催化体系的催化性能、循环使用性能、催化机理、催化降解产物及最终产物。结果表明:所构筑的催化体系在温和(室温、中性)及复杂水体环境中(酸性、无机盐)对地塞米松的降解率均为100%,但在碱性条件下,该催化体系对地塞米松的降解率因双氧化水分解过快而降低了28%;该催化体系经过6次循环使用后,对地塞米松的降解率仍达到95%;过氧化物模拟酶在双氧水的作用下产生对水体有机污染物降解起主要作用的高价铁氧活性种,而羟基自由基起次要作用;经过60 min反应,该催化体系将地塞米松降解为对环境不存在二次污染的小分子有机酸。该仿生催化体系的构筑为仿生催化材料在工业废水中的应用提供了新视角。

添加改性生物炭对黑土氮素吸附及淋溶特性的影响

【目的】探究金属离子改性生物炭对黑土氮素吸附和迁移特性的影响。【方法】以玉米秸秆为原材料,在450℃煅烧1.5 h条件下制备生物炭(BC),分别用KCl、ZnCl_(2)、FeCl_(3)溶液对其进行金属离子负载改性(分别命名为K-BC、Zn-BC和Fe-BC),并进行表征分析和氮素吸附试验,筛选出最佳改性生物炭;然后在黑土中添加质量分数0.3%的最佳改性生物炭(TB),以黑土作为对照(CK),探究这2个吸附体系的氮素吸附和迁移特性。【结果】Fe-BC对NO_(3)^(-)-N和NH_(4)^(+)-N的吸附量分别为24632.79和5253.68 mg/kg,确定Fe-BC为最佳金属离子改性生物炭。Fe-BC的比表面积和平均孔径较BC提升了9.35和6.67倍。CK和TB在pH为3时对NO_(3)^(-)-N的吸附量最大,CK在pH为9时对NH_(4)^(+)-N的吸附量最大,TB在pH为5时对NH_(4)^(+)-N的吸附量最大。相较于准二级动力学方程,Elovich方程均能更好地描述CK、TB对NO_(3)^(-)-N和NH_(4)^(+)-N的吸附动力学特征;相较于Freundlich方程,Langmuir方程均能更好地描述CK、TB对NO_(3)^(-)-N和NH_(4)^(+)-N的吸附等温线;CK、TB对NO_(3)^(-)-N的吸附反应是自发、放热且无序的,对NH_(4)^(+)-N的吸附反应是自发、吸热且无序的。在氮素迁移试验中,TB对NO_(3)^(-)-N和NH_(4)^(+)-N的累积淋失量分别比CK减少53.19%和30.54%。【结论】黑土中添加Fe-BC可以有效增加对NO_(3)^(-)-N和NH_(4)^(+)-N的吸附量,降低黑土中NO_(3)^(-)-N和NH_(4)^(+)-N的淋失量,从而有效减少黑土中氮素的流失。