生物法回收贵金属铂纳米颗粒及其机制

利用自行分离的粪肠球菌Z5(Enterococcus faecalis Z5)菌株(保藏号CCTCC M2012445)回收贵金属铂,探讨了其在外源电子供体条件下以纳米颗粒形式回收溶液中化合态铂的可能性,研究了铂初始浓度、生物量、温度以及p H值对回收过程的影响,探讨了粪肠球菌Z5回收铂纳米颗粒过程的可能机制.结果表明,粪肠球菌Z5菌株可以回收铂纳米颗粒,回收过程主要包括生物吸附和生物还原.铂初始浓度为286.46 mg·L~(-1)、生物量为3.2 g·L~(-1)、温度50℃以及p H值为6时为其最佳回收条件.X射线衍射(XRD)和透射电镜(TEM)分析表明,回收产物为5 nm左右粒径的铂纳米颗粒,主要分布于细胞周质.X射线电子能谱(XPS)分析显示,Pt(Ⅳ)首先被还原为Pt(Ⅱ),然后被还原为Pt(0),且从Pt(Ⅱ)还原成Pt(0)为限制步骤,傅里叶红外(FTIR)分析显示菌体表面的羟基和酰胺基官能团可能在回收过程中起作用.     

Humic substances. Part III. sorptive interactions with environmental chemicals†

The formation of covalent binding to DNA of a carcinogen is now widely accepted to represent a classical mechanism of tumour induction in mammals. This mechanism does not operate with metals since no covalent binding of these agents to DNA does occur. Nevertheless, somatic mutations as typical consequences of DNA‐damage have been reported to be induced by metals in various model systems. Beside DNA‐alkylation such damages can be caused by changes in the conformation of DNA or in the fidelity of DNA‐repair. The activity of the repair enzymes DNA‐polymerases is indeed impaired by many metal ions at least in vitro. It is not yet established whether these mechanisms are also important in the intact mammalian organism. Much evidence has accumulated during the last years that a disturbance of the balance of cations and especially metal ions represents another possible mechanism of tumour induction. The tumours found with high doses of chelating agents such as nitrilo‐triacetic acid (NTA) have to be discussed in this context. Since most—if not—all of the speculative mechanisms of metal carcinogenesis resemble classical pharmacological reactions the existence of a threshold level is likely. So metal carcinogenesis will not be a problem of the environmental contamination at trace levels but a problem of occupational medicine.     

苯胺在铂电极上电解特征的研究

采用循环伏安法考察了苯胺在铂电极上不同浓度、pH值和不同扫描速率等条件下的电化学反应特性。结果表明:在酸性条件下出现明显的氧化峰而中性和碱性条件下没有;在循环初期只有1个氧化峰,峰电势Ep≈1.0V,随着扫描的进行出现2个氧化峰,Ep≈1.0V,0.5V。     

Distribution of Platinum group elements in road dust in Beijing metropolitan area, China

Dust samples collected from the Beijing metropolitan area (China) were evaluated to determine the distribution and the concentration of platinum group elements (PGEs). The dust particles that were smaller than 100 mesh size fraction (150 μm) were analyzed after aqua regia digestion. Concentrations[RL2] of Pt, Rh, and Pd were found to be between 3.96 and 356.3 ng/g, 2.76 and 97.11 ng/g, and 0.1 and 124.9 ng/g, respectively, in the urban areas of Beijing, whereas for the background samples collected from the suburbs of Beijing, the concentration of Pt, Pd, and Rh were very low and ranged from 0.1 to 0.9 ng/g, 0.5 to 1.4 ng/g, and 0.8 to 2.2 ng/g, respectively. The[RL3] distributions of PGEs in road dust were an accurate reflection of the levels of pollution and were found to match with the local traffic conditions. A strong positive correlation was established among all the elements found in road dust. This suggests that emissions of abraded fragments from vehicle exhausts may be the source of the high concentration of Pt, Rh, and Pd in road dust along the main roads of Beijing.     

Influence of micro-organisms on the dissolution of metallic platinum emitted by automobile catalytic converters

Platinum emitted by automotive catalyst converters mainly exists in the metallic form, which is not bioavailable. Several investigations showed that finely dispersed metallic platinum is dissolved in organic matrices to a significantly high degree [1,2]. In an exclusion experiment, observations were made as to whether the transformation of Pt(0) and other platinum compounds is mainly of a chemical nature or is influenced by micro-organisms. A previous experiment [2], concerning the interaction of several platinum compounds with a clay-like humic soil was repeated under sterile conditions to rule out the influence of micro-organisms. During the time of interaction (3–60 d), no significant differences were observed between the sterile and non-sterile modes. Thus, the dissolution of metallic platinum into soluble species, observed previously within this time period [2], seems to be mainly of a chemical nature. On leave from Liaoning University, Department of Chemistry, 110036 Shenyang, PR China     

室温下消除CO的催化剂

本文考察了活性炭复合载体负载的、采用铂和钯金属络合物为初始化合物制备的负载型贵金属催化剂,在CO氧化反应中的催化性能。从中筛选出可在室温下消除CO的催化剂(编号CO-20-2),并试验了该催化剂在干、湿两种原料气氛下的活性和稳定性。与国内外用于同种反应的催化剂相比较,其活性和稳定性均较好。采用活性炭复合载体和与其匹配的活性组分初始物质Na_2PtCl_6和Pd(OAc)_2时,适宜的H_2还原温度范围为100—200℃,CO-20-2催化剂可在室温至45℃的低温范围内连续消除空气内的CO。     

土壤氧化还原电位测定方法的探讨与研究

是选用铂电极直接测定法来测定土壤的氧化还原电位,该方法是采用铂电极作为氧化还原电极,饱和甘汞电极作为参比电极,两者之间存在电位差的原理而测得的。通过大量的试验数据,表明该方法是简便易行的,对于一般的土壤都有实际参考价值。最后,对此过程中遇到的问题进行了深入的探讨和研究,并提出了具体解决方案。     

道路环境PGEs多介质累积规律

为了研究道路环境PGEs多介质累积规律,选择上海市5条道路,同步采集灰尘、土壤及植物样品,对其中铂族元素(PGEs)含量水平进行分析.结果表明,灰尘中Rh、Pd、Pt平均浓度分别为24.92、88.39、22.28 ng/g,土壤中Rh、Pd、Pt平均浓度分别为3.64、17.45、0.97 ng/g,植物中Rh、Pd、Pt平均浓度仅分别达到2.66、6.39、0.57 ng/g,灰尘PGEs浓度远高于土壤及植物,土壤与植物中Pt、Rh浓度水平较接近;道路环境PGEs分布呈现一定规律性,但与交通流量关系并不密切;路边植物对道路灰尘PGEs吸附能力表现为Pt>Pd>Rh,其中,对Pt、Pd吸附作用非常明显,对Rh几乎不存在吸附作用,路边植物对土壤PGEs的吸收能力为Pd>Rh>Pt,Pd的生物有效性最大;多介质PGEs比例值很接近或部分重合,且均在上海市道路灰尘PGEs比值范围内,反映出上海市道路环境PGEs来源相同且均来自汽车VECs.     

Bioaccumulation of platinum group metals on some fish species ( Oreochromis niloticus,Penaeus laspisulcates,Scylla serrate,Galaxias brevipinnis and Mollusc ) in the Pra estuary of Ghana

Catalytic converters have been designed to solve the problem of pollution from automobiles. However, recent studies have shown that the platinum group metals (PGMs) that are used in the design are being deposited alongside highways. The objective of this study was to measure the levels of PGMs that bioaccumulate in Oreochromis niloticus, Penaeus laspisulcates, Scylla serrate, Galaxias brevipinnis and Mollusc in the river Pra estuary along a major highway in Ghana. Chemical analysis using neutron activation analysis showed accumulation of the PGMs in all the biota species analysed. The S. serrate and mollusc showed higher accumulation than the other species. The mollusc and the other fish species in the estuary are consumed in Ghana, and therefore there is the need to educate the population on the effect of the PGMs on their health.     

高效负载型光催化剂制备及其加铂修饰技术

通过光催化氧化五氯苯酚钠实验,结合对催化剂晶型结构、比表面积的表征分析,优化钛酸四丁酯水解制备TiO₂负载型催化剂并加铂修饰的制备条件:R值、烧结温度、粘合剂添加量、空心玻璃珠粒径大小及催化剂中铂含量,从而制备出高效、实用的负载加铂修饰型半导体光催化剂.实验结果表明,当R=10,温度为650℃烧结1h,TiO₂∶硅酸钠∶空心玻璃珠=10∶2.5∶20(W),铂在催化剂中的重量百分比为1.4%～1.6%,空心玻璃珠的粒径为0.5mm时,所制备的加铂修饰负载型催化剂催化活性、使用寿命和牢固度均比较理想.用该催化剂做光催化实验,当反应液初始五氯苯酚钠浓度为100mg/L、pH值为6.5,催化剂投加量为2g/L,通氧气量为1.6mL/s,光照强度为30kW/m²时,五氯苯酚钠2 h光催化氧化率达92.0%.