复杂矿石中滑石的测定

含滑石复杂矿石试样经650℃焙烧,使其中绿泥石、菱镁矿等变得能迅速溶于1+1 HCl中,而滑石溶解率很低。残渣用HF-HClO_4或KOH处理,用火焰原子吸收法或滴定法测定MgO,计算滑石量。10余种共存矿物在一定范围内不干扰测定。     

合浦珠母贝贝壳珍珠层EDTA可溶性基质蛋白对无定形碳酸钙稳定性的影响

通过红外光谱、扫描电镜、能谱等方法探讨了合浦珠母贝贝壳珍珠层EDTA可溶性基质蛋白(ESM)对无定形碳酸钙(ACC)晶型转化的影响。试验结果显示,合浦珠母贝贝壳珍珠层ESM在镁离子存在的条件下能够显著抑制ACC的转化,并减少最终诱导形成的方解石中的镁离子含量。同时,珍珠层ESM具有调节方解石晶体晶貌的作用。     

酒石酸异构体对EDTA间接滴定法测定矿石中三氧化二铝的影响

应用EDTA间接滴定法测定铝土矿、高岭土、黏土等矿石中的三氧化二铝,试验了不同种类的酒石酸掩蔽钛对三氧化二铝测定结果的影响。建议选择左旋体或右旋体酒石酸作掩蔽剂,尽量不要选择内消旋体酒石酸,更不能选择外消旋体酒石酸。采用酒石酸钾钠作掩蔽剂,三氧化二铝的测定结果良好,方法快速、简便。     

Degradation Pathway of the Photochemical Oxidation of Ethylenediaminetetraacetate (EDTA) in the UV/H2O2-process

The degradation pathway for the oxidation of EDTA in the UV/H₂O₂-process was investigated. In absence of iron ions, the mineralization of EDTA is dominated by the reaction of the HO-radicals generated by the photolysis of H₂O₂. The organic degradation products iminodiacetate (IMDA), glycinate, oxamate, glyoxylate, oxalate and formate, and the inorganic degradation products carbon dioxide, ammonia, nitrate, nitrite, and cyanate were found. In the presence of iron ions, photolytic decarboxylation processes inside the complex get an important role during degradation, and the organic degradation products ethylenediaminetriacetate (ED3A), ethylenediaminediacetate (EDDA), ethylenediaminemonoacetate (EDMA) were also found. By combining product studies with balances of carbon and nitrogen, the degradation pathway in the UV/H₂O₂-process could be elucidated. The degradation of EDTA was fast (k_deg = 0.012 s^–1), and no toxic degradation products were identified. Therefore, the process is well suited for the elimination of EDTA in water treatment.     

淋洗剂乙二胺四乙酸对重金属污染土工程特性的影响

以重金属铅（Pb2+）污染土和淋洗剂乙二胺四乙酸（EDTA）为研究对象,通过批次试验研究了不同浓度EDTA的淋洗对Pb2+污染土的渗透特性、持水特性、压缩特性、抗剪强度等工程特性的影响,为淋洗修复后土壤的二次利用提供参数支持。基于矿物成分、孔隙结构等微观试验,揭示了土壤工程特性变化的内在机制。研究结果表明,当淋洗剂EDTA浓度从0增加到0.15 mol/L,经淋洗修复后的污染土壤pH值从7.94下降到5.12,渗透系数降低超过一个数量级,黏聚力降低50%以上,而内摩擦角增大,持水性能提高,孔隙比从0.81下降到了0.76。微观试验的结果表明,随着淋洗剂浓度的增大,土壤中的蒙脱石、钠长石和伊利石矿物含量减少,石英矿物含量增加,其中蒙脱石含量从7.87%下降到了0.07%,而石英矿物含量增加了11.09%;淋洗后土壤单位质量进汞量由0.22 ml/g降低到0.15 ml/g,土壤总孔隙体积减少。重金属污染土淋洗修复工程在考虑重金属去除率及经济性指标的同时,还应考虑淋洗剂对土壤工程特性的弱化。     

Refining P nuclear magnetic resonance spectroscopy for marine particulate samples: Storage conditions and extraction recovery

Solution ³¹P nuclear magnetic resonance (NMR) spectroscopy has recently been used to characterize phosphorus species within marine particles. However, the effects of sample collection, storage and preparation have not been thoroughly examined. In this study, samples of settling particulates collected from a 1200-m sediment trap located in Monterey Bay, California, were subjected to various storage options (i.e., no storage, refrigeration, freezing, and oven-drying and grinding) prior to extraction for solution ³¹P-NMR spectroscopy. Freezing, refrigerating and drying samples for periods of up to 6 months prior to extraction with 0.25 M NaOH + 0.05 M Na₂EDTA increased the concentration of extracted P by an average of 16% relative to samples extracted without storage. Pre-extraction storage also introduced some minor changes in P speciation, by increasing the percentage of orthophosphate by up to 15% and decreasing the percentage of pyrophosphate by up to 5%, relative to the abundances of these P species in samples extracted without storage. Drying caused the biggest changes in speciation, specifically decreasing more extensively the relative percentage of pyrophosphate compared to other treatments. Nevertheless, observed changes in speciation due to sample storage within a specific sample were small relative to differences observed among samples collected sequentially in the same area, or reported differences among samples collected at different locations. Samples were also analyzed by solid-state ³¹P-NMR spectroscopy before and after extraction, to examine extraction-related changes in P speciation. Comparison of solution with solid-state ³¹P NMR indicates that extraction with NaOH–EDTA removes the majority of organic esters, but only a variable portion of phosphonates (39–67%). In addition, there was preferential extraction of Ca-associated phosphate over Mg-, Fe- and Al-associated phosphate. Solution ³¹P NMR enables much higher resolution of P species within samples, particularly when it is important to speciate orthophosphate monoesters and diesters, or if polyphosphates are present. However, combining solid-state ³¹P NMR with solution ³¹P NMR spectroscopy for marine particles should be conducted when examining inorganic P speciation and the abundance of phosphonates.     

Selection of the most appropriate method to determine the carbonate content for engineering purposes with particular regard to marls

Because of the influence of carbonates on the geotechnical properties of foundation and construction materials in civil engineering, a simple, precise, and inexpensive method of determining soil-carbonate content is needed. A large number of methods exist to determine the carbonate content in soils; but, for diverse reasons (precision (accuracy), cost, sensitivity, etc.) not all are appropriate in a civil-engineering laboratory. In the present work, different laboratory methods to determine the carbonate content in soils have been compared in order to choose the most appropriate one. The most suitable method has been selected on the basis of a number of general criteria: precision (accuracy), equipment cost, operating and maintenance costs, staff requirements, and sensitivity of the equipment. According to these general criteria, three methods can be considered suitable: flame photometry, volumetric calcimeter, and EDTA complexometry. These three methods present errors of less than 5%, involve low to medium cost, and the maintenance operations are simple. In addition, a suitability index has been defined (depending on three specific criteria: degree of precision (accuracy), level of standardization, and suitability of the operation method and type of ion analysed) which enabled the selection of the most appropriate from among the three methods. For the study, marl samples were taken from quarries used to construct the impermeable cores of three dams in the upper Guadalquivir River Basin (S Spain), as well as Standard samples were made with pure and inert calcium carbonate. Finally, it is concluded that the volumetric method (Bernard calcimeter) is the overall best technique to determine the carbonate content in civil-engineering laboratories.     

阳极泥及碲回收物料中高含量碲的测定

采用重铬酸钾容量法，测定铜铅阳极泥及碲回收物料中高含量碲。针对阳极泥样品成分复杂的特征，确定了最佳溶样介质；探讨了Cu^2 ,Cd^2 ,Bi^3 ,Ag^ ,Sb(Ⅲ）,As（Ⅲ），Pb^2 ,Se（Ⅳ），Sn（Ⅳ），Au(Ⅲ）等共存元素的影响及其消除方法；改善了滴定条件。方法适用于w(Te)＞1％碲的测定，样品分析结果与原子吸收法测定结果一致，RSD（n＝5）为0.4％－4.1％。     

A comparison of iron limitation of phytoplankton in natural oceanic waters and laboratory media conditioned with EDTA

The solubility of iron in oxic waters is so low that iron can be a limiting nutrient for phytoplankton growth in the open ocean. In order to mimic low iron concentrations in algal cultures, Ethylenediaminetetraacetate (EDTA) is commonly used. The presence of EDTA enables culture experiments to be performed at a low free metal concentration, while the total metal concentrations are high. Using EDTA provides for a more reproducible medium. In this study Fe speciation, as defined by EDTA in culture media, is compared with complexation by natural organic complexes in ocean water where Fe is thought to be limited. To grow oceanic species into iron limitation, a concentration of at least 10⁻⁴ M EDTA is necessary. Only then does the calculated [Fe³⁺] concentrations resemble those found in natural sea water, where the speciation is governed by natural dissolved organic ligands at nanomolar concentrations. Moreover, EDTA influences the redox speciation of iron, and thus frustrates research on the preferred source of Fe-uptake, Fe(III) or Fe(II), by algae. Nowadays, one can measure the extent of natural organic complexation in sea water, as well as the dissolved Fe(II) state, and can use ultra clean techniques in order to prevent contamination. Therefore, it is advisable to work with more natural conditions and not use EDTA to create iron limitation. This is especially important when the biological availability of the different chemical fractions of iron are the subject of research. Typically, many oceanic algae in the smallest size classes can still grow at very low ambient Fe and are not easily cultivated into limitation under ambient sea water conditions. However, the important class of large oceanic algae responsible for the major blooms and the large scale cycling of carbon, silicon and other elements, commonly has a high Fe requirement and can be grown into Fe limitation in ambient seawater.