Behaviour of palladium(II), platinum(IV), and rhodium(III) in artificial and natural waters: influence of reactor surface and geochemistry on metal recovery

The recovery of dissolved platinum group elements (PGE: Pd(II), Pt(IV) and Rh(III)) added to Milli-Q^® water, artificial freshwater and seawater and filtered natural waters has been studied, as a function of pH and PGE concentration, in containers of varying synthetic composition. The least adsorptive and/or precipitative loss was obtained for borosilicate glass under most of the conditions employed, whereas the greatest loss was obtained for low-density polyethylene. Of the polymeric materials tested, the adsorptive and/or precipitative loss of PGE was lowest for fluorinated ethylene propylene (Teflon^®). The loss of Pd(II) in freshwater was significant due to its affinity for surface adsorption and its relatively low solubility. The presence of natural dissolved organic matter increases the recovery of Pd(II) but enhances the loss of Pt(IV). The loss of Rh(III) in seawater was significant and was mainly due to precipitation, whereas Pd(II) recovery was enhanced, compared to freshwater, because of its complexation with chloride. The results have important implications regarding protocols employed for sample preservation and controlled laboratory experiments used in the study of the speciation and biogeochemical behaviour of PGE.     

次生栎林酸沉降中SO2-4含量和pH值的变化特征

对下蜀次生栎林不同降水组份中硫含量和ｐＨ 值进行连续的观测与分析;揭示了ＳＯ２ －４ 和ｐＨ 值在不同降水组份中的变化规律以及ＳＯ２ －４ 与其它化学成分的相互关系,结果为进一步阐明本区酸性沉降物对森林生态系统的影响提供了理论依据。     

磷酸酯合成中有机磷和无机磷的La3+滴定法测定

为了便于监控磷酸酯合成反应过程及其分离和纯化过程等,主要研究了硝酸镧沉淀滴定法测定有机磷酸酯合成中有机磷和无机磷的含量,该方法快速、简便、准确度高,在浓度为10-4mol/L时可以准确测定.对有机磷酸酯合成的无机磷和有机磷用磷钼酸铵分光光度法和La3 滴定法作对比分析,测定结果基本一致.     

On-line precipitation/dissolution system for the preconcentration and determination of manganese traces by atomic absorption spectrometry

Flame atomic absorption spectrometry was used for the determination of Mn in biological material following preconcentration by precipitation. The proposed preconcentration method is based on the continuous precipitation of Mn(II) as hydrated Mn(IV) oxide in ammonia buffer and dissolution of the precipitate with hydrogen oxalate or dilute nitric acid. The sensitivity of the Mn determination is increased by the presence of hydrogen peroxide, which raises the rate of oxidation of Mn(II) to Mn(IV). By using a time-based technique (at a sample loading rate of 4 ml min⁻¹) a concentration factor of up to 55 was obtained using 24 ml of sample. The effect of concurrent cations was investigated; the most adverse effect was exerted by Fe(III), which interfered at concentrations 50 times higher than that of Mn(II).     

中国大地形对冻雨天气云微物理过程的影响

云贵高原的冻雨是中国南方冬季最严重的气象灾害。利用天气研究和预报模式(weather research and forecasting model, WRF),对云贵高原大地形进行了敏感性实验,模拟了不同地形高度对大气环流、云微物理参量及冻雨分布的影响,结果显示：随着云贵高原大地形的抬升,准静止锋的锋线一直维持在24°N附近,但锋面越来越陡,表明高原大地形是形成云贵准静止锋的主要因素,准静止锋长时间滞留在贵州中东部和湖南西部,是该区冻雨高发的原因。随着高原的抬升,从全境的云滴碰并增长逐渐在高原东部出现冰晶融化过程,高原主体上的冻雨以过冷暖雨机制为主,而低海拔的东部地区以融化机制为主。随着高原抬升,高空逆温层及冻雨区均从贵州西北向贵州中部及东部地区移动,逆温层的存在及其冷-暖-冷的垂直结构是冻雨形成非常重要的因子。当云贵高原降至原地形的一半时,冻雨量最大,其后随着高原抬升,冻雨量开始减少。该研究有助于更深入了解云贵高原大地形对冻雨形成、范围和强度的影响机制。     

山西省土壤湿度时空分布及气候因素的耦合

了解山西省土壤湿度状况变化规律,可以为农业旱情监测提供科学依据。本论文利用2017年3月到2018年2月山西省土壤湿度数据、降水量数据和气温数据,利用线性趋势和相关分析等方法分析研究区土壤湿度的时空变化以及土壤湿度对气候变化的响应。结果表明山西省的平均土壤湿度分布特征为南高北少,东高西少,呈现出东南向西北递减的趋势。在季际-月际时间尺度分布下,土壤湿度在秋季达到高峰,且各区域表层土壤湿度与空气温度有着显著的负相关关系,而与降水量有着显著的正相关关系。     

沉淀单点滴定法与双点滴定法研究

导出了沉淀单点滴定法与双点滴定法计算式。以银电极为指示电极 ,Ag 标准溶液为滴定剂 ,对Cl-、Br-、I-及SCN-等离子的测定进行了研究 ;对影响测定结果准确度的因素进行了讨论。实验发现 ,在α =1 .0～ 1 .1的条件下 ,单点滴定法有较高的准确度 ;在α1 ≈ 1 .0～ 1 .1、ΔV =0 .5～ 1 .0mL的条件下 ,双点滴定法有较高的准确度     

MnOx/SAPO-11催化剂的制备、表征及其低温NH3-SCR活性

分别采用浸渍法、柠檬酸络合法以及沉淀法在SAPO-11分子筛上负载MnO_x,制备了一系列MnO_x/SAPO-11催化剂。考察了催化剂的低温NH₃选择性催化还原(SCR) (NH₃-SCR) NO_x的性能。结果表明,沉淀法制备的负载量为20%(w)的MnO_x/SAPO-11催化剂表现出最优异的低温NH₃-SCR性能及N₂选择性。通过X射线衍射(XRD)、扫描电镜(SEM)、能量散射谱(EDS)、原子吸收光谱(AAS)、N₂吸附-脱附、X射线光电子能谱(XPS)、H₂程序升温还原(H₂-TPR)、NH₃程序升温脱附(NH₃-TPD)以及NO/O₂程序升温脱附-质谱(NO/O₂-TPD-MS)等多种表征手段对催化剂的结构及表面性质进行分析。表征结果显示,采用不同方法制备催化剂时,其表面MnO_x的存在形式和晶相结构不同。沉淀法制备的催化剂表面存在无定型态MnO_x以及MnO₂晶型,具有较大的介孔及外表面积、更多比例的Mn⁴⁺和化学吸附氧,同时表面存在对反应有利的中强酸以及强酸。因此,催化剂在低温SCR反应阶段能够生成重要中间产物NO₂,从而表现出最佳低温活性。同时,三种制备方法均能使MnO_x相对均匀分散在SAPO-11表面。SAPO-11对催化剂表面MnO_x物种的形成具有一定的影响,从而影响催化剂的酸性,拓宽了MnO_x的活性温度窗口,提高了催化剂的N₂选择性。     

Study of photophysical properties AlBaq5

Pure and Ba²⁺ doped Alq₃ complexes were synthesized by simple precipitation method at room temperature, maintaining stoichiometric ratio. These complexes were characterized by XRD, UV–vis and FT-IR and photoluminescence (PL) spectra. XRD analysis reveals the polycrystalline nature of the synthesized complexes, while UV and FTIR confirm the molecular structure and the completion of quinoline ring formation and presence of quinoline structure in the metal complex. PL spectra of Alq₃ compared with barium doped complexes exhibit highest intensity in comparison to Alq₃ phosphor, which proves that barium enhances PL emission intensity of Alq₃ phosphor. The excitation spectra of the synthesized complexes are in the range of 300–480 nm with a broad peak in the range of 429–440 nm and shoulder at 380 nm, but with varying intensity. The emission wavelength lies in the range of 501–506 nm. Among all the synthesized complexes, AlBa₂q₅ exhibits maximum emission intensity. These remarkable properties of AlBaq₅ could be considered as promising materials as optoelectronic materials as well as green light emissive materials for OLEDs, PLLCD and solid state lighting applications.     

四氧化三钴粉末的沉淀法制备及表征

以硝酸钴为钴源,碳酸铵为沉淀剂,采用沉淀法制备四氧化三钴粉体。采用TG、XRD、IR、激光粒度分析仪等对前驱体碱式碳酸钴和产物四氧化三钴进行了表征及分析。研究了焙烧温度、反应物浓度和反应时间等因素对产物的影响。