Speciation and characterization of arsenic in Ketza River mine tailings using X-ray absorption spectroscopy

Ketza River mine tailings deposited underwater and those exposed near the tailings impoundment contain approximately 4 wt % As. Column-leaching tests indicated the potential for high As releases from the tailings. The tailings are composed dominantly of iron oxyhydroxides, quartz, calcite, dolomite, muscovite, ferric arsenates, and calcium-iron arsenates. Arsenopyrite and pyrite are trace constituents. Chemical compositions of iron oxyhydroxide and arsenate minerals are highly variable. The XANES spectra indicate that arsenic occurs as As(V) in tailings, but air-drying prior to analysis may have oxidized lower-valent As. The EXAFS spectra indicate As-Fe distances of 3.35-3.36 A for the exposed tailings and 3.33-3.35 A for the saturated tailings with coordination numbers of 0.96-1.11 and 0.46-0.64, respectively. The As-Ca interatomic distances ranging from 4.15 to 4.18 A and the coordination numbers of 4.12-4.58 confirm the presence of calcium-iron arsenates in the tailings. These results suggest that ferric arsenates and inner-sphere corner sharing or bidentate-binuclear attachment of arsenate tetrahedra onto iron hydroxide octahedra are the dominant form of As in the tailings. EXAFS spectra indicate that the exposed tailings are richer in arsenate minerals whereas the saturated tailings are dominated by the iron oxyhydroxides, which could help explain the greater release of As from the exposed tailings during leaching tests. It is postulated that the dissolution of ferric arsenates during flow-through experiments caused the high As releases from both types of tailings. Arsenic tied to iron oxyhydroxides as adsorbed species are considered stable; however, iron oxyhydroxides having low Fe/As molar ratios may not be as stable. Continued As releases from the tailings are likely due to dissolution of both ferric and calcium-iron arsenates and desorption of As from high-As bearing iron oxyhydroxides during aging.     

Lab-on-Chip Measurement of Nitrate and Nitrite for In Situ Analysis of Natural Waters

Microfluidic technology permits the miniaturization of chemical analytical methods that are traditionally undertaken using benchtop equipment in the laboratory environment. When applied to environmental monitoring, these "lab-on-chip" systems could allow high-performance chemical analysis methods to be performed in situ over distributed sensor networks with large numbers of measurement nodes. Here we present the first of a new generation of microfluidic chemical analysis systems with sufficient analytical performance and robustness for deployment in natural waters. The system detects nitrate and nitrite (up to 350 μM, 21.7 mg/L as NO(3)(-)) with a limit of detection (LOD) of 0.025 μM for nitrate (0.0016 mg/L as NO(3)(-)) and 0.02 μM for nitrite (0.00092 mg/L as NO(2)(-)). This performance is suitable for almost all natural waters (apart from the oligotrophic open ocean), and the device was deployed in an estuarine environment (Southampton Water) to monitor nitrate+nitrite concentrations in waters of varying salinity. The system was able to track changes in the nitrate-salinity relationship of estuarine waters due to increased river flow after a period of high rainfall. Laboratory characterization and deployment data are presented, demonstrating the ability of the system to acquire data with high temporal resolution.     

Kinetics of Water Uptake by Food Powders

The water uptake by several food materials that included animal and vegetable proteins and starch materials was studied. The amount q of water taken up by a sample powder during time t was described by the equation q = Qt/(B + t), where Q is the total water uptake of equilibrium and B is the time required to sorb Q/2. The rate of water uptake was proportional to the square of the amount of water that must still be absorbed to reach equilibrium. A specific rate constant for the process was calculated as (BQ)^?1.     

Sensory Evaluation of Taste of Alkali-ion Water and Bottled Mineral Waters

ABSTRACT: The sensory evaluation of alkali‐ion water and bottled mineral water was performed by panelists and their preferences for the taste of alkali‐ion water was surveyed. Consequently, alkali‐ion water made from tap water was found to taste better than any bottled mineral water; however, the activated carbon filtration water, which was also made from tap water, was found to taste better than alkali‐ion water. Furthermore, smell, taste, feeling in the throat, aftertaste, and general impression of the mineral water, alkali‐ion waters, and activated carbon filtration water were evaluated using the 1‐pair comparison method. Consequently, alkali‐ion water and activated carbon filtration water were more highly rated than commercial bottled mineral water.     

探讨离子交换树脂在水处理中的应用

本文首先从离子交换树脂结构和分类、离子交换原理、离子交换树脂应用范围、离子交换树脂回收再利用等方面阐述离子交换树脂水处理工艺,然后从仪器和试剂、离子交换树脂复苏类型、复苏原理及复苏结果等方面阐述离子交换树脂再生复苏工艺,再从仪器和试剂、复合材料制备与测定、吸附量测定、有机染料测定、测定结果分析等方面阐述离子交换树脂活性...     

天然高分子水处理剂在染料废水处理中的应用

用于水处理的天然高分子及其衍生物主要有纤维素、淀粉、木质素、壳聚糖,本文简要概述了四类天然高分子水处理剂在染料废水处理中的应用研究现状.     

天然高分子水处理剂在染料废水处理中的应用

用于水处理的天然高分子及其衍生物主要有纤维素、淀粉、木质素、壳聚糖，本文简要概述了四类天然高分子水处理剂在染料废水处理中的应用研究现状。     

天津海域水环境质量评价系统的开发与研究

天津海域水环境质量评价系统建设将对地区海洋水环境信息化、海洋工程环境评价、海水资源合理利用和相关业务部门工作效率的提高起到促进作用,为海洋水环境管理与保护决策提供必要依据.文中在对天津海域水环境的主要评价标准、评价方法和系统总体结构进行了研究.采用VB 6.0和SQL Server2000进行系统的开发,此评价系统本着低成本、开发简单、快捷、方便的原则,实现了用户管理、数据管理、以及图表输出等主要功能,满足了目前海洋水环境数据分析、评价和管理的需要,达到了辅助决策的目的.     

离子交换法提取木瓜皮中果胶的动力学研究

以木瓜皮为原料,分别研究了离子交换树脂法和酸提法提取果胶的动力学模型,获得速率常数和表观活化能,经过有效性检验和模型预测能力验证,模型均能很好预测果胶提取的动力学过程。离子交换法提取果胶的活化能Ea为23.68kJ/mol,与酸提法获得的37.88kJ/mol相比明显降低,离子交换树脂法提取木瓜皮中果胶明显优于酸提法。在树脂用量为5%、料液比为1∶30(g/mL)、浸提液pH值为1.5条件下,离子交换树脂法提取木瓜皮中果胶的最佳浸提温度为80℃,动力学分析优化最佳结果,得T_max=117.3min,果胶得率达17.47%,与试验结果相吻合。     

Kinetics of Water Sorption by Soybean and Pigeonpea Grains

Kinetics of liquid water sorption by soybean (Glycine max) and pigeonpea (Cajanus cajan) seeds was studied at several temperatures. The data could be accurately correlated in terms of an empirical model involving a single rate constant. The temperature dependence of the rate constant followed Arrhenius relation. Swelling of grains due to water sorption was slightly less than the volume of water imbibed. This loss related to the energy of activation of the water sorption process.     

天然饮用矿泉水生产新工艺研究

本文在对低温灭菌技术系统研究的基础上，针对目前国内天然饮用矿泉水生产中灭菌工艺所存在的问题，结合笔者多年矿泉水生产的工艺实践，提出了实用有效的矿泉水生产新工艺，实践证明，按此新工艺，配合严格的生产管理，可以确保生产出绝对无菌的饮用矿泉水。     

离子交换树脂快速催化黄水酯化

采用732#阳离子交换树脂直接催化黄水和乙醇进行酯化反应.单因素和正交实验结果表明,温度和pH条件是主要影响因素,在乙醇/黄水比为6:4、树脂用量60 g/L、pH2、40℃条件下处理3 d,己酸乙酯、丁酸乙酯、乙酸乙酯和乳酸乙酯含量分别较黄水提高7.5倍、0.83倍、7.3倍和3.3倍.该酯化技术操作简单、效果显著,可提高黄水回收利用效率.     

离子色谱法测定饮用天然矿泉水中溴酸盐

采用美国Dionex公司ICS-1100型离子色谱仪,应用IonPac AS22型阴离子分析柱,4.5mmol/L Na2CO3+0.8mmol/L NaHCO3淋洗液等度淋洗,在ASRS300(4mm)阴离子抑制器后加装CRD300二氧化碳去除装置,温控电导检测器,进样量300μL,通过计算峰面积测定饮用天然矿泉水中溴酸盐。校正曲线系数r=0.9998,检出限为4.54μg/L,RSD为0.42%~1.90%,加标回收率在96.2%~101.3%之间。     

Speciation of arsenic in Dutch total diets: methodology and results

In the last decade 311 duplicate portions of the 24-h diet of Dutch citizens were collected and lyophilized. All samples were assayed for total arsenic and, in addition, the 20 samples which ranked highest in total arsenic were selected for arsenic speciation i.e., the separate determination of organic-bound arsenic and inorganic arsenic. For the determination of total arsenic, the test portion is wet-digested and the digest reduced with KI/SnCl2/Zn to give AsH3 which is measured by molecular absorption spectrometry. Inorganic arsenic is also measured as AsH3 after acid extraction of the test portion and subsequent NaBH4 reduction of the extract. The residue of the acid extraction and the NaBH4-reduced extract are combined, wet-digested and the digest reduced with NaBH4 to give AsH3 originating from organic-bound arsenic. Samples spiked at different levels with inorganic and organic-bound arsenic were analysed and gave recoveries for inorganic arsenic of 94% to 122% (n = 6) and for organic-bound arsenic of 87% to 104% (n = 6). On average, the inorganic fraction is 30% of the total arsenic intake; range 3% to 50% (n = 14). The inorganic arsenic fraction decreases with increasing level of total arsenic intake. The highest oral inorganic arsenic intake was 60 micrograms; the tolerable daily intake (TDI) for a 60-kg individual is 120 micrograms inorganic arsenic. Organic and inorganic arsenic measured were summed and compared with the results of the total arsenic determination; differences were less than 15%. (Since inorganic arsenic is a contaminant and not an additive, the abbreviation TDI is preferred here over ADI (acceptable daily intake) which is retained for additives.)     

Speciation of arsenic in Dutch total diets: methodology and results

Summary In the last decade 311 duplicate portions of the 24-h diet of Dutch citizens were collected and lyophilized. All samples were assayed for total arsenic and, in addition, the 20 samples which ranked highest in total arsenic were selected for arsenic speciation i.e., the separate determination of organic-bound arsenic and inorganic arsenic. For the determination of total arsenic, the test portion is wet-digested and the digest reduced with KI/SnCl₂/Zn to give AsH₃ which is measured by molecular absorption spectrometry. Inorganic arsenic is also measured as AsH₃ after acid extraction of the test portion and subsequent NaBH₄ reduction of the extract. The residue of the acid extraction and the NaBH₄-reduced extract are combined, wet-digested and the digest reduced with NaBH₄ to give AsH₃ originating from organic-bound arsenic. Samples spiked at different levels with inorganic and organic-bound arsenic were analysed and gave recoveries for inorganic arsenic of 94% to 122% (n=6) and for organic-bound arsenic of 87% to 104% (n=6). On average, the inorganic fraction is 30% of the total arsenic intake; range 3 % to 50% (n=14). The inorganic arsenic fraction decreases with increasing level of total arsenic intake. The highest oral inorganic arsenic intake was 60 gg; the tolerable daily intake (TDI) for a 60-kg individual is 120 g inorganic arsenic. Organic and inorganic arsenic measured were summed and compared with the results of the total arsenic determination; differences were less than 15%. (Since inorganic arsenic is a contaminant and not an additive, the abbreviation TDI is preferred here over ADI (acceptable daily intake) which is retained for additives.)

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Arsenbindungsformen in holländischer Ganztagskost —Analysenmethode und Ergebnisse

Zusammenfassung Im letzten Jahrzehnt wurden 311 Doppelproben der Ganztagskost, inklusive Trinkwasser und Getränke, von Einwohnern der Niederlande gesammelt und gefriergetrocknet. Alle Proben wurden auf den Gesamt-Arsengehalt untersucht und von zwanzig Proben, deren Gesamt-Arsengehalt am höchsten war, wurde der Gehalt an organisch und anorganisch gebundenem Arsen bestimmt. Zur Gesamt-Arsengehaltbestimmung wurde die Untersuchungsprobe naß aufgeschlossen und anschließend mit KI/SnCl₂/Zn zu AsH₃ reduziert und durch Molekularabsorptionspektrometrie erfaßt. Anorganisches Arsen wird, nach saurer Extraktion der Untersuchungsprobe und anschließend, nach Reduktion mit NaBH₄, ebenfalls als A_sH₃ gemessen. Der Rückstand der sauren Extraktion sowie der NaBH₄-reduzierte Extrakt werden vereinigt, naß aufgeschlossen und die erhaltene Lösung mit NaBH₄ reduziert, das entstandene AsH₃ stammt vom organisch gebundenen Arsen. Einigen Proben (n = 6) wurde, auf verschiedenen Niveaus, organisch sowie anorganisch gebundenes Arsen zugesetzt. Die Wiederfmdungsraten für anorganisches Arsen betrugen 94% bis 122% und für organisches Arsen 87% bis 104%. Im Schnitt ist 30% der gesamten Arsenzufuhr anorganischer Herkunft; Bereich 3% bis 50% (n =14). Der anorganische Arsenanteil nimmt mit steigender Gesamt-Arsenzufuhr ab. Die höchste anorganische Arsenzufuhr betrug 60 g pro Person; TDI (Tolerable Daily Intake) für eine 60-kg-Person: 120 g anorganisches Arsen. Eine Bilanzstudie ergab einen Meßunterschied von weniger als 15% zwischen dem Gesamt-Arsengehalt und der Summe des organisch und anorganisch gebundenen Arsens.

     

ICP-MS测定饮用天然矿泉水中微量元素锑

采用电感耦合等离子体质谱(ICP-MS)对饮用天然矿泉水中微量元素锑进行分析,通过在线加入内标校正基体效应和接口效应,测定元素校正曲线相关系数在0.9995以上,元素检出限0.009μg·L-1,RSD%10(n=12)加标回收率在94.0%~106.0%之间。