An economic and sensitive method for extracting chromium speciation in airborne inhalable dust,using a green sample treatment coupled with electrothermal atomic absorption

ABSTRACT

A new approach of cloud point extraction CPE procedure is optimized for hexavalent chromium determination in airborne dusts. Triton X-114 is used as a surfactant and 1-(2-pyridylazo)-2-naphthol as a specific complexing agent for the trivalent chromium’s removal from the aqueous phase to isolate hexavalent chromium compounds. The parameters influencing the extraction protocol (pH, surfactant concentration, and temperature are optimized. The obtained detection and quantification limits are 0.1 and 0.4 μg/L, respectively. The linearity is verified, with a regression coefficient close to 0.999 and the extraction recovery exceeds 99%. The method was successfully applied to analyze airborne samples collected from workplaces.     

Selenium Speciation Studies from Soan-Sakesar Valley,Salt Range,Pakistan

Abstract

A regional study of Selenium (Se) speciation in surface waters, groundwaters, and saturation extracts from Soan-Sakesar valley Salt-Range, Pakistan was started in March 1994 and completed in October 1996. Groundwaters, streams, and springs had median concentrations of: total Se 48, 404.5, and 82 μg/l; Se^+VI 40, 350 and 51 μg/l; Se^+IV 8, 48 and 29 μg/l; Se^-II 0, 6.5 and 2.0 μg/l, respectively. The concentration of Se exceeded the recommended water quality guidelines for drinking and irrigation water of 10 and 20 μg/l, respectively. In saturation extracts, median total Se, Se^+VI, Se^+IV and Se^-II were 190, 146, 37 and 7.0 μg/l, respectively. Uchhali, Khabbaki and Jahlar lake water samples had the mean concentration of: total Se 2103, 670 and 297 μg/l; Se^+VI 1777, 470, and 233 μg/l; Se^+IV 291, 166 and 39 μg/l; Se^-II 35, 34 and 25 μg/l, respectively. The Sakesar limestone Formation of Eocene age rich in shales and fossils (median Se concentration 7.2 μg/kg) are considered to be the source of selenium that have enriched soils of Soan-Sakesar valley. Selenim speciation results show the abundance of selenate in all the environmental samples. A linear relationship between Se^+VI and pH (R²= 0.84, 0.58, 0.88, 0.82, and 0.91; significant at the 0.05 level) for groundwater, saturation extract, stream, spring, and lake waters were noted, suggesting that the Se^+VI in the samples is highly associated with pH. Linear relationships were established between Se^+VI and Mg, NO₃, and SO₄ for groundwater (R²= 0.24, 0.16, and 0.64; significant at the 0.01 level) and surface water (R²= 0.96, 0.14, and 0.91; significant at the 0.001 level). This suggests the high concentrations of Mg, NO₃ and SO₄, which strongly adsorb and compete with selenium for surface site, increases the Se^+VI fraction. The results show that the higher percentage of selenate on other species in the analyzed samples is favored by higher pH and oxidizing environments of the valley.     

有机物中微量砷测定方法的改进

在对有机物中微量砷测定方法综合分析的基础上，选用了砷斑法￣［１］与Ａｇ－ＤＤＴＣ法￣［２］相结合的方法检测有机物中的微量砷。重点对Ａｇ－ＤＤＴＣ法的操作内容作了两处改进。实验表明，新方法检测有机物中的微量砷快速、准确。     

Rapid Small-Scale Column Tests for Arsenate Removal in Iron Oxide Packed Bed Columns

Arsenate breakthrough in column studies with a porous granular ferric hydroxide (GFH) was investigated in model waters and groundwaters. In this study, the use of rapid small-scale column tests (RSSCTs) initially designed for simulating the removal of organic compounds by granular activated carbon was extended for arsenate adsorption onto GFH. Adsorption kinetic studies and a comparison of laboratory RSSCT performance versus pilot-scale performance suggests that proportional diffusivity (PD) RSSCT scaling approaches are more valid than constant diffusivity (CD) approaches for arsenate onto GFH. Adsorption densities from column tests (qcolumn) were calculated at the point in the breakthrough curve when arsenate equaled 10 μg/L in the column effluent. For a simulated 2.5 min empty-bed contact time (EBCT), a model water (pH=8.6) had qcolumn values of 0.99 to 1.5 mgAs/gGFH versus 0.02 to 0.28 mgAs/gGFH with a comparable pH and EBCT in a natural groundwater. The differences were attributed to the silica, phosphate, vanadium, and other adsorbable inorganics in the groundwater. At pH 7.6 to 7.8, qcolumn values from PD-RSSCTs in the three natural waters were comparable (1.5±0.3 mgAs/gGFH) and higher than CD-RSSCT qcolumn values (0.57±0.26 mgAs/gGFH) in the three natural waters. All the RSSCTs captured changes in water quality (source water and pH) and operational regimes (e.g., EBCTs) and could be used to aid in the selection and design of arsenic removal media for full-scale treatment facilities.     

Sm-EDTMP稳定常数的测定及其在血浆模型中的平衡组分

为了解153 Sm EDTMP 在血液中的平衡组分,采用电位滴定法测定了 EDTMP 的质子化常数和 Sm EDTMP的稳定常数。EDTMP的质子化常数为:lgβ2 =22.69±0.02,lgβ3 =30.54±0.03,lgβ4 =36.93±0.02,lgβ5=42.15±0.01,lgβ6 =45.02±0.03,lgβ7 =46.14±0.02;Sm EDTMP的稳定常数为: lg KSmL=22.62±0.02,lg KSmLH=29.93±0.02,lg KSmLH2 =36.18±0.03。在生理pH条件下,EDTMP主要以LH3 形式存在, Sm EDTMP 主要以 SmLH 形式存在。血浆模型中,在生理 pH 条件下, Sm 主要以带负电荷的SmLH和SmL形式存在,Sm EDTMP通过人体肾脏排泄;在低 pH(pH<6)条件下,以 Sm 柠檬酸组分存在,表明153Sm EDTMP在人体中肝摄取很低。同时,平衡组分中游离 Sm3+ 含量很低,说明 Sm EDTMP有很高的血浆稳定性,不用加入过量配体来防止标记物解离。EDTMP在血浆模型中主要以 LH3 形式存在,没有出现EDTMP的钙配合物组分,说明配体EDTMP不会使患者血钙明显降低。     

锑氧粉砷浸出工艺研究

通过对锑氧粉中砷物相的分析,根据三氧化二砷的性质,采用碳酸钠高温焙烧—碳酸化除砷—真空过滤—水洗—真空过滤工艺,将锑氧粉中的元素砷转变为砷酸钠浸出,对影响浸出的几个因素进行了研究,择取优化条件,砷的浸出率可达到94%左右。     

难处理硫化矿生物湿法冶金研究进展（Ⅰ）微生物氧化工艺技术研究

生物湿法冶金技术与传统矿业氧化工艺相比，成本低、无污染，具有广阔的工业应用前景。本文着重评述了国内外在浸矿微生物、培养基的优化、细菌的接种量、温度、酸度、矿石粒度、矿浆浓度、浸出液中As(Ⅲ)和As(Ⅴ)浓度等方面的研究进展。     

氟化钠和8-羟基喹啉联合掩蔽氢化物发生原子荧光法直接测定环境水样中的Sb(Ⅲ)和Sb(Ⅴ)

研究了氢化物发生原子荧光光谱法 (HG AFS)直接测定环境水样中Sb(Ⅲ )时Sb(Ⅴ )及其他元素的干扰情况 ,选择了最佳掩蔽剂及测定条件 ,表明采用氟化钠和 8 羟基喹啉联合掩蔽在 3mol·L- 1 的盐酸介质中可有效消除各种干扰 ,而且在测定过程中不会引起形态的改变 ,其检测限为 0 .1ng·ml- 1 ,加标回收率在 92 .2 %～ 1 0 5 .0 %之间。     

Preparation of poly (isophthalamide-graft-methacrylamide) and its utilization in the modification of cellulose acetate ultrafiltration membranes

Methacrylamide was grafted on to poly (isophthalamide) (PIPA-g-MAA) to improve its solubility and hydrophilicity. Then, PIPA-g-MAA incorporated high performance cellulose acetate ultrafiltration (CA) membranes were prepared by phase inversion technique and physical properties of the membranes were studied by various analytical methods. The efficiency of these membranes in the removal of arsenic from aqueous stream was studied and an effort has been taken to correlate the separation efficiency with morphology. Overall results suggest that membrane hydrophilicity, structure and performance were improved significantly by the addition of PIPA-g-MAA. Thus PIPA-g-MAA can be considered as an effective modification agent for CA membranes.     

Effect of pine sawdust on the behavior of arsenic and sulfur during slow heating pyrolysis of Shanxi Tuanbo-2 coal

Effect of pine sawdust on the removal of arsenic and sulfur during Shanxi Tuanbo-2 coal pyrolysis was investigated. Results showed that adding pine sawdust could increase the removals of arsenic and sulfur during Shanxi Tuanbo-2 coal pyrolysis, and when the ratio of the pine sawdust was 50%, the arsenic removal was the highest; at this ratio, the total sulfur removal also was the highest. Adding pine sawdust also increased pyritic sulfur and organic sulfur removal. Furthermore, results also indicated that adding pine sawdust made arsenic associated with sulfates and monosulfides and arsenic in stable forms escape more easily.