Use of copper shavings to remove mercury from contaminated groundwater or wastewater by amalgamation

The efficacy of copper shavings (Cu(0)) for the removal of Hg2+ from aqueous solution by amalgamation is demonstrated. Two kinds of copper shavings were investigated: (a) chemically processed shavings (Fluka) and (b) recycled shavings from scrap metal. Batch sorption experiments yielded very high retardation coefficients of 28 850-82 830 for the concentration range studied (1-10 000 microg/L Hg2+ dissolved in distilled water or in a 0.01 M CaCl2 matrix solution). Sorption data were well-described bythe Freundlich isotherm equation. Kinetic batch sorption experiments showed that 96-98% of Hg2+ was removed within 2 h. Column experiments were performed with a mercury solution containing 1000 microg/L Hg in a 0.01 M CaCl2 matrix with a flow rate of 0.5 m/d. No mercury breakthrough (c/c(0) = 0.5) could be detected after more than 2300 percolated pore volumes, and the high retardation coefficients determined in the batch studies could be confirmed. Copper was released from the shavings due to the amalgamation process and to copper corrosion by oxygen, resulting in concentrations of mobilized copper of 0.2-0.6 mg/L. Due to their high efficiency in removing Hg2+ from aqueous solution, the use of copper shavings for the removal of mercury from contaminated water is suggested, employing a sequential system of mercury amalgamation followed by the removal of mobilized copper by an ion exchanger such as zeolites. Possible applications could be in environmental technologies such as wastewater treatment or permeable reactive barriers for in situ groundwater remediation.     

铁锂云母精矿浸出液萃取法提锂研究

以铁锂云母矿石经焙烧—水浸获得水浸液为研究对象,明晰了溶液中钙、镁离子对萃取过程中两相分离的影响,考察了碳酸钠和氢氧化钠用量、水油相比对钙镁脱除效果及脱杂浸出液中锂萃取效果的影响。结果表明：铁锂云母矿石浸出液分别加入锂当量100%和镁摩尔量4倍的碳酸钠和氢氧化钠,在常温下反应1 h后,液固分离获得脱杂浸出液,钙、镁脱除率分别为>99.9%和82.53%;脱杂浸出液采用实验室改性后的M54-100-Cyanex923-磺化煤油萃取体系在O/A=1.5下模拟三级逆流萃取,Li、Na萃取率分别为90.85%和0.04%,载锂有机相在O/A=25下采用5.5 mol/L HCl模拟三级逆流反萃,Li的反萃率>99.9%,富锂反萃液中锂含量在26 g/L左右,一步实现锂的提纯和富集。     

四丁基溴化铵-碘化钾-水体系浮选分离汞(Ⅱ)的研究

研究了四丁基溴化铵-碘化钾体系分离汞(Ⅱ)的行为及汞(Ⅱ)与其他金属离子分离的条件。实验结果表明,在水溶液中,汞(Ⅱ)与四丁基溴化铵和碘化钾形成不溶于水的三元缔合物[HgI4][TBAB]2,此三元缔合物沉淀浮于水相上层形成界面清晰的液-固两相。当四丁基溴化铵和碘化钾的浓度分别为6.0×10-4mol/L和5.0×10-3mol/L,Hg(Ⅱ)可与Rh(Ⅲ),Fe(Ⅱ),Sn(Ⅳ),Cr(Ⅲ),Mn(Ⅱ),Ce(Ⅲ),Al(Ⅲ),Ga(Ⅲ),Co(Ⅱ),V(Ⅴ),W(Ⅵ),Ni(Ⅱ),Zn(Ⅱ)和Mo(Ⅵ)分离。对合成水样中Hg(Ⅱ)进行分离和测定,Hg(Ⅱ)的浮选率在99.3%以上,其他金属离子的浮选率都在2.9%以下。该方法在微量汞的分离和富集分析中有一定的实用价值。     

3,5-二溴水杨醛罗丹明B酰肼的合成及其在汞检测中的应用

合成了3,5-二溴水杨醛罗丹明B酰肼(RBDBH)荧光探针,并分别采用元素分析、红外光谱(IR)和核磁共振(NMR)进行了表征;系统探讨了汞(Ⅱ)对RBDBH探针的荧光增强效应的条件和应用,建立了测定汞(Ⅱ)的荧光光度新方法。实验表明:于5 mL比色管中,依次加入25 μL 1.000×10^-3 mol/L RBDBH溶液、适量Hg²⁺标准溶液、2.5 mL乙腈、2.2 mL pH 7.0的Tris-HCl缓冲溶液,用水定容至刻度,固定激发波长和发射波长分别为520、570 nm,用1 cm比色皿进行测定,汞(Ⅱ)浓度在0.36～4.4 μmol/L范围内与其对应的荧光强度呈良好的线性关系,相关系数为0.997 4。方法检出限为0.30 μmol/L。将RBDBH荧光探针应用于废水中汞(Ⅱ)的测定,结果与原子吸收光谱法(AAS)基本一致,相对标准偏差(RSD,n=5)为1.9%～2.3%。     

Iodide-Enhanced Electrokinetic Remediation of Mercury-Contaminated Soils

This study investigates using an iodide-enhanced solution at the cathode during electrokinetic treatment to optimize the removal of mercury from soils. The experimental program consisted of testing two types of clayey soils, kaolin, and glacial till, that were initially spiked with 500 mg/kg of Hg(II). Experiments were conducted on each soil type at two voltage gradients (1.0 or 1.5 VDC/cm) to evaluate the effect of the voltage gradient when employing a 0.1 M KI solution. Additional experiments were performed on each soil type to assess the effect of using a higher iodide concentration (0.5 M KI) when using a 1.5 VDC/cm voltage gradient. The tests conducted on the kaolin soil showed that when the 0.1 M KI concentration was employed with the 1.0 VDC/cm voltage gradient, approximately 97% of the mercury was removed, leaving a residual concentration of 16 mg/kg in the soil after treatment. The tests conducted on glacial till indicated that it was beneficial to use the higher (0.5 M KI) iodide concentration and the higher (1.5 VDC/cm) voltage gradient to enhance mercury removal, because, under these conditions, a maximum of 77% of the mercury was removed from the glacial till, leaving a residual concentration of 116 mg/kg in soil after electrokinetic treatment. Compared to kaolin, the lower mercury removal from the glacial till soil is attributed to the more complicated soil composition, such as the presence of carbonates and organic matter, which caused Hg(II) to adsorb to the soil and/or exist as an immobile chemical species.     

Modeling Mass Removal during In Situ Air Sparging

A model was developed to simulate mass removal during in situ air sparging. The model captures the physical characteristics of the air plume and employs conventional methods to simulate mass transfer. A parametric study was conducted using the model to assess how chemical properties, the operational method, and media affect mass removal during in situ air sparging. Mass removal is particularly sensitive to Henry's law constant, and the aqueous diffusion coefficient when Henry's law constant is high. Simulations of pulsed and continuous air injection show that pulsed injection can yield greater mass removal than continuous air injection for certain pulse cycles. Mass removal is generally greater at higher injection rates, but the increase in mass removal diminishes as the injection rate increases. Parametric analysis also showed that mass is removed faster when air channels are narrower or more tortuous (i.e., in coarser or more well-graded formations).     

A solvent extraction study of silver(I), palladium(II) and mercury(II) with 2-tert-dodecylthiopyridine

2-tert-Dodecylthiopyridine was synthesized from 2-chloropyridine and tert-dodecanethiol in order to examine its extraction properties for various metals. It was found to have good selectivity for the extraction of palladium(II) and mercury(II) over platinum(II) and -(IV) and base metals from chloride media; silver(I) was found to be almost completely extracted from nitric acid (0.01–5 mol/dm³ HNO₃). Palladium(II) and mercury(II) were completely extracted from hydrochloric acid over the range 0.01–2 and 0.01–0.5 mol/dm³ HCl, respectively. The rate of extraction of palladium(II) from hydrochloric acid was much faster than when using dialkylsulfide and triisobutylphosphine sulfide extractants. An aqueous mixture of thiourea and hydrochloric acid was found to be effective as stripping solution for palladium(II). The extent of stripping was dependent on the concentrations of either thiourea or hydrochloric acid.     

钨精矿中痕量汞的电化学冷蒸气发生-原子荧光光谱测定法

在断续流动条件下,采用自制的电化学流通池作为汞蒸气发生器,建立了电化学冷蒸气发生法-原子荧光光谱联用技术对汞的分析方法。在优化的实验条件下,汞的荧光强度在0～5.0μg/L范围内与浓度呈良好的线性关系,汞的检出限为1.3 ng/L。对1μg/L Hg测定的相对标准偏差为1.5%(n=11)。方法应用于钨精矿中汞的测定,样品加标回收率在97%～103%之间。方法准确可靠,灵敏度高。     

Benzene Nonaqueous Phase Liquids Removal under Air-Sparged Conditions

The dissolution, diffusion, and volatilization of a free-phase benzene glob in the presence of air sparging were measured in laboratory-scale air sparging reactors and modeled using a dissolution–diffusion–volatilization (DDV) model. The estimated dissolution rate coefficients (Kf) from the DDV model ranged from 0.0050 to 0.017 mm/min while the estimated volatilization rate coefficients (KL) ranged from 0.012 cm/min to 0.029 mm/min. The DDV model fitted well the aqueous phase migration of benzene for air channels spaced at 45 and 60 mm. For air channels spaced at 30 mm, the model fitted the aqueous migration at most locations except above the benzene glob where the model underestimated the experimentally determined concentrations. However, the mass removed using the gas phase concentrations as predicted by the model were 65% of the actual mass removed. These observations suggest that other mass transport mechanisms may influence benzene mass removal, especially when the air channels are close to the benzene glob.     

The fetoplacental pressor effects of low-dose acetylsalicylic acid and angiotensin II in the ex vivo cotyledon model

OBJECTIVE: Our purpose was to investigate perfusion pressure changes ex vivo induced by angiotensin II on fetoplacental vasculature pretreated with low-dose acetylsalicylic acid. STUDY DESIGN: Two cotyledons from each of 12 placentas were perfused. The intervillous space of one cotyledon was infused with acetylsalicylic acid (5 x 10(-5) mol/L) similar to the serum concentration of women receiving daily low-dose aspirin therapy (60 to 81 mg). The control cotyledon was infused with an equivalent amount of normal saline solution. Two doses of angiotensin II, 1 x 10(-11.5) and 1 x 10(-10) moles, were injected as boluses into the chorionic arteries of each cotyledon. A 3 x 10(-7) mole dose of angiotensin II was also injected into the intervillous space. Statistical analysis was performed with analysis of variance, and results are expressed as mean pressure change in millimeters of mercury +/- SEM. RESULTS: Perfusion pressure response did not vary between cotyledons pretreated with acetylsalicylic acid and control cotyledons when 3 x 10(-7) moles of angiotensin II was injected into the intervillous space (8.0 +/- 1.9 mm Hg vs 9.8 +/- 1.6 mm Hg, p = 0.59). There were no differences between cotyledons in pressure response to 1 x 10(-11.5) moles of angiotensin II injected into the fetal circuit (5.9 +/- 0.8 mm Hg vs 6.7 +/- 0.9 mm Hg, p = 0.51). However, in the cotyledons pretreated with acetylsalicylic acid there was a decrease in the pressor response to 1 x 10(-10) moles of angiotensin II (14.1 +/- 1.4 mm Hg vs 21.5 +/- 3.3 mm Hg, p = 0.05). CONCLUSIONS: Low-dose aspirin infused into the intervillous space decreases vasoconstriction elicited by angiotensin II in the fetoplacental compartment. This suggests that maternal low-dose aspirin therapy has effects in the fetoplacental circulation in addition to its effects in the maternal circulation.     

Factors affecting the determination of total mercury in biological samples by continuous-flow cold vapor atomic absorption spectrophotometry

The acidic reduction of Hg using a continuous-flow analytical system was evaluated. With 25% SnCl2 as the reductant, characteristic concentrations (sensitivities) of 0.44 microgram/L (open cell) and 0.29 microgram/L (flow-through cell) were obtained using inorganic Hg2+ standards in 1.5% HCl. When CH3Hg+ standards were used, absorption signals were an order of magnitude lower, indicating that Sn(II) is incapable of producing Hg degree from organic Hg in this acidic reduction system. Addition of CdCl2 to the SnCl2 reductant, as suggested by Magos (1) for the reduction of organomercurials under alkaline conditions, was without beneficial effect. Similarly, combining Sn with another reducing agent (hydroxylamine hydrochloride), or a strong alkaline solution (40% NaOH), in the reaction coil of the flow-through system did not significantly enhance the Hg absorption signal for either inorganic or organic Hg. Recovery of Hg from spiked liver homogenates digested at 70-80 degrees C using a HNO3/H2SO4/HCl procedure and stabilized with 0.5 mM K2Cr2O7 was > 85% using either inorganic Hg2+ or CH3Hg+, indicating that this digestion procedure successfully breaks the C-Hg bond to form readily reducible Hg species. Using L-cysteine to stabilize standards of inorganic Hg2+ in HCl caused significant depressions of the Hg absorption signal at L-cysteine concentrations > 0.001% (approximately 0.5 mM); 0.1% L-cysteine caused total suppression of the Hg signal. These results indicate that: (1) acidic reduction of Hg by Sn in this continuous-flow system requires breakdown of organomercurials prior to analysis; (2) tissue digestion using HNO3/H2SO4/HCl followed by the addition of K2Cr2O7 to stabilize Hg2+ achieves this breakdown and allows good recovery of total Hg; and (3) use of L-cysteine to complex and prevent losses of Hg should be avoided in systems using acidic reduction of Hg. Concentrations of endogenous tissue sulfhydryls are generally lower than those associated with depressed absorbance signals during the acidic reduction of Hg.     

巯基葡聚糖凝胶分离富集5-(对羧基苯偶氮)-8-羟基喹哪啶分光光度法测定微量汞(Ⅱ)

研究了在CTMAB-OP微乳溶液存在下,5-(对羧基苯偶氮)-8-羟基喹哪啶(5-CPAHQD)与汞(Ⅱ)发生显色反应的条件,建立了测定微量汞(Ⅱ)新的高灵敏度分光光度法。实验结果表明,在醋酸-醋酸钠介质中,5-(对羧基苯偶氮)-8-羟基喹哪啶与汞(Ⅱ)发生灵敏的显色反应,生成络合比为2∶1的橙红色络合物。络合物的最大吸收峰位于508 nm,表观摩尔吸收系数为3.5×105L.mol-1.cm-1,在10 mL溶液中汞(Ⅱ)量在0.01~1.2μg之间符合比耳定律,检出限为0.3 mg/L,并且该显色反应具有较强的抗干扰能力,用于水、铅锌矿样品中微量汞(Ⅱ)的测定,结果与原子吸收光谱法相一致,方法的回收率在97%~104%之间,其相对标准偏差(n=6)≤4.5%。     

1,3-二［（4-硝基苯基重氮基）］苯基三氮烯的合成及其与汞Ⅱ的显色反应

合成了新显色剂1，3-二［（4-硝基苯基重氮基）］苯基三氮烯（简称DNBDBT）,并研究了在Triton X-100存在下其与HgⅡ的显色反应。结果表明，在pH 10.0的Na2B4O7-NaOH缓冲介质中，HgⅡ与该试剂形成稳定的红色络合物，最大吸收波长位于564 nm，表观摩尔吸光系数为1.15×105 L·mol-1·cm-1，汞的质量浓度在0~0.6 μg/mL范围内服从比尔定律。用于废水中汞Ⅱ的直接测定，相对标准偏差为1.3%~2.0%，回收率为98%~103%。     

复杂铜钴矿浸出溶液处理试验

以复杂铜钴矿浸出溶液为原料,采用M5774萃取铜,硫酸反萃,铜的萃取率和反萃率均大于99%,萃余液用SO_2/空气混合气氧化中和除铁、锰,除铁后液铁和铝均小于0.005g/L,锰没有完全除掉,采用活性氧化镁沉淀镍和钴,在较优条件下,镍、钴沉淀率分别为97.73%和94.33%,用活性氧化钙沉淀锰和镁。     

顺序注射氢化物发生-原子荧光光谱法同时测定环境水样中铋和汞

建立了一种顺序注射氢化物发生-原子荧光光谱法同时测定水样中的Bi和Hg含量的方法。考察了光电倍增管负高压、铋和汞灯电流、原子化器高度、载气流量、屏蔽气流量等因素对测定结果的的影响。研究发现:载流HCl的浓度为0.3~0.6 mol/L,KBH4浓度为4 g/L,稳定剂K2Cr2O7浓度为5 g/L时,同时测定铋和汞的效果最佳。在最佳实验条件下,铋和汞的检出限分别为0.005 8μg/L和0.007 5μg/L。方法用于河水、井水和池水水样中铋和汞的测定,加标回收率为91.0%~109%,相对标准偏差小于3.4%,被测水样中共存的离子对铋和汞的测定没有干扰。     

Mercury exposure from dental amalgam fillings: absorbed dose and the potential for adverse health effects

This review examines the question of whether adverse health effects are attributable to amalgam-derived mercury. The issue of absorbed dose of mercury from amalgam is addressed first. The use of intra-oral Hg vapor measurements to estimate daily uptake must take into account the differences between the collection volume and flow rate of the measuring instrument and the inspiratory volume and flow rate of air through the mouth during inhalation of a single breath. Failure to account for these differences will result in substantial overestimation of the absorbed dose. Other factors that must be considered when making estimates of Hg uptake from amalgam include the accurate measurement of baseline (unstimulated) mercury release rates and the greater stimulation of Hg release afforded by chewing gum relative to ordinary food. The measured levels of amalgam-derived mercury in brain, blood, and urine are shown to be consistent with low absorbed doses (1-3 micrograms/day). Published relationships between the number of amalgam surfaces and urine levels are used to estimate the number of amalgam surfaces that would be required to produce the 30 micrograms/g creatinine urine mercury level stated by WHO to be associated with the most subtle, pre-clinical effects in the most sensitive individuals. From 450 to 530 amalgam surfaces would be required to produce the 30 micrograms/g creatinine urine mercury level for people without any excessive gum-chewing habits. The potential for adverse health effects and for improvement in health following amalgam removal is also addressed. Finally, the issue of whether any material can ever be completely exonerated of claims of producing adverse health effects is considered.     

Removal of Dissolved- and Free-Phase Benzene Pools from Ground Water Using In Situ Air Sparging

This paper presents the results of a laboratory investigation performed to study the use of air sparging to remediate dissolved-phase and free-phase [or non-aqueous-phase liquid (NAPL)-phase] benzene pools from ground water. The specific objectives of the study were (1) to assess how air injection rate affects the mass transfer and transport of dissolved- and NAPL-phase pools; and (2) to determine the effect of ground-water flow on the removal of dissolved- and NAPL-phase pools during the application of air sparging. A total of five 2D physical model tests were performed in a homogeneous coarse sand profile subjected to both static ground water and ground-water flow conditions. Three different air injection rates were used in a static ground-water condition, and two different air flow rates were used in soil profiles subjected to ground-water flow (hydraulic gradient = 0.011). All tests were performed with similar initial dissolved- and NAPL-phase benzene conditions. Injected air traveled within a parabolic zone of influence (in channel mode) when subjected to both static ground water and ground-water flow conditions, indicating that ground-water flow (for the ground-water velocities tested) did not affect the injected air zone of influence. An increase in air injection rate led to faster contaminant removal; however, at higher air injection rates, a threshold rate of removal was reached above which further increases in injection rate are a waste of effort. Additionally, air injected into the soil profile reduced the hydraulic conductivity within the zone of influence. This in turn led to lower ground-water flow rates, allowing for effective interception and treatment of a migrating NAPL plume. Higher air injection rates led to further reductions in hydraulic conductivity, allowing for substantial control of the NAPL plume in the downgradient direction. Overall, this study showed that air sparging can be used to effectively remediate dissolved- and NAPL-phase benzene.     

离子交换法从钼酸铵溶液中分离钼钒的研究

对采用离子交换法从钼酸铵溶液中除钒进行了研究。着重考察了DP-1螯合型树脂从钼酸铵溶液中分离钒。在pH值为7．18，钼浓度为50g／L，接触时间为30min，处理料液为10倍树脂体积时，除钒率可达99．84％，料液中的钒可从0．638g／L降至0．007g／L以下。用2mol／L的NaOH做解析剂，解析效果很好。树脂用盐酸转型后，重复使用性能稳定。     

Comparison of Liquid and Gas-Phase Photooxidation of MTBE: Synthetic and Field Samples

The feasibility of photooxidation treatment of methyl tert-butyl ether (MTBE) in water was investigated using two systems: (1) a slurry falling film photoreactor and (2) an integrated air stripping with gas phase photooxidation system. Methyl tert-butyl ether-contaminated synthetic water and field samples from contaminated sites were used for these studies. Using a TiO2 slurry (0.1 g/L; Degussa P25) flowing down at a rate of up to 0.26 L/min over the inner surface of a glass tube surrounding a 1-kW medium pressure mercury lamp, more than 99% of MTBE in the synthetic samples, initially at 1 mg/L, was degraded within 90 min. The major degradation products from MTBE were tert-butyl alcohol, tert-butyl formate, and small amounts of acetone. However, the degradation of MTBE and its byproducts in contaminated groundwater samples was hindered significantly by dissolved metals such as Fe2+, chloride ions, and aromatic organic species. Integrating air stripping with gas-phase photocatalysis is an an effective alternative that would not be affected by the water chemistry. The reaction rates for MTBE degradation in the gas phase are orders of magnitude faster than in aqueous solution.     

分散液相微萃取光度法测定水中痕量铜

以氯仿为萃取剂,甲醇为分散剂,铜试剂(二乙基二硫代氨基甲酸钠)为鳌合剂,建立了分散液相微萃取-分光光度法测定水中痕量铜的新方法。于50 mL离心试管中加入一定量的Cu²⁺标准溶液、50 μL 1.0 g/L铜试剂溶液,加水稀释至近50 mL,用1 mol/L盐酸调节pH值为3.0,定容。然后将3.25 mL由氯仿与无水甲醇组成的体积比为3∶10的混合液快速打入该离心管中,使之混合形成均匀浊相,萃取4 min后在3 000 r/min的条件下离心分离2 min,再抽取下层萃取液置于光程为1 cm的微型石英比色皿中。以空白试剂为参比,在波长为440 nm处测定其吸光度,结果表明,铜质量浓度在0.5~10 μg/L范围内与其对应的吸光度呈良好的线性关系,相关系数(r)为0.993 9,方法检出限为0.069 μg/L。将实验方法应用于水样中痕量铜的测定,测得结果与火焰原子吸收光谱法(FAAS)基本一致,相对标准偏差(RSD,n=5)为3.1%~4.0%。