Identification Of Mercury Species Research Articles

Identification of mercury species in spent fluorescent lamps and mercury recovery by distillation

The discarding of spent fluorescent lamps, one of the most significant sources of mercury usage in industry, might cause mercury release into the environment when suffering from breakage. The reclamation disposal of fluorescent lamps for mercury recycling is essential, while how to achieve highly efficient conversion of various mercury species into elemental mercury vapor is a key challenge. Herein, the distillation method was adopted for mercury recycling from phosphor powder. The results show that the contents of elemental mercury and oxidized mercury vapor filled in the lamps were 150–3500μg and 5–20μg, respectively. The mercury release sustained for 13(±2) h, with a maximum mercury concentration of 4500μg/m3. The mercury in phosphor can be desorbed to an undetected level when distilling at 600 °C under vacuum for 30 min, while that would be achieved at 700 °C when distilling under atmospheric pressure. This suggests that the vacuum distillation was favorable for the conversion of oxidized mercury into elemental mercury. The variation of mineral phase, particle size distribution and morphology of phosphor after distillation was insignificant, which guaranteed the recycling of phosphor simultaneously accompanying with mercury recycling. This work clarified the mercury release behavior during lamps crushing and provided a feasible way for mercury recycling.

Identification of mercury species in coal combustion by-products from power plants using thermal desorption-atomic fluorescence spectrometry on-line coupling system

Along with the environmental protection policies becoming strict in China, the air pollution control devices (especially selective catalytic reduction (SCR)) are widely equipped in coal-fired power plants. The installation and run of these devices will inevitably affect mercury (Hg) species distribution in coal fired by-products such like fly ash (FA) and gypsum. In this work, a new on-line coupling system based on atomic fluorescence spectrometry (AFS) with a home-made chromatographic workstation was successfully developed to identify Hg species through thermal programmed desorption (TPD). The influences of matrix, furnace temperature, and carrier gas flow on analytical performance were investigated and the parameters were optimized. The FA and gypsum samples from coal-fired power plants equipped with SCR were collected and the mercury species were analyzed by the developed coupling system. HgCl2 and HgO were the main species in FA, while Hg2Cl2 and HgO were the main species in gypsum. All of Hg species in the studied FA and gypsum samples were released below 400 °C. A sequential extraction procedure was applied to further verify the operational Hg species including mobile and non-mobile fractions in FA and gypsum samples. This study demonstrated that AFS coupled with TPD procedure was an effective method to analyze Hg species in coal combustion by-products from power plants.

Migration and identification of mercury species in wet flue gas desulfurization system using temperature programmed decomposition

The environmental problem concerning Hg pollution has received worldwide attention. Coal fired power plants are responsible for large amounts of Hg emission and produce abundant by-products in particular gypsum which is capable of extensive use. In this study, the migration of Hg in the gypsum production process and effluent treatment process in a typical wet flue gas desulfurization (WFGD) system was investigated and the temperature programmed decomposition technique was applied to identified Hg species in these products. Hg concentration in both the solid and liquid fraction of samples obtained in wet flue gas desulfurization system were determined by atomic fluorescence spectroscopy. The results indicated that gypsum accounted for a small proportion (29.9%) of Hg while the majority of Hg was transported to effluent treatment process where over 99.6% Hg was removed. The amount of Hg discharged from WFGD in the drainage, gypsum, and desulfurization sludge were 0.04 t/yr, 13.56 t/yr, and 9.56 t/yr, respectively. Desulfurization environment promoted HgS formation and lead to HgS being dominant in gypsum. The alkaline environment in the effluent treatment process contributed to the formation of HgO which was regarded as the primary Hg compound and accounted for 49.5%, 54.8%, and 78.5% of the total Hg in the neutralization tank, precipitation tank, and flocculation tank, respectively. The occurrence of HgCl2 in the solid fraction attributed to absorption of solid particles when it precipitated and was enhanced by the addition of chemicals. There was no obvious difference in the proportion of HgSO4 in the effluent treatment process. Systematic studies on difference in the partitioning of Hg species enables a better understanding on Hg behavior and provides conferences on targeting removal of Hg species in WFGD system.

Identification of Mercury Species in Liquid Hydrocarbons

Crude oil and natural gas may contain traces of mercury depending on the origin. Mercury contamination of oil feedstocks may cause problems in both upstream and downstream operations. Mercury also has toxic effects on human health. Therefore, mercury should be removed from oil and natural gas products at the production facility before shipping. Identification of the mercury species in hydrocarbons is very important for effective removal from oil and gas. Mercury species analysis was investigated using GC-ICP-MS. Metallic mercury analysis used various sample injection procedures for GC. Ionic mercury analysis compared Grignard (butylmagnesium chloride) with sodium tetraphenylborate agents for the derivatization technique and confirmed that both reagents provided good results. The present study optimized mercury species analysis for liquid hydrocarbons using GC-ICP-MS.

A comparison of devices using thermal desorption for mercury speciation in solids

The goal of this work is to emphasize the reliability of the thermal desorption technique in identifying mercury species. The analysis of mercury species in solids is essential for assessing the risk of disposal or re-use of mercury-contaminated materials. This study evaluates the accuracy and reliability of thermal desorption as a technique for identifying mercury species by means of different thermo-desorption devices. For this purpose, mercury species present in samples related with coal utilization processes were identified. Three devices were compared for analyzing samples free of carbon or with a low carbon content (fly ashes, gypsums and soils), and a new equipment was developed to analyze samples with a high carbon content (coal). In spite of the fact that the first three devices employ different experimental conditions (i.e., heating rate, gas flow and carrier gas), the mercury species identified in the samples were comparable in all cases. The need for new equipment for mercury speciation in materials containing carbon was a consequence of interferences produced from the pyrolysis products of the organic matter. The new device consists of two furnaces and two gas inlets to allow thermal oxidation of organic pyrolysis products and the identification of mercury species in carbonaceous samples. This new approach offers the application of thermal desorption to mercury speciation in all types of materials contaminated with mercury.

Mercury compounds characterization by thermal desorption

The ability to accurately determine metal mercury content and identify different mercury species in solid samples is essential for developing remediation and control strategies. The aim of the present study is to characterize mercury compounds based on thermal desorption. For this purpose a series of samples was prepared and the operational parameters—heating velocity, carrier gas—were optimized. Fifteen commercial mercury compounds were analyzed for use as fingerprints. The results of the study show that the identification of mercury species by the method of thermal desorption is possible. The temperature of desorption increased according to the following order HgI2<HgBr2<Hg2Cl2åHgCl2<Hg(CN)2<HgCl2O8·H2O<Hg(SCN)2<HgS (red)<HgF2<Hg2(NO3)2·2H2O<Hg(NO3)2·H2O<HgO (yellow, red)<Hg2SO4<HgSO4. A comparison of the estimated total mercury content with the mercury content calculated by integrating the area of the desorption curve shows that recoveries of 79–104% for HgS can be estimated. The proposed method represents a significant step forward in direct mercury analysis in solid samples.