Clean and efficient treatment of high-mercury leachate produced from remediation of mercury-polluted soil has become a huge challenge for environmental scientists. In this work, cement solidification was firstly adopt...Clean and efficient treatment of high-mercury leachate produced from remediation of mercury-polluted soil has become a huge challenge for environmental scientists. In this work, cement solidification was firstly adopted to treat the high-concentration mercury leachate, which had high alkalinity. Different mercury concentrations, namely 3.120 mg/L Hg mercury leachate and 9.243 mg/L Hg mercury concentrated leachate, were separately solidified by Portland cement. The results indicated that simply using the cement can properly solidify both the leachates to meet the waste landfill standard, with liquid （mL）/solid （g） ratio （US ratio） of 4：10-6：10. In order to make full use of mercury in the leachates, a Hg extraction method was subsequently carried out under different experimental parameters, such as temperature and pH value. It was shown that the Hg extraction ratio could reach as high as 99.84% and almost all the mercury in the leachate could be transformed to HgS precipitate; moreover, the Hg concentration in the treated leachate was reduced from 3.120 to 0.005 mg/L at pH 2.98 and 30℃, which was much less than the limit of the national standard, indicating that the leachate had been completely cleaned and could be discharged freely. Hence, simple cement solidification renders high-mercury leachate nontoxic, and the Hg extraction method can successfully recover the Hg and enable the residual leachate to be discharged safely.展开更多
A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not on...A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.展开更多
Mercury（Hg）, mainly in cinnabar species, has been used in medicine for thousands of years in China, and worldwide concern has been raised on its toxicity. In this work, the amount of bioaccessible mercury in 16 Chin...Mercury（Hg）, mainly in cinnabar species, has been used in medicine for thousands of years in China, and worldwide concern has been raised on its toxicity. In this work, the amount of bioaccessible mercury in 16 Chinese patent medicines（CPMs） was measured by using an in vitro simulated digestion system, consisting of simulated gastric and intestinal fluid, to investigate the bioavailability of mercury in CPMs and evaluate its potential risk to human health. Total mercury and mercury in the gastrointestinal extracts were measured by inductively coupled plasma mass spectrometry（ICP-MS）. The levels of total Hg in 16 CPMs ranged from not detected to 11.89 mg/g, with a mean value of 1.13 mg/g, while the extractable Hg ranged from not detected to 4.37 μg/g, with a mean value of 0.42 μg/g.Mercury bioaccessibility varied significantly in the investigated CPMs, depending on the ingredient. Compared to the CPMs without cinnabar（2.5%–30.9%）, the percentage of mercury in the gastrointestinal supernatants for CPMs with cinnabar was quite a bit lower（0.037%）. By comparing with the Food and Agricultural Organization/World Health Organization Joint Expert Committee on Food Additives（FAO/WHO） safety guideline, the average daily intake dose（ADD） of Hg in the medicines was then calculated to access the risk of mercury to human health from taking CPMs.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51672025,51572020,51372019)Major Projects of Science and Technology in Shanxi Province(No.MC2016-03)
文摘Clean and efficient treatment of high-mercury leachate produced from remediation of mercury-polluted soil has become a huge challenge for environmental scientists. In this work, cement solidification was firstly adopted to treat the high-concentration mercury leachate, which had high alkalinity. Different mercury concentrations, namely 3.120 mg/L Hg mercury leachate and 9.243 mg/L Hg mercury concentrated leachate, were separately solidified by Portland cement. The results indicated that simply using the cement can properly solidify both the leachates to meet the waste landfill standard, with liquid （mL）/solid （g） ratio （US ratio） of 4：10-6：10. In order to make full use of mercury in the leachates, a Hg extraction method was subsequently carried out under different experimental parameters, such as temperature and pH value. It was shown that the Hg extraction ratio could reach as high as 99.84% and almost all the mercury in the leachate could be transformed to HgS precipitate; moreover, the Hg concentration in the treated leachate was reduced from 3.120 to 0.005 mg/L at pH 2.98 and 30℃, which was much less than the limit of the national standard, indicating that the leachate had been completely cleaned and could be discharged freely. Hence, simple cement solidification renders high-mercury leachate nontoxic, and the Hg extraction method can successfully recover the Hg and enable the residual leachate to be discharged safely.
基金supported by the National Natural Science Foundation of China (No. 51376109)
文摘A considerable amount of Hg is retained in flue gas desulfurization（FGD） gypsum from Wet Flue Gas Desulfurization（WFGD） systems. For this reason, it is important to determine the species of Hg in FGD gypsum not only to understand the mechanism of Hg removal by WFGD systems but also to determine the final fate of Hg when FGD gypsum is disposed. In this study, Temperature Programmed Decomposition（TPD） and Sequential Chemical Extraction（SCE） were applied to FGD gypsum to identify the Hg species in it. The FGD gypsum samples were collected from seven coal-fired power plants in China, with Hg concentrations ranging from 0.19 to 3.27 μg/g. A series of pure Hg compounds were used as reference materials in TPD experiments and the results revealed that the decomposition temperatures of different Hg compounds increase in the order of Hg_2Cl_2〈 HgCl_2〈 black HgS 〈 Hg_2SO_4〈 red HgS 〈 HgO 〈 HgSO_4. The Hg compounds existing in FGD gypsums identified by TPD included HgCl_2, Hg_2Cl_2, Hg_2SO_4, black HgS and red HgS, of which mercury sulfides were the primary compounds. The results of SCE indicated that Hg was mainly distributed in the strongly complexed phase. The low Hg content in FGD gypsum increases the ambiguity of assigning extraction fractions to certain Hg species by SCE. The fact that the primary compounds in FGD gypsum are HgS phases leads the leaching of Hg in the natural environment to be quite low, but a considerable amount of Hg may be released during the industrial heating process.
基金supported by the National Basic Research Program (973) of China (No. 2013CB430004)the National Natural Science Foundation of China (Nos. 21120102040, 21075130)
文摘Mercury（Hg）, mainly in cinnabar species, has been used in medicine for thousands of years in China, and worldwide concern has been raised on its toxicity. In this work, the amount of bioaccessible mercury in 16 Chinese patent medicines（CPMs） was measured by using an in vitro simulated digestion system, consisting of simulated gastric and intestinal fluid, to investigate the bioavailability of mercury in CPMs and evaluate its potential risk to human health. Total mercury and mercury in the gastrointestinal extracts were measured by inductively coupled plasma mass spectrometry（ICP-MS）. The levels of total Hg in 16 CPMs ranged from not detected to 11.89 mg/g, with a mean value of 1.13 mg/g, while the extractable Hg ranged from not detected to 4.37 μg/g, with a mean value of 0.42 μg/g.Mercury bioaccessibility varied significantly in the investigated CPMs, depending on the ingredient. Compared to the CPMs without cinnabar（2.5%–30.9%）, the percentage of mercury in the gastrointestinal supernatants for CPMs with cinnabar was quite a bit lower（0.037%）. By comparing with the Food and Agricultural Organization/World Health Organization Joint Expert Committee on Food Additives（FAO/WHO） safety guideline, the average daily intake dose（ADD） of Hg in the medicines was then calculated to access the risk of mercury to human health from taking CPMs.
