การทำปรอทจากอุตสาหกรรมกาซธรรมชาติให้บริสุทธิ์ และผลกระทบต่อสภาวะแวดล้อมในห้องปฏิบัติการ / นันทนิตย์ วานิชาชีวะ = Purification method for mercury from natural gas industry and environmental impact on laboratory site / Nantanit Wanichacheva
Mercury, a by-product from natural gas refining process from the gulf of Thailand was found to contain some impurties such as black scum, heavy metals in the form of amalgum and many undissolve solids which is not suitable for any applications. Public awareness of its toxicity raises environmental concern about its storage and its disposal. Therefore the objective of this study was to purify this mercury for dental applications. Black scum and contaminated hydrocarbons were cleaned by washing with surfactant. Then, the mercury was further purified by either washing with dilute solution of nitric acid of triple vacuum distillation. The first method was performed by washing mercury with dilute nitric acid with varying concentration between 1, 2, 3, 4, 5, 6 % W/V. The second method was done by distilling mercury 1 - 3 times under vacuum at 192° c and 10 millibar pressure. The purity of mercury was monitored by determining trace metals such as Fe, Ni, Pb, Mn, Cu, Co, Cd with atomic absorption spectrophotometer. It was found that the purity of mercury was increased from 99.99878 - 99.99881 % (W/W) in original product to 99.99926 - 99.99929 % (W/W) by washing with 6% (W/V) nitric acid. Triple distillation gave mercury with the purity upto 99.99976 - 99.99979 % (W/W). The mercury optained from both treatments was found to be suitable for dental applications inwhich the purity of imported mercury for such usage was at 99.99898 - 99.99901 % (W/W). The fact that mercury vaporizes at room temperature and Its vapor is toxic, therefore this study needed to monitor the amount of mercury in working area and the accumulation in exposed staffs during September 1996 to June 1997. It was found that mercury vapor rose in some laboratory involving the handling of mercury. Excessive mercury content in urine from exposed person was detected in certain months. Fortunately, this problem was solved when all the safety regulation was implimented and safety system was in operation. This research indicated that mercury purification in laboratory could be done without any impact on environment and personnels involved.
