A Method of Mercury Removal from Topsoil Using Low-Thermal Application

Abstract

Mercury contamination in the environment is problematic due to the unusual physical properties and well-recognized toxicity of this common metal. The bioavailability of mercury depends strongly on its chemical speciation. Anthropogenic mercury and its compounds appear in soil as "hot spots" located close to industrial facilities that used or produced mercury. The nature of the chemical production process, transportation and disposal practices often determined the chemical composition and distribution of mercury in the surrounding soils. Current ex situ soil remediation methods are expensive, produce undesirable side effects to the environment and usually involve transportation of contaminated soil. In this project, sponsored by the U.S. Department of Energy, a low-cost, simple approach to removing mercury from soil was evaluated. The process uses low-temperature thermal desorption of volatile metallic mercury and its compounds, and subsequent vapor capture. The project consisted of laboratory and plot-scale experiments. The laboratory efforts evaluated theoretical calculations of mercury removal as a function of time and temperature. The plot-scale experiment was a practical application of the laboratory results. For both experiments, mercury-polluted soil was obtained from a chemical production facility located in southern Poland. In laboratory experiments, at temperature 373 K total mercury concentration decreased in soil by nearly 32%. In plot-scale experiments, at temperature 440 K, about 60-70% of total mercury was removed from the soil. At the end of the experiment, a test of soil biological activity was performed to check if the high temperature applied to the soil did not impair the soil growth properties. There was no negative effect of temperature found.

Thermal Treatment of Mercury Mine Wastes Using a Rotary Solar Kiln

“…In these thermal devices, the off-gas generated is passed through a filtration system, where Hg 0 , finally, is collected [3,4]. Several mercury desorption experiments have demonstrated the feasibility of mercury removal at temperatures between 127 and 600 °C [5][6][7][8]. Experimental remediation of mercury-polluted soils by low-temperature thermal desorption has also shown mercury removal of over 99% in sand [8] and the volatilization of at least 99% of mercuric sulfide from polluted soil [5].…”

Sustainable remediation of mercury contaminated soils by thermal desorption

“…These data provide easily available Hg for plants which is the essential Hg from the agricultural point of view. Kucharski et al (2005) investigated the remediation of Hgcontaminated soil using thermal desorption with operating conditions of 100°C for 10 days and found that the most mobile and toxic Hg species were removed. In the present work, it is observed that another factor to consider besides time is the temperature increase since the concentration of these species changes with it.…”

In situ remediation technologies for mercury-contaminated soil

“…In addition to Bloom's method (Miller et al 2013), there are other procedures used to determine the fractions of Hg in soil and how these fractions changed as a result of a remediative process. For example, many studies separate soil-bound Hg into six fractions: water soluble (extraction with deionized water), exchangeable (extraction with 1 M CH 3 COONH 4 ), elemental mercury (by heating in an oven for 48 h at 373 K), fulvic and humic acids (extraction with 1 M KOH and acidification to pH 2), organic and sulfide (extraction with 0.1 M HNO 3 and H 2 O 2 ), and the residual (extraction with aqua regia) (Biester and Scholz 1997;Di Giulio and Ryan 1987;Kucharski et al 2005). A sequential extraction procedure proposed by the Community Bureau of Reference (BCR) (Ure et al 1993) was also adopted by researchers for Hg fractionation Subires-Munoz et al 2011).…”

“…3). Kucharski et al (2005) tested thermal desorption at laboratory and pilot scale using mercury-contaminated soils from a chlor-alkali production site in southern Poland, with an ultimate goal to apply this process in situ. In the laboratory experiment, soil temperature was raised from 40 to 60°C, while in the pilot-scale experiment, soil was heated to a maximum average temperature of 167°C.…”

“…The ground cover can also prevent moisture from infiltrating the treatment area. In addition to the health and safety concerns, pyrolysis of organic matter during heat treatment may cause explosions and damage the equipment (USEPA 2007a), and application of a high temperature may impact ecological health at the (Kucharski et al 2005). Nevertheless, ISTD provides a way to permanently recover mercury from the subsurface, albeit at a high cost (Table 5).…”