Application of solar thermal desorption to remediation of mercury-contaminated soils

Solar thermal desorption at temperatures up to 500 degrees C is an innovative technology applied to the removal of mercury and arsenic from soil polluted by mining operations. As the soil is heated in a low and high-temperature solar system, the pollutant vapor pressure rises, producing mass transfer to the gas phase, which is then extracted by vacuum pumps and blower systems. In the UPC low-temperature experiments, removal of mercury from the polluted soil was as much as 76%. The experimental results show that volatilization of mercury is only significant when the temperature is above approximately 130 degrees C, which agrees with the predominant mercury solid phases detected. PSA middle-temperature experiments, showed that when soil and mine waste samples were heated to 400-500 degrees C, mercury elimination was significant (41.3-87%). However, the results from heating to 320 degrees C or below 300 degrees C, indicated little or negligible removal, possibly, because the fluid dynamics in the fluidized-bed module and the presence of cinnabar and pyrite rich-Hg as dominant mineral phases. These results show the potential for efficiently removing mercury and other pollutants from solid matrices (soil, waste, etc.) at low temperatures. (C) 2009 Elsevier Ltd. All rights reserved.