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

Abstract

Solar thermal desorption at temperatures up to 500 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 s much as 76%. The experimental results show that volatilization of mercury is only significant when the temperature is above approximately 130 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 C, mercury elimination was significant (41.3–87%). However, the results from heating to 320 C or below 300 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.Spanish Ministry of Science and Technology (project REN2003-09247-C04-03 and ENE2006-13267-C05-01/ALT) and 2003–2004 Technical and Scientific Infrastructure Program (FEDER CIEM-E008