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Arsenic Encapsulation Using Portland Cement With Ferrous Sulfate/Lime And Terra-BondTM Technologies - Microcharacterization And Leaching Studies
RANDALL, P. M. Arsenic Encapsulation Using Portland Cement With Ferrous Sulfate/Lime And Terra-BondTM Technologies - Microcharacterization And Leaching Studies. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier Science Ltd, New York, NY, 420:300-312, (2012).
To study the molecular structure and arsenic release of Terra-BondTM and a modified Portland cement technology to treat arsenic-type materials.
This work reports the results of an investigation on the treatment and encapsulation of arsenic-containing materials by Portland cement with ferrous sulfate and lime (PFL) and Terra-BondTM, a commercially available patented technology. The arsenic materials treated were: chromated copper arsenate (CCA)-containing wood materials; scorodite-rich mine tailings from the La Trinidad Mine in California; and a soil/smelter dust mixture from the Anaconda Superfund site spiked with monosodium methyl arsenate (MSMA) to simulate an organoarsenic soil material. Results from XANES spectra for the PFL treatment of CCA-containing samples showed that arsenic has a predominant pentavalent form (As +5), and the PFL treatment process did not alter the arsenic oxidation state. There were, however, distinct differences observed for XANES spectra fo untreated and PFL treated scorodite-rich mine tailing which changed the arsenic coordination structure from a mixture of As (+3/+5) to exclusively As (+5). Both S/S techniques reduced the amount of arsenic released in the leaching tests. In most cases, the amount of arsenic released from wastes treated by the Terra-BondTM technique was lower than that released from wastes treated by the PFL technique. The pH of the solution significantly affected the leachability, with the amount of arsenic released increasing with pH. Sequential extraction results indicate that sodium hydroxide was favorable in releasing arsenic in the mine tailings. This is due to ligand displacement reactions of hydroxyl ions with arsenic species and high pH conditions that prevent the readsorption of arsenic. There was a greated reduction in arsenic released with treatment of the CCA wood treater waste materials and La Trinidad mine tailings over Montana soil. Cost analysis indicates that the PFL process is in the $200 - 400/ton range and Terra-BondTM process is in the $325 - 525/ton range. Refinement of technology recipes will be needed to ensure long-term containment of the arsenic.