U.S. Environmental Protection Agency, National Risk Management Research Laboratory, Land Remediation and Pollution Control Division, 26 W. Martin Luther King Drive, Cincinnati, OH 45268, USA.
Sci Total Environ. 2012 Mar 15;420:300-12. doi: 10.1016/j.scitotenv.2011.12.066. Epub 2012 Feb 13.
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-Bond™, a commercially available patented technology. The arsenic materials included: chromated copper arsenate (CCA)-treated 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. SEM/EDS and XRD spectra of PFL treated samples showed similarity across all three waste materials while Terra-Bond treated samples showed predominance of elemental sulfur. SEM/EDS of PFL treated samples showed that calcium was imbedded in the structure while micrographs of Terra-Bond treated samples showed the appearance of an epoxy material on the surface. The epoxy material appears to be responsible for encapsulating and reducing the leachability of arsenic. 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. But, distinct differences were observed for XANES spectra of 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. Most cases show lower amounts of arsenic released from wastes treated by the Terra-Bond™ technique when compared to 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.
本工作报道了利用硫酸亚铁和石灰（PFL）与 Terra-Bond™（一种商业上可获得的专利技术）对含砷材料进行处理和封装的研究结果。砷材料包括：铬酸铜砷酸盐（CCA）处理过的木材材料；加利福尼亚州拉特里尼塔矿的富含硫砷铁矿尾矿；以及来自安纳康达超级基金场地的土壤/冶炼厂粉尘混合物，其中添加了单甲基砷酸酯（MSMA）以模拟有机砷土壤材料。PFL 处理样品的 SEM/EDS 和 XRD 光谱在所有三种废物材料中均显示出相似性，而 Terra-Bond 处理样品则显示出元素硫的优势。PFL 处理样品的 SEM/EDS 表明钙嵌入在结构中，而 Terra-Bond 处理样品的显微照片显示表面出现了环氧树脂材料。环氧树脂材料似乎负责封装和降低砷的浸出率。PFL 处理含 CCA 样品的 XANES 光谱表明，砷主要以五价形式存在（As +5），且 PFL 处理过程未改变砷的氧化态。但是，对于未处理和 PFL 处理的富含硫砷铁矿尾矿的 XANES 光谱观察到明显差异，砷的配位结构从（+3/+5）混合态变为纯（+5）。两种 S/S 技术都减少了浸出试验中释放的砷量。在大多数情况下，与 PFL 技术相比，用 Terra-Bond™技术处理的废物释放的砷量更少。溶液的 pH 值对浸出率有显著影响，随着 pH 值的升高，释放的砷量增加。顺序提取结果表明，氢氧化钠有利于从尾矿中释放砷。这是由于羟基离子与砷物种的配体置换反应以及高 pH 值条件阻止了砷的再吸附。
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