U.S. Geological Survey , Crustal Geophysics and Geochemistry Science Center, MS964D, Denver Federal Center, Denver, Colorado 80225, United States.
U.S. Geological Survey , Colorado Water Science Center, Denver Federal Center, Denver, Colorado 80225, United States.
Environ Sci Technol. 2017 Oct 3;51(19):11235-11243. doi: 10.1021/acs.est.7b01719. Epub 2017 Sep 11.
It has been shown that EPA Method 3060A does not adequately extract Cr(VI) from chromium ore processing residue (COPR). We modified various parameters of EPA 3060A toward understanding the transformation of COPR minerals in the alkaline extraction and improving extraction of Cr(VI) from NIST SRM 2701, a standard COPR-contaminated soil. Aluminum and Si were the major elements dissolved from NIST 2701, and their concentrations in solution were correlated with Cr(VI). The extraction fluid leached additional Al and Si from the method-prescribed borosilicate glass vessels which appeared to suppress the release of Cr(VI). Use of polytetrafluoroethylene vessels and intensive grinding of NIST 2701 increased the amount of Cr(VI) extracted. These modifications, combined with an increased extraction fluid to sample ratio of ≥900 mL g and 48-h extraction time resulted in a maximum release of 1274 ± 7 mg kg Cr(VI). This is greater than the NIST 2701 certified value of 551 ± 35 mg kg but less than 3050 mg kg Cr(VI) previously estimated by X-ray absorption near edge structure spectroscopy. Some of the increased Cr(VI) may have resulted from oxidation of Cr(III) released from brownmillerite which rapidly transformed during the extractions. Layered-double hydroxides remained stable during extractions and represent a potential residence for unextracted Cr(VI).
已证明 EPA 方法 3060A 不能充分提取铬矿石加工残渣（COPR）中的六价铬。我们对 EPA 3060A 的各种参数进行了修改，以了解碱性提取过程中 COPR 矿物的转化，并提高从 NIST SRM 2701（一种标准的 COPR 污染土壤）中提取六价铬的效率。NIST 2701 中溶解的主要元素是铝和硅，它们在溶液中的浓度与六价铬有关。提取液从方法规定的硼硅酸盐玻璃器皿中浸出了额外的铝和硅，这似乎抑制了六价铬的释放。使用聚四氟乙烯器皿和对 NIST 2701 进行强烈研磨增加了提取的六价铬量。这些改进措施，再加上将提取液与样品的比例增加到≥900 mL g 和 48 小时的提取时间，导致最大释放量为 1274 ± 7 mg kg Cr(VI)。这高于 NIST 2701 认证的 551 ± 35 mg kg，但低于之前通过 X 射线吸收近边结构光谱法估计的 3050 mg kg Cr(VI)。一些增加的六价铬可能是由于从布朗米勒石中释放的三价铬在提取过程中迅速氧化所致。层状双氢氧化物在提取过程中保持稳定，是未提取的六价铬的潜在归宿。
