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Modifications to EPA Method 3060A to Improve Extraction of Cr(VI) from Chromium Ore Processing Residue-Contaminated Soils
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2017-09-11 00:00:00 , DOI: 10.1021/acs.est.7b01719 Christopher T. Mills 1 , Carleton R. Bern 2 , Ruth E. Wolf 3 , Andrea L. Foster 4 , Jean M. Morrison 1 , William M. Benzel 5
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2017-09-11 00:00:00 , DOI: 10.1021/acs.est.7b01719 Christopher T. Mills 1 , Carleton R. Bern 2 , Ruth E. Wolf 3 , Andrea L. Foster 4 , Jean M. Morrison 1 , William M. Benzel 5
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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–1 and 48-h extraction time resulted in a maximum release of 1274 ± 7 mg kg–1 Cr(VI). This is greater than the NIST 2701 certified value of 551 ± 35 mg kg–1 but less than 3050 mg kg–1 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).
中文翻译：
修改EPA方法3060A以改善铬矿加工残渣污染土壤中六价铬的提取
已经表明，EPA方法3060A不能从铬矿石加工残渣（COPR）中充分萃取Cr（VI）。我们修改了EPA 3060A的各种参数，以了解碱性提取过程中COPR矿物的转化，并改善了NIST SRM 2701（一种受COPR污染的标准土壤）中Cr（VI）的提取。铝和硅是从NIST 2701中溶解的主要元素，它们在溶液中的浓度与Cr（VI）相关。萃取液从方法规定的硼硅酸盐玻璃容器中浸出了额外的Al和Si，这似乎抑制了Cr（VI）的释放。聚四氟乙烯容器的使用和NIST 2701的强烈研磨增加了Cr（VI）的提取量。这些改进结合增加的萃取液与样品的比值≥900mL g–1和48小时的萃取时间导致最大释放量为1274±7 mg kg –1 Cr（VI）。这大于NIST 2701的551±35 mg kg –1认证值，但小于3050 mg kg –1 Cr（VI）先前通过边缘结构光谱的X射线吸收估计的值。某些增加的Cr（VI）可能是由从褐闪石释放出的Cr（III）的氧化引起的，而在提取过程中，褐铁矿会快速转化。层状双氢氧化物在萃取过程中保持稳定，并且代表未萃取的Cr（VI）的潜在停留时间。
更新日期：2017-09-11
中文翻译：
修改EPA方法3060A以改善铬矿加工残渣污染土壤中六价铬的提取
已经表明，EPA方法3060A不能从铬矿石加工残渣（COPR）中充分萃取Cr（VI）。我们修改了EPA 3060A的各种参数，以了解碱性提取过程中COPR矿物的转化，并改善了NIST SRM 2701（一种受COPR污染的标准土壤）中Cr（VI）的提取。铝和硅是从NIST 2701中溶解的主要元素，它们在溶液中的浓度与Cr（VI）相关。萃取液从方法规定的硼硅酸盐玻璃容器中浸出了额外的Al和Si，这似乎抑制了Cr（VI）的释放。聚四氟乙烯容器的使用和NIST 2701的强烈研磨增加了Cr（VI）的提取量。这些改进结合增加的萃取液与样品的比值≥900mL g–1和48小时的萃取时间导致最大释放量为1274±7 mg kg –1 Cr（VI）。这大于NIST 2701的551±35 mg kg –1认证值，但小于3050 mg kg –1 Cr（VI）先前通过边缘结构光谱的X射线吸收估计的值。某些增加的Cr（VI）可能是由从褐闪石释放出的Cr（III）的氧化引起的，而在提取过程中，褐铁矿会快速转化。层状双氢氧化物在萃取过程中保持稳定，并且代表未萃取的Cr（VI）的潜在停留时间。
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