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Highly efficient remediation of groundwater co-contaminated with Cr(VI) and nitrate by using nano-Fe/Pd bimetal-loaded zeolite: Process product and interaction mechanism.
Environmental Pollution ( IF 7.6 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.envpol.2020.114479
Yinhai He 1 , Hai Lin 1 , Mingke Luo 2 , Junfei Liu 2 , Yingbo Dong 1 , Bing Li 1
Affiliation  

Hexavalent chromium and nitrate co-contaminated groundwater remediation are attracting extensive attention worldwide. However, the transformation pathways of chromium and nitrate and the interplay mechanism between them remain unclear. In this work, zeolite-supported nanoscale zero-valent iron/palladium (Z-Fe/Pd) was synthesized and used for the first time to simultaneously remediate Cr(VI) and nitrate. Transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses confirmed that nanoscale zero-valent iron/palladium was successfully loaded onto zeolite and it exhibited good dispersibility and oxidation resistance. Results of batch experiments showed that the Cr(VI) and nitrate removal efficiencies decreased from 95.5% to 91.5% to 45% and 73%, respectively, with the initial solution pH increasing from 3.0 to 8.0. The removal rates and efficiencies of Cr(VI) and nitrate under anoxic conditions were higher than those under open atmosphere because the dissolved oxygen diminished the electron selectivity toward the target pollutants. Moreover, the presence of Cr(VI) inhibited nitrate reduction by forming Fe(III)-Cr(III) hydroxide to impede electron transfer. Cr(VI) removal was promoted by nitrate, within limits, by balancing the consumption and generation rate of Fe3O4, which enhanced electron migration from the Fe(0) core to the external surface. The removal capacities of Cr(VI) and nitrate reached 121 and 95.5 mg g-1, respectively, which were superior to the removal capacities of similar materials. Results of product identification, XRD, and XPS analyses of spent Z-Fe/Pd indicated that the reduction of Cr(VI) was accompanied by adsorption and co-precipitation, whereas the reduction of nitrate was catalyzed by the synergism of Fe(0) and Pd(0). An alternative to the simultaneous remediation of Cr(VI) and nitrate from groundwater under anoxic conditions is provided.

中文翻译:

纳米Fe / Pd双金属负载沸石对Cr(VI)和硝酸盐共污染的地下水的高效修复:过程产物和相互作用机理。

六价铬和硝酸盐共污染的地下水修复在全世界引起广泛关注。然而,铬和硝酸盐的转化途径以及它们之间的相互作用机理仍不清楚。在这项工作中,合成了沸石负载的纳米级零价铁/钯(Z-Fe / Pd),并首次用于同时修复Cr(VI)和硝酸盐。透射电子显微镜,X射线衍射和X射线光电子能谱分析证实,纳米级零价铁/钯已成功加载到沸石上,并表现出良好的分散性和抗氧化性。批处理实验的结果表明,Cr(VI)和硝酸盐的去除效率分别从95.5%降低到91.5%,45%和73%,初始溶液的pH从3.0增加到8.0。在缺氧条件下,Cr(VI)和硝酸盐的去除率和效率高于在露天环境下,因为溶解的氧降低了电子对目标污染物的选择性。此外,Cr(VI)的存在通过形成Fe(III)-Cr(III)氢氧化物来阻碍电子转移,从而抑制了硝酸盐的还原。硝酸盐在一定范围内通过平衡Fe3O4的消耗和生成速率促进了Cr(VI)的去除,从而增强了电子从Fe(0)芯到外表面的迁移。Cr(VI)和硝酸盐的去除能力分别达到121和95.5 mg g-1,优于同类材料的去除能力。产品鉴定结果,XRD,废Z-Fe / Pd的XPS和XPS分析表明,Cr(VI)的还原伴随着吸附和共沉淀,而硝酸盐的还原则由Fe(0)和Pd(0)的协同作用催化。提供了一种在缺氧条件下同时修复地下水中的Cr(VI)和硝酸盐的替代方法。
更新日期:2020-04-03
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