Reduction of nitrobenzene in aqueous and soil phases using carboxymethyl cellulose stabilized zero-valent iron nanoparticles
Reduction of nitrobenzene in aqueous and soil phases using carboxymethyl cellulose stabilized zero-valent iron nanoparticles
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DOI：
10.1016/j.cej.2017.09.066
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发表时间：
2018-01-15
影响因子：
15.1
通讯作者：
Zhao, Dongye
中科院分区：
文献类型：
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作者：
Cai, Zhengqing;Fu, Jie;Zhao, Dongye
零价铁（ZVI）在水相中还原降解硝基苯（NB）等多种有机污染物方面已得到广泛研究。然而，很少有人知道的有效性降解土壤吸附NB，稳定的ZVI纳米粒子往往需要促进交付的反应性材料到受污染的土壤。在这项研究中，稳定ZVI纳米粒子的制备使用食品级和低成本的多糖，羧甲基纤维素（CMC），作为稳定剂;和纳米粒子进行了测试，NB在水和土壤相的还原降解。与未稳定的ZVI相比，CMC稳定的ZVI纳米颗粒基于表观伪一级反应速率常数（对于稳定的ZVI为0.643 min（-1））降解NB快3.7倍。近90%的电子捐赠ZVI有效地用于NB还原反应的化学计量。溶解性有机物（TOC）在10-50 mg/L时对NB转化为亚硝基苯的影响不大，但使苯胺生成率降低30-58%，较高的pH值（> 8）有利于NB的还原。基于还原中间体和计算化学分析，确定了反应途径，表明CMC稳定的ZVI纳米颗粒迅速将NB转化为亚硝基苯，但随后的中间体（亚硝基苯）的转化。苯羟胺苯胺）相对较慢。在模拟土壤上，CMC稳定的ZVI纳米粒子在ZVI投加量为0.6 g/L时，可完全还原吸附在土壤上的NB（0.01 mmol/g），且反应受有效电子的限制，而非脱附。研究结果表明，CMC稳定的ZVI纳米粒子具有促进NB污染土壤和地下水原位修复的潜力。
Zero valent iron (ZVI) has been extensively studied for reductive degradation of a host of organic pollutants including nitrobenzene (NB) in the water phase. However, little is known about the effectiveness for degrading soil-adsorbed NB, for which stabilized ZVI nanoparticles are often required to facilitate delivery of the reactive materials into contaminated soil. In this study, stabilized ZVI nanoparticles were prepared using a food-grade and low-cost polysugar, carboxymethyl cellulose (CMC), as a stabilizer; and the nanoparticles were tested for reductive degradation of NB in both water and soil phases. Compared to non-stabilized ZVI, CMC-stabilized ZVI nanoparticles degraded NB 3.7 times faster based on the apparent pseudo-first order reaction rate constant (0.643 min(-1) for stabilized ZVI). Nearly 90% of electrons donated by ZVI were effectively used for NB reduction according to the reaction stoichiometry. Dissolved organic matter at 10-50 mg/L as TOC had little effect on NB conversion into nitrosobenzene, but decreased aniline formation rate by 30-58%; and higher pH (> 8) favored the NB reduction. Based on the reduction intermediates and computational chemistry analysis, the reaction pathway was determined, showing that CMC-stabilized ZVI nanoparticles rapidly converted NB to nitrosobenzene, but the subsequent conversion of the intermediates (nitrosobenzene. phenylhydroxylamine. aniline) was relatively slower. When tested for reductive degradation of NB pre-sorbed on a model soil, CMC-stabilized ZVI nanoparticles could completely reduce the soil-sorbed NB (0.01 mmol/g) at a ZVI dosage of 0.6 g/L, and the reaction was limited by available electrons rather than desorption. The findings indicate that CMC-stabilized ZVI nanoparticles hold the potential to facilitate in-situ remediation of NB-contaminated soil and groundwater.