Department of Agricultural Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 106, Taiwan.
Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong.
Chemosphere. 2020 Jul;250:126155. doi: 10.1016/j.chemosphere.2020.126155. Epub 2020 Feb 12.
Aggregation of nanoparticles (NPs) can hinder the degradative reactivity of particles towards organic pollutants as it reduces available surface area for reaction. This limitation may be circumvented by applying dispersant to improve colloidal stability of nanoparticle suspension. This study examined the removal of hexabromocyclododecane (HBCD), a recently listed persistent organic pollutant, by carboxymethylcellulose (CMC) stabilized nanoscale zerovalent iron (CMC-NZVI) and bimetallic Ni/Fe nanoparticles (CMC-Ni/Fe) under the influence of suspension chemistry. The mass-normalized removal rate constants of HBCD by CMC-Ni/Fe NPs increased with lower particle aggregation. However, the coating could introduce diffusion resistance as HBCD diffused through the CMC layer to the Fe surface. The activation energy was estimated to be 26.8 kJ mol, indicating the overall reaction process was neither surface-limited nor diffusion-controlled. The reactivity of CMC-Ni/Fe NPs toward HBCD was not affected by aqueous initial pH substantially. Common monoanions (Cl, NO, and HCO) generally enhanced HBCD adsorption but diminished its debromination. The removal rate did not differ significantly among the studied monoanions over a concentration of 2.5-10 mM except HCO. Overall, CMC coating can stabilize Ni/Fe NPs, increase their adsorption of HBCD, provide buffer pH capacity, and overcome common inhibition effects of anions in water. These findings suggested the high potential of using CMC-Ni/Fe NPs for in-situ remediation.
纳米颗粒（NPs）的聚集会阻碍颗粒对有机污染物的降解反应性，因为它减少了反应的可用表面积。通过应用分散剂来提高纳米颗粒悬浮液的胶体稳定性，可以克服这种限制。本研究考察了羧甲基纤维素（CMC）稳定的纳米零价铁（CMC-NZVI）和双金属 Ni/Fe 纳米颗粒（CMC-Ni/Fe）在悬浮液化学性质的影响下对六溴环十二烷（HBCD）的去除效果，HBCD 是一种最近被列入的持久性有机污染物。CMC-Ni/Fe NPs 对 HBCD 的质量归一化去除速率常数随着颗粒聚集度的降低而增加。然而，涂层可能会引入扩散阻力，因为 HBCD 通过 CMC 层扩散到 Fe 表面。活化能估计为 26.8 kJ/mol，表明整个反应过程既不是表面限制的，也不是扩散控制的。CMC-Ni/Fe NPs 对 HBCD 的反应活性受水初始 pH 值的影响不大。常见的单价阴离子（Cl、NO 和 HCO）通常会增强 HBCD 的吸附，但会降低其脱溴。在 2.5-10 mM 浓度范围内，除了 HCO 之外，研究的单价阴离子对 HBCD 的去除速率没有显著差异。总的来说，CMC 涂层可以稳定 Ni/Fe NPs，增加它们对 HBCD 的吸附，提供缓冲 pH 能力，并克服水中常见阴离子的抑制作用。这些发现表明 CMC-Ni/Fe NPs 在原位修复方面具有很高的潜力。
