College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, People's Republic of China.
J Hazard Mater. 2011 Dec 30;198:7-12. doi: 10.1016/j.jhazmat.2011.10.002. Epub 2011 Oct 6.
This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L(-1)) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11.5 to 2.5. The optimal CMC/Fe mass ratio for the dechlorination of 2,4-D was determined to be 5/1, and the removal of 2,4-D was evidently hindered by an overdose of CMC.
本文描述了羧甲基纤维素钠（CMC）稳定的 Pd/Fe 纳米粒子的合成及其在实验室控制条件下对 2,4-二氯苯氧乙酸（2,4-D）脱氯的应用。为此，进行了批处理实验，以了解 CMC 对 Pd/Fe 纳米粒子表面特性、2,4-D 的最佳去除率和其他表面相互作用机制的影响。我们的实验结果表明，添加 CMC 可显著提高 Pd/Fe 纳米粒子的颗粒稳定性和化学反应活性。透射电子显微镜（TEM）分析表明，CMC 稳定的 Pd/Fe 纳米粒子分散良好，与未稳定的 Pd/Fe 纳米粒子在几分钟内沉淀相比，纳米粒子在悬浮液中可保持数天。纳米粒子的等电点（IEP）从 pH 6.5 转移到 2.5，表明 CMC 稳定的 Pd/Fe 纳米粒子在更宽的 pH 范围内带负电荷。我们的批处理实验表明，CMC 稳定的 Pd/Fe 纳米粒子（0.6 g Fe L(-1)) 能够去除更高水平的 2,4-D，仅产生一个中间产物 2-氯苯氧乙酸（2-CPA）和最终的有机产物苯氧乙酸（PA），而非稳定的 Pd/Fe 纳米粒子或微米级 Pd/Fe 颗粒则不能。随着反应 pH 从 11.5 降低到 2.5，2,4-D 的去除率从 10%增加到近 100%。确定最佳 CMC/Fe 质量比为 5/1，可用于 2,4-D 的脱氯反应，并且过量的 CMC 会明显阻碍 2,4-D 的去除。
