Abstract:
Palladized iron (Pd/Fe) represents one of the most common modification strategies for nanoscale zero-valent iron (nZVI). Most studies prepared Pd/Fe by reducing iron salts and depositing Pd species on the surface of pre-synthesized nZVI, which can be called the two-step method. In this study, we proposed a one-step method to obtain Pd/Fe by the concurrent formation of Fe0 and Pd0 and investigated the effects of these two methods on 4-chlorophenol (4-CP) removal, with carboxymethylcellulose (CMC) coated as a surface modifier. Results indicated that the one-step method, not only streamlined the synthesis process, but also Pd/Fe-CMCone-step, synthesized by it, exhibited a higher 4-CP removal rate (97.9%) compared to the two-step method material Pd/Fe-CMCtwo-step (82.4%). Electrochemical analyses revealed that the enhanced activity of Pd/Fe-CMCone-step was attributed to its higher electron transfer efficiency and more available reactive species, active adsorbed hydrogen species (Hads*). Detection of intermediate products demonstrated that, under the influence of Pd/Fe-CMCone-step, the main route of 4-CP was through hydrodechlorination (HDC) to form phenol and H* was the main active specie, supported by EPR tests, quenching experiments and product analysis. Additionally, the effects of initial 4-CP concentration, initial pH, O2 concentration, anions such as Cl-, SO42-, HCO3-, and humic acid (HA) were also investigated. In conclusion, the results of this study suggest that Pd/Fe-CMCone-step, synthesized through the one-step method, is a convenient and efficient nZVI-modifying material suitable for the HDC of chlorinated organic compounds.
摘要:
钯铁(Pd/Fe)代表了纳米级零价铁(nZVI)最常见的改性策略之一。大多数研究通过还原铁盐并在预先合成的nZVI表面沉积Pd物种来制备Pd/Fe,这可以称为两步法。在这项研究中,我们提出了一种通过同时形成Fe0和Pd0来获得Pd/Fe的一步法,并研究了这两种方法对4-氯苯酚(4-CP)去除的影响,用羧甲基纤维素(CMC)作为表面改性剂。结果表明,一步法,不仅简化了合成过程,还有Pd/Fe-CMCone步骤,由它合成,与两步法材料Pd/Fe-CMC两步法(82.4%)相比,表现出更高的4-CP去除率(97.9%)。电化学分析表明,Pd/Fe-CMCone-step的活性增强归因于其更高的电子转移效率和更多的可用反应性物种,活性吸附氢物种(Hads*)。对中间产品的检测表明,在Pd/Fe-CMCone-step的影响下,4-CP的主要途径是通过加氢脱氯(HDC)形成苯酚,H*是主要的活性物质,由EPR测试支持,淬火实验和产品分析。此外,初始4-CP浓度的影响,初始pH值,O2浓度,阴离子如Cl-,SO42-,HCO3-,和腐殖酸(HA)也进行了研究。总之,这项研究的结果表明,Pd/Fe-CMCone-step,通过一步法合成,是一种方便有效的nZVI改性材料,适用于氯化有机化合物的HDC。