Enhanced hydrodechlorination of 4-chlorophenol through carboxymethylcellulose-modified Pd/Fe nanosuspension...

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-CMC_one-step, synthesized by it, exhibited a higher 4-CP removal rate (97.9%) compared to the two-step method material Pd/Fe-CMC_two-step (82.4%). Electrochemical analyses revealed that the enhanced activity of Pd/Fe-CMC_one-step was attributed to its higher electron transfer efficiency and more available reactive species, active adsorbed hydrogen species (H_ads*). Detection of intermediate products demonstrated that, under the influence of Pd/Fe-CMC_one-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^-, SO₄^2-, HCO₃^-, and humic acid (HA) were also investigated. In conclusion, the results of this study suggest that Pd/Fe-CMC_one-step, synthesized through the one-step method, is a convenient and efficient nZVI-modifying material suitable for the HDC of chlorinated organic compounds.