High-energy ball milling enhancing the reactivity of microscale zero-valent aluminum toward the activation of persulfate and the degradation of trichloroethylene

Abstract

Microscale zero-valent aluminum (mZVAl), an excellent electron donor, presents great potential in the field of water treatment. However, surface inherent oxide film impedes its development and application. High-energy ball milling is a promising approach to enhance the reactivity of mZVAl. In this study, taking nontoxic and biodegradable stearic acid (SA) as the process control agent (PCA), ball milled mZVAl (termed as mZVAlbm) was prepared and employed to activate persulfate (PS) for the degradation of trichloroethylene (TCE). Firstly, the role of ball milling on the surface morphology, structure and reactivity of mZVAl was revealed by SEM, BET, XRD, XPS characterizations and H2 evolution experiments. The results demonstrated that high-energy ball milling, as a severe plastic deformation method, can partially break the native oxide film on mZVAl surface and expose fresh surfaces, thereby appreciably increasing its reactivity. Secondly, the underlying mechanisms of mZVAlbm excelling pristine mZVAl in activating PS were evaluated through TCE degradation process. In mZVAlbm/PS system, complete degradation and dechlorination of TCE were achieved and corresponding rate (kobs,TCE) increased by 96 times, while traces of TCE were removed in pristine mZVAl/PS system due to the hindrance of surface oxide film. Additionally, sulfate radical (SO4−) and hydroxyl radical (OH) were identified as the predominant active species. Finally, mZVAlbm surface corrosion mechanism in the presence of PS was also deeply clarified. After reaction, the corrosion products, namely Al-(hydr)oxide, precipitated on mZVAlbm surface, decreasing its reactivity, but ball milling again can easily regenerate mZVAlbm. In a word, high-energy ball milling as a pretreatment method can remarkably enhance the reactivity of mZVAl toward PS activation, achieving the rapid and efficient removal of contaminants from water.