Broadening the pH range of molecular oxygen activation for zero-valent aluminum by ball-milling surface modification

In the zero-valent aluminum (Al0)/O2 system, due to the oxide film covering the Al0 surface and secondary passivation occurring during the reaction, the drawbacks of long induction period (∼2 h) and requiring strong acidic conditions (pH < 4) limit its wide application. It is possible to achieve efficient activation of molecular oxygen over a wide pH range for Al0 by ball milling (BM) surface modification. In this study, a novel wide-pH-applicable and zero-induction-period Al0-based composite was synthesized with one-pot BM method by directly mixing solid-phase microscale Al0, ethylenediaminetetraacetic acid ferric sodium salt (FeEDTA) and carbon nanotubes (CNTs). The excellent performances under different reaction conditions and the characterizations of Al0-based composite were analyzed. At initial pH of 2–10, the removal efficiency of phenol by Al0-based composite was more than 95% under atmospheric conditions without any induction period. Through BM process, the oxide layer of Al0 was destroyed by FeEDTA and further activating Al0 surface and increasing its reactivity. Meanwhile, CNTs were attached on the fresh Al0 surface to prevent secondary passivation and catalyze the reduction reaction between inert Al0 and O2. This study provides a green and convenient strategy for realizing the extensive application of Al0/O2 system.