Zero-Valent Aluminum for Oxidative Degradation of Aqueous Organic Pollutants

摘要

Oxidative degradation of aquatic organic contaminants using zero-valent aluminum (ZVAI) in the presence of dissolved oxygen (O_2) was investigated. The metal corrosion process in acidic conditions (pH <4) was accompanied by electron transfer from ZVAI to O_2, which led to the simultaneous generation of Al~(3+) and hydrogen peroxide (H_2O_2). The oxidation of 4-chlorophenol (4-CP), a model substrate, was initiated by the generation of hydroxyl radicals (HO~·) via electron transfer from Al~0 to H_2O_2. Degradation was initiated after an induction period of about 2 h, during which the native oxide layer was dissoluted. The HO~·-mediated oxidation reaction was completely quenched by adding methanol as a radical scavenger. Systematic studies on the effects of ZVAI loading, pH, and surface oxide content revealed that the oxide layer dissolution controlled the Al~0-mediated oxidation of 4-CP. The proposed process is similarly compared with the zero-valent iron (ZVI) system, but the ZVAl/O_2 system showed a higher oxidation capacity compared with ZVI/ O_2 because of the stability of aquo-complexed Al~(3+) ions over a wider pH range. The degradation of phenol, nitrobenzene, and dichloroacetate was also successfully achieved with ZVA;. The present study proposes the ZVAl/O_2 process as a viable method of oxidative water treatment.