Zero-Valent Aluminum for Oxidative Degradation of Aqueous Organic Pollutants

Abstract

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 Al3+ and hydrogen peroxide (H2O2). The oxidation of 4-chlorophenol (4-CP), a model substrate, was initiated by the generation of hydroxyl radicals (HO center dot) via electron transfer from Al-0 to H2O2-Degradation was initiated after an induction period of about 2 h, during which the native oxide layer was dissoluted. The HO center dot- 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 All-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 Al3+ ions over a wider pH range. The degradation of phenol, nitrobenzene, and dichloroacetate was also successfully achieved with ZVAI. The present study proposes the ZVAl/O-2 process as a viable method of oxidative water treatment.