Valorization of aluminum waste as a heterogeneous catalyst for activation of oxone for sulfate radical-based advanced oxidation process

Abstract

Abstract While zero valent aluminum (ZVAl) is considered as a promising catalyst for Oxone activation, relevant studies are very limited and ZVAl is typically obtained by chemical-reagent grade aluminum. However, as aluminum is the third richest element on earth, many aluminum wastes (AWs) are readily available for preparing ZVAl without energy-intensive mining and metalworking. Herein, we propose for the first time to valorize AWs to prepare ZVAl via HCl-pretreatment; the resulting HCl-pretreated AW (HPAW) is evaluated for Oxone activation by decolorizing Amaranth (AMR) dye as a model test. Oxone activation behaviors by HPAW are investigated by examining various effects on AMR decolorization, including dosages of HPAW and Oxone, temperature, initial pH, and co-existing compounds. Even though electrons from HPAW can induce the formation of OH , the resulting OH could not effectively decolorize AMR. However, the electrons from HPAW can “activate” Oxone to generate SO 4 - , which completely and rapidly decolorizes AMR. This effective AMR decolorization is attributed to SO 4 - and also to OH derived from the reaction of water with SO 4 - . The Oxone activation by HPAW is much favorable under neutral conditions and at elevated temperatures, whereas the presence of co-existing compounds (e.g., NaCl and anionic surfactant) inhibits Oxone activation and then AMR decolorization significantly. HPAW can be also reused for Oxone activation even without regeneration. These features demonstrate that AW can be valorized easily by HCl-pretreatment and becomes an efficient heterogeneous catalyst for Oxone activation.