Oxalate-assisted oxidative degradation of 4-chlorophenol in a bimetallic, zero-valent iron–aluminum/air/water system
2016
Fan, Jinhong | Wang, Hongwu | Ma, Luming
The reaction of zero-valent iron and aluminum with oxygen produced reactive oxidants that can oxidize 4-chlorophenol (4-CP). However, oxidant yield without metal surface cleaning to dissolve the native oxide layer or in the absence of ligands was too low for practical applications. The addition of oxalate (ox) to dissolved oxygen-saturated solution of Fe⁰–Al⁰ significantly increased oxidant yield because of the dissolution, pH buffer, and complexing characteristics of ox. Ox-enhanced reactive oxidant generation was affected by ox concentration and solution pH. The critical effect of ox dosing was confirmed with the reactive species of [Feᴵᴵ(ox)₀] and [Feᴵᴵ(ox)₂ ²⁻]. Systematic studies on the effect of the initial and in situ solution pH revealed that 4-CP oxidation was controlled by the continuous release of dissolved Fe²⁺ and Al³⁺, their fate, and the activation mechanisms of O₂ reduction. The degradation pathway of 4-CP in ox-enhanced Fe⁰–Al⁰/O₂ may follow the 4-chlorocatechol pathway. The robustness of the ox-enhanced Al⁰–Fe⁰–O₂ process was determined with one-time dosing of ox. Therefore, ox is an ideal additive to enhancing the Fe⁰–Al⁰/O₂ system for the oxidative degradation of aqueous organic pollutants.
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