The reductive transformation of 4-cyanonitrobenzene (4-CNB) was examined in batch suspensions of synthetic goethite containing ascorbic acid or cysteine at pH 7. Both ascorbic acid and cysteine promote the reductive dissolution of goethite, which facilitates the reductive transformation of 4-CNB. Transformation rates are dependent upon ascorbic and cysteine concentrations (1.0-7.5 mM) and surface loading. Particle size comparisons were made with nano-sized, intermediate-sized, and micro-sized goethite rods. Goethite particles acquired from Bayer behaved similarly to micro-sized particles. Studies were also conducted with aluminum-amended goethite. The results of this study provide evidence that naturally occurring organic molecules can play an indirect role in the transformation of reducible organic compounds in iron-oxide containing environments. Generally, a neutral pH is less favorable for the reductive dissolution of ferric oxides and more favorable for Fe(II) adsorption, but neutral pH conditions can generate sufficient concentrations of Fe(II) to affect chemical transformation. Results of this effort may elucidate the fate of reducible organic compounds in aqueous systems.

Role of naturally occurring reductants in the dissolution of synthetic goethite: Effect of concentration and pH

247th National Meeting (2014)

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