Electrochemical Oxidation for Denitrification of Ammonia: A Conceptual Approach for Remediation of Ammonia in Poultry Barns

Abstract

Ammonia in poultry barns produced by microbial action on the birds’ excreta can be removed by scrubbing into aqueous solution at pH ∼4. However, disposal of the resulting solution remains a problem. In this work, ammonia was oxidized electrochemically in the presence of unreactive electrolytes (NaClO4, Na2SO4), but the conditions were not compatible with treatment inside or outside a poultry barn (high pH, closed electrochemical reactor, and high ammonia concentration). Efficient denitrification is possible without pH adjustment of the scrubbed solution when chloride ion is also present in the scrubbing solution. This reaction is based on electrochemical hypochlorination, which is similar to breakpoint chlorination for the chemical elimination of ammonia. This work confirms a recent mechanistic proposal that efficient denitrification at pH ∼3 is the result of concomitant oxidation of water and acidification at the anode, but shows in addition that the mechanisms of both chemical and electrochemical hypochlorination are similar at acidic pH. These results allow us to propose that ammonia scrubbed into acidic brine can be oxidized to elemental nitrogen with high current efficiency without pH adjustment and without chemical additives, providing a “green” solution to the problem at hand