Oxidation of ammonia by ferrate(VI)

The kinetics of ammonia oxidation by ferrate(VI) was determined as a function of pH (7.5-11.0) and temperature (10-35 degrees C). The rates decrease with increase in pH. The pH dependence is probably related to protonation of ferrate(VI) and ammonia. The theoretical curve through data gave the rate constants; k(7)(HFeO4- + NH4+) = 8.46 +/- 0.50 x 10(-1) M-1 s(-1); ks(FeO42- + NH4+) = 1.26 +/- 0.11 x 10(-1) M-1 s(-1); k(10)(FeO42- + NH3) = 1.19 +/- 0.10 x1 0(-1) M-1 s(-1). The activation parameters, Delta H-not equal and Delta S-not equal were found to be 67.3 +/- 3.5 kJ/mol and 33.1 +/- 0.2 J/mol.K, respectively. When ferrate(VI) was used in excess relative to ammonia in the oxidation reaction, 22 % of ammonia removal was achieved. The usefulness of ferrate(VI) to remove ammonia from wastewater is discussed.