https://doi.org/10.1016/j.cej.2013.08.116
In the above paper, the effect of the presence of O2 on the inhibiting ammonia escape was investigated and the results are shown in Fig. 9. It is known that the addition of metal ions reduced the escape of ammonia. In this case, the presence of O2 promoted the inhibition of Co(II) on ammonia escape. For example, the concentration of ammonia escape was reduced from 8100 to 7000 μL/L when O2 was added. The authors suggested that [Co(NH3)6]3+ had a very stable complex constant of 1.58 × 1035, and the complexation ability of Co3+ with free ammonia was very stronger than Co2+ , thus a stronger inhibition effect on ammonia escape was achieved in the presence of oxygen. The authors also studied the mechanism of ammonia escape inhibition in section 4.4.1 using UV-Vis.