Magnesium oxide is a metal oxide that dissolves in water and forms an insoluble precipitate of magnesium hydroxide. In ammonia nitrogen wastewater, NH4+ combines with OH- ions in Mg(OH)2 to form NH3. And in the case of stirring or aeration, ammonia nitrogen is discharged into the waste water in the form of NH3, thereby achieving the purpose of removing ammonia nitrogen.
Secondly, magnesium oxide also plays a role in alkalinity. MgO+H2O⇌Mg(OH)2 Mg(OH)2+ NH4+⇌NH3↑+H2O+Mg2+ stirring or aeration, make NH3 out of the wastewater and balance in the positive direction. Then MgO is dissolved to achieve the purpose of removing ammonia nitrogen.
In addition, temperature is also a factor affecting the reaction. As the temperature increases, the solubility of the gas decreases, so the higher temperature is more conducive to the volatilization of ammonia.
①The effect of adding magnesium oxide and agitating to treat ammonia-nitrogen wastewater is inferior to the effect of using aeration treatment under the same conditions.
②The effect of magnesium oxide on ammonia nitrogen wastewater is enhanced with increasing temperature.
③At normal temperature, the removal rate of ammonia nitrogen in ammonia-nitrogen wastewater increases with the amount of magnesium oxide added, and increases with the increase of aeration time. When the amount of magnesium oxide added is 2g/L, the aeration time is 2h, the ammonia nitrogen removal rate reaches 99.66%, and the ammonia nitrogen removal effect is obvious.
However, with the further extension of the aeration time and the further increase in the amount of magnesium oxide added, the ammonia nitrogen removal rate is not significantly improved. It is concluded that the best condition for the treatment of ammonia-nitrogen wastewater by magnesium oxide is that the amount of magnesium oxide is 2g/L and the aeration time is 2h.
In short, magnesium oxide is inexpensive, and the remaining magnesium oxide after treatment of ammonia-nitrogen wastewater is also rarely dissolved in water and is discharged as a precipitate. Therefore, magnesium oxide does not form secondary pollution to wastewater, it is a green water treatment agent.