One of the main influencing factors of eutrophication of rivers and lakes is ammonia nitrogen pollution. At present, my country’s annual output of synthetic urea and ammonia is more than 40 million tons. The production of various ammonia nitrogen products causes enterprises to discharge large amounts of ammonia nitrogen wastewater. At the same time, nature produces ammonia nitrogen wastewater during the process of garbage fermentation. The total amount exceeds hundreds of millions of tons every year, which has a great impact on the natural environment.
The mechanism of magnesium oxide treating ammonia nitrogen wastewater
Magnesium oxide is a metal oxide. When dissolved in water, it will form an insoluble precipitate, magnesium hydroxide. In ammonia nitrogen wastewater, NH4+ combines with OH- ions in Mg(OH)2 to generate NH3. Under stirring or aeration, ammonia nitrogen is discharged from the wastewater in the form of NH3, thereby achieving the purpose of removing ammonia nitrogen.
Secondly, magnesium oxide also plays an alkaline role in it.
MgO+H2O=Mg(OH)2
Mg(OH)2+NH4+NH3↑+H2O+Mg2+
Stirring or aeration causes NH3 to detach from the wastewater, and the equilibrium proceeds in the positive direction, and then magnesium oxide 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 high temperatures are more conducive to the volatilization of ammonia.
①The effect of adding magnesium oxide and using stirring to treat ammonia nitrogen wastewater is worse than using aeration treatment under the same conditions.
②The effect of magnesium oxide in treating ammonia nitrogen wastewater increases as the temperature increases.
③At normal temperature, the removal rate of ammonia nitrogen in ammonia nitrogen wastewater increases with the increase in the amount of magnesium oxide added, and also increases with the increase in aeration time. When the amount of magnesium oxide added is 2g/L and the aeration time is 2 hours, the ammonia nitrogen removal rate reaches 99.66%, and the ammonia nitrogen removal effect is obvious.
However, as the aeration time is further extended and the amount of magnesium oxide added is further increased, the ammonia nitrogen removal rate does not increase significantly. It is concluded that the best conditions for treating ammonia nitrogen wastewater with magnesium oxide are the amount of magnesium oxide used is 2g/L and the aeration time is 2h.
In short, the price of magnesium oxide is cheap, and the remaining magnesium oxide after treating ammonia nitrogen wastewater is rarely soluble in water and will be discharged in the form of precipitation. Therefore, magnesium oxide will not cause secondary pollution to wastewater and is a green water treatment agent.
