Method for capturing carbon dioxide and nitrogen oxides in flue gas and conversion thereof to carbon source and nitrogen source needed for algae growth

A method for treating a flue gas, comprising:

• step (A):
• desulfurizing a flue gas to obtain a desulfurized flue gas, wherein the flue gas comprises nitrogen oxides, sulfur oxides, and carbon dioxide, wherein the nitrogen oxides comprise nitric oxide;
• step (B):
• providing oxygen to react with the nitric oxide in the desulfurized flue gas for an oxidation reaction to obtain an oxidized flue gas, wherein the oxidized flue gas comprises nitrogen dioxide and carbon dioxide;
• step (C):
• rinsing the oxidized flue gas with water to dissolve nitrogen dioxide in the oxidized flue gas in water to obtain a rinsed flue gas and a nitric acid solution;
• step (D):
• contacting the rinsed flue gas with a basic solution to absorb the carbon dioxide in the rinsed flue gas by the basic solution to obtain a basic-washed flue gas and a weak basic solution, wherein the pH value of the basic solution is from 9.5 to 14, and the pH value of the weak basic solution is from 8 to 9;
• and
• step (E):
• adjusting the pH value of the nitric acid solution to 6.5 to 8 by adding sodium hydroxide to obtain a pH-adjusted sodium nitrate solution.