Figure 1.
![The effectiveness of chemical reduction of nitrate using nanoscale iron powder with different initial nitrate concentrations and the metal to solution ratio 4 g Fe0/dm3, [14]:](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/64706f7083f1392090d6979d/j_acee-2019-046_fig_001.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKKK2F7PAQ%2F20260221%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20260221T134255Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEOP%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJIMEYCIQCVxvfM7B9cX9AL5RKkwvWN%2FDV6Uc%2BhB%2FeCfMVBGaU2XgIhAKQ3BTZepptDSCUmn3aBb2c8U%2FO%2FbHRQ0FJN%2BddmKrSOKsUFCKz%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQAhoMOTYzMTM0Mjg5OTQwIgxwk3UdKxgwAthKCd4qmQVrfHz81grPYNSw40TgPMYbI2%2BirmQIwKFyH2srsZRCJ65VRjgvXbtOLWPOJkqYXOSkopOyArZyPY%2FfCAf%2BesQN7N2T%2Fy%2FdhN%2FKDMjbzzKK%2BOeY3qXAtO8yijKNXpZuhpVIZJH0%2BgdGMsHq2CW3zvXNwXI%2Fk7On7ddGWIxt%2BKDbUzw0UAkCSKqRT4kxjbdzLoMuJqgC7oX8YGKlmshj9fQxeaPuZmSl8hrOmDZQ%2FUMmiU4brBu9BVCMo8lcDsSDSP5qdBLzLI%2F2mFP2i0SQmOZk%2Bj3pQDJxX6PnlHU6AhnMhNVgB85KsQhnCLJ7hIEPE5Q29Wy3de1YSxSZ6iYtFpqCYIBrGyLiDYTBurlBxtAXMjfV4A3%2BDqhyD6bCEHDsVfZJpsws%2BpWNbfgLahtNJTV0Eimd7f8h0Ec3UXwrRDnTxbSavdvuk5BbJe2Y%2BOP1CCkNqt6tTKI5tl9pRtNZDtzhnNXIN2fdXeuTUYb02OpENJIsCm%2BJkiUKyM5ShEoopHFFQkQ6dr4DlFWcSVXhWO8YVUduFi%2FNJ6AiH5T1wD6W7MZFVe70YmBl1F%2Bbu2HIiX9AoA3xPfMuwVxj%2FoMxJUCDn2L9tkdOwolLX2ekXiDJ22QR6CEQ9fKsUTLTeVkejgfk4tCtJ1tCvpRJGKrr%2BuiN2i8OeOVCU5CdSefyBeTGAl1bbHdliuXgpYs8R0B6ZDRJozX7YEsgoW95KEy440h%2BQqSYE9kJ4YatUMQbio%2FWuV%2FClDZv2nXWk9jKebaoKYeLVIz6AkscByg4w9rUG5%2F2RP84NwLlrz2A33TQ2x34JSHb1v4wRueA2UwZh6Z0BuZBp4VKFN7xh%2FghMf0kUl90qqhZ8WsjHVBD9j2xpjjM4d%2B16SO%2FSSJFITCanObMBjqwAf%2Fh%2FpzJ0Jsd00NzE0YIPk%2Fe21QBlm4oiTxML19oJvLKHdodVr50VUs1yNzFEmnqWD3UEqj8a5hoaF%2Fb3U%2FEzCx%2Buo4OSFOEguZuslu8xGFye4NJVyPcVf6I75KtrVdi5VpZWL%2FPalMEZN8u1yW0OiByWb1vyjBUUSO%2BSh34gVQFOENSOiVKkEP%2B7mESXZOeN7mR3sZQzjxAhC5WBIKPLKTfR4RCTVUsn9YBwh253YPb&X-Amz-Signature=b2d4f38af95525bdfc8a55c79449b07d6b09da6ceb9089e888cffff3ca3b45fc&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 2.
![Effects of pH on nitrate removal with iron powder (160–200 mesh). Test conditions: 20 g Fe0/dm3 and 50 mg/dm3 NO3-N solutions, [5]](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/64706f7083f1392090d6979d/j_acee-2019-046_fig_002.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKKK2F7PAQ%2F20260221%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20260221T134255Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEOP%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJIMEYCIQCVxvfM7B9cX9AL5RKkwvWN%2FDV6Uc%2BhB%2FeCfMVBGaU2XgIhAKQ3BTZepptDSCUmn3aBb2c8U%2FO%2FbHRQ0FJN%2BddmKrSOKsUFCKz%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQAhoMOTYzMTM0Mjg5OTQwIgxwk3UdKxgwAthKCd4qmQVrfHz81grPYNSw40TgPMYbI2%2BirmQIwKFyH2srsZRCJ65VRjgvXbtOLWPOJkqYXOSkopOyArZyPY%2FfCAf%2BesQN7N2T%2Fy%2FdhN%2FKDMjbzzKK%2BOeY3qXAtO8yijKNXpZuhpVIZJH0%2BgdGMsHq2CW3zvXNwXI%2Fk7On7ddGWIxt%2BKDbUzw0UAkCSKqRT4kxjbdzLoMuJqgC7oX8YGKlmshj9fQxeaPuZmSl8hrOmDZQ%2FUMmiU4brBu9BVCMo8lcDsSDSP5qdBLzLI%2F2mFP2i0SQmOZk%2Bj3pQDJxX6PnlHU6AhnMhNVgB85KsQhnCLJ7hIEPE5Q29Wy3de1YSxSZ6iYtFpqCYIBrGyLiDYTBurlBxtAXMjfV4A3%2BDqhyD6bCEHDsVfZJpsws%2BpWNbfgLahtNJTV0Eimd7f8h0Ec3UXwrRDnTxbSavdvuk5BbJe2Y%2BOP1CCkNqt6tTKI5tl9pRtNZDtzhnNXIN2fdXeuTUYb02OpENJIsCm%2BJkiUKyM5ShEoopHFFQkQ6dr4DlFWcSVXhWO8YVUduFi%2FNJ6AiH5T1wD6W7MZFVe70YmBl1F%2Bbu2HIiX9AoA3xPfMuwVxj%2FoMxJUCDn2L9tkdOwolLX2ekXiDJ22QR6CEQ9fKsUTLTeVkejgfk4tCtJ1tCvpRJGKrr%2BuiN2i8OeOVCU5CdSefyBeTGAl1bbHdliuXgpYs8R0B6ZDRJozX7YEsgoW95KEy440h%2BQqSYE9kJ4YatUMQbio%2FWuV%2FClDZv2nXWk9jKebaoKYeLVIz6AkscByg4w9rUG5%2F2RP84NwLlrz2A33TQ2x34JSHb1v4wRueA2UwZh6Z0BuZBp4VKFN7xh%2FghMf0kUl90qqhZ8WsjHVBD9j2xpjjM4d%2B16SO%2FSSJFITCanObMBjqwAf%2Fh%2FpzJ0Jsd00NzE0YIPk%2Fe21QBlm4oiTxML19oJvLKHdodVr50VUs1yNzFEmnqWD3UEqj8a5hoaF%2Fb3U%2FEzCx%2Buo4OSFOEguZuslu8xGFye4NJVyPcVf6I75KtrVdi5VpZWL%2FPalMEZN8u1yW0OiByWb1vyjBUUSO%2BSh34gVQFOENSOiVKkEP%2B7mESXZOeN7mR3sZQzjxAhC5WBIKPLKTfR4RCTVUsn9YBwh253YPb&X-Amz-Signature=a73ca8a56901669145cd8927b96c1805cb835cc86776d39c85a4f9708b18a53f&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Figure 3.
![Concentration of nitrate with iron powder (160–200 mesh). Metal to solution ratio 4 g Fe0/dm3. Initial pH 2, [5]](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/64706f7083f1392090d6979d/j_acee-2019-046_fig_003.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKKK2F7PAQ%2F20260221%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20260221T134255Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEOP%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJIMEYCIQCVxvfM7B9cX9AL5RKkwvWN%2FDV6Uc%2BhB%2FeCfMVBGaU2XgIhAKQ3BTZepptDSCUmn3aBb2c8U%2FO%2FbHRQ0FJN%2BddmKrSOKsUFCKz%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQAhoMOTYzMTM0Mjg5OTQwIgxwk3UdKxgwAthKCd4qmQVrfHz81grPYNSw40TgPMYbI2%2BirmQIwKFyH2srsZRCJ65VRjgvXbtOLWPOJkqYXOSkopOyArZyPY%2FfCAf%2BesQN7N2T%2Fy%2FdhN%2FKDMjbzzKK%2BOeY3qXAtO8yijKNXpZuhpVIZJH0%2BgdGMsHq2CW3zvXNwXI%2Fk7On7ddGWIxt%2BKDbUzw0UAkCSKqRT4kxjbdzLoMuJqgC7oX8YGKlmshj9fQxeaPuZmSl8hrOmDZQ%2FUMmiU4brBu9BVCMo8lcDsSDSP5qdBLzLI%2F2mFP2i0SQmOZk%2Bj3pQDJxX6PnlHU6AhnMhNVgB85KsQhnCLJ7hIEPE5Q29Wy3de1YSxSZ6iYtFpqCYIBrGyLiDYTBurlBxtAXMjfV4A3%2BDqhyD6bCEHDsVfZJpsws%2BpWNbfgLahtNJTV0Eimd7f8h0Ec3UXwrRDnTxbSavdvuk5BbJe2Y%2BOP1CCkNqt6tTKI5tl9pRtNZDtzhnNXIN2fdXeuTUYb02OpENJIsCm%2BJkiUKyM5ShEoopHFFQkQ6dr4DlFWcSVXhWO8YVUduFi%2FNJ6AiH5T1wD6W7MZFVe70YmBl1F%2Bbu2HIiX9AoA3xPfMuwVxj%2FoMxJUCDn2L9tkdOwolLX2ekXiDJ22QR6CEQ9fKsUTLTeVkejgfk4tCtJ1tCvpRJGKrr%2BuiN2i8OeOVCU5CdSefyBeTGAl1bbHdliuXgpYs8R0B6ZDRJozX7YEsgoW95KEy440h%2BQqSYE9kJ4YatUMQbio%2FWuV%2FClDZv2nXWk9jKebaoKYeLVIz6AkscByg4w9rUG5%2F2RP84NwLlrz2A33TQ2x34JSHb1v4wRueA2UwZh6Z0BuZBp4VKFN7xh%2FghMf0kUl90qqhZ8WsjHVBD9j2xpjjM4d%2B16SO%2FSSJFITCanObMBjqwAf%2Fh%2FpzJ0Jsd00NzE0YIPk%2Fe21QBlm4oiTxML19oJvLKHdodVr50VUs1yNzFEmnqWD3UEqj8a5hoaF%2Fb3U%2FEzCx%2Buo4OSFOEguZuslu8xGFye4NJVyPcVf6I75KtrVdi5VpZWL%2FPalMEZN8u1yW0OiByWb1vyjBUUSO%2BSh34gVQFOENSOiVKkEP%2B7mESXZOeN7mR3sZQzjxAhC5WBIKPLKTfR4RCTVUsn9YBwh253YPb&X-Amz-Signature=3fdf7be842b402e27b8c5451e72ba8110378344b2d692bdb4489d63b6a8a621e&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Reducing agents for nitrate chemical reduction, [5]
| Reducing agent | E°, V | pH | Nitrogen conversion products | Other by-products | Process indicators |
|---|---|---|---|---|---|
| Al (metal) | -2.30 | Alkaline | NH2, NO2- , N2 | Al.(OH)3 | - |
| Fe (metal) | -0.037 | Acidic | NO2- | Fe3+ | - |
| -0.771 | Alkaline | N2 | Fe2O3, OH- | - | |
| Zn (metal) | -1.245 | Alkaline | NH3, NO2-, N2 | Zn(OH)2 | Catalysator |
| NH4+ | +0.27 | Acidic | N2O, N2 | - | High pressure and temperature, Cl- ions |
| HCO2H | -0.199 | Acidic | N2O, N2, NH3 | CO2 | Rh/C |
| Acidic | N2 | CO2, H2 | High pressure and temperature | ||
| CH3OH | +0.017 | Acidic | NH4+ | HCO3- | High pressure and temperature |
| NH3OH+ | -0.05 | Acidic | N2O | - | - |
| NH2OH | -1.05 | Alkaline | N2O | OH- | Cu2+ |
| Fe2+ | +0.771 | Acidic | NO, N2O, N2 | Fe3+ | - |
| -0.56 | Alkaline | NH3 | Fe(OH)3, OH- | Cu2+, Ag+ |
Effectiveness of electrochemical reduction in the presence of NaCl solution, [12]
| no. | Type of anode | NaCl concentration in solution [g/dm3] | Initial nitrate-N concentration [g/dm3] | Final nitrate-N concentration [mg/dm3] | Reaction by-products | Effectiveness |
| 1 | Ti/Pt | 0.75 | 100 | 24.6 | ammonia | 75.4% |
| 2 | 1.00 | 100 | 23.8 | - | 76.2% | |
| 3 | Ti/IrO2 | 0.50 | 100 | 17.3 | ammonia | 82.7% |
| 4 | 0.75 | 100 | 22.6 | - | 77.4% |