A method of removing nitrates from water by utilization of a zero-valent iron/oxidizing agent/zeolite synergetic system

Abstract

A method of removing nitrates from water by utilization of a zero-valent iron / oxidizing agent / zeolite synergetic system is provided. The zero-valent iron is common iron powder. The oxidizing agent is a common oxidizing agent used in water treatment. The zeolite is natural zeolite or artificial zeolite. The method is characterized in that: the oxidizing agent in the system oxidizes and strips a passivation layer formed on the surface of the zero-valent iron to allow electrons in the zero-valent iron to be transferred continuously to the outside, so that the zero-valent iron maintains high reduction activity to reduce the nitrates into ammonia nitrogen. Then efficient selective absorption of the zeolite to the ammonia nitrogen is utilized to remove the ammonia nitrogen in the water body. The method is environmental friendly, simple, feasible, low in cost, and capable of being efficiently used for treatment of waste water containing nitrates of industrial enterprises and nitrate restoration and removal for underground water.

Description

technical field [0001] The invention belongs to the technical field of water treatment, in particular to a method for removing nitrate in water by utilizing a zero-valent iron / oxidant / zeolite synergistic system. Background technique [0002] With the rapid development of economy, the pollution of my country's water environment is becoming more and more serious. Among them, nitrate nitrogen pollution in groundwater has become a very important environmental problem, directly affecting people's production and life (Chen Jianyao et al., 2006). Nitrate in groundwater will not only damage the water quality (Kang Haiyan, 2007), but after nitrate enters the human body, it will be converted into nitrite through the action of nitrate reductase, which is extremely harmful and will cause infantile methemoglobinemia (Kostraba et al , 1992) and have carcinogenic, teratogenic and mutagenic effects on humans (Jennifer et al, 1998; Grahan et al, 1999; Janos, 2001). Therefore, how to econom...

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Problems solved by technology

Choea et al. (2004) obtained a nitrate removal rate of 81% under the condition of maintaining the pH of the water body at 3.0, but such a low pH value has made the water body unusable. At the same time, in order to maintain the low pH value of the water body, the reaction process It needs to be adjusted with strong acid or weak acid buffer, which in turn leads to the pollution of other anions in the water body, and the acidity adjustment process will significantly increase the treatment cost

The passivation phenomenon of zero-valent iron is the biggest shortcoming that restricts zero-valent iron technology. During the reaction process of zero-valent iron and nitrate, a passivation layer will gradually be formed on the surface, which will greatly reduce its reaction rate (Huang et al, 2005; Westerhoff et al, 2003), the passivation phenomenon seriously restricts the efficiency of zero-valent iron to reduce and convert nitrate, and to solve the passivation phenomenon requires additional physical and chemical technologies such as maintaining low pH of the water body and adding ultrasonic waves

In addition, the reduction and removal of nitrate products by zero-valent iron technology is not complete. Although some nitrates will eventually be converted into nitrogen during the reaction process, more than 80% of the final product is still ammonia (Kielemoes et al, 2000), Does not actually remove nitrogen from water bodies, still presents environmental risks

Although the nano-zero-valent iron technology that has emerged in recent years has a higher reaction rate than ordinary zero-valent iron, the preparation cost of nano-scale zero-valent iron is still high, and the passivation problem faced in the application of ordinary iron powder, Nano zero valent iron is still unavoidable

The reduction of nitrate by zero-valent iron has the advantages of rapidity, simplicity, and low cost, and has the potential to be popularized. However, its use is severely restricted by passivation and the need to adjust acidity.

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