Heavy metal wastewater (such as cadmium, nickel, mercury, zinc, etc.) is one of the industrial wastewater that causes serious environmental pollution and poses a significant threat to human health. Its water quality and quantity are related to production processes. The primary method for controlling heavy metal pollution is to reform production processes and avoid or reduce the use of highly toxic heavy metals; Secondly, it is necessary to adopt reasonable process flow, scientific management and operation, reduce heavy metal usage and loss with wastewater flow, and minimize the amount of discharged wastewater as much as possible. After long-term research, it has been found that heavy metal wastewater treatment technologies mainly include precipitation, physicochemical, electrochemical, biochemical, and a series of new technologies that have emerged in recent years. The specific situation is as follows.

Technology for treating heavy metal wastewater

1. Precipitation method

The sedimentation method treatment mode is "heavy metal wastewater+precipitant → precipitate", which is filtered to remove heavy metal ions. Its essence is that heavy metals in heavy metal wastewater generally cannot be decomposed and destroyed, and can only transfer their existing positions and change their physical and chemical forms. Including neutralization precipitation, chelation precipitation, sulfide precipitation, etc.

2. Neutralization precipitation method

The neutralization precipitation method is a method of removing heavy metal ions from wastewater by adding alkaline neutralizing agents to form hydroxide or carbonate precipitates with lower solubility. Its applicable objects are acid alkali wastewater and heavy metal ions in residual solutions after treatment. Its advantages are simple operation, but its disadvantages include a large amount of sediment, high moisture content, severe secondary pollution, and difficulty in meeting emission standards for certain ions.

3. Chelating precipitation method

The chelation precipitation method utilizes the characteristic of DTCR containing a large number of polar groups to capture heavy metal cations (such as Hg2+, Cd2+, Cu2+, Pb2+, Mn2+, Ni2+, Zn2+, Cr3+, etc.) in wastewater under natural conditions. After generating a large amount of insoluble chelates, they precipitate and precipitate, achieving the goal of capturing and removing heavy metal ions. The chelation precipitation method has many advantages such as mature technology and simple operation, and is widely used in industries such as electronics and electroplating. How to reduce the cost of chelating agents and the subsequent treatment of filter residue is still worth further research.