- chemical conversion technology.
At present, chemical conversion technology is used to treat heavy metals. There are three main methods for wastewater: chemical precipitation, electrolysis, and adsorption. The chemical precipitation method is a method of synthesizing ferrite by a chemical reaction to precipitate heavy metals in the wastewater. This method is also the earliest studied technology for treating heavy metal wastewater. The electrolysis method is capable of recovering valuable metals, and has the advantages of simple equipment and convenient operation. The disadvantages are low efficiency and high energy consumption. Adsorption is one of the most cost-effective methods for treating heavy metal wastewater. The practice is to adsorb heavy metal ions in the wastewater to the active surface of the adsorbent. Activated carbon is the most commonly used of many adsorbents. The adsorption amount is large, the adsorption capacity is strong, and the adsorption of heavy metal ions is the advantage of the activated carbon. The disadvantage is that the service life is short and the cost is high.
2. Physical and chemical concentration technology
(1) Electrodialysis. Electrodialysis uses a novel ion exchange membrane that separates heavy metal ions as they pass through the ion exchange membrane. The advantage of this method is that it saves energy and contributes to the comprehensive utilization of wastewater. However, the frequent replacement of the ion exchange membrane for the replacement of the ion exchange membrane is a disadvantage of this method during operation. The reason for this disadvantage is that concentration polarization is generated during the operation process and scaling occurs.
(2) Membrane separation and concentration technology.
The advantages of membrane separation and concentration technology are simple equipment, convenient operation, no phase change, etc., but this method also has disadvantages. The membrane module is more susceptible to contamination and is more expensive. Therefore, the local area should increase the support for the comprehensive utilization of straw, promote the commercialization and resource utilization of straw, increase the yield and separation efficiency of membrane modules, and add metal complexing agents to improve the selectivity of the membrane. It is also possible to form a membrane module using an inorganic material such as zeolite to adsorb heavy metals.
(3) Phytoremediation method.
Plants can absorb nutrients, precipitate impurities, and enrich soil. The phytoremediation method uses the characteristics of these plants to purify contaminated soil. Surface water can also reduce the content of heavy metals, and finally the pollution is treated and the environment is repaired. This method saves energy, improves energy efficiency, and effectively controls greenhouse gas emissions while dealing with heavy metal pollution.