Through the immersion test of heavy metal contaminated soil, the removal ability of the three heavy metals Pb, Cd, and Zn in the contaminated soil by HCl, citric acid, and EDTA were compared, and the effectiveness of the extraction of these three extractants on the soil heavy metals was studied. Impact. The results showed that as the concentration increased, the removal of Pb, Cd, and Zn by the three extractants increased. The ability of EDTA to remove 3 kinds of heavy metals is far greater than the other 2 kinds of extractants. The order of the removal rate of HCl and citric acid for the three heavy metals is Cd>Zn>Pb, and the order of the removal rate of the three heavy metals by EDTA solution is Pb>Cd>Zn. The extraction of HCl and citric acid improves the availability of Pb in the soil and reduces the availability of Cd and Zn. EDTA extraction reduces the availability of Pb, Cd, and Zn in the soil, and the effectiveness of these three heavy metals is lower than the treatment of HCl and citric acid. It can be seen that EDTA is more suitable than HCl and citric acid as an extractant for the treatment of heavy metal contaminated soil. Although HCl and citric acid can also significantly remove heavy metals in the soil, its effect of improving the effectiveness of soil Pb is worth noting.
How to use heavy metal traps to solve heavy metal exceeding standards?
In the process of electro-galvanizing operations, the problem of sewage treatment often troubles business owners. Therefore, the treatment of heavy metal sewage by electro-galvanizing has become a major problem in front of galvanizing enterprises. Since the chemical substances generated after the electrogalvanizing operation can pollute the water quality, once the galvanizing operation is completed, the sewage must be discharged immediately, otherwise it will have a certain impact on the water source, and even cause the water source to become abnormal use.
Hazard: Heavy metal (such as cadmium, nickel, mercury, zinc, etc.) wastewater is one of the most severe environmental pollution and the greatest harm to humans. Its water quality and quantity are related to the production process. The heavy metals in wastewater generally cannot be decomposed and damaged, and can only be transferred to their existing position and change their physical and chemical shapes. The heavy metal pollution of water bodies has become one of the most severe environments in the world today.
Method: In view of the characteristics of heavy metal wastewater, the commonly used treatment methods now include: chemical precipitation, oxidation recovery treatment, solvent extraction, adsorption, etc.
1. Chemical precipitation method The chemical precipitation method is a method of changing the dissolved heavy metals in heavy metal wastewater into water-insoluble heavy metal compounds, including neutralization precipitation and sulfide precipitation methods.
2. Chemical recovery method The chemical recovery method is one of the earliest used management techniques, which is widely used in our country. Its management principle is simple, the operation is easy to grasp, and it can withstand the impact of large amounts of water and high-concentration wastewater. Chemical recovery method is used to treat Cr-containing wastewater. Lime is generally used for alkalization, but there is more waste residue; NaOH or Na2CO3 is used to reduce sludge.
3. Solvent extraction method Solvent extraction method is a method commonly used to separate and purify substances; due to the liquid-liquid contact, it can be operated successively, and the separation effect is better. When using this method, it is necessary to choose an extractant with higher selectivity. The heavy metals in the wastewater generally exist in the form of cations or anions. Although the extraction method has great advantages, the loss of solvent in the extraction process and the large energy consumption during the regeneration process make this method have certain limitations, and its application is greatly restricted.
4. Adsorption method Adsorption method is a useful method to remove heavy metal ions by using the same structure of the adsorbent. The adsorbents used to treat electroplating heavy metal wastewater by adsorption method include activated carbon, humic acid, sepiolite, polysaccharide resin and so on. Activated carbon is simple in equipment and is widely used in wastewater treatment. However, activated carbon has low regeneration power and it is difficult for the treated water quality to meet the reuse requirements. It is generally used for pretreatment of electroplating wastewater. The content of heavy metals in the treated wastewater is significantly lower than the general discharge standards for wastewater.
Conclusion Now the heavy metal-containing wastewater discharged in the process of human industrial production has brought great harm to the ecological environment. For the handling of heavy metal wastewater, it is first necessary to control the discharge of heavy metal ions in the polluted water body from the source of pollution, and to deal with the polluted water body together in a really useful way; add Semfrey environmental protection material heavy metal capture agent to handle the heavy metal wastewater It has the advantages of low cost, high efficiency and convenience, and no secondary pollution to the environment. It has the advantages that other chemical methods and physical methods cannot replace.