Heavy metal ion deep removal process and technology

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This post was last edited by Qingfeng Xuchi on 2022-3-8 17:19 Heavy metal wastewater usually contains a large amount of metal ions that are difficult to degrade. Among them, heavy metal ions such as zinc, iron, copper, lead, etc., including mercury, lead, arsenic, cadmium, chromium, etc. are toxic. This will result in the presence of large amounts of heavy metal ions in wastewater quality and soil. These heavy metal ions will be transferred to animals and plants, and then transferred to the human body or directly affect the water source, causing excessive heavy metal content in the human body, causing heavy metal poisoning. There are several treatment methods for heavy metal wastewater: biological treatment, physical treatment and chemical coagulation and sedimentation. With the improvement of heavy metal ion discharge standards in sewage, heavy metal ions cannot be completely removed by a single method. Nowadays, the combination of biological method + chemical precipitation method is more commonly used to remove heavy metals. Among them, chemical precipitation methods are divided into alkali agent neutralization coagulation, coagulation and redox methods with coagulants such as ferrous sulfate or polymeric ferric sulfate, and heavy metal chelating agents, etc. Removal of heavy metal ions by chemical precipitation method 1) Neutralization and coagulation method by adding alkali agent, adjusting by adding pH neutralizers such as caustic soda and compound alkali, so that the same type of heavy metal ion wastewater reaches the precipitation pH value of the heavy metal, or the pH value of wastewater containing multiple metal ions is adjusted in stages to form sedimentation sludge. Then heavy metal ions in the water are removed through air flotation scraping or sedimentation mud discharge. 2) Coagulation methods such as ferrous sulfate or polymerized ferric sulfate, by adding coagulants such as ferrous sulfate, polymerized ferric sulfate, and PAM. Through coagulation and precipitation, the metal salt substances suspended in the water are adsorbed, coagulated and precipitated. 3) Redox method, such as alkali sulfide, ferrous sulfate and other coagulants have strong redox properties. After ferrous sulfate is added to the wastewater for hydrolysis, Cr6+ is reduced to slightly toxic Cr3+ (comparison of ferrous sulfate and pyrolysis treated hexavalent chromium), and then the coagulant aids such as polyacrylamide are added to quickly react to form Cr(OH)3 precipitation and then separate. 4) Coagulation breaking method, this method is mainly used for heavy metal wastewater containing complexes. The heavy metal treatment process in this kind of wastewater mostly adopts water inlet → alkali adjustment → complex breaking (adding sodium sulfide + ferrous sulfate) → coagulation (ferrous sulfate) → precipitation → water effluent/advanced treatment/recycling. The heavy metal ions in the wastewater can be removed through coagulation by using the complexation-breaking agent to dissolve and break the complexation, and then reacting with the metal ions in the water through strong coagulation and flocculant to produce precipitation. 5) There is another more convenient and faster way, which is to choose ion exchange resin, which can be applied to heavy metal ion treatment in many industries. The traditional precipitation method cannot meet the increasing environmental protection requirements (such as the electroplating table 3 nickel content requirement of less than 0.1 mg/l). According to the characteristics of specific heavy metal ions, the special functional groups of the chelating resin are used to form complexes with heavy metal ions to achieve recycling and deep removal of heavy metal ions. CH-90Na has specific selectivity for removing copper, nickel, lead, zinc, cobalt, manganese, etc., especially in the treatment of nickel ions and complexed nickel. It has a strong binding effect and application advantages, and is suitable for direct adsorption of nickel in an acidic environment (pH value around 3). For strongly complexed nickel, it is necessary to break the complex first and then remove the nickel (such as EDTA nickel). The saturated adsorption capacity is approximately 50g/l. Ion exchange resin is simple to operate, has a wide removal range, is economical and practical, and is currently a widely used method for treating heavy metal wastewater. Reference indicator water volume: 150 tons/day ； water quality: Copper content 3mg/l, lead 2mg/l ； Water output index: 0.06mg/l or less ； running time: 24 hours continuous operation ；