1. Oxidation method - oxidants such as when treating wastewater containing #, hypochlorite is commonly used to oxidize the # ions in it under alkaline conditions, decomposing them into low-toxic # acid salts. It is then further degraded into non-toxic carbon dioxide and nitrogen.
2. Neutralization, coagulation and precipitation method ------- alkali solution, flocculant, heavy metal capture agent. For example, in the ion exchange chromium removal process, the cation exchange column regeneration waste liquid contains heavy metals. Strongly acidic waste liquid with ions (Zn2+, Cr3+, Fe3+, etc.) can be neutralized by regenerating the waste alkali liquid from the anion exchange column after removing the acid radicals or adding alkali to precipitate it in the form of hydroxide. For example, adding polymer flocculant can change the settling performance and separation performance of this sediment.
3. Neutralization and precipitation method---------Alkali liquid such as acidic wastewater is neutralized with alkaline wastewater or alkaline substances are added to form a sediment.
4. Ferrite method-------The alkaline electroplating wastewater is treated to produce iron hydroxide or other heavy metal hydroxide precipitation, and the heavy metals are transferred into highly magnetic ferrite through the oxidation reaction. in body crystallization. This method can be used to treat chromium-containing wastewater. The chemical method has simple equipment, low investment, and wide application. However, sludge is often left and needs further treatment, and the electroplating wastewater is dispersed, making it difficult to centrally process and utilize the sludge.
5. The evaporation concentration method uses heat sources and evaporators to directly concentrate wastewater under normal pressure or negative pressure. This method is more economical to treat high-concentration wastewater, and is often used in conjunction with three-stage countercurrent rinsing, air-water spraying, or ion exchange. At present, titanium tube thin film evaporators and evaporation kettles are widely used in production to concentrate chromium-containing wastewater, #containing wastewater, etc., which is also one of the main treatment processes of closed-circuit circulation.
6. The ion exchange method uses exchangeable ions (H+, Na+, OH-, etc.) on the active groups of the ion exchange resin to remove cations and anions in wastewater. This method of treating electroplating wastewater can not only recycle water, but also recover metal ion solution. This method has been used to treat wastewater containing gold, nickel, copper, cadmium, chromium, etc. In recent years, weak acid and weak alkali macroporous resins have been artificially synthesized and specially used to treat electroplating wastewater. They can be used to remove chromium, nickel and copper, as well as # complex anions of some metals respectively. Generally speaking, the ion exchange method requires a large initial investment and requires a high level of operation and management, but the treatment effect is stable. Because it can reuse metal and water, it is one of the main treatment methods for achieving closed-circuit circulation of electroplating wastewater. The main problem is that the regeneration waste liquid will contain impurity ions such as sodium, iron, and chlorine, which cannot be directly reused in the plating tank. Discharging it into the environment will cause pollution.
7. Activated carbon adsorption method. Activated carbon has a very large microporous structure and a huge surface area. Usually, the surface area of ??1g of activated carbon reaches 700~1700m2, so it has extremely strong physical adsorption force and can effectively absorb wastewater. Heavy metal ions such as hexavalent chromium ions (Cr6+) in the When the activated carbon reaches adsorption equilibrium, heating, acid soaking, alkali soaking, etc. can be used to remove the adsorbed matter and regenerate the activated carbon.