Treatment of Waste Water from Electroplating Zinc in a Rolling Mill
Almost all types of surface treatments involve either the application of a coating to protect the substrate or the removal of material from the substrate in order to alter its properties. One of the most common and versatile of these surface treatments is electroplating, and this process can be used to apply a variety of metals, such as zinc, to a variety of substrates in order to improve their corrosion resistance, mechanical properties, or aesthetical properties.
The electroplating process involves the use of an electric current to apply a thin layer of metal to the substrate. The metal ions are attracted to the negatively charged cathode, and the anode is negatively charged in order to supply the ions for the process. Although electroplating offers many benefits to the substrate, it also produces a large amount of waste water that needs to be treated in order to reduce environmental pollution.
The waste water produced from the electroplating process of a rolling mill that uses zinc as a coating material, typically consists of zinc ions, heavy metals, and other dissolved ions related to the metal plating process. In order to reduce the environmental impact of this waste water, several techniques can be used to treat it and reduce its contamination.
One of the most common techniques used to reduce the contamination associated with electroplating waste water is coagulation and flocculation. This process involves adding a coagulative agent, such as polyacrylamide polymers, to the water in order to destabilize the colloidal particles and promote flocculation. This causes the heavy metals, zinc ions, and other dissolved ions to form larger particles which can be removed from the waste water by sedimentation, flotation, or other filtration techniques.
In addition to coagulation and flocculation, ion exchange can also be used to treat the electroplating waste water. This process involves the use of resins that act as an artificial sorbent and exchange the dissolved ions in the waste water with other ions that have a lower toxicity. The most common ions used in ion exchange are sodium, calcium, and magnesium, as they are typically less toxic than the heavy metals and zinc ions present in electroplating waste water.
Finally, reverse osmosis can be used to treat the waste water produced from the electroplating process of a rolling mill. Reverse osmosis is a process in which water is forced through a semi-permeable membrane, which removes the contaminants from the water. This technique can be used to remove heavy metals, high salinity, and other contaminants from the waste water, making it safe enough for reuse or disposal.
In summary, the electroplating process used in a rolling mill can produce a large amount of waste water that must be treated in order to reduce environmental contamination. The most common techniques used to treat the waste water include coagulation and flocculation, ion exchange, and reverse osmosis. These processes can remove the heavy metals and zinc ions from the waste water, making it safe for reuse or disposal.
