Seek methods to remove heavy metal ions from wastewater
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I work at a small dyeing and printing factory. Since the city has issued regulations requiring zero wastewater discharge, the factory must implement a complete recycling system for water used in production. I hope that experts can provide me with a viable solution. At present, the heavy metal ions in the wastewater treated by the factory still exceed the allowed levels. Is there any way to address this issue? I bow my head here first! QQ: 270613437 I hope all experienced folks will be kind enough to offer their guidance!
Heavy metals can be precipitated by adding lime!
Zero emissions require the use of ultrafiltration and reverse osmosis. And what’s tricky is the concentrated water resulting from reverse osmosis; I also want zero emissions – there are no waste discharge outlets! Apart from heavy metals, the only option is chemical precipitation; using lime is relatively inexpensive
It’s just about adding lime for alkalization, unless there are any special circumstances
What heavy metals are contained in it? Lime is not a panacea.
The treatment of heavy metals mainly relies on sedimentation tanks, and the methods used vary depending on the type of heavy metal. For example, the pH value can be adjusted to induce the formation of hydroxide precipitates; in some cases, the pH value is slightly altered and air is used to create carbonate precipitates. In other cases, certain ions such as sulfide ions can be added to form sulfide precipitates. LZ, could you please tell me what the theoretical ions of heavy metals in your wastewater are? That will help with the analysis
OP, there are many types of heavy metals; which specific type are you referring to? You can find some relevant information on the forum.
Oxidation/reduction potential control techniques, hydroxide precipitation (pH control), inorganic sulfide precipitation, organic sulfide precipitation, silicate precipitation, carbonate precipitation, coprecipitation, treatment techniques involving binding to insoluble matrices, adsorption techniques, ion exchange techniques, as well as passivation, extraction, displacement precipitation, hydrophobicization treatment, biological treatment, electrochemical methods, etc.
The effect is the same when using calcium carbide slag; the cost is lower, and the working environment is better. The solid waste that settles down needs to be sent to a waste treatment facility or buried.
What are the heavy metal ions in wastewater? I’ll give you a specific method.
Heavy metal ions generally refer to: Cr6+, U6+, Te3+, Co3+, Se6+, Pu3+, Hg2+, Mn4+, and so on.
If the water contains ions such as Cr6+, U6+, Te3+, Co3+, Se6+, Pu3+, Hg2+, and Mn4+ simultaneously, the silicate precipitation method is used. An equivalent amount of ferrous sulfate is added based on the concentration of Cr6+ ions, thereby reducing hexavalent chromium (Cr+6) to trivalent chromium (Cr+3); trivalent chromium ions are more easily precipitated； For silicates, 425-grade cement is used; the reaction between heavy metal ions in the solution and silicate ions does not result in crystalline silicates in a fixed ratio, but rather yields a mixture that can be considered to be composed of hydrated metal ions combined with aluminosilicates or silica in various proportions. This silicate precipitate has low solubility over a wide pH range (2–11).
It is recommended that you consult resin adsorption manufacturers for technical support. For high-concentration organic wastewater, I don’t think reverse osmosis is a suitable option; however, using tree branches for adsorption followed by treatment with acids and bases seems to be a viable approach. It is advised to first conduct pilot tests to select the appropriate resin, and then work together with the resin manufacturer to find a solution
First of all, thank you all. I’m not really sure exactly which heavy metal ions are present in it; this is wastewater from a dyeing and printing factory. The test results from the county water treatment station only indicate that the levels of heavy metals are excessive, but I don’t know specifically which heavy metal ions are in excess. I would appreciate it if anyone with experience in dealing with wastewater from dyeing and printing factories could advise me. Please forgive my ignorance! I’m begging you all! Sincere bow!
Find out which metal ion is present in excess, and opt for ion adsorption – it is a relatively thorough method for treated water.
It’s still necessary to know the types and levels of heavy metal ions in order to handle them properly; otherwise, it might be impossible for anyone to help you. Targeted methods must be used to deal with heavy metal ions; otherwise, it will be ineffective and useless.