Technical assistance: Removal of complexed nickel from electroplating wastewater

The chelating agent can be broken down first, followed by the precipitation of metal ions. However, given the wide variety of sources of industrial wastewater, this process route is difficult to implement and comes at high costs. A complexation method can also be employed to treat the wastewater containing complexing agents, thereby controlling the COD value; for this process, an appropriate complexing agent must be selected.

Um, may I ask what method can be used to break the connection? I’ve tried a few methods, but they didn’t work.

This post was last edited by cdpulin on 2012-7-13 at 11:48. TMT15, our plasticizing agent supplier in Beijing, reacts directly with heavy metal ions to cause precipitation; it can also effectively remove complexes, with excellent results. Several orders of magnitude lower than the **standard requirement. 138 1731 1897

This post was last edited by cdpulin on 2012-2-17 at 11:34. Complex ions are best hydrolyzed under acidic conditions. What method do you use to break down cyanide? If it is an alkaline method, the metal ions in the cyanide-containing wastewater will instead form metal cyanide complexes. It is recommended that the process be adjusted to an acidic treatment method: first, acidify the wastewater to a pH of 2–3 using sulfuric acid. Taking advantage of the low vapor pressure of HCN, this allows HCN to be separated from the wastewater. This process should preferably be carried out under negative pressure, and the wastewater may need to be heated; an ideal temperature for the entire reaction is 30 degrees Celsius. Under acidic conditions, the reduction of cyanide promotes the forward progression of the hydrolysis reaction; the copper and nickel resulting from this hydrolysis can be precipitated by adding alkali. It would be ideal if the wastewater contained SCN, as this would allow for the formation of valuable by-products alongside the hydrolysis of the complexes. HCN gas can be recovered using caustic soda to be used as a raw material.

My method for removing cyanide involves using sodium hypochlorite to do so without any reactions occurring; after that, heavy metals are removed, but this process must take place under alkaline conditions. After the cyanide is removed, metals like copper can be easily removed, but nickel simply cannot be eliminated in this way. I’d like to try using electrolysis to see if it works. Has anyone done this before? I hope you can give me some advice.

Well, all these methods have been tried, and even the adsorption effect of activated carbon is not very noticeable. I wonder if you have tried the electrolysis method.

This post was last edited by cdpulin on 2012-2-17 at 11:36. Sodium hypochlorite, hypochlorous acid, chlorine gas, and chlorine dioxide can only break down CN ions in their non-complexed form; complexes are stable, especially those of copper and nickel. They behave like organic substances and are very stable in alkaline conditions. The complexation reaction can be reversed only under acidic conditions. I have completed four such projects: in Tongguan, Shaanxi; Songyuan, Henan; Central South China, Hunan; and Tianyang, Guangxi. If there’s a chance, we can discuss this in more detail.

Friend upstairs, I’m wondering whether CN will turn into HCN under acidic conditions; HCN is a volatile and toxic substance. Additionally, it is said that the original poster used various methods to treat nickel; please list them so that everyone can benefit from them. Besides oxidation, are there any other better methods to destroy complex ions?

This is very difficult; just analyze the complexation reaction to see why. Moreover, it’s extremely dangerous, as hydrogen cyanide is highly toxic!

OP, you might consider heavy metal chelators, as they are also chelating agents that can help break down cyanide.