Is this new for you? What operation or mine are you working at? It sounds as if this is the first time you have done this. Your second question indicates you have not done this before.

Before you can electroplate gold out of a cyanide solution that contains hydrogen peroxide (or any other oxidizer) you was first get rid of any excess oxidizer. With hydrogen peroxide this done by heating the solution first to a slow boil and then allowing it to cool. You can determine the optimum current density for metal recovery through testing will a hull cell. As a side note electro winning does not normally well below 10 ppm Au in solution.

Yes, it's new for me, we’re doing plating and I’m trying to recover Au from CN I will try this method after electro winning, how do we test if there is no more Au in the solution?

Make test with kitazato flask and precipitate with Zn dust and Lead Acetate, as Merrill Crowe process but in scale, later assay by fire the dust make test with a volume of 100 ml of problem solution. Use a vacuum pump with kitazato flask!

What volume of solution do you have to treat? Will this be a one-time operation or a regular operation? Do you have an atomic absorption spectrophotometer in your facility? DO you have a fire assay facility available?

Is there any method besides using Zinc Dust and Lead acetate?

Use AA machine.

It's one time operation. No spectrophotometer and no fire assay. We can test percentage Au if it comes in solid form using zinc dust or foil. But how to test the solution have no Au left over or not?

Sorry did not see earlier comments about the absence of AAS/FA; suggest you access Vogel's text on Qualitative Analyses there are a number of easy colorimetric techniques to define the presence of soluble Au.

There is a qualitative simple method called gaseous test u can use to indicate presence of gold remain in barren solution.