During the pre-plating treatment of galvanized square pipes, impurities such as ferric oxide and iron oxide must be cleaned by acid pickling solution. In this way, a large amount of acid pickling waste liquid will inevitably be produced and accumulated in the consumption line.
For a long time, hydrochloric acid has been widely used in hot-dip galvanizing enterprises to stop pickling of steel and steel square pipes. In the original way, the waste hydrochloric acid is passed through the river after neutralization, which is one of the more serious pollution sources in the water area, but also a waste of resources. With the progress of people's environmental awareness and the adjustment of national policies, according to the request of the development of circular economy, these waste acids can never be discharged into rivers.
There are many disposal methods for waste acid at home and abroad. Different disposal methods are suitable for different types of waste acid. The detailed use of which methods depends on the characteristics of waste acid.
As far as hydrochloric acid is concerned, a considerable amount of waste hydrochloric acid containing iron will be produced. If the waste liquid is discharged directly, it will seriously pollute the environment and waste resources. Some materials show that hydrogen chloride gas can be produced by concentrated distillation and acidification of waste acid, which can be absorbed into hydrochloric acid and then treated as mother liquor of acidification preparation, without secondary pollution and zero discharge, thus completing the resource disposal of waste hydrochloric acid containing iron from industrial acid pickling. The recovery rate of chlorine in waste acid reaches 85%, and the mass concentration of industrial Refined Hydrochloric acid reaches 34%. At the same time, the by-products of oxidized scarlet and phosphate fertilizer are obtained.
If the application of waste acid is touched, although filter press can not be used for filtration treatment, it is possible to use non-semi-permeable membrane dialysis, but this touches the cost problem of semi-permeable membrane dialysis equipment. Because of its high cost, hot-dip galvanizing enterprises are often not used, so it is better to replace new acid.
If the corrosion inhibitor is added to the acid solution, the iron ion content will be reduced considerably. It can be used repeatedly as a component of iron ion concentration which needs to be preserved in the new acid. This is because the iron ion content of a certain concentration in the acid is beneficial to the acid effect.