Why is the purification of chromic acid mist not yet satisfactory in China?
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I am currently working on a project to treat the chromic acid mist emissions from electroplating factories. Nowadays, environmental regulations are becoming increasingly strict; many electroplating factories in major cities have moved to other locations, and Germany has also stopped using the electroplating process that involves hexavalent chromium. The main reason is the severe contamination caused by this chromic acid; it seems that we are still lacking in methods for purifying it. The removal efficiency of conventional packed towers is only 95%-99%, which is not sufficient to meet the emission standards outlined in Table 3, let alone achieve zero pollution emissions. I checked some foreign websites and found that their fillers and demisters claim to be able to achieve a level of 0.002 mg/m3; I’m not sure if this is true or not. What do you all think?
Mainly, the operating environment is not enclosed, so it is not possible to create a negative pressure environment. If more investment is made, there are ways to deal with the acidic mist in the paint factory environment.
It’s not just acid mist; there are also acid washing wastewater, as well as wastewater containing large amounts of heavy metals such as chromium and nickel. This wastewater is discharged directly into public sewage treatment plants without any treatment, and eventually makes its way back into rivers and thus into the food chain.
Currently, aside from military-related projects, it is very difficult to obtain emission limits for heavy metals (the five categories listed as hazardous) during the environmental impact assessment for other industrial projects. As a result, some companies take advantage of policy loopholes by not reporting processes that involve the emission of heavy metals when submitting their applications. Local authorities, in an effort to attract investment and boost GDP, turn a blind eye to this issue, which leads to widespread volatilization and emission of heavy metal ions.
What solutions are available for handling situations in enclosed environments? Chromic acid mist is a liquid, so the approach of using gas absorption cannot be applied.
The VOCs in the painting process are in liquid form, so gas absorption is used in the painting workshop. Alternatively, a local negative pressure in the operating area can be used to prevent the leakage of chromic acid mist.