Original Article:
Investigation of chemical associations and leaching behavior of heavy metals in sodium sulfide hydrate stabilized stainless steel pickling sludge
Peidong Su, et al.
Process Safety and Environmental Protection, 2019, 123, 79-86.
10.1016/j.psep.2019.01.001
The metal pickling and passivation processes involved in the production of stainless steel products often lead to the generation and accumulation of stainless steel pickling sludge (SSPS). SSPS contains a large amount of heavy metals, which may be harmful to the environment and human health. Therefore, it is of great significance to develop feasible SSPS processing technology to make SSPS an environmentally friendly material.
In this study, researchers treated SSPS by chemical stabilization using sodium sulfide (Na2S) and evaluated the leaching toxicity of heavy metals in SSPS before and after treatment. The leaching results of HJ/T 299 and HJ/T 300 show that Cr and Ni are the main elements that cause SSPS to be harmful to the environment.
Among them, sodium sulfide has the most obvious chemical stabilization effect on Cr heavy metals, which is achieved in the following way:
The leached Cr in the HJ/T 299 test is likely to be Cr(VI), and within the pH range of 8~9, Cr(VI) mainly exists in the form of CrO42-. In this case, the addition of Na2S can reduce Cr(VI) to Cr(III) through the reaction in equation (1), which may be the main reason for the decrease of Cr leaching concentration after stabilization.
According to the BCR test results, compared with the original SSPS, the Cr in the form of F2 dropped sharply from 55.21% in the original SSPS to about 10% in the stable product. It is clear that most of the F2 reacts with sodium sulfide and converts to F3 and F4. The very low F0 ratio and rather high F3 and F4 ratios after stabilization imply that Cr(VI) in pristine SSPS is stabilized.
Chemicals Related in the Paper:
| Catalog Number | Product Name | Structure | CAS Number | Price |
|---|---|---|---|---|
| ACM27610453 | Sodium sulfide hydrate |  |
27610-45-3 | Price |
| ACM1318844 | Sodium Sulfide Nonahydrate |  |
1318-84-4 | Price |
