Technical assistance: Questions regarding arsenic removal by sulfidation method
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The last edit to this post was made by hesonchang214 on 2010-4-21 at 17:05. After sulfidation, the arsenic content in the wastewater from colored metal smelting for acid production can be reduced to below 1 mg/L in some plants; however, my experiments did not yield such results. I tried changing the amount of sodium sulfide used, as well as the temperature, reaction time, and acid concentration, yet the arsenic content in the wastewater remained at 4.0 g/L. If you have done it, please give an introduction. Thank you!
Take a close look at the principle to see where there’s a problem. Principle of arsenic removal by sulfidation: Arsenic removal is generally carried out using the lime method and the sulfidation method. The lime method for arsenic removal requires a high pH; when producing calcium supplements using the superphosphate aqueous leaching method, a high pH will **increase phosphorus loss**. Therefore, the vulcanization method was used for arsenic removal in the experiment. The principle of arsenic removal by sulfidation is as follows: hydrogen sulfide (H2S) is used as a precipitant to convert arsenic into insoluble sulfides, according to the reaction: 2As3++3H2S→As2S3↓+6H+. However, As2S3 can dissolve in alkaline sulfides such as sodium sulfide (Na2S), with the reaction being: As2S3+3S2-→2AsS33- (thioarsenite). Thioarsenite is very unstable and immediately decomposes into the corresponding insoluble sulfide (As2S3) while releasing hydrogen sulfide gas, as shown by the reaction: 2AsS33-+6H+→2H3AsS3→As2S3↓+3H2S↑
Is there any good method for dealing with the resulting As2S3, such as through pressure-induced redox reaction to produce As2O3? Or reducing stannous chloride to elemental arsenic?
Did you see it in the literature, or have you witnessed it firsthand with actual measurement data? How much can you achieve through your own experiments? Issues related to water treatment can be discussed at Huan-Bao-Tong. Not everything in the literature is that reliable.
Reaching below level 1 directly is quite difficult; in-depth arsenic removal could be considered, and further discussion is possible