Very strange problems have arisen in the treatment of polluted acids
Thread Content
One of our company’s projects focuses on the treatment of acidic waste; the waste acid discharged from the sulfuric acid system has an arsenic content of around 5000 mg/L and a acidity level of about 5%. Treatment is carried out using the lime-iron salt method; aeration oxidation is employed for the initial lime neutralization, achieving an arsenic removal rate of >99%. The residual arsenic level was around 10 mg/L, but after adding 8 ml/L of polyferric sulfate and stirring for 2 hours followed by pressure filtration, the arsenic content in the filtrate reached around 20 mg/L. After that, the dosage of polyferric sulfate was adjusted to 20 ml/L, but the arsenic content in the effluent remained around 20 mg/L; I don’t understand why Seeking advice from experts
This post was last edited by CoCo070563 on 2015-9-9 at 10:47. Polyferric sulfate has a certain acidity; its addition reduces the acidity of the entire system. Arsenic acid dissolves as a result, leading to an increase in its concentration. It is possible to measure the pH of the filtered liquid. Another point is that the quality of ferric sulfate polymer should be more closely monitored, with tests conducted to check for toxic substances in it. Polyferric substances available on the market often contain toxic impurities.
The arsenic level is too high; the iron salt oxidation method cannot be used directly. It is necessary to first remove a large amount of arsenic using the sulfidation method before applying the iron salt method
Ferrous sulfate polymer is an acidic salt; when added to water it undergoes hydrolysis and becomes acidic, which lowers the pH of the wastewater. The precipitated alum floccules that were formed initially dissolve again under acidic conditions