What is the optimal ratio of Fe2+ from Fenton oxidation to hydrogen peroxide?

It depends on the type of wastewater you are dealing with. Based on my experience, for 1 kg of FeSO4*7H2O, 0.4 kg of 100% H2O2 is used, with the criterion being that no H2O2 remains after the reaction.

The original poster is generous; I can’t add any more points today, I’ll make it up tomorrow.

Thank you! I am seeking your advice on what the approximate optimal ratio of hydrogen peroxide to COD is in Fenton oxidation; I am working with cyanide-containing wastewater. Furthermore, is it better to use Fenton oxidation for complete oxidation to meet the standards directly, or to carry out partial oxidation followed by biochemical treatment? I’ve just started doing this kind of experiments; please give me your guidance.

Complete oxidation is costly; the cost of oxidation methods is already higher than that of biochemical methods. There is no need for full oxidation either – one can purchase some iron sheets and build a small-scale simulation setup (including biochemical processes), and use both together to conduct experiments in order to determine an optimal range.

My company produces hydrogen peroxide, and we use Fenton oxidation to treat the wastewater generated during production. My knowledge of this method is limited to its use for treating the wastewater from our own company; I have not conducted any thorough experiments on it. Based on my experience, COD is not very accurate in indicating the organic content in wastewater. Moreover, the inorganic impurities and solid particles present in most wastewaters can affect the ability of hydrogen peroxide to release *OH reactive groups. In addition, the hydrogen peroxide itself present in the wastewater can also influence the COD measurement results. Therefore, using COD directly to determine the amount of hydrogen peroxide required is only effective in small-scale tests; it tends to cause problems when applied in industrial settings, unless the wastewater source is extremely stable. My approach is to control COD in stages: for COD levels below 1000, the amount of hydrogen peroxide used is 0.8 kg/m3 of wastewater (100% hydrogen peroxide); for COD levels between 1000 and 2000, the amount used is 1.2 kg/m3; and for COD levels between 2000 and 3000, it is 1.6 kg/m3. Of course, it is also necessary to make appropriate adjustments based on experience, taking into account factors such as the turbidity, odor, and color of the wastewater. The Fenton oxidation method can directly meet the standards, meaning that the COD of the treated water is less than 100. However, if the COD is too high, such as exceeding 3000, or if the wastewater contains a large amount of solid particles, multiple treatment steps are often required, which increases the treatment costs. I don’t know much about biochemical treatment. I’m not sure if the above explanation can help you.

Could you please tell me how ferrous sulfate and hydrogen peroxide are added? Do you operate on a continuous basis or intermittently? Please give me some advice!

There are also many posts and materials on Fenton oxidation in the forum; I believe the original poster has referred to them as well, but they can only serve as a reference after all. To truly find the appropriate ratio for a specific type of wastewater, it can only be determined through experimentation. If the facility does not have the necessary testing conditions, the wastewater can be taken to a facility that does have such conditions for testing.

1. Use a method of continuous water inflow and continuous chemical addition. 2. As for the ratio of COD:H2O2:Fe2+, it isn’t fixed; it depends on the molecular structure of the pollutants in the incoming water. Conduct some preliminary tests to determine the appropriate ratio (a common one is 1:1.1:0.8)

Generally, the amount of hydrogen peroxide is 1.2 times that of COD. As for the amount of ferrous sulfate, it’s best to conduct experiments to determine it; typically, its amount is 1/10 to 1/20 of that of hydrogen peroxide (on a molar basis). This post was last edited by la9975956 on 2009-4-24 06:17

If COD is less than 200 ppm, the amount of hydrogen peroxide used is one thousandth； Ferrous sulfate is 0.5 per thousand; give it a try! ! This is how I handled it.

Generally, the processes following FENTON are neutralization, flocculation, and sedimentation. If a high amount of hydrogen peroxide is used, it continues to be released into the water after the reaction takes place in the sedimentator, making sedimentation more difficult; therefore, the proportion of ferrous sulfate should be slightly higher. Hydrogen peroxide: ferrous sulfate; 1:1 or even 1.5 ratios have been used as well, with the former value being in milliliters and the latter in grams (the weight including crystalline water). If the subsequent process is air flotation, 1:0.5 is better. We usually conduct a simple screening test in the laboratory to determine the final dosage ratio. In actual engineering practice, it has been found that in some Fenton reactions carried out with air as a stirring agent, the amount of air should not be excessive; too much air is not conducive to the subsequent precipitation process.

What I’ve worked with involves mixing through violent agitation; the pH of the incoming water is around 7.3. Theoretically, sulfuric acid should be added to lower the pH, followed by the addition of ferrous sulfate and hydrogen peroxide. Chemicals are also used in the effluent stage to promote sedimentation, and alkali is added to raise the pH. Due to high costs, this approach has not been used, and I’m not aware of the proportions of these chemicals. If the COD is also 200 mg/L, I would like to know the dosage ratio as well

One can conduct experiments on their own to determine the best ratio; we have done this before. With different water qualities, the ratios may vary, but the difference won’t be very large.

The ratio is different; ours is 1:4