I'm currently doing research about Fenton oxidation in CSTR. So, I should feed the wastewater, Fe(II) catalyst, and hydrogen peroxide to 1-L reactor continuously.
How is the best feeding strategy for this case? I've some idea about feeding strategy in this case, but I don't know which is the best.
1) I dissolve Fe(II) in wastewater stock solution and wastewater in the reactor, then I feed hydrogen peroxide separately.
2) I just dissolve Fe(II) in wastewater stock solution and feed hydrogen peroxide separately.
3) I dissolve Fe(II) in hydrogen peroxide and feeding this Fenton's reagent and wastewater separately.
Which is the best feeding strategy? Thanks before.
Interesting question! Are you studying real wastewater matrices, or only a synthetic wastewater (deionized water with spiked concentration of a certain pollutant?
If a synthetic wastewater matrix will be used, you can predict by construction (and solving) the mass balances for each scenario. In that case, just construct the mass balances for each system. The feeding strategy that predicts the highest pollutant removal will be your feeding method of preference.
When real wastewater matrices will be used, it might be very difficult to predict in advance which strategy will deliver you the best results. Maybe it will be better to perform experimental runs which each of your mentioned methods to find out which strategy gives you the best results.
I use real wastewater from textile industry. Textile wastewater have high COD and I want to decrease its COD and study its kinetic using continuous Fenton oxidation treatment. I've tried those 3 feeding strategies, but the COD removal isn't significant and fluctuative. I used hydrogen peroxide dosage = 4 . initial COD and Fe(II) = 2/9 . moles of hydrogen peroxide. Can you give some possible reason for this case? Thanks.
Fenton's process should be an appropriate method for the treatment of industrial wastewaters which are characterized by a high COD content, so it it is a bit strange that only a poor COD removal is experimentally observed. In the Fenton process is recommended as a typical range for
However, in your description above, nothing was mentioned about the initial pH value of your wastewater. Remind that the Fenton process is usually inefficient when the solution under treatment has a pH value higher than 5. When the pH value of the wastewater is to high, Fe3+ ions willl tend to precipitate as iron(III)hydroxide, and hydrogen peroxide will decompose in H2O2 and O2. This will result in a significantly lower production of OH* radicals, and hence a lower process efficiency.
In the most ideal case, the pH value should be adjusted to pH = 2. You can use sulphuric for doing this pH correction. At the optimal pH value of 2, the optimal dose Fe2+ / H2O2 of is approximately 1:3.(on weight basis). When you have a very high COD concent I also would recommended you to use 5 parts of Fe2+ for one part of COD (also on weight basis).
Thank you for your answers. I've adjusted pH of wastewater to pH 2. I just worried about dosage of hydrogen peroxide and Fe(II). Could you give journals about the optimum conditions you said above?
I also want to ask, can Fenton oxidation process decrease COD effectively if the initial COD of wastewater has been already low enough (for example 300 ppm)? Because I read in website that Fenton process can be used as effective method to decrease COD if the initial COD pf wastewater > 500 ppm. Thanks.
The Fenton reaction does not reduce soluble organics; the peroxide will but is expensive and requires a significant reaction time relative to the time needed for the Fenton reaction. The Fenton reaction needs a high saline solution. Sea water can be used for this purpose.
There's also some data wich indicates that mineralization starts just when color removal is complete. How long you carried out the treatment?
Hi~I would like to recommend a research to you in our previous research. The key point here is H2O2 and Fe2+ both act as a OH initiator as well as OH scavenger, therefore I think in practice, high concentration of H2O2 or Fe2+ should be inhibited. So a step-wise addition is better. However, It will surely lower the Fenton reaction rate since concentration of reactants is not as high as one-time addition.
I ever tried multi-point addition, which is adding H2O2 to Fe2+ solution from multiple points, to avoid localized high concentration of H2O2. The link is attached below(The abstract is written in English).
http://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra20242j#!divAbstract
Article Influence of multi-point addition of H2O2 on ORP of Fe2+/H2O2 system
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