Hi all,
From a thorough literature and patent search, there are lots of articles talking about using chelant to complex iron instead of iron shows improvement over conventional Fenton process (ferrous react with hydrogen peroxide). The chelant approach claims the benefits to have redox reaction at higher pH, vs. pH 3-4 for conventional Fenton process.
I did some lab experiment by complexing ferrous with EDTA and react with hydrogen peroxide. I am completely surprised there is no reaction at all regardless of pH 3 or 5. In contrast, the conventional Fenton reaction just performs well. After both tests, I increase the pH to 7 and add some anoinic flocculant. The conventional one works as expected with floc formation, while the EDTA one has no floc and the effluent just looks like it is. In both cases, I keep the iron and peroxide concentration the same for comparison.
I could explain the EDTA complex iron pretty well which might reduce reactivity with peroxide, and since EDTA keeps it soluble it does not function as coagulant at pH 7. But why my experiment and proposed explanation is completely different than literature? Am I wrong somewhere? Is chelant-iron complex approach realistic for large-scale applications?
Thanks,
Shawn
From a thorough literature and patent search, there are lots of articles talking about using chelant to complex iron instead of iron shows improvement over conventional Fenton process (ferrous react with hydrogen peroxide). The chelant approach claims the benefits to have redox reaction at higher pH, vs. pH 3-4 for conventional Fenton process.
I did some lab experiment by complexing ferrous with EDTA and react with hydrogen peroxide. I am completely surprised there is no reaction at all regardless of pH 3 or 5. In contrast, the conventional Fenton reaction just performs well. After both tests, I increase the pH to 7 and add some anoinic flocculant. The conventional one works as expected with floc formation, while the EDTA one has no floc and the effluent just looks like it is. In both cases, I keep the iron and peroxide concentration the same for comparison.
I could explain the EDTA complex iron pretty well which might reduce reactivity with peroxide, and since EDTA keeps it soluble it does not function as coagulant at pH 7. But why my experiment and proposed explanation is completely different than literature? Am I wrong somewhere? Is chelant-iron complex approach realistic for large-scale applications?
Thanks,
Shawn