Study Of Nanoscale Zero-Valent Iron Impregnated Activated Carbon For Fenton-Mediated Degradation Of Methyl Orange

With the advantages of high utilization rate of H₂O₂, wide applicability of PH scope and the renewability of the catalyst, heterogeneous Fenton oxidation technology is playing an important role on the development of Fenton technology.With the development of nanotechnology, heterogeneous Fenton technology, based on nanometer zero-valent iron ?nZVI?, has received the widespread attention.But colloidal properties of nZVI makes it easy to reunite and therefore reduce its activity, so people began to study the immobilization of nZVI and its catalytic performance.This study put forward a through of supporting nZVI on the activated carbon, and establish an heterogeneous nZVI/H₂O₂ Fenton system.Study choose a typical azo dye methyl orange as the goal pollutant, to discusses the feasibility and effectiveness of removing nonbiodegradable organic by the heterogeneous system.Study optimized the conditions, surface modification of AC and supporting time, to get optimized conditions to make nZVI/AC, and characterized the optimized nZVI/AC. Then conform its efficiency, survey its ability of removing methyl orange, and explore its action mechanisms.According to the study, optimized condition is:acid modified activated carbon, support one time. nZVI/AC got on those conditions has more iron content, much attachment firmness and better renewability. The density of nZVI/AC is almost the same with common activated carbon, and the specific surface area of nZVI/AC is a little higher. The dominate phase of iron supported on activated carbon is nanometer zero-valent iron, which average particle size is 38.25 nm.Results showed that when the pH was 3, the catalyst dosage was 3 g/L, the amount of hydrogen peroxide used was 11.76 mM, the treatment of methyl orange was the best. After 120min, the removal rate of 15 mg/L methyl orange reached 93.78%. Dosing of EDTA inhibited the nZVI surface passivation phenomenon, promote the Fenton reaction. Under aerobic conditions, on the other hand, makes the nZVI/AC more advantageous to generate H₂O₂ and ·OH. Under the condition of pH 7 and 100 mg/L EDTA, system can make the removal rate of methyl orange increase of 10.55%.Different system methods show that support nZVI on the activated carbon can significantly improve the removal rate. nZVI/H₂O₂ system belongs to the heterogeneous Fenton system, its action mechanism includes two aspects:the adsorption of activated carbon, and the heterogeneous Fenton oxidation.The synergy improve the efficiency of the single function. The main active species oxide system of is ·OH, also there may exist intermediate-valent iron species.Activated carbon adsorption conforms to the Freundlich model for methyl orange, and is given priority to multilayer adsorption and pseudo-second-order kinetics equation. The internal diffusion and membrane diffusion are adsorption rate control steps.Research shows that the concentration of H₂O₂, dosing quantity of nZVI/AC and initial pH will affect the decomposition rate of H₂O₂, which meet the secondary reaction kinetics for [nZVI/AC] and [H₂O₂].