(225g) Heterogeneous Fenton Oxidation of Synthetic Dye in Water With Surface-Modified Iron-Amended Activated Carbon | AIChE

(225g) Heterogeneous Fenton Oxidation of Synthetic Dye in Water With Surface-Modified Iron-Amended Activated Carbon


Kan, E. - Presenter, University of Hawaii
Kim, J. R., University of Hawaii
Santiano, B., University of Hawaii at Manoa
Kim, H., University of Hawaii

The present study aims to develop effective adsorption and oxidation of synthetic dye in wastewater by using newly synthesized nano iron catalyst-deposited activated carbon. Recently synthetic dye-containing wastewater has gained more attention due to its mass discharge, high toxicity and low biodegradation. For enhancing adsorption of dye and oxidative regeneration of dye-exhausted activated carbon, the novel synthesis of nano iron-deposited granular activated carbon (GAC) was developed. It was to amend ferrous iron onto the acid-pretreated GAC followed by Fe amendment onto the acid-pretreated GAC when pH of iron solution was higher than the pH at point of zero charge (pH, pzc) of the GAC. Methylene blue (MB) in water was adsorbed onto the iron-amended GAC (Fe-GAC) followed by single or multiple applications of H2O2. Batch experiments were carried out to study the adsorption isotherm and kinetics at at 20°C and pH 6 with the initial concentration of 20-200 mg/L and the solution pH of 6.0. It showed that the adsorption isotherm for MB onto Fe-GAC followed Langmuir isotherm, yielding maximum monolayer adsorption capacity (qm) of 238.1 ± 0.78 mg/g which is higher than the virgin GAC with qm of 175.4 ± 13.6 mg/g at 20°C and pH 6. The kinetics of adsorption results indicated that pseudo-second order kinetics represented adsorption of MB. The heterogeneous Fenton oxidation of MB in the Fe-GAC showed increasing the H2O2 concentration from 7 to 140 mmol H2O2/mmol MB led to enhancing  the oxidation efficiency of MB in the GAC from 62.6% to 100%, respectively. The half-life of the H2O2 showed the range between 1.4 to 39.4 h depending on the H2O2 concentrations at a fixed iron loading of 6 mg Fe/g GAC. The oxidation of MB in the GAC increased at the higher initial concentration of H2O2 and Fe2+ because of the increased generation of hydroxyl radicals. Further enhancement of oxidation of MB in the Fe-GAC was made by the multiple injection of H2O2 whileminimizing OH radical scavenging often occurring at high concentration of H2O2. The re-adsorptive capacity of the Fe-GAC showed 87-92% over the repeated multiple cycle of adsorption and oxidation of MB indicating effective treatment of MB in wastewater. Further works will include development of diffusion-reaction model and the optimization of the operating conditions over the repeated cycles of adsorption and oxidation.