Abstract
Introduction: Heterogeneous Fenton is one of the Advanced Oxidation Processes (AOPs) and has been proven to be effective on azo dye degradation. However, a low-cost catalyst and factors affecting the processes of this system were further investigated.
 Methods: In this study, pellets of iron alumina pillared bentonite (PFeAPB) were prepared by dispersing iron ions on alumina pillared bentonite pellet. Catalyst activity and lifetime were investigated via efficiencies of Methyl Orange (MO) decolorization and Chemical Oxygen Demand (COD) removal, a typical dye type of textile wastewater. Characteristics of the PFeAPB catalyst were examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, and X-ray fluorescence (XRF).
 Results: Results of batch experiments showed that specific surface area of the PFeAPB catalyst was 111.22 m2/g higher than its precursor by 2 times (57.79 m2/g). Goethite, Hematite and Maghemite phases with approximately 11.5% of iron elements containing in the catalyst were detected via XRD and XRF. Experimental conditions of pH, initial MO solution, Hydrogen Peroxide concentration, reaction time and catalyst loading were 2.0 ± 0.1, 12.7 mmol/L, 150 min and 20 g/L, respectively, to achieve 88.68 ± 5.69% of MO decolorization and 50.27 ± 6.05% of COD removal while dissolved iron in this heterogeneous Fenton process was below standard limit (2 ppm). Catalyst activity decreased by 5.22% in decolorization efficiency after the two first reusages.
 Conclusion: These primary results showed the potential of applying PFeAPB catalyst in heterogeneous Fenton process with low iron leaching into water.
Highlights
Heterogeneous Fenton is one of the Advanced Oxidation Processes (AOPs) and has been proven to be effective on azo dye degradation
Experimental conditions of pH, initial Methyl Orange (MO) solution, Hydrogen Peroxide concentration, reaction time and catalyst loading were 2.0 ± 0.1, 12.7 mmol/L, 150 min and 20 g/L, respectively, to achieve 88.68 ± 5.69% of MO decolorization and 50.27 ± 6.05% of Chemical Oxygen Demand (COD) removal while dissolved iron in this heterogeneous Fenton process was below standard limit (2 ppm)
The results showed that increasing time from 15 to 180 minutes led to enhanced decolorization efficiency of MO from 2.09±0.66% to 75.23±5.35%, respectively, and in a sequence of H2O2
Summary
Heterogeneous Fenton is one of the Advanced Oxidation Processes (AOPs) and has been proven to be effective on azo dye degradation. Homogeneous Fenton processes are commonly applied to treat textile wastewater These processes still have some disadvantages of iron treatment, sludge, and strict operation under acidic condition. Heterogeneous Fenton processes have been introduced to overcome disadvantages of homogeneous Fenton processes These processes apply iron catalysts which are immobilized on the surface of the adsorbent and combined with hydrogen peroxide (H2O2) to generate hydroxyl radicals (·OH) 1,2, possibly minimizing iron leaching into water and operating under less acidic condition, enabling the catalyst to be reused and recycled. Specific surface area of bentonite clay can be increased by intercalating inorganic/organic cations into expandable clay layers (so-called cation pillared bentonite) They are fabricated by cation exchange with polyoxycations of silica-alumina layers, calcinated 5,6. Alumina pillared bentonite may be used as a good supporter to be impregnated with irons which are active sites of heterogenous Fenton catalysts
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