Preparation Of Iron Oxide/Bentonite And Their Fenton Reaction Degradate Orange ?

Dye wastewater has high chromaticity, high toxicity, large emissions and complex components, the conventional wastewater treatment methods are difficult to degrade dye wastewater. Heterogeneous Fenton reaction system has wide treatment range, speed reaction, and effective degradation rate for organic waste water while avoid secondary pollution.With FeOOH/bentonite as the base material, ?-Fe2O3/bentonite catalyst was prepared by roasting method, and Fe3O4/bentonite catalyst was prepared by hydrogen atmosphere reduction method. ?-Fe2O3/bentonite catalyst and Fe3O4/bentonite catalyst were used for removal orange II dye in solution respectively, studying the catalytic activity and determining the best preparation technology of the two catalysts. The two catalysts were characterized by SEM, EDS and XRD for investigating its structure characteristics.Then mechanical activation method was used to activate the catalytic activity of FeOOH/bentonite catalyst, ?-Fe2O3/bentonite catalyst and Fe304/bentonite catalyst, determining the effect of mechanical activation on catalytic activity of the three catalytic. The study can provide important reference for the preparation of composite materials by deep processing of bentonite. The obtained technology can provided theoretical basis of develop new type of high efficiency and stable bentonite-based heterogeneous catalyst, and degradation of actual dyeing wastewater. The results of the study were as follows:(1) The optimum process conditions for preparation of ?-Fe2O3/bentonite by roasting method were as follows:[OH-]/[Fe3+]=1.5:1, Fe/bentonite=5 mmol�g-1, roasting temperature 500?, and roasting time 2 h. ?-Fe2O3/bentonite prepared by roasting method had good Fenton-like catalytic activity. The removal rate of 40 mg�L-1 of Orange II reached 95.5% under the conditions of reaction temperature 30?, ?-Fe2O3/bentonite catalyst dosage 0.2 g�L-1, H2O2 dosage 19.6 mmol�g-1, solution pH 3, and reaction time 5 h.The ?-Fe2O3/bentonite catalyst showed good stability and low iron leaching amount. The removal rate of Orange ? is higher than 88% and the total iron ion concentration in reaction solution is lower than 0.4 mg�L-1 at the end of each recycling experiment.Iron compounds were effectively immobilized on bentonite and converted to ?-Fe2O3 by hydrogen reduction during preparation process, and prepared ?-Fe2O3/bentonite was a catalytic composite material with decentralized structure, obvious pores and excellent morphology.(2) The optimum process conditions for preparation of Fe3O4/bentonite by hydrogen atmosphere reduction method were as follows:[OH-]/[Fe3+]=1:1, Fe/bentonite=10 mmol�g-1, reduction temperature 200?, and reduction time 30 min. Fe3O4/bentonite prepared by hydrogen atmosphere reduction method had good Fenton-like catalytic activity, stability and magnetic separation performance. The removal rate of 40 mg�L-1 of Orange II reached 96.9% under the conditions of reaction temperature 30?, Fe3O4/bentonite catalyst dosage 0.2 g�L-1, H2O2 dosage 19.6 mmol�g-1, solution pH 3, and reaction time 1 h. Iron compounds were effectively immobilized on bentonite and converted to Fe3O4 by hydrogen reduction during preparation process, and prepared Fe3O4/bentonite was a catalytic composite material with decentralized structure, obvious pores and excellent morphology.The optimum process conditions for using Fe3O4/bentonite by hydrogen atmosphere reduction method to degrade the Orange II were as follows:the degradation rate of 40 mg�L-1 of Orange ? reached 98.1% under the conditions of reaction temperature 30?, Fe3O4/bentonite catalyst dosage 0.4g �L-1, H2O2 dosage 10 mmol�g-1, solution pH 3, and reaction time 1 h. The Fe3O4/bentonite catalyst showed good stability and low iron leaching amount. The removal rate of Orange ? is higher than 95% and the total iron ion concentration in reaction solution is lower than 1.4 mg�L-1 at the end of each recycling experiment.(3) Mechanical activation method can improve the catalytic activity of FeOOH/bentonite catalyst. The optimum preparation conditions of FeOOH/bentonite catalyst by mechanical activation are as follows:using 15 mL stainless steel ball(?=10mm) mix with 15 mL stainless steel ball(0=6mm) as milling media, the media filling rate was 30%,0.5 g FeOOH/bentonite catalyst start to mechanical activate in frequency of 20 Hz in 40 min. In the experimental conditions as catalyst dosage of 0.2 g�L-1, pH3.0, reaction temperature 30?, H2O2 dosage of 19.6 mmol�g-1, reaction time 2 h, the FeOOH/bentonite catalyst which mechanical activate by the optimal conditions removal of Orange II from 26.3% to 92.3%. The FeOOH/bentonite catalyst by mechanical activation showed good stability and low iron leaching amount. The removal rate of Orange II is higher than 84% and the total iron ion concentration in reaction solution is lower than 1.2 mg�L-1 at the end of each recycling experiment.Mechanical activation method can improve the catalytic activity of ?-Fe2O3/bentonite catalyst. The optimum preparation conditions of ?-Fe2O3/bentonite catalyst by mechanical activation are as follows:using 15 mL stainless steel ball(?=10 mm) mix with 15 mL stainless steel ball(?=6 mm) as milling media, the media filling rate was 30%,0.5g ?-Fe2O3/bentonite catalyst start to mechanical activate in frequency of 20 Hz in 60 min. In the experimental conditions as catalyst dosage of 0.2 g�L-1, pH3.0, reaction temperature 30?, H2O2 dosage of 19.6 mmol�g-1, reaction time 1 h, the ?-Fe2O3/bentonite catalyst which mechanical activate by the optimal conditions removal of Orange II from 14.5% to 93.6%. The ?-Fe2O3/bentonite catalyst by mechanical activation showed good stability and low iron leaching amount. The removal rate of Orange II is higher than 88% and the total iron ion concentration in reaction solution is lower than 0.7 mg�L-1 at the end of each recycling experiment.The catalytic activity of Fe3O4/bentonite catalyst by mechanical activation showed a gradual downward trend with the extension of mechanical activation time. The comparison result was as follows:using FeOOH/bentonite as raw materials, we can obtain iron oxide/bentonite Fenton-like catalyst which has higher catalytic activity and stability by combine roasting and mechanical activation.