Removal Of Arsenic From Water By Controlled Synthesis Alpha Fe₂O₃ With Specific Crystal Facet

The treatment of arsenic pollution in groundwater is a global environmental problem,which is widespread and has a great impact on human health.Fe₂O₃ is widely present in nature and has a good arsenic adsorption effect.It is an excellent arsenic removal material.Because the exposure of Fe₂O₃ to different surfaces will affect its related properties,it is of great significance to study the effects of Fe₂O₃ on different surfaces on adsorption and photocatalytic removal of arsenic.In this paper,hydrothermal method is used to synthesizeα-Fe₂O₃ with{001}facet,{104}facet,and{113}facet.The adsorption and photocatalytic experiments of arsenic ions with three kinds of synthesizedα-Fe₂O₃ were used to determine the effect of the surface ofα-Fe₂O₃ on the arsenic removal performance,and the performance was compared with that of commercialα-Fe₂O₃.The XRD test results show that the Fe₂O₃ synthesized by hydrothermal reaction isα-Fe₂O₃.The SEM test shows that the synthesizedα-Fe₂O₃ exposes the{001}facet,{104}facet,and{113}facet,respectively,and the morphology is clear and distributed.The BET test results show that the specific surface area of the{001},{104},and{113}α-Fe₂O₃ is 13.0 m²/g,6.8 m²/g,and 4.6 m²/g,respectively.According to the adsorption kinetics experiment,all three kinds ofα-Fe₂O₃ conform to the pseudo-second-order kinetic model,indicating that there are common electron pairs or electron exchanges during the adsorption of arsenic ions.According to the adsorption thermodynamic experiment,the adsorption process of arsenic ions by three kinds ofα-Fe₂O₃conforms to the Langmuir model,indicating that the adsorption process of arsenic ions is single-layer adsorption rather than multi-layer adsorption,and the adsorption is dynamic equilibrium.Combining the adsorption kinetics and adsorption thermodynamic experiment results,the adsorption capacity ofα-Fe₂O₃ to As（V）is stronger than that of As（III）,and it is more conducive to the adsorption of As（V）under acidic conditions.At the same time,at p H=7,the equilibrium adsorption capacity ofα-Fe₂O₃ is{001}>{104}>commercial>{113}.It is worth mentioning that the equilibrium adsorption capacity of{001}α-Fe₂O₃ is about 3 times that of commercialα-Fe₂O₃.According to the experiment of arsenic removal,the first adsorption and then catalytic,the catalytic removal ability of As（III）under neutral conditions is ranked as follows:{113}>{104}>{001}>commercial,and the catalytic effect ofα-Fe₂O₃ on{001},{104}and{113}facets is affected by p H values.The catalytic effect is relatively good under neutral conditions and relatively weak under alkaline conditions.Comparative experiments were performed successively and simultaneously through adsorption and catalysis processes.Under acidic and alkaline conditions,the{001}and{104}α-Fe₂O₃ catalyzed the removal of arsenic has been improved,but the improved effect still lower than the under neutral conditions one,indicating that after the dark adsorption of As（III）,it will hinder the first-step reaction that affects the Fe₂O₃ catalytic arsenic removal,and the photochemical corrosion of Fe₂O₃ is partially hindered to affect the next photocatalytic oxidation.Simultaneous adsorption catalysis can alleviate this effect to some extent.The{113}α-Fe₂O₃ is less affected by this.Through the determination of iron ion concentration,it was found that the three kinds ofα-Fe₂O₃ are more prone to photochemical corrosion under acidity,and the iron ion concentration after catalysis still lower than the sanitary standards for drinking water.