Preparation of Inorganic Micro-nano Materials by Selfassembly and Their Degradation of Congo Red

Author:Su Ying Chun

Supervisor:han xiao jun


Degree Year:2019





Due to the rapid technological and industrial development,environmental problems become a challenging scientific task all over the world,especially water pollutants.Many technologies have been developed to remove toxic pollutants from water.Among them,adsorption,Fenton-like reaction and photocatalystic have attracted extensive attentions due to their advantages,such as simplicity,and high removal efficiency.Benefit from advancements in micro-nanotechnology,more and more researchers focus on the fabrication of micro-nano materials.The micro-nano materials as adsorbents or catalysts are considered as potential candidates for water treatment.Based on inorganic micro-nano materials,calcium phosphate hollow microspheres,copper hydroxide hollow micro spheres,iron molybdate micro-nanowires and ZnO/Ag-Ag2O flower-like microspheres were prepared by self-assembly method for the adsorption and degradation of organic dye Congo red.The transient salt aqueous solution/ethanol interface was discovered through adding different salt aqueous solution into ethanol.The clear salt aqueous solution/ethanol interface can be observed,which is not conflict with the common phenomenon that ethanol and water are mutually soluble in any proportion.The salt aqueous solution/ethanol interface is a special phenomenon formed under specific conditions.Only with acid ions containing oxygen,the interface can be formed.We hypothesize the hydrogen bonds are fromed between acid ions containing oxygen and water molecules.The salts catch the surrounding water molecules causing a special salt aqueous solution/ethanol interface.Due to the complex interactions among acid ions containing oxygen,water and ethanol,the transient interface is formed.Based on this special and transient interface,an interfacial self-assembly method was proposed for inorganic micro-nano hollow spheres preparation.The calcium carbonate and calcium phosphate hollow microspheres were successfully synthesized by interfacial self-assembly on the transient salt aqueous solution/ethanol interface.The forming processes were recorded to clearly observe the salt aqueous solution/ethanol interface.The interfacical self-assembly carried out at room temperature.The formation of calcium carbonate hollow microspheres took 1.2s,while the formation of calcium phosphate hollow microspheres was only0.3s.The effects of the reactant concentration and dosage,the amount of water,the concentration of salt solution and the stirring time on the morphology and size of hollow microspheres were studied.The calcium phosphate hollow microspheres were used as environmentally friendly,biocompatible and non-toxic adsorbent to remove organic dye Congo red.Inspired by the salt aqueous solution/ethanol interface,the salt aqueous solution/acetone interface was also discovered for the preparation of Cu(OH)2inorganic hollow microspheres.The formation process of Cu(OH)2 hollow microspheres on the salt aqueous solution/acetone interface was clearly observed.The existence of the salt solution/acetone interface was confirmed.Compared with the self-assembly at the salt aqueous solution/acetone interface,the self-assembly reaction at the salt aqueous solution/ethanol interface was slower.It took 2 s,which is about three times of time to form the hollow spheres at the CuSO4 aqueous solution/ethanol interface(0.6 s).With the addition of Cu(OH)2 inorganic hollow microspheres,the degradation efficiency was improved by 92.92%.Cu(OH)2inorganic hollow microspheres can be used as adsorbent and catalyst for Fenton-like degradation for Congo red.By using self-assembly at room temperature and hydrothermal method,the different morphologies of ferric molybdate,including micro-nanowires,bowknot-like microstructures,and urchin-like microstructures,were controlled by reaction temperature and reactants concentration.The room temperature self-assembly method is very simple and suitable for industrial mass production.The ferric molybdate micro-nanowires were used as adsorbents and Fenton-like catalysts to remove Congo red.The degradation capacity for 250 mg/L Congo red was up to 231.41 mg/g(92.56%removal),which showed their excellent degradation ability at high dye concentrations.The ferric molybdate micro-nanowires exhibited great potential for organic pollutant removal.Zn(OH)1.68(SO4)0.16·0.58H2O hollow microspheres were synthesized through interface self-assembly using ZnSO4 solution/ethanol interface combining with ostwald ripening process.Nanosheets were grown on the surface of Zn(OH)1.68(SO4)0.16·0.58H2O hollow microspheres through ostwald ripening at room temperature.Three-dimensional(3D)pompon-like Zn(OH)1.68(SO4)0.16·0.58H2O hollow microspheres were formed.The method reduced both the processing temperature and reaction time compared with conventional ripening,which reduced production cost and simplified production condition.After thermal treatments,the3D pompon-like ZnO microspheres were prepared.3D pompon-like ZnO microspheres were decorated with Ag-Ag2O nanoparticles by the reduction of silver nitrate.Coupling with Ag-Ag2O nanoparticles,the adsorption and photocatalytic activity of 3D pompon-like ZnO microspheres for Congo red was enhanced.The degradation efficiency of Congo red and methylene blue was increased by 13.07 and17.52%respectively.The total organic carbon removal efficiency of methylene blue by ZnO/Ag-Ag2O was 94.28%.The pompon-like ZnO/Ag-Ag2O microspheres may find great application in organic pollutant treatments.