Design And Synthesis Of Hierarchical Transition Metal Oxides For Fluoride Elimination

Fluoride pollution has become an environmental issue of worldwide concern.Adsorption is considered the most cost-effective and environmentally friendly method for removing additional fluoride.However,low adsorption capacity and long adsorption equilibrium time limit the practical application of many adsorbents.Hierarchical transition metal oxides can provide abundant active sites for fluoride removal owing to their large specific surface area and porous structure.At the same time,metal oxides with a high-affinity element for fluoride can improve adsorption performance and selectivity.Therefore,the design and synthesis of hierarchical porous metal oxide adsorbents with structural and composition advantages can effectively eliminate fluoride from aqueous solutions.The research contents of this thesis are as follows:1.Herein,novel hierarchical flower-like zinc-magnesium-aluminum ternary metal oxide(CZMA)microspheres were successfully prepared for the first time by a simple-green hydrothermal strategy without any surfactant or template combined with a calcination process and were employed as an adsorbent for adsorptive removal of additional fluoride.The adsorbent was characterized by diverse microscopic,spectroscopic,diffractometric,and thermal analysis techniques.The flower-like microspheres with a mean diameter of 8.74 ?m were assembled by nanosheets with thicknesses of approximately 100 nm.The adsorption property for fluoride on the precursor and the CZMA was analyzed by batch experiments.The results showed that the fluoride uptake behavior of the samples could precisely be fitted by the Langmuir isothermal model,and the maximum adsorption capacity reached up to 84.24 mg/g at 298 K under neutral conditions.The pseudo-second-order model accurately described the adsorption kinetics data.Moreover,the regeneration experiment revealed that the samples have excellent reusability.XPS,FT-IR,and Zeta potential results indicated that the underlying fluoride adsorption mechanism of the samples can be ascribed to ion exchange and electrostatic interactions.Tests of high-fluorinated groundwater in the Kuitun area of Xinjiang demonstrated that the CZMA is an efficient and rapid adsorbent candidate for water purification in environmental remediation.2.Herein,innovative hydrangea-like hierarchical porous zinc-zirconium oxide microspheres(HPZZ)were synthesized through a simple hydrothermal reaction and calcination process for enhanced fluoride adsorption in aqueous solutions.Benefiting from its distinctive structural and component advantages,the newly designed adsorbent delivered superior adsorption performance(107.41 mg/g),which outperformed most reported metal oxide-based adsorbents.Time-dependent experiments discovered that the formation mechanism of the precursor experienced nucleation,growth,self-assembly,and Ostwald ripening.Furthermore,coexisting anions had insignificant effects on the HPZZ.More importantly,the adsorption mechanism between the HPZZ and fluoride could be attributed to electrostatic interactions,complexation,and ion exchange.Interestingly,the exhausted adsorbent could be regenerated for four cycles.A practical application test verified that the HPZZ was a rapid and effective adsorbent for groundwater purification.Therefore,this work brings a novel active material for fluoride decontamination,with the current work providing great significance in environmental restoration.3.In this study,the synthesis of novel hierarchical hollow manganese-magnesium-aluminum ternary metal oxide(MMA)via a simple and green hydrothermal strategy coupled with the calcination process.Combining the advanced structure and functional advantages of strong affinity Mn,Mg,and Al species for fluoride into a hierarchical hollow structure with satisfactory accessible adsorption surface,which could remarkably boost the migration and diffusion of fluoride and provide more mass diffusion pathways for fluoride elimination.Overall findings from universal characterization techniques and batch experiments validated that the potential adsorption mechanisms were electrostatic interactions,complexation,and ion exchange.As such,the present method expands the toolbox for accurate design and synthesis of advanced efficient adsorbent materials for environmental remediation applications.