The Application Of Etched Ti₃AlC₂-Based Materials In The Sorption Of Environmental Pollutants

In recent years,with the rapid development of industrialization,heavy metal ions and radionuclides inevitably released into environmental media.There is no doubt that the release of heavy metal ions and radionuclides is seriously threaten to the public health and ecosystem stability.The microstructure and chemical species of these pollution ions are related to their migration transformation and biological toxicity.Therefore,the investigation on the interface using the simple adsorption method was beneficial for research migration regularity of contaminalt in the environment.During the past decades,adsorbent materials and performance have undergone great process.On the basis of the previous study,the science researcher constant to synthesis high-performance environmental-friendly adsorbent materials,and explore how to reveal the interaction mechanism between pollutants molecules and adsorbents at the molecular level by using theoretical model calculation.Since the discovery of two-dimensional(2D)graphene in 2004,graphene has aroused interdisciplinary attention and research highlights due to its outstanding properties.The 2D materials endow unprecedented physical,electronic,chemical,and optical properties.Recently,a new and growing family of two-dimensional(2D)transition-metal carbides,nitrides,and carbonitrides(MXene)was discovered and reported by scientists.Benifited from the unique electronic and structural properties,Mxene has attracted more and more attention.As an important and new generation of nanomaterials,Mxenes become one of most important systems of energy and environmental catalysis.In recent years,Mxene-based materials have also gradually emerged in the wastewater treatment field.However,the lack of functional groups and the high toxicity of procedures involving fluoride to the environment somehow restricts itsscope of potential applications.Additional,to the best of our knowledge,the related studies using theoretical calculation are rarely found in the literature.It is very difficult to make theoretical guidance for the further design and synthesis of high-performance materials in environmental pollution cleanup.In view of the above shortcomings and limitations,with several representative Ti3AlC2-based nanoadsorbents as example,we have done some works on the preparation of functionalized Mxenes nano-adsorbent with high stability and abundant functional groups using fluoride-free method,and have made some evaluations in the physicochemical behavior of pollutants in environmental system.(1)Construction of LDH functionalized ultrathin mxene nanosheets for the selective adsorption of U(Ⅵ)and Eu(Ⅲ).In order to overcome the defects of the application of ultrathin Mxene in the removal of radionuclides,we investigated the application of LDH functionalized ultrathin Mxene composites in the selective adsorption of radionuclides.A major challenge for radionuclide nuclide adsoprtion via multilayer Mxene material results from its very narrow interlayer space(less than 2 A),which greatly hindered the accessibility of radionuclides with large hydrated ion radii.Considering the strong vander Waals forces of interlayers,delamination of multilayered mxene into super thin nanoflakes using organic intercalated method was a feasibility strategy,which may lead to the larger specific surface,less layer Mxene interlayer spacing.However,the stability of the thin layer nano-sheet will be greatly reduced in the presence of water and dissolved oxygen.To some extent,once the high surface area is combined with plentiful oxygen-containing functional groups of these LDHs,and the highly stability of LDH functionalized ultrathin nanosheet was successful synthesized,which overcomes the limitation of poor stability and less surface functional groups.Finally,M-LDH was further applied as a high efficiency and the highly selective adsorption of radionuclides.(2)Experimental and theoretical calculation investigation on efficient Pb(II)adsorption on etched Ti3AlO2 nanofibers and nanosheets.The last research work was devoted to the design of functional Mxene materials with the purposes of solving the limitations of poor stability,low specific surface area and few functional groups.Compared with the traditional hydrofluoride acid etching method,an effective fluoride-free method towards the synthesis of a well ayered structured and functionalized Ti3AlC2 is technologically important for wastewater purification.On the basis of the previous investigation,we further realize the controllable synthesis of TibAlC2 based nano-adsorbent using the fluorine-free method.By varying the NaOH concentration,the different morphologies(nanofibers and nanosheets)etched TI3AIC2 samples are obtained.In consideration of the pemiciousness of Pb(Ⅱ)ions,the adsorption ability of the etched TH3AIC2 nanomaterials were evaluate.In particular,the XPS analysis revealed the underlying interaction mechanism with Pb(Ⅱ).which was mainly dominated by outer-sphere surface complexation and cation exchange.More importantly,the DFT calculations further verified that the feasibility of the functional etched-Ti3AlC2 materials for environmental pollution clean-up.(3)On the basis of the the last chapter research,we further prepared two-dimensional TisAlCi-derived titanate nanocomposites by simple oxidation and alkalization with TAC as the precursor from the perspective of fluorine-free preparation and the introduction of more oxygen-containing functional groups.The urchin-like T-NTO nanofibers and kelp-like T-KTO nanosheets were successfully prepared by varing the alkali source and were confirmed as effective adsorbents for Pb(II)removal.The obtained products were characterized by infrared,Raman and XPS characterization.The adsorption behavior of Pb(Ⅱ)on Ti3AlC2 derived titanate was explored by the batch experiment.At pH=5.0 and 298 K,the maximum adsorption capacities of T-NTO and T-KTO for Pb(Ⅱ)were 328.9mg/g and 248.3mg/g,respectively.In summary,combination of FT-IR、Raman and XPS analysis,the possible mechanism was well elaborated.More importantly,the resulting T-NTO nanofibers showed a superior potential for Pb(Ⅱ)adsorption due to its higher specific surface area and stronger ion exchange capacity.Herein,the multiple advantages,including fluoride-free methodology and high adsorption capacities,clearly identify MAX@titanate as a promising candidate for Pb(Ⅱ)remediation.