Study On Structure Modulation And Adsorption Performance Of Manganese/ Iron Oxide Based Materials

Adsorption technology applied in pollution treatment is more and more extensive with the aggravation of environmental pollution.Asorption process has the advantages of easy operation and low cost,and the key to its development and application is to develop efficient adsorbents.Therefore,the study of the structure-activity relationship between the adsorbent structure and the adsorption process will provide important the-oretical basis for the design and preparation of efficient adsorbents.In this work,the pore structure and chemical structure regulation of iron and manganese oxides,which are rich in reserves in the earth's crust,including the construction of micro-mesoporous structure,electron spin structure regulation,the synthesis and atomically dispersion of amorphous chemical structure oxide adsorbent,and their effects on the the adsorption properties to typical pollutants such as organic dyes,antibiotics and toxic metal ion,are systematically studied.Firstly,for the construction of micro-mesoporous composite structure,birnessite nanoparticles with ultra-short microporous structure were synthesized using the method of permanganate reduction at room temperature.The short microporous structure plays a key role in reducing the internal diffusion resistance and improving the exposure de-gree of adsorption sites.The adsorption capacity of the short microporous hydrolusite to metal ions increases by 2.15 times and 1.84 times,and the adsorption rate constant increases by two orders of magnitude comparing with the long microporous nanorods and nanoflakes.Meanwhile,abundant micro mesoporous structures were introduced into the nanospheres assembled by iron oxide nanosheet by the thermal-driven topolog-ical phase transformation,and the adsorption capacity increases by 2.7 times,and the adsorption rate constant increases by 2.5 times.These results show that the construction of micro-mesoporous composite structure can effectively improve the adsorption rate and capacity of the adsorbent.The mechanism of spin state transition and its influence on adsorption process were studied by regulating the spin state quantum chemical structure of metal oxides.Supported iron oxide in quantum size was synthesized through the limited space con-structed by titania quantum dots and mesoporous molecular sieves.DFT theoretical calculation and experimental results reveal the mechanism of the interaction between molecular sieve carrier and oxide on the transition of iron oxide from high spin to low spin.The electron transferring from the low spin iron oxide toe molecular sieves gives the strong positive charge surface to the adsorbent,and the interaction between the low spin iron ion and the anion is greatly strengthened.Their synergistic effect improves the adsorption ability to anionic dyes,antibiotics and arsenates,thus the adsorption rate of low-spin iron oxide is more than two orders of magnitude higher than that of ordinary iron oxide and commercial activated carbon,the adsorption capacity is more than 8times of that of commercial activated carbon,and the removal rate of pollutants in ac-tual wastewater is more than 95%.The enhanced adsorption ability to pollutants was realized through the regulation of oxide crystal chemical structure.The hyperdispersed amorphous manganese oxide adsorbent was synthesized by enhancing the interaction between the precursor and the support.By using hydrophilic molecular sieve and amphiphilic carbon black as carrier growing amorphous manganese oxide adsorbent,the residual concentration of heavy metal ions in water can reach the national standard(GB 25466-2010)after adsorption treatment,and the effective removal of low concentration metal ions,soluble water and acid substances in fuel oil was realized with removal efficiency higher than 90%.Fur-thermore,the atom level dispersion of hydroxyl iron oxide on the surface of molecular sieve was realized through the precise control of the loading amount,and it shows high selective adsorption ability to lead ions.The adsorption capacity reaches higher than1000 mg g^-1,and the selection coefficient is three orders of magnitude higher than the naormal iron oxide and iron hydroxide.These results show that the design of fine chem-ical structure is an effective way to improve the adsorption selectivity,and provides a new strategy for the development of functional adsorption materials.