Studies On The Synthesis And Adsorption Properties Of Porous Mgo And Mg-Al Composite Oxide

Due to its special structure morphology, surface properties, hollow porous metaloxide showed a great applications in catalysis, adsorption and separation, medicine,functional additives and other areas, especially in adsorption. In this paper, a series ofporous magnesium oxide and magnesium aluminum composite oxides with differentmorphologies and structure were prepared with controllable preparation method. Theadsorption capacities of the samples were evaluated by adsorbing pollutants in water(anionic azo dyes golden orange, hexavalent chromium) and the greenhouse gascarbon dioxide.1Hollow porous magnesium oxide materials with cubic structure werepreparaed by hydrothermal method with magnesium as magnesium source, ureaprecipitant, sodium polyacrylate (PAAS) as template. The structural characteristicsof the sample phase composition, morphology, textural properties, basic sites andits adsorption of AO7were measured by XRD, SEM, TEM, FT-IR, N2-adsorptiondesorption, CO2-TPD and UV spectrophotometer testing methods. Within3hadsorption on MgO samples towards AO7reach adsorption equilibrium, second-orderequation and langmuir isotherm model can well describe the adsorption process. Theexperimental results indicate that the MgO cubes exhibited much more favorableadsorption properties than the sample prepared without PAAS and the commercialMgO. The maximum adsorption capacities of MgO cubes towards AO7and CO2reached3388mg/g and315.6μmol/g, respectively. It was much higher than the othertwo samples. Furthermore, the MgO cubes an be easily regenerated by calcinationprocess. After four recycling process, the adsorption capacity can keep90%of thefirst time.(2) A series of hierarchical porous calcined Mg-Al Layered Double Hydroxides(LDOs) were prepared by hydrothermal homogeneous precipitation and followedcalcination method using magnesium nitrate as magnesium source, aluminum nitrateas aluminum source, urea as precipitation agent, P123, F127and PAAS as the Structure Directing Agents (SDAs). The phase structure, morphology, texturalproperties and adsorption performance towards Cr(VI) of the as-prepared sampleswere comparatively characterized and measured by XRD, SEM, N2-adsorptiondesorption, CO2-adsorption and UV spectrophotometer testing methods. It wasfound that the microscale Mg-Al LDO with coexisted spheroid and rod-like structureusing P123as the SDA has a specific surface area of131.8m2/g, pore volume of0.31cm3/g and average pore size of9.6nm, CO2adsorption capacity can reach0.793mmol/g and Cr(VI) adsorption capacity can reach46.5mg/g under certainconditions. The adsorption process matchs the pseudo-second-order kinetic modelwell. The as-prepared Mg-Al LDO has good recyclable adsorption property, and thushas the potential to be used in the removal of Cr(VI) from wastewater.(3) A series of Mg-Al composite oxide were prepared by hydrothermal-roastingmethod using magnesium nitrate and aluminum nitrate as metal salts, ammonia asprecipitant. By loading tetraethylenepentamine to prepare amino load Mg-Alhydrotalcite. The phase structure, morphology, textural properties and adsorptionperformance towards Cr(VI) of the as-prepared samples were comparativelycharacterized and measured by XRD, SEM, N2-adsorption desorption,FT-IR, CO2-adsorption and UV spectrophotometer testing methods. The results showed that thestructure of Mg-Al composite oxide change into a bi-metal layered structure afterloading amino. The morphology of amino lord samples did not change significantly,the specific surface area, pore volume, pore size are smaller compare with theMg-Al composite oxide, but the CO2and Cr(VI) adsorption capacity has greatlyimproved, the adsorption capacity were reached0.52mmol/g and35.49mg/g, theywere increased by271%and43%, respectively.