Controlled Synthesis Of Porous MgO Adroption Materials And Their Adsorption Behavior

How to effectively remove the organic dyes and heavy metal ions in the sewage has become one of the efforts of the researchers.Traditional adsorbent materials have many common problems such as low specific surface area,low saturated adsorption capacity and slow adsorption rate.Therefore,it is important to prepare adsorbent with high specific surface area,high saturated adsorption capacity and fast adsorption rate.In this paper,the spray drying method and the template method are used to prepare MgO adsorbents with large surface area and high saturated adsorption capacity.The nano MgO powder is synthesized via spray drying method.Furthermore,the effects of heat treatment temperature on the morphology,specific surface area and adsorption properties of the spray drying powder are studied.With the increase of heat treatment temperature,the specific surface area of nano Magnesium Oxide decreased,average pore size increase and the adsorption performance decreased.When the heat treatment temperature is 400 ^oC,the pure MgO of the phase is obtained,and its specific surface area is 140.5 m²�g^-1.Nano-MgO powder shows excellent adsorption capacity to Congo red,Pb²⁺and Cd²⁺,and the experimental data feetting the Langmuir adsorption isotherm model and pseudo-second-order adsorption kinetics model.The MgO is obtained with calculated heat treatment temperature in 400 ^oC,which saturated adsorption amount of Conge red,Pb²⁺and Cd²⁺are 1480 mg�g^-1,5211 mg�g^-1,2419 mg�g^-1respectively.The prepared nano MgO shows good regeneration performance for the adsorption of Congo red.After 5 cycles,the removal efficiency for Congo red is 84%.Study on the adsorption mechanism of nano MgO to Congo red,Pb²⁺and Cd²⁺.Conge red adsorption is mainly based on electrostatic attraction between?SO₃^-and MgO?OH₂⁺,while Pb²⁺and Cd²⁺adsorption is due to electrostatic attraction and ion exchange mechanism.The ion exchange is due to the substitution of Pb²⁺and Cd²⁺in the solution for the Mg²⁺in the MgO lattice.The ordered mesoporous MgO material is prepared with three block copolymer F127 as a template.The effects of aging time,relative humidity,and magnesium content on its order,pore size and specific surface area are systematically studied.When the aging time is less than 24 h,the ordered mesoporous structure can not be formed,but with the increase of magnesium content,the specific surface area of the ordered mesoporous is reduced and the pore size increases.The ordered mesoporous MgO were obtained on the conditation that relative humidity is 40%RH,nitrate content is 0.4 g,aging time is 36 h.The prepared MgO exhibit high specific surface area(382.5 m²�g^-1),the average pore size is 3.8 nm,pore volume is 0.37cm³�g^-1.The saturated adsorption of ordered mesoporous MgO for Congo red,Pb²⁺and Cd²⁺are 3004.6 mg�g^-1,3073.5 mg�g^-1 and 1485.1 mg�g^-1,respectively.The resol can interact with the PEO segments of F127 templates by hydrogen-bonding interactions and associate with inorganic Mg²⁺species by chelating,the PEO domains are decorated by resol and Mg²⁺species,forming cylindrical core�shell micelles with F127microdomains covered by the resol/Mg²⁺composites.Moreover,with the evaporation of solvents,the curvature decreases,and the micellar shrinkage and self-assembly form orderly arrangement materical.In nitrogen atmosphere,template agents are removed and on the oxide atmosphere,carben was removed to formed ordered mesopores MgO.