Fabrication Of Green Mesoporous FeOOH/?-Al₂O₃ Composite Spherical Particles And Their Adsorption Of Hazards From Aqueous Solutions

The safety of drinking water was focused by people all over the world.In the past several years,some typical geochemistry diseases,resulted from the hazards in groundwater and surface water,occurred in many countries and regions?e.g.USA,India,Chili and China?,especially for the people who live in the remote countries of developing nations.In order to remove the hazards from water,various methods have been developed,and the adsorption as an advanced method for treating contaminated water,has been applied popularly due to its simple and economic natrues for households and small village.The absorbent plays a key role to treat the contaminated water.On the basis of the properities of active alumina and nanoscale iron oxides,we try to develop a composite absorbent,mesoporous FeOOH/?-Al₂O₃ composite spheres,to remove the harmful elements?e.g.fluoride,arsenate and Congo red?.The main contents of this dissertation were followed.?1?Mesoporous?-alumina spheres were obtained by calcining alumina gel at 600?for 2 h,which was prepared by sol-gel and oil-drop technologies with the raw material aluminum isopropoxide and the soft template regent F127 which was induced to control the porous microstructure of alumina.?2?Mesoporous?-Al₂O₃ spheres loaded nanoscale FeOOH were fabracited.After the as-prepared spherical alumina particles were soaked in the ferrous sulfate solution for 5 h,then iron ion was reduced by sodium borohydride aqueous solution,alumina spheres loaden nanoscale iron were separated and dried on vaccum oven.?3?The as-prepared mesoporous FeOOH/?-Al₂O₃ composite spheres were applied to remove the hazards?e.g.fluoride,arsenate and Congo red?in water.?4?The morphology and microstructure,texture natures,crystal structure and the chemistry contents of as-prepared absorbents were characterized and determined by scan electron microscopy?SEM?,transmission electron microscopy?TEM?,surface area analyzer,X-ray diffraction?XRD?,inductive couple plasma?ICP?,respectively.The mainly results and innovation points were obtained.?1?Mesoporous?-Al₂O₃ spheres were obtained.Firstly,the press process of alumina sol through oil column was analyzed and the surface tensions were determined by surface area analyzer,we found the kerosene was contributed to form spherical alumina gel.Secondly,the pH value of solution and the induced regent affected the formation of spherical alumina.Finally,the calcining temperature affected texture natures of spherical alumina,and the phase transformation of alumina was explained.So,the option was obtained?oil kerosene,pH 1.5-1.8,1.37 mol/L aluminum isopropoxide,heat treatment at 600?2h?,and the mesoporous?-Al₂O₃spheres were prepared with the mean diameter,pore diameter and special surface area,¹.5 mm,11.99 nm,192.6 m²/g,respectively.?2?Mesoporous FeOOH/?-Al₂O₃ composite spherical particles were prepared.The as-prepared?-Al₂O₃ beads were soaked in ferrous sulfate aqueous solution,and iron ions were reduced by sodium borohydride.Then the?-Al₂O₃ beads landed nanoscale iron were separated and dried in the vaccum oven at 75?.Finally,mesoporous Fe OOH/?-Al₂O₃ composite spheres were obtained.And as-prepared FeOOH/?-Al₂O₃ spherical particles with the mean diameter,pore diameter and special surface area,¹.5 mm,10.32 nm,207.6 m²/g,respectively,were characterized by SEM,TEM,XRD,XPS,and surface area analyzer.?3?Mesoporous FeOOH/?-Al₂O₃ revealed more advanced capacity to defluoride than mesoporous?-Al₂O₃ spheres.At 25?,the adsorbing equilibrium of fluoride?10mg/L?was obtained for 120 min with the residual fluoride 0.94 mg/L which is lower than the guided value by World Health Organization?WHO?,and it reached 93%removal rate on fluoride.It might not only enhance defluoride rate,but also progress the defluoride capacity.After performing some experiments,we found that the suitable pH was 6.0-7.0.Meanwhile,the results on adsorbing equilibrium of different fluoride concentrations were modeled by different models which were valued by regression coefficient?R²?,and the Languir model was suitable to explain the isotherm equilibrium,the most uptake amount is 27.8 mg/g.At the same time,the pseudo second order model could be used to describe the kinetic process of defluoride,and adsorption of fluoride could be explained by a proton shifting mechanism.?4?Mesoporous FeOOH/?-Al₂O₃ composite spheres revealed more advanced capacity to remove arsenate than mesoporous?-Al₂O₃ spheres.At 10?,the adsorbing equilibrium of arsenate?10 mg/L?was obtained for 90 min without the residual arsenate which is lower than the guided value by World Health Organization?WHO?.It might not only enhance the removal rate of arsenate,but also progress the removal capacity of arsenate.After performing some experiments,the composites revealed high removal rate of arsenate at wide pH range?from 3.0 to 10.0?.Meanwhile,the results on adsorbing equilibrium of different arsenate concentration were modeled by different models,which were valued by regression coefficient?R²?,and the Freundlich model was suitable to explain the isotherm equilibrium.At the same time,the adsorbing arsenic from water on meoporous FeOOH/?-Al₂O₃ composite spheres is a spontaneous exothermal process,the pseudo second order model could be used to describe the kinetic process of removal of arsenate,and adsorption of arsenate could be explained by a proton shifting mechanism.?5?Mesoporous FeOOH/?-Al₂O₃ composite spheres revealed more advanced capacity to Congo red than mesoporous?-Al₂O₃ spheres.At 35?,the adsorbing equilibrium of congo red?10 mg/L?was obtained for 90 min and it reached 99%removal rate on Congo red.It might not only enhance the Congo red rate,but also progress the removal capacity of Congo red.After performing some experiments,the asprepared mesoporous composite spheres revealed high removal rate of Congo red at pH 6.2.Meanwhile,the results on adsorbing equilibrium of different Congo red concentration were modeled by different models,which were valued by regression coefficient?R²?,and the Frundlich model and the intraparticle diffusion model were suitable to explain the isotherm equilibrium that showed the adsorption progress was complicated.At the same time,the adsorbing Congo red from water on the mesoporous FeOOH/?-Al₂O₃ composite spheres is a spontaneous exothermal process,the pseudo second order model could be used to describe the kinetic process of removal of Congo red,and adsorption of Congo red could be explained by a proton shifting mechanism.?6?Mesoporous FeOOH/?-Al₂O₃ composite spheres with adsorbing selectivity could remove the negative ions which include inorganic compound?fluoride,arsenate?and organic compound?Congo red?.The second pollution for drinking water is elimillated because of the large sizes and the availability for the recycle of mesoporous FeOOH/?-Al₂O₃ composite spheres.