Study On The Preparation Of Highly Dispersible Fine Magnesium-aluminum Hydrotalcite By High Gravity Method And Its Adsorption Performance

Using magnesium nitrate and aluminum nitrate as raw materials,the flake-shaped micro-magnesium-aluminum hydrotalcites with uniform particle size distribution and high dispersion were prepared by the high-gravity method.The morphology and particle size distribution of magnesia-aluminum hydrotalcite prepared by traditional hydrothermal synthesis method and high-gravity method were compared.The mechanism of agglomeration between the fine particles of magnesium-aluminum hydrotalcite was analyzed.The influence of isobutanol azeotropic distillation drying process on the dispersibility of the product was investigated.These samples were characterized by SEM,XRD and LPSD（laser particle size distribution analyzer）.The results show that the high-gravity rotating bed can be used to prepare flake-shaped micro-magnesium-aluminum hydrotalcite with complete crystals and uniform particle size distribution,with a particle size of 1.5-2.5μm.Heterogeneous azeotropic distillation can effectively prevent powder agglomeration during the drying process of the fine magnesium-aluminum hydrotalcite,and prepare highly dispersible samples.The greater the speed of the supergravity bed,the greater the centrifugal force generated.As the speed of the supergravity bed increases,the average particle size of the prepared magnesium-aluminum hydrotalcite samples becomes smaller.The dispersant PEG has an obvious dispersing effect on the generated magnesia-aluminum hydrotalcite.When the polymerization degree of PEG increases from 400 to 1000,the average particle size of the magnesia-aluminum hydrotalcite decreases with the increase of the degree of polymerization.When the PEG polymerization degree is greater than 1000,as the PEG polymerization degree increases,the average particle size of the prepared magnesium-aluminum hydrotalcite sample gradually increases.With the increase of the material flow rate,the particle size of the prepared magnesium-aluminum hydrotalcite sample decreases first and then increases.When the material flow rate is 300 m³/h,the reaction material stays in the supergravity field for a long time and has no cycle dead Angle,which is the best reaction condition.At this time,the particle size distribution of the prepared sample is the narrowest.The adsorption of fluoride ions on magnesia-aluminum hydrotalcite and its calcined products prepared by high gravity method and traditional hydrothermal method were studied.The saturated adsorption capacity of SGRB-LDHs,SGRB-LDO,CT-LDHs and CT-LDO for fluoride ion is 35.73 mg/g,107.05 mg/g,23.97 mg/g and96.96 mg/g,respectively.SGRB-LDO shows stronger adsorption capacity for fluoride ions.The optimal adsorption conditions are:temperature is 35℃,dosage is 2.0 g/L,p H value is 8.The adsorption isotherm of F^-by SGRB-LDO conforms to the Langmuir model,and the adsorption kinetics conforms to the quasi-second-order rate model.After SGRB-LDO is recycled for 4 times,the maximum adsorption capacity of fluoride ions is kept above 100 mg/g.It is a reusable and environmentally friendly adsorption material with good performance.The adsorption of uranyl ions on magnesium-aluminum hydrotalcite prepared by high gravity method was studied.The results show that under the conditions of C₀ of 35mg/L,p H=6,t of 120 min,m of 10 mg,and T of 50℃,the adsorption capacity of Mg-Al-LDHs for uranyl ions is 118.57 mg/g.The results show that the prepared Mg-Al hydrotalcite has a good adsorption property for uranyl ions and is a potential adsorption material for the treatment of uranium-containing wastewater.The adsorption process of Mg-Al-LDHs on UO₂²⁺is simulated more accurately by using the pseudo-second-order kinetic equation.The process of Mg-Al-LDHs adsorption of uranyl ions,△H>0,indicates that the adsorption process is an endothermic reaction.△S>0,indicates that the solid-liquid interface disorder increases during the adsorption of UO₂²⁺by the modified grapefruit skin.△G<0,the adsorption process is a spontaneous entropy-dominated process.The adsorption process of uranyl ions by Mg-Al-LDHs can be better described by Langmuir equation and Freundlich equation,but the adsorption process can be described more accurately by Langmuir isotherm adsorption equation.