Silica white was prepared with the method of molten NaOH-carbonation decomposition from the laterite nickel ore,and the content of NiO in the residue reached 2.71%.The results showed that the extraction ratio of SiO2 increased with increasing reaction time and mass ratio of alkali to ore,and with decreasing particle size of the laterite nickel ore.Furthermore,the extraction ratio of SiO2 increased firstly and then decreased with increasing reaction temperature.XRD analysis indicated that the product was amorphous.FT-IR analysis indicated that the product was hydrated silicon dioxide.SEM morphology showed that the product was of uniform particle size with average particle size about 100 nm.The physical and chemical properties of the product conformed with the national standards of chemical industry.
By using industrial sodium silicate solution as raw material,high purity SiO2 powder was successfully synthesized by the split-step carbonation method.The relations between pH value of end point and the removal percentage of impurity at the first carbonation and the purity and yield of product SiO2 powder at the second carbonation were studied.The SiO2 powder was characterized by using XRD,SEM,IR and composition analysis.The results showed that when the pH value of end point at the first carbonation was 10.9,the purity of SiO2 prepared was up to 99.9%.The SiO2 powder synthesized was amorphous with regular sphere shape,uniform size and no reunion.The reaction mechanism was also discussed.
Mono-disperse spherical silicon dioxide was synthesized in 2-propanol-H2O-NH3 system by the ultrasonic hydrothermal method.The catalyst ammonia acted as strong nucleophilic reagent.With orthogonal experiments,the effects of ultrasonic power,reaction temperature,stirring intensity and molar ratio on the size of silicon dioxide were studied.The results indicated that the diameter of silicon dioxide increased greatly with increasing ultrasonic power and molar ratio.The size of silicon dioxide also increased with increasing temperature and stirring intensity,but with a less extent.The process of forming mono-disperse spherical silicon dioxide could be divided into two steps: hydrolysis and condensation,with hydrolysis as the key step.Mono-disperse spherical silicon dioxide was characterized with XRD,TEM,DTA and IR,and the results showed that the sample was noncrystalline with regular shape and uniform granularity and there was a large amount of hydroxyl group in the SiO2 sample.
