Synthesis And Characterization Of High Activated Magnesia

Superfine high-active magnesium oxide is a new type of high-functional fine inorganic material. It is an aggregate of nanosized particulates which have a particle diameter of l~2000nm. Due to its ultrafine particulates, MgO with iodine adsorption value of above 120mg/g has special function in the properties of heat, light, electicity, mechanics and chemisty, compared with bulk meterials. Superfine high-active MgO is mainly used in following aspects: accelerator and activator of chlorobutyl, butyl, acrylonitrile-butadiene and fluorine rubber; fillings of sizing agent, plastic, paint and paper; meterials to produce ceramic, enamel, fireproof meterials and MgO cement; antacial and laxative in medical field. Superfine high-active MgO can also be used as high-effective dissociation adsorbent to adsorb noxious chemical materials such as chloro-hydrocarbons, organo phosphorous cumpounds and acidic gases owing to its high surface chemical activity.In this thesis, various methods to prepare superfine high-active MgO both home and abroad at present are studied in detail. And these methods are analysed and compared. By now, the main preparation methods of superfine high-active MgO include carbonization, precipition, acid digestion and microwave radiation. All these methods have their merits and demerits, during which the carbonization method has more advantages. For instance,the meterials needed can easily be found in Hebei province, and the cost of production is low. What is more, the process condition is full-developed, therefore this method can easily be applied to commercial production. The main aspects studied in this thesis include:(1) The influence of magnesium basic carbonate, the precursor in the carbonation method, on MgO activity and particle size under conditions of different stoving temperature, pyrolysis style and grit number.Heavy magnesium liquor is synthetized under ordinary temperature and pressure. Pumping filtrated magnesium basic carbonate is stoved under 343K and 373K separately with other conditions fixed. It is found that the influence of stoving temperature on production activity is unremarkable. Heavy magnesium liquor prepared under the same condition is pyrolyzed by microwave heating and electric furnace heating separately with other conditions fixed. MgCO3 got by these two heating processes are calcined under same conditions and MgO is prepared. Results show that the activity of MgO got by these two pyrolysis processes has certain differences but not very remarkable.(2) The influence of magnesium basic carbonate on MgO activity and particle size under conditions of different calcining time, calcining temperature and surface active agent.Heavy magnesium liquor is synthetized under ordinary temperature and pressure and is pyrolyzed by electric furnace heating. MgCO3 is got bystoving under 343K, and MgO is prepared from MgCO3 under different calcining conditions. Results show that the MgO activity is greatly influenced by calcining temperature and time. Production are characterized by SEM and XRD, which indicate that the better the crystallinity is, the lower the production activity is.(3) The influence of Mg(OH)2, the precursor in bittern-ammonia method, on MgO activity and particle size under different calcining time and temperature.Conditions that influence MgO activity in bittern-ammonia method are investigated. Results show that calcining time and temperature have great effects on MgO during this method. The activity of MgO prepared by carbonization and bittern-ammonia methods separately are compared. It is shown that the temperature range in carbonization method is wider than that of bittern-ammonia method, and the activity of MgO got by the former method is higher than the latter .