Phillipsite-synthesis-from-fly-ash-prepared-by-hydrothermal-treatment-with-microwave-heating

AdvancedPowderTechnol.,Vol.17,No.4,pp.369–382(2006)©VSPandSocietyofPowderTechnology,Japan2006.Alsoavailableonline-www.vsppub.comOriginalpaperPhillipsitesynthesisfromflyashpreparedbyhydrothermaltreatmentwithmicrowaveheatingKUNIHIROFUKUI∗,KAZUHIROARAI,KEIJIKANAYAMAandHIDETOYOSHIDADepartmentofChemicalEngineering,GraduateSchoolofEngineering,HiroshimaUniversity,Higashi-Hiroshima739-8527,JapanReceived29August2005;accepted3November2005Abstract—CoalflyashwastreatedhydrothermallywithNaOHaqueoussolutionat373Kusingmicrowaveheatingandconventionalheating.X-raydiffractionandenergydispersiveX-rayfluo-rescencemeasurementsindicatedthatthecrystalstructureandchemicalcompositionoftheproductpowderdonotdependontheheatingmethod.However,microwaveheatingreducestheparticlesizeofsynthesizedphillipsite.Moreover,microwaveheatingmakesthewaitingtimeforthebeginningofcrystallizationmuchshorterthanconventionalheating,althoughitreducesthecrystalgrowthrateslightly.Itwasalsofoundthatmicrowaveheatingpromotestherateofincreaseoftheadsorptioncapacityoftheproductpowder.ChangesintheionconcentrationsinNaOHaqueoussolutionandthepeakintensityandadsorptioncapacityoftheproductpowdersuggestthatmicrowaveheatingmainlyhaseffectsonnucleationandcrystalgrowthofphillipsite.Weproposedanewheatingprocedure,‘partialmicrowaveheating’,whichhastheadvantagesofbothmicrowaveheatingandconventionalheating.Thisheatingprocedurecandevelopthecrystallinityandadsorptioncapacityoftheproductwithoutreducingthecrystalgrowthrate.Keywords:Flyash;microwave;phillipsite;hydrothermaltreatment.1.INTRODUCTIONInJapan,over7.5millionstonsofflyasharegeneratedperyearbythermalpowerplants,etc.,asindustrialwastes.Theamountofdischargedflyashisexpectedtoincreasemonotonouslyintheyearsahead[1]and40%offlyashisreclaimedfromthesea[2].Therefore,effectivewaystoreuseflyashshouldbequicklydeveloped.Onenewwayproposedtoreuseflyashisbysynthesizingphillipsite,whichcanbeusedasadsorbents,catalysts,etc.,usingthehydrothermaltreatmentmethod[3–8].Previouslywehavereportedtheeffects