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五硼酸钾、偏硼酸钾和四硼酸钾溶液中硼酸根离子类型、密度及电导率研究（英文）.docx

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五硼酸钾、偏硼酸钾和四硼酸钾溶液中硼酸根离子类型、密度及电导率研究（英文） AStudyontheBorateIonSpecies,Density,andConductivityinPotassiumPentaborate,PotassiumMetaborate,andPotassiumTetraborateSolutions Introduction Boratesarecompoundscontainingtheboron-oxygennetwork,andtheyhaveattractedtheinterestofscientistsandengineersduetotheiruniquepropertiessuchashighheatresistance,lowthermalexpansion,andhighchemicalstability.Inaddition,boratecompoundsshowaninterestingfeatureinsolutionastheyexistindifferentformsofionspeciesdependingonthepHandtheborontooxygenratio.Amongboratecompounds,potassiumpentaborate(K5B5O10),potassiummetaborate(KBO2),andpotassiumtetraborate(K2B4O7)arewidelyusedinvariousapplicationsincludingglassproduction,detergentformulation,andagriculture.Inthisstudy,weinvestigatetheborateionspecies,density,andconductivityinthethreepotassiumboratesinaqueoussolutions. BorateIonSpecies BoratesaremainlycomposedofBO3andBO4unitsthatconnectinatetrahedralortrigonalplanarstructure.DependingonthepH,theborateionspeciesinsolutionchangefrommonoborateanions(BO33-)and/ormetaborateanions(BO2-)todiborateanions(B2O53-)andfinallytotetraborateanions(B4O72-)insequenceasshowninthereactionequationsbelow. 2BO3^2-+H2O⇔BO2^-+BO33^-+H+ 3BO3^2-+H2O⇔B2O53^-+BO33^-+H+ 4BO3^2-+H2O⇔B4O72^-+BO33^-+H+ Inacidicconditions,thepredominantspeciesisBO33-,whichispresentasmonobasicordibasicboratedependingonthepHandtheborontooxygenratio.Inneutralconditions,metaborateanionsBO2-areformed,whichexistasmonomersordimers.AsthepHincreases,B2O53-andB4O72-speciesareformedthroughthecombinationofBO2-andBO33-units.Theformationofthesehigher-orderboratespeciesresultsinahighviscosityandlowmobilityoftheborateionsinsolution,affectingtheboratesolubilityandthesurfacetension. Density Thedensityofpotassiumboratesolutionsdependsontheconcentration,temperature,andborateionspecies.Generally,thedensityincreaseswiththeconcentrationduetotheincreasednumberofionsinthesolution.However,thedensitydecreasesasthetemperatureincreasesduetothedecreaseinthesolventdensity.Thetypeofboratei