ChemistryofRareEarthElementsinWastewater
Introduc8on
As clean water becomes scarce, the removal of contaminants from wastewater is becoming
increasinglyimportant.Nutrientssuchasphosphorus(P)intheformofphosphate(PO43-)serveasa
foodsourceforalgae.RecentlyexcessiveamountsofPinnaturalwatershaveledtolargealgalblooms
which release toxins into the water and deplete dissolved oxygen concentraEons. These
consequences result in the death of other fresh water species and the contaminaEon of drinking
watersources.1Asaresult,newregulaEonsarebeingputintoplacethatgreatlyrestrictthedischarge
of P into the environment. New wastewater treatment plant discharge permits are requiring ever
lowerPconcentraEonsintheeffluent.TheselowerpermitlimitscanbedifficulttoreachwithexisEng
technology.RareEarth(RE)technologyhasemergedasaviablealternaEvetechnologywhichcanhelp
reduce the effluent P concentraEon through chemical addiEon alone. RE technology from Neo
Chemicals&Oxides(Neo)isaliquidcoagulantthatcontainstherareearth(RE)elementslanthanum
(La)andcerium(Ce).Thispaperisintendedtoexplainthechemistry,applicaEonandtoxicityofREin
treaEngwastewater.
RareEarthChemistryinWastewater
Therareearthelementsarethesetof15elementswithatomicnumbers57-71aswellasYSrium(Y,
Atomicnumber:39).TheyarelocatedonthelowerporEonoftheperiodictablesomeEmesreferred
to as the f-block. UnEl about 60 years ago, not much was known about these elements. The term
“rare earth” is actually a misnomer because the elements are not rare. For example, the two RE
elements of interest to this paper, La and Ce, are the 26th and 28th most abundant elements in the
Earth’scrust,respecEvely.2Innature,rareearthelementsarefoundinover100mineralswithmajor
depositsinIndia,SouthAfrica,Brazil,Australia,Malaysia,andtheUSA.2Therareearthsingeneraland
parEcularlyLaandCeformverystrongbondswithoxyanionslikephosphateandcarbonate.TheLa
andCebondwithphosphateissofavoredthatcommonrareearthcontainingmineralscontainrare
earth phosphate. This strong bonding is the basis for the use of rare earths as phosphate removal
agents.RareearthbasedproductslikethosefromNeohavebeenusedforphosphateremovalfrom
waterinmulEpleindustrieslikeaquariumwatertreatment,3 poolandspawatertreatment,4 andlake
remediaEon.5 Inwastewatertreatmentseveralpatentswerepublishedcirca1970describingtheuse
of rare earth salts for precipitaEon and removal of phosphate.6 All of this demonstrates rare earth
basedproductsareeffecEveatremovingPinavarietyofwatertreatmentapplicaEons.
Thetypicalcoagulantsusedinwastewatertreatmentareiron(Fe)andaluminum(Al)based.Febased
coagulants include ferric chloride, ferrous sulfate, and ferrous chloride among others. Al based
coagulants include aluminum sulfate (alum), sodium aluminate, and polyaluminum chloride (PAC).
RecentlyREtechnologyhasemergedasaviablealternaEvetechnologyforPremoval.Theprinciple
differencebetweenFe,AlandREbasedproductsisthemechanismbywhichtheyremovephosphate,
asshowninFigure1.TherehasbeensomedebateaboutthemechanismofFeandAlbasedproducts.
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OriginallyitwasthoughtthatFeandAlformedFePO4orAlPO4,butrecentstudieshaveshownthat
the mechanism is more complicated. Smith has reported that the mechanism actually consists of a
two-stepprocess.AmetaloxidesuchasAl2O3orFe2O3iniEallyformswhichisfollowedbyadsorpEon
ofphosphateontothemetaloxidesurface.7 Thismechanismisconsistentwiththeobservedneedfor
increasing amounts of Fe or Al at low phosphate concentraEons, i.e. the adsorpEon process is less
efficientwhenthereisliSlephosphatepresent.
Incontrast,themechanismforrareearthremovalofphosphateisastraighgorwardmetalphosphate
precipitaEon resulEng in the formaEon of the mineral rhabdophane, which is a stable form of RE
foundinnature.TheprecipitaEonreacEoncanbedescribedbytheequaEon
RE3++PO43-!REPO4·H2O
WhileREcanreactinasimilarmechanismtothatofFeandAlviatheformaEonofaRE(OH)3which
can adsorb phosphate, the precipitaEon reacEon with phosphate to form rhabdophane is greatly
favored.
AnotherdifferencebetweenFe,Al,andREbasedcoagulantsisthemolarraEoofthecoagulantmetal
toPthatisneededtoremovePtothedesiredlevel.Thephosphateremovalperformanceofvarious
Fe, Al, and RE based coagulants vs the molar raEo of coagulant to P is shown in Figures 2 and 3.
Regardless of starEng P concentraEon, addiEon of the RE as CeCl3 resulted in the lowest P
concentraEonbeingachievedwhentheRE:PraEowas1:1.Bycomparison,FeandAlbasedcoagulants
need to be dosed at higher mole raEos (at least 2.5:1 (Fe or Al):P) in order to achieve similar P
concentraEons.
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Figure2.Premovalvs.molarra1oforvariouscoagulants.BeginningPconcentra1onof2.5mg/L.
Figure3.Premovalvs.molarra1oforvariouscoagulants.BeginningPconcentra1onof1.0mg/L.
TheREtoPreacEonmechanismaccountsforthenear1:1RE:PmolarraEoobservedforPremoval.In
thiswayREtechnologyisuniqueamongcoagulants.
TheaddiEonofREtechnologytowastewaterhasthepotenEaltoremovemulEpledifferentanions.In
addiEontoPasphosphate,therareearthelementsinREtechnologycanforminsolublecomplexes
with carbonate (CO32-), hydroxide (OH-), and fluoride (F-). Examples of these reacEons are shown in
Table I. Also listed in Table I is the precipitaEon pH range, the solubility product (Ksp) and
concentraEonofREcalculatedfromtheKsp.TheKspisameasurementofthesolubilityofasolidandis
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calculatedbymulEplyingtheequilibriumconcentraEonsofthecaEonandanionwitheachraisedto
thepowerofitsstoichiometricequivalent.Forexample,forCePO4
Ksp=[Ce3+][PO43-]
whileforCeF3
Ksp=[Ce3+][F-]3
ThelowertheequilibriumconcentraEon,thesmallertheKsp,andthusthemoreinsolublethesolid.
ForpracEcalpurposes,thesmallertheKspisthelesssolublethereacEonproduct.AsacomparaEve
example,theKspoftablesalt(NaCl)is3.73x101.ThisKspis26ordersofmagnitudegreaterthanthatof
ceriumphosphateandthusNaClisverysolubleandceriumphosphateisveryinsoluble.
TableI.CommonreacEonsbetweenrareearthsandanions
Anion
ReacEonthatformsaninertsolid
PrecipitaEon
pHrange
Ksp,,
EquilibriumFree
REinSoluEon,
ppm(pH7)
Phosphate
La+3(aq)+PO4-3(aq)→LaPO4·H2O(s)
Ce+3(aq)+PO4-3(aq)→CePO4·H2O(s)
>2
5.0x10-25
9.9x10-8
Carbonate/Bicarbonate
(HCO3-dominantatpH7)
2La+3(aq)+3HCO3-(aq)→La2(CO3)3(s)+3H+(aq)
2La+3(aq)+3CO3-2(aq)→La2(CO3)3(s)
2Ce+3(aq)+3HCO3-(aq)→Ce2(CO3)3(s)+3H+(aq)
2Ce+3(aq)+3CO3-2(aq)→Ce2(CO3)3(s)
>3.5
~8x10-36
0.01
HydroxideAlkalinity
La+3(aq)+3OH-(aq)→La(OH)3(s)
2La(OH)3+6OH-!La2O3+6H2O
Ce+3(aq)+3OH-(aq)→Ce(OH)3(s)
2Ce(OH)3+6OH-!Ce2O3+6H2O
>4
1.0x10-22
0.19
Fluoride
La+3(aq)+3F-(aq)→LaF3(s)
Ce+3(aq)+3F-(aq)→CeF3(s)
3-8
1.8x10-19
1.26
TypicalwastewatereffluentneedstobeinthepHrangeof6-9andasseeninTableIthepHrange
whereREwillprecipitatetheseanionsiswellwithinthisrange.Alsothelowestequilibriumfreeion
concentraEon calculated from the Ksp in Table I is for the reacEon with phosphate. This is further
evidencethatREwillfavorprecipitaEonofP.
CaseStudiesinWastewaterTreatmentPlants
REtechnologyhasrecentlybeenusedtotreatPtomeetthelowdischargelimitof0.075mg/L.A2
MGDwastewatertreatmentplantdischargingintoalakeinMinnesotahasbeenevaluaEngmethods
to remove P to this level for its upcoming permit. The influent P averages around 2 mg/L but can
rangefrom1-4mg/L.IniEallyatrialwasdonetoevaluatetheuseofacombinaEonofPACandferric
chloride.WhilethistrialwassuccessfulinmeeEngthedischargelimitof0.075mg/L,numerousother
issuesaroserelatedtofiltraEonfromtheincreaseddosageofcoagulant.LaterwhenREtechnology
wasevaluated,theeffluentTPdroppedrapidlyandwithin7dayswasbelowthetargetlimitof0.075
mg/L(seeFigure4below).
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Figure4.TPdischargeatMinnesotaPlantusingRareEarthTechnology
Figure5.CoagulantdoseandTPdischargeatMinnesotaplantusingRareEarthTechnology
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The iniEally high dose rate rapidly gets the RE into the system and can then be lowered while
maintainingtheTPdischargelimit.ThismethodiseffecEveforrapidlyloweringthePandopEmizing
thedosetomeetthePdemand.WhencomparedtotheprevioustrialusingacombinaEonofPACand
ferric chloride, the use of RE technology had several advantages. The first of which was the lack of
seSlingorfiltraEonissues.Secondlythedoserateofcoagulantwasmuchlower. ThePACandferric
chloridetrialhadcombinedcoagulantdoseratesofnear180GPDwhileREtechnologywasbelow35
GPD.
RE technology has also been used recently in a 3 MGD waste water treatment plant in Wisconsin
wherethedischargelimitforTPisalso0.075mg/L.InfluentTPinthisplantvariesbetween2and5
mg/L.OverthecourseofthistrialtheinfluentTPincreasedslightly.DespitethisincreasetheEffluent
TPremainedbelowthedischargelimit.Asinthetrialdescribedabove,theiniEalcoagulantdosewas
high and resulted in a rapid decrease in the effluent TP concentraEon. The dose was then lowered
overEmeandtheeffluentTPremainedbelowthelimit.
Figure6.InfluentandEffluentTPwithCoagulantDoseusingRETechnology
Another wastewater treatment plant discharging into a stream that leads to Lake Erie has permits
whichlimitthedischargeofAlto1.1mg/LandPto1.0mg/L.ThisisacasewheretheeffluentPlevels
arenotextremelylowbuttheamountofAlthatcanbeusedislimited.TheinfluentPwasinthe3-4
mg/Lrange.OperatorsaSemptedtomeetthePdischargelimitbyalternaEvelydosingferricchloride
orPACpriortotheprimaryandsecondaryclarifiers.Ferricchloridewasdosedathighdosagerates
and was unable to meet the P discharge limit. Switching to PAC put a limit on the dosing amount
because PAC is Al based and would increase the discharge of Al. With RE technology the plant was
able to meet both permits using a moderate dose of rare earth. The data from the plant is shown
belowinFigures7and8.TheresultsshowthattheaddiEonofREwasmoreeffecEveatremovalofP
andhadtheaddedbenefitofnotaddingAltothesystem.
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Figure7.TotalPhosphorusbeforeandaOerREtechnology.
Figure8.TotalAluminumbeforeandaOerREtechnology.
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RE technology has also been used in terEary treatment. A 30 MGD municipal plant equipped with
advancedphysicaltreatment(mulE-mediafiltraEonandcarboncontactors)wasusingalumtoremove
Pfromwastewater.WithalumthefinaleffluentPconcentraEonachievedwas0.09ppmTP.WhenRE
technologywasevaluatedasanalumreplacement,thePconcentraEonachievedwas0.07ppmTPin
thefinaleffluent(seeFigure9below).
Figure9.EffluentPconcentra1onbeforeandaOerREtechnologyaddi1on
These four examples of the use of RE technology to remove P from wastewater demonstrate the
abilitytobeaneffecEvealternaEvetotheuseoftypicalFeandAlbasedcoagulants.TheyshowRE
technologycanbeusedtoachieveverylowdischargelimitsinavarietyofplantsizesanddosepoints.
ToxicityofREtechnologyinWastewater
The toxicity of chemical addiEves to wastewater should be tested to determine the effect of the
addiEvesontheecosystem.IdeallytheaddiEvewilldowhatitisdesignedtodo,onlybedischargedin
aminimalamount,andnothaveanyadverseeffectsontheecosystem.Toconfirmthis,theEPAhas
published methods for measuring the toxicity of effluents, the Whole Effluent Toxicity (WET) test.8 GenerallytheWETtestwillmeasurethenumberoforganismsthatwillsurviveinwaterwithadosed
amount of either plant effluent or the chemical addiEve. Freshwater organisms are Ceriodaphnia
dubia (daphnid), Daphnia pulex and Daphnia magna (daphnids), Pimephales promelas (fathead
minnow), Oncorhynchus mykiss (rainbow trout) and Salvelinus fonEnalis (brook trout). The
concentraEon that will kill 50% of the organisms is known as the LC50. Other numbers such as the
NOEL (No Observed Effect Level), NOAEL (No Observed Adverse Effect Level), and LOAEL (Lowest
ObservedAdverseEffectLevel)canalsobedeterminedfromthistesEng.Todate,REtechnologyhas
been implemented in over 40 faciliEes in the USA since 2014. Every facility has passed effluent
complianceWETtesEngwhileusingREtechnology.
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Inanefforttotestworst-casetoxicityoftheaddiEves,itishelpfultoassumetheyarenotremovedin
the treatment process and are discharged directly. LC50 values from published EPA documents and
recentNeostudiesareshowninTableIIbelowforCeriodaphniaspeciesandPimephalespromelas.As
ofthiswriEng,weareunawareoftoxicitystudiesconductedwithFebasedcoagulants.
TableII.LC50ofAlandREforCeriodaphniaandPimephalesspecies.
Coagulant
CeriodaphniaspeciesLC50
(mg/L)
Pimephalespromelas(fatheadminnow)LC50(mg/
L)
Al
3.69
>18.9
RE
9.2
107.3
ThemeasuredLC50ofREforCeriodaphniaspeciesiscomparabletothatofthereportednumbersfor
Al coagulants. This indicates that RE elements have similar toxicity to Al for Ceriodaphnia. However
theLC50ofREforPimephalespromelasismuchhigherthanthereportedvalueforAl.Thisindicates
thatREsarelesstoxictoPimephalespromelasthanAl.
The insoluble material generated (sludge) from rare earth addiEon to wastewater has also been
tested.ThetypicalconcentraEonofRECl3inREtechnologyis780g/L,appliedatavolumetricdosage
rate of 1:53,000, yields approximately 12 mg REPO4/L. This value is lower than the conservaEvely
calculatedsafelimitof14mgREPO4/Lfordrinkingwater.9Thetreatedwateristhenfurtherprocessed
through a solids/liquid separaEon system such as a clarifier or filter. Any rare earth solids that
precipitatewouldthereforeberemoved,withtheactualrareearthphosphateconcentraEonlikelyto
bemuchlowerthan12mg/Latthepointofdischarge.10TheprimarypotenEalforhumanexposureto
RE technology treated water would be through consumpEon of treated water, whereas aquaEc
organismscouldbeexposedatanypointayertreatmentofawaterbodywithREtechnology.Thus
liSletonoharmfuleffectsareexpectedfromsolidsgenerated.
Generally rare earths have a low toxicity raEng.11 ,12 There are no known human toxicity studies of
ceriumphosphate.However,lanthanumcarbonate,acommonlyusedhumandrugforkidneydisease,
hasbeenextensivelystudied.13 IntheacidicmammaliangastrointesEnaltract,lanthanumcarbonate
breaksdownandcombineswithphosphatetoformlanthanumphosphate,thusulEmatelyremoving
the phosphate from the human body. This process is similar to the way RE technology removes
phosphate from water bodies. Therefore, the extensive human and animal studies of lanthanum
carbonate also address the final lanthanum product in the human body, namely lanthanum
phosphate.
Lanthanum carbonate, and therefore lanthanum phosphate, has very low toxicity in humans and
animals. There is no indicaEon that lanthanum phosphate is genotoxic (causes cancer or other
significant health problems).14 In a bioassay to determine potenEal genotoxicity, the major
component of RE technology, cerium chloride, was found to rapidly form cerium phosphate in the
biologicalsystemand,likelanthanumphosphate,wasnotgenotoxic.Giventhesimilarchemistryand
environmentalbehavioroflanthanumphosphateandceriumphosphate,thereisnoreasontobelieve
thatceriumphosphatewouldhavedifferenttoxicityandshouldbeconsiderednon-toxicforhumans
atthelowconcentraEonslikelytobeencounteredinwatertreatedwithREtechnology.
The toxicity of the sludge generated towards denitrificaEon bacteria has also been studied in
unpublishedsludgerespiraEoninhibiEonstudies.Therareearthsolidspresentinthesludgewouldbe
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those discussed earlier such as REPO4, RE2(CO3)3, and RE(OH)3. A study conducted by Intrinsic
TechnologiesforNeofoundnotoxicitytowardsacEvatedsludgemicrobes.Asacomparison,forCeO2
theEC50forinhibiEonofrespiraEonwasgreaterthan1000mg/L.15 BasedonthistheaddiEonofRE
towastewatertreatmentshouldhavenoeffectonthemicrobes.
NeohasalsoevaluatedtheeffectoflandapplyingthesludgegeneratedintreatmentplantsusingRE
basedcoagulants.ThisstudywasperformedbyRichardWolkowski,Ph.D.(ExtensionSoilScienEstat
UniversityofWisconsin-Madison)atAlfisolSoilManagement,LLC.Inthisstudy,Pavailabilitytocorn
from rare earth biosolids was invesEgated and compared to P availability from a commercial P
ferElizer and ferric biosolids. Corn was chosen for the study as it is the most common crop treated
withbiosolidsandisgrownonfourmillionacresinWisconsin.Rareearthbiosolidsproducedsoilwith
PavailabilitybetweenPferElizerandferricbiosolidsasmeasuredbythechangeinsoiltestP.Thecorn
whole-plantdrymaSeryieldeitherwasunaffectedbytherareearthbiosolids.Thus,theapplicaEon
ofrareearthbiosolidsisnotexpectedtoaffectthegrowthandyieldofcornwhenappliedatnormal
ratesthatsupplythecornNrequirement.
Conclusion
TheuseofREtechnology,arareearthbasedcoagulant,toremovePfromwaterisquiteeffecEve.The
basisforthisisthesolidsformedresemblenaturallyoccurringmineralswhichhaveverylowsolubility.
FurthermorethesemineralformshavelowsolubilityatthenormalpHofwastewaterwhichispH6-9.
ThusthewatertreatedwithREtechnologywillhavelowconcentraEonsofRE,andP.Toxicitystudies
have also shown RE based coagulants and the precipitates formed when used in wastewater to be
non-toxic to have low toxicity. Furthermore the presence of RE in the land applied sludge has no
observed impact on the growth of corn plants. For these reasons RE based coagulants are a viable
opEonforuseinwastewatertreatment.
DuetothechemistryoftherareearthelementsfoundinREtechnology,highlyinsolublesolidsare
expectedtoformwhenREisappliedinwastewatertreatment.Assuch,theconcentraEonof
solubleREintheeffluentisexpectedtobequitelow.Rareearthshavebeenshowntohavelow
toxicityandlowenvironmentalimpact.
1hSp://www.circleozlue.org/2016/water-quality/epa-announces-naEonal-wastewater-nutrient-polluEon-census/
2Greenwood,N.N.;Earnshaw,A.ChemistryoftheElements,2ndEd.;BuSerworth-Heinemann:Oxford,2001.
3Forreferencesregardingrareearthuseinaquariumssee
1.
2.
3.
Knop,D.NewPhosphateFighter?CoralMagazine,2009,6(6),p2-11.
Zhang,Y.;Wong,K.S.Lanthanumchlorideorlanthanumcarboxylatefororthophosphateremovalinseawater
aquarium-afeasibilitystudy,Environmentallaboratory,ZOEDivision,OceanPark,HongKong
Yaiullo,J.FeaturedAquarium:AtlanEsMarineWorld.AdvancedAquarist.February2007,VolumeVI.(hSp://
www.advancedaquarist.com/2007/2/aquarium)
4Forreferencesregardingrareearthuseinpoolsandspassee
1.
2.
3.
4.
5.
Mills,D.J.RemovalofPhosphatefromWater.U.S.Patent6,946,076,Sep.20,2005.
Mills,D.J.TreatmentofSwimmingPoolWaters.U.S.Patent6,146,539,Nov.142000.
Kulperger,R.;Okun,R.;Munford,G.MethodsandComposiEonsUsingLanthanumforRemovingPhosphatefrom
Water.U.S.Patent6,524,487,Feb.25,2003.
Kulperger,R.;Okun,R.;Munford,G.MethodsandComposiEonsUsingLanthanumforRemovingPhosphatefrom
Water.U.S.Patent6,338,800,Jan.15,2002.
Lowry,R.N.PhosphateRemoval…Revisited.Pool&SpaMarke1ngmagazine,2003,27(7),p57.
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5ForreferencesregardingrareearthuseinlakeremediaEonsee
1.
2.
Peterson,S.A.NutrientInac1va1onasaLakeRestora1onProcedure:LaboratoryInves1ga1ons,U.S.Govt.Print.
Off.,1974.
hSp://www.sepro.com/phoslock/
6Forpatentsregardingrareearthuseinwastewatersee
1.
2.
Kleber,E.V.;Recht,H.L.RemovalofPhosphatefromWasteWater.U.S.Patent3,956,118,May11,1976.
Daniels,S.L.;Parker,D.G.RemovalofPhosphatefromWasteWater.U.S.Patent3,617,569,Nov.2,1971.
7Hanlon,C.ScoSSmith:UnderstandingandMaximizingPhorphorusRemovalINFLUENTS,Fall2015,p8-9.
8MethodsforMeasuringtheAcuteToxicityofEffluentsandReceivingWaterstoFreshwaterandMarineOrganisms,Fiyh
Ed.October2002.U.S.EnvironmentalProtecEonAgencyEPA-821-R-02-012.
9TheoralreferencedoseforthesimilarcompoundLanthanumPhosphateis0.5mg/kg-day(NSFInternaEonal2010as
citedbyUnitedStatesEnvironmentalProtecEonAgency(USEPA).2012.Rareearthelements:AreviewofproducEon,
processing,recycling,andassociatedenvironmentalissues.EPA/600/R-12/5721.August.).Thusthesafedailyexposure
levelofarareearthphosphateis0.5mg/kg-day*70kg=35mg/day(assuminga70kgperson).Usingthe80%upper
ceiling(UnitedStatesEnvironmentalProtecEonAgency(USEPA).2000.Methodologyforderivingambientwaterquality
criteriafortheprotecEonofhumanhealth.OfficeofWater,EPA-822-B-00-004.October.Availableonline:hSp://
water.epa.gov/scitech/swguidance/standards/upload/2005_05_06_criteria_humanhealth_method_complete.pdf)
contaminantexposurefromwaterthesafeconcentraEonis0.5mg/kg-day*70kg*0.8/(2L/dayconsumed)=14mg/L.
10REPO
4willbedetectedinatotalphosphorustest.Assumingall12mg/LREPO4wasdischarged,theTPmeasuredwould
be1.6mgP/L,whichismuchhigherthannewdischargepermitscomingintoeffect(<1or<0.1).
11Kilbourn,B.T.Cerium:AGuidetoItsRoleinChemicalTechnology.Molycorp,Inc.:Fairfield,NJ,1992.
12Haley,T.J.PharmacologyandToxicologyoftheRareEarthElements.J.Pharm.Sc,1965,54,663.
13Forreferencessee
1.
2.
3.
FoodandDrugAdministraEon(FDA).2004.ReviewandEvaluaEonofNewToxicologyDataSubmiSedwith
Fosrenol®NDAResubmission(NDA21-468).Availableonline:hSp://www.accessdata.fda.gov/drugsagda_docs/
nda/2004/21-468_Fosrenol_Pharmr.pdf
Hutchison,A.J.,etal.2009.Lanthanumcarbonatetreatment,forupto6years,isnotassociatedwithadverse
effectsontheliverinpaEentswithchronickidneydiseaseStage5receivinghemodialysis.ClinNephrol.
71:286-95.
Finn,W.F.,etal.2005.Along-term,open-labelextensionstudyonthesafetyoftreatmentwithlanthanum
carbonate,anewphosphatebinder,inpaEentsreceivinghemodialysis.CurrMedResOpin.21:657-64.
14ANOHSC(AustralianNaEonalOccupaEonalHealthandSafetyCommission).1998.Availableonline:hSps://
www.nicnas.gov.au/__data/assets/word_doc/0015/20175/NA606FR.docx.
15ToxicologicalReviewofNanoCeriumOxide.Prospect2010
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