Environmental Engineering Reference
In-Depth Information
later.in.this.chapter.describe.the.use.of.this.BNP.to.degrade.chlorinated.solvents.in.
groundwater.
10.1.2
p
artiCle
C
haraCteristiCs
The.particle.size.and.other.characteristics.of.nZVI.depend,.in.part,.on.the.method.of.
synthesis.[7-9]..Two.studies.have.measured.the.actual.particle.sizes.in.commercially.
available.nZVI..These.studies.also.provided.information.on.the.surface.area.of.the.
particles. and. their. elemental. composition.. The. particle. size. and. resultant. surface.
area.affect.the.mobility.and.reactivity.of.the.iron.nanoparticles.
Nurmi.et.al..[12].tested.nZVI.samples.from.Toda.Kogyo.Corporation's.RNIP-
10DS.product..The.manufacturer.indicates.that.the.nZVI.particles.are.approximately.
70. nm. in. diameter. and. have. a. surface. area. of. 29. square. meters. per. gram. (m
2
/g)..
RNIP-10DS.is.produced.by.reacting.iron.oxides.(goethite.and.hematite).with.hydro-
gen. at. temperatures. between. 200. and. 600
°
C.. The. resulting. iron. particles. contain.
Fe
0
.and.Fe
3
O
4.
(in.total,.approximately.70.to.30%.iron.and.30.to.70%.oxide).based
.
on. x-ray. diffraction. analysis. (XRD).. X-ray. photoelectron. spectroscopy. indicated.
that.the.particles.also.contained.trace.amounts.of.S,.Na,.and.Ca..Nurmi.et.al..[12].
used. transmission. electron. microscopy. (TEM). to. examine. the. particle. geometry..
The.nZVI.consisted.of.aggregates.of.small,.irregularly.shaped.particles.of.a.nearly.
crystal. Fe
0
. core. with. an. outer. shell. of. polycrystalline. iron. oxide.. TEM. indicated.
that.the.average.particle.size.in.RNIP-10DS,.as.received,.was.38.nm.and.the.average.
surface.area.25.m
2
/g.
In.another.study,.the.Polylon.division.of.Crane.Co..commissioned.Lehigh.Uni-
versity. and. the. Whitman. Companies. Inc.,. through. ARCADIS,. to. characterize. the.
iron.particles.in.four.samples.of.PolyMetallix™.nZVI.[13]..The.method.for.synthesiz-
ing.PolyMetallix™.nZVI.was.not.speciied,.other.than.to.indicate.that.Polylon.had.
treated.some.of.the.product.samples.via.physical.size.reduction.and/or.the.addition.
of.a.dispersing.agent.after.the.initial.synthesis..Three.of.the.samples.were.analyzed.
within. approximately. 2. weeks. of. manufacture.. The. fourth. sample. was. analyzed.
more.than.4.months.after.manufacture..In.general,.the.age.of.the.sample.affected.the.
particle.size.more.than.did.the.post-synthesis.treatments..TEM.showed.that.the.nZVI.
comprised.generally.spherical.particle.clusters,.with.some.of.the.clusters.agglomer-
ated..The.older.sample.showed.greater.agglomeration..The.mean.particle.size.for.the.
samples.analyzed.within.2.weeks.of.manufacture.ranged.from.66.0.to.68.5.nm;.the.
mean.nZVI.size.for.the.older.sample.was.186.8.nm..Each.of.these.means.represented.
a.particle.size.distribution..For.example,.the.particles.in.the.aged.sample.ranged.in.
size.from.37.7.to.512.7.nm,.with.most.of.the.particles.between.125.and.300.nm..The.
study.concluded,.in.part,.that:
“While.the.PSD.[particle.size.distribution].is.an.important.quality.assurance.and.qual-
ity.control.parameter,.it.alone.is.not.a.suficient.indicator.of.nZVI.reactivity.or.eficacy.
in.a.given.remediation.scenario..It.is.important.to.emphasize.that.nZVI.in.general.are.
highly. reactive. materials. and,. as. such,. their. surface. and. intrinsic. properties. change.
rapidly.over.time.from.the.time.of.manufacture.”
