Environmental Engineering Reference
In-Depth Information
illustrate.both.the.potential.for.nanomaterials.to.enter.wastewater.streams.and.the.
dificulty.in.making.such.an.estimate.when.the.details.of.product.manufacture.are.
proprietary.
Coincidentally,. both. examples. concern. the. discharge. of. silver. when.
washing.clothes.
7.1.1 C
ase
s
tudy
: s
ilver
C
are
™
w
ashing
m
aChine
Samsung's. SilverCare™. option. on. several. models. of. washing. machine. uses. silver.
ions.to.sanitize.laundry.
Samsung.reportedly.spent.$10M.to.develop.this.technology.
[6].
The.details.of.the.technology.are,.understandably,.proprietary.
Company.litera-
ture.describes.the.technology.in.several.ways.
According.to.one.account.[6],.the.sys-
tem.electrolyzes.pure.silver.into.nano-sized.silver.ions.“approximately.75,000.times.
smaller.than.a.human.hair”;.assuming.that.a.human.hair.is.approximately.60.to.120.
micrometers.(µm).wide.[4],.then.the.silver.nanoparticles.would.be.on.the.order.of.1.
nm.in.diameter.
Elsewhere.[7],.Samsung.described.their.system.as.follows:
“[A].grapefruit-sized.device.alongside.the.[washer].tub.uses.electrical.currents.to.nano-
shave.two.silver.plates.the.size.of.large.chewing.gum.sticks.
The.resulting.positively.charged.
silver.atoms.—.silver.ions.(Ag
+
).—.are.injected.into.the.tub.during.the.wash.cycle.”
These.two.descriptions.differ.enough.to.make.it.unclear.whether.the.silver.is.released.
as.a.true.nanoparticle.(ca..1.nm.diameter).or.as.ionic.silver.
(Silver.has.an.atomic.
diameter.of.0.288.nm.and.an.ionic.radius.of.0.126.nm.[8],.and.thus.silver.ions.are.
smaller.than.the.nanoparticle.size.range.of.1.to.100.nm.)
Based.on.the.electrolysis.
process,.both.may.be.present.
Key.and.Maas.[9].indicate.that.electrolysis.of.a.silver.
electrode.in.deionized.water.produces.colloidal.silver.containing.both.metallic.silver.
particles.(1.to.25.wt%).and.silver.ions.(75.to.99.wt%).
The.silver.particles.observed.in.
colloidal.silver.generally.range.in.size.from.5.to.200.nm;.a.particle.1.nm.in.diameter.
would.consist.of.31.silver.atoms.
This.information.suggests.—.but.certainly.does.not.
conclusively.prove.—.that.the.SilverCare™.washing.machine.discharges.a.mixture.
of. silver. ions. and. silver. nanoparticles.
Silver. ions,. rather. than. nanoparticles,. may.
comprise.most.of.the.mass.
Samsung.has.offered.several.indications.of.the.amount.of.silver.released.when.
washing.a.load.of.clothing.
Their.product.literature.notes.that.electrolysis.of.silver.
generates.up.to.400.billion.silver.ions.during.each.wash.cycle.[6,.10].
The.two.chew-
ing-gum. sized. plates. of. silver. reportedly. last. for. 3000. wash. cycles. [10].
Finally,.
Samsung.reportedly.has.indicated.that.using.a.SilverCare™.washing.machine.for.a.
year.would.release.0.05.g.silver.[11].
With.respect.to.the.sanitizing.function.that.this.release.of.silver.provides,.Sam-
sung.has.indicated.that.the.silver.ions.“eradicate.bacteria.and.mold.from.inside.the.
washer”. and. “stick. to. the. fabric”. of. clothes. being. washed. to. provide. antibacterial.
function.for.up.to.30.days.[10].
A.Samsung.representative.stated.that.“silver.nano.
ions.can.easily.penetrate.'non-membrane.cell'.[sic].of.bacteria.or.viruses.and.sup-
press. their. respiration. which. in. turn. inhibit. [sic]. cell. growth.
On. the. other. hand,.
Silver.Nano.is.absolutely.harmless.to.the.human.body”.[6].
While.Samsung.has.marketed.this.antibacterial.action.as.a.beneit.to.customers,.
some.consumers.have.become.concerned.about.the.potential.consequences.of.using.
