Bio- and Nanotechnology Offer High Performance for Water Cleanup - Bionanotechnology: Global Prospects - page 418

come. in. contact. with. the. active. media.. Water. low. through. ine. materials. is. extremely.
slow.and.requires.considerable.pressure.to.obtain.acceptable.low.rates..Attention.is.being.
given.by.many.organizations.to.the.development.of.ilters.and.media.that.take.advantage.
of.the.properties.of.nanomaterials.for.removal.of.contaminants.from.water,.particularly.
carbon.nanotubes,.which.are.being.examined.for.cleanup.of.brackish.water.or.the.selective.
absorption.of.contaminants. 4 .While.such.nanomaterials.have.been.shown.to.be.extremely.
effective,.cost.and.application.on.larger-scale.systems.are.still.major.issues.
Other.approaches 5 .described.are.ligand.nano-coatings.capable.of.binding.multiple.lay-
ers. of. heavy. metal. contaminants.. One. end. of. the. ligand. attaches. to. a. high. surface. area.
substrate.(such.as.surface-modiied.zeolites),.and.the.other.binds.to.the.contaminant..Once.
contaminants. have. saturated. the. surface. area,. they. often. can. be. removed. by. additional.
processing. and. the. media. regenerated. for. re-use.. Laboratory. testing. has. demonstrated.
that. a. wide. range. of. organics,. metals,. and. inorganics. can. be. removed,. as. well. as. some.
bacteria.and.viruses.
MetaMateria.utilizes.nanomaterials.and.proprietary.process.technology.to.prepare.par-
ticles,. whiskers,. and. platelets. for. nano-enabled. products. that. can. take. advantage. of. the.
unique.properties.afforded.by.these.nanomaterials.for.the.removal.of.contaminants.from.
drinking.water..Figure.21.2.shows.nanoscale.whiskers..These.nanomaterials,.when.prop-
erly.prepared,.can.have.1,000.times.the.surface.area.of.a.typical.sand.ilter.bed.
In. order. for. one. to. take. advantage. of. nanomaterials,. they. need. to. be. part. of. a. system.
through. which. contaminated. water. will. easily. low. and. allow. contaminants. to. come.
into. contact. with. the. speciic. nano-iltration. media. selected. for. water. cleanup,. such. as.
for.removal.of.metal.ions.(e.g.,.As,.Pb,.Mn,.Se,.Fe).or.hydrocarbons,.or.nutrients.such.as.
phosphates..Porous.materials.are.found.to.be.highly.effective.carriers.for.nanomaterials.
selected.for.removal.of.speciic.contaminants.from.water.

MnO 2 Whiskers

16-Aug-06 Mn02 WD 6.2 mm 20.0 kV ×10 k 5 um

FIGURE 21.2
Nanoscale.MnO 2 .whiskers.grown.within.a.porous.structure.