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Potential Application in Water Treatment
Nano-adsorbents can be readily integrated into existing treatment processes in
slurry reactors or adsorbers. Applied in the powder form, nano-adsorbents in slurry
reactors can be highly efficient since all surfaces of the adsorbents are utilized and
the mixing greatly facilitates the mass transfer. However, an additional separation
unit is required to recover the nanoparticles. Nano-adsorbents can also be used in
fixed or fluidized adsorbers in the form of pellets/beads or porous granules loaded
with nano-adsorbents. Fixed-bed reactors are usually associated with mass transfer
limitations and head loss; but it does not need future separation process. Applications
of nano-adsorbents for arsenic removal have been commercialized, and their performance and cost have been compared to other commercial adsorbents in pilot tests
[54]. ArsenXnp is a commercial hybrid ion-exchange medium comprising iron
oxide nanoparticles and polymers. ADSORBSIA™ is a nanocrystalline titanium
dioxide medium in the form of beads from 0.25 to 1.2 mm in diameter. Both nanoadsorbents were highly efficient in removing arsenic and ArsenXnp required little
backwash [54, 55]. The estimated treatment cost for ArsenXnp is $0.25–
$0.35/1000 gal if the medium is regenerated, similar to $0.37/1000 gal of Bayoxide
E33, a high- performance granular iron oxide adsorbent [54, 56]. ArsenXnp and
ADSORBSIA™ have been employed in small- to medium-scale drinking water
treatment systems and were proven to be cost competitive.
Membranes and Membrane Processes
The basic goal of water treatment is to remove undesired constituents from water.
Membranes provide a physical barrier for such constituents based on their size,
allowing the use of unconventional water sources. As the key component of water
treatment and reuse, they provide high level of automation and require less land and
chemical use, and the modular configuration allows flexible design [4]. A major
challenge of the membrane technology is the inherent trade-off between membrane
selectivity and permeability. The high energy consumption is an important barrier to
the wide application of pressure-driven membrane processes. Membrane fouling
adds to the energy consumption and the complexity of the process design and operation. Furthermore, it reduces the lifetime of membranes and membrane modules.
The performance of membrane systems is largely decided by the membrane
material. Incorporation of functional nanomaterials into membranes offers a great
opportunity to improve the membrane permeability, fouling resistance, and mechanical and thermal stability, as well as to render new functions for contaminant degradation and self-cleaning.
Current and Potential Applications for Water and Wastewater Treatment
Potential Application in Water Treatment
Nano-adsorbents can be readily integrated into existing treatment processes in
slurry reactors or adsorbers. Applied in the powder form, nano-adsorbents in slurry
reactors can be highly efficient since all surfaces of the adsorbents are utilized and
the mixing greatly facilitates the mass transfer. However, an additional separation
unit is required to recover the nanoparticles. Nano-adsorbents can also be used in
fixed or fluidized adsorbers in the form of pellets/beads or porous granules loaded
with nano-adsorbents. Fixed-bed reactors are usually associated with mass transfer
limitations and head loss; but it does not need future separation process. Applications
of nano-adsorbents for arsenic removal have been commercialized, and their performance and cost have been compared to other commercial adsorbents in pilot tests
[54]. ArsenXnp is a commercial hybrid ion-exchange medium comprising iron
oxide nanoparticles and polymers. ADSORBSIA™ is a nanocrystalline titanium
dioxide medium in the form of beads from 0.25 to 1.2 mm in diameter. Both nanoadsorbents were highly efficient in removing arsenic and ArsenXnp required little
backwash [54, 55]. The estimated treatment cost for ArsenXnp is $0.25–
$0.35/1000 gal if the medium is regenerated, similar to $0.37/1000 gal of Bayoxide
E33, a high- performance granular iron oxide adsorbent [54, 56]. ArsenXnp and
ADSORBSIA™ have been employed in small- to medium-scale drinking water
treatment systems and were proven to be cost competitive.
Membranes and Membrane Processes
The basic goal of water treatment is to remove undesired constituents from water.
Membranes provide a physical barrier for such constituents based on their size,
allowing the use of unconventional water sources. As the key component of water
treatment and reuse, they provide high level of automation and require less land and
chemical use, and the modular configuration allows flexible design [4]. A major
challenge of the membrane technology is the inherent trade-off between membrane
selectivity and permeability. The high energy consumption is an important barrier to
the wide application of pressure-driven membrane processes. Membrane fouling
adds to the energy consumption and the complexity of the process design and operation. Furthermore, it reduces the lifetime of membranes and membrane modules.
The performance of membrane systems is largely decided by the membrane
material. Incorporation of functional nanomaterials into membranes offers a great
opportunity to improve the membrane permeability, fouling resistance, and mechanical and thermal stability, as well as to render new functions for contaminant degradation and self-cleaning.
Current and Potential Applications for Water and Wastewater Treatment