Page 255 - Materials Chemistry, Second Edition

236 Life Cycle Assessment of Wastewater Treatment

A wide assortment of agricultural waste and residues has been investigated for the
removal of heavy metals. This chapter assesses the practicality of using agricultural
waste biomass for heavy metal removal in light of

• Heavy metal adsorption limits of agricultural waste biomass
• The impacts of working parameters for process advancement
• Adsorption instruments
• Change strategies for creating better adsorbents

11.5.4 MeMbrane filTraTion
Membrane filtration innovations with various sorts of films indicate awesome guar-
antee for heavy metal removal due to their high efficiency, simple operation, and
space-saving features (Kurniawan et al., 2006; Barakat and Schmidt, 2010). The
membrane forms used to remove metals from wastewater are ultra-filtration (UF),
reverse osmosis (RO), nanofiltration, and electro-dialysis.

11.5.4.1 Ultra-Filtration
UF is a membrane procedure working at low transmembrane weights for the removal
of dispersed and colloidal material. UF uses films that permit the passage of water
and low–atomic weight solutes while retaining macromolecules and hydrated metal
particles, which are bigger than the pore size of the membrane (Samper et al., 2009).
Since the pore sizes of UF films are bigger than dispersed metal particles as hydrated
particles or as low–atomic weight constructions, these particles would easily pass
through UF films. To achieve high removal efficiency for metal particles, micel-
lar enhanced ultra-filtration (MEUF) and polymer improved ultra-filtration (PEUF)
have been proposed.
MEUF has turned out to be a successful separation strategy to remove metal
particles from wastewater. This separation strategy uses the addition of surfactants
to wastewater. Whenever the concentration of surfactants in fluid systems is above
the critical micelle concentration (CMC), the surfactant particles will assemble into
micelles that can bind metal particles to form extensive metal-surfactant structures
(Landaburu-Aguirre et al., 2009). The micelles containing metal particles can be
retained by a UF film with pore sizes smaller than micelle sizes, while the untrapped
species promptly go through the UF film. To achieve the best results, surfactants of
electric charge opposite to that of the particles to be removed must be used. Sodium
dodecyl sulfate (SDS), an anionic surfactant, is regularly chosen for the compre-
hensive removal of heavy metal particles in MEUF. For MEUF, a surfactant is used
to make micelles, while for complexation–ultrafiltration, complexation agents, for
example, poly(ethylenimine) (PEI) and poly(acrylic acid), are used to specifically
bind cations.
PEUF has likewise been proposed as an achievable strategy to separate an awe-
some assortment of metal particles from fluid streams. PEUF uses water-solvent
polymer to complex metallic particles and form a macromolecule having a higher
sub-atomic weight than the sub-atomic weight cut-off of the film. The macromol-
ecules will be retained when they are pumped through UF film. From that point