Environmental Engineering Reference
In-Depth Information
Naturally occurring materials, such as various types of zeolites, bauxite, laterite, dolo-
mite, shale, limestone, calcite, vermiculite, and iron-rich sands, have been examined.
Zeolites (hydrous aluminum silicates) (Sakadevan and Bavor, 1998) can contain calcium,
ferric, magnesium, and titanium oxides at much lower concentrations. Bauxite is a natu-
rally occurring mixture of hydrous aluminum oxides and aluminum hydroxides and can
also be high in ferric oxides. Laterite is low-grade bauxite (Wood and McAtamney, 1996)
that is high in iron oxides and aluminum hydroxides. Shale is a issile rock formed by the
consolidation of clay, mud, or silt, and has high concentrations of iron and aluminum (Pant
et al.,
2001). Several industrial and wastewater by-products have also been examined as
phosphorous sorption media. These include blast furnace slag, steel furnace slag, red mud,
ly ash, HiClay Alumina, and aluminum- and iron-based water treatment residuals. All of
these materials are either rich in aluminum, iron, and/or calcium.
Engineered media are more expensive but also much more effective. These media typi-
cally contain iron, aluminum, calcium, or lanthanum, and are engineered to produce high
surface area and good hydraulic properties. Examples include activated alumina, which
is characterized by high aluminum content, high speciic surface area, and high macropo-
rosity. Lightweight expanded clay aggregates contain iron. PhosLock™ is a bentonite clay
treated by an ion-exchange process where lanthanum ions displace sodium ions within the
clay matrix (5%). Modiied diatomaceous earth utilizes lanthanum oxide and lanthanum-
aluminum oxide to remove phosphorus, also used for arsenic and arsenate removal (Misra
and Lenz, 2003). Other engineered media developed for arsenic removal have also been
evaluated for phosphorus removal, including deposition of active nano-iron materials onto
a porous polymer resin (Layne-RT) or activated carbon. Product prepared by MetaMateria
uses nano-iron oxide crystals grown within a highly porous iron ceramic (Meta-PO4™).
Testing shows much higher capacity than naturally occurring minerals or activated alu-
mina (Safferman et al., 2007). A summary of performance for various media is shown in
Table 31.1.
TABLE 31.1
Examples of Phosphorus Sorption Media
Sorption Media
Capacity (mg/g)
Reference
Lightweight aggregate
0.037
Zhu et al. (1997)
Steel furnace slag
0.38
Mann (1997)
Blast furnace slag
0.4
Mann (1997)
Zeolite
0.46
Drizo et al. (1999)
Bauxite
0.61
Drizo et al. (1999)
Fly ash
0.63
Mann (1997)
Shale
0.65
Drizo et al. (1999)
Limestone
0.68
Drizo et al. (1999)
Zeolite
2.15
Sakadevan and Bavor (1998)
Hematite
1.43
Sakadevan and Bavor (1998)
Goethite
16.4
Oh et al. (1999)
Alumina
17.1
Oh et al. (1999)
Allophane
51
Oh et al. (1999)
Meta-PO4 >10 mg/L
80+
Helferich (2011)
Meta-PO4 <10 mg/L
40
Helferich (2011)
