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244 4. Adsorption and Ion Exchange

large surface area (~900 m 2 /g) and an apparent density of approximately 0.50 g/cm 3 . With
the exception of coconuts, this type of carbon is harder than other types, thus being more
resistant to abrasion, and can be more vigorously backwashed without damage. Bituminous
GAC is one of the most frequently used carbons for the treatment of low concentrations of
low molecular weight organic compounds in water.
Lignite GA C : This presents a total surface area of 650 m 2 /g and an apparent density of
0.50 g/cm 3 , approximatelyand specif . It is usually used for liquid-phase adsorption, , ically
in decolorizing applications because it has a higher percentage of meso (transitional) and
C, macro pores than bituminous GA and therefore is appropriate for larger molecules.
v
Cs Coconut-shell-based GA : These hae a high portion of micropores and present sur-
face areas generally oer 1000 m v 2 /g and apparent densities of about 0.50 g/cm 3 . Being
v
manufactured mainly from ve material, they do not exhibit the fully de v eloped
getati
e
pore structure of coal-based carbons. y are used in both v- and liquid-phase appli- apor The
cations. Coconut shell–based carbon is slightly more expensive to produce than coal-based
v
GAC, since about only 2% of the raw material is recoerable as GA versus 8–9% for C,
coal-based carbons. In Table 4.1, the basic properties of common materials used in the
manufacture of actiated carbon are presented. v
A look into activated carbon
v
Activated carbon is an adsorbent eely used for the purification of
xtensi
water and gaseous waste streams. In relation to water treatment, it is
fecti generally efve in removing large organic molecules and nonpo-
, ater lar compounds from w and its use is suggested for the follo w-
ing compounds (EPA, 2000):

(a) Organic compounds : aromatic solvents (benzene, toluene,
nitrobenzenes, and xylene), chlorinated aromatics (PCBs,
chlorobenzenes, chloronaphthalene, endrin, and toxaphene),
phenols and chlorophenols (cresol, resorcinol, and nitrophe-
nols), polynuclear aromatics (acenaphthene, benzopyrenes,
naphthalene, and biphen pesticides and herbicides (DDT aldrin, chlordane,
yl),
,
,
BHCs, heptachlor carbofuran, atrazine, simazine, alachlor and aldicarb), chlorinated ,
Table 4.1

Basic properties of common materials used in the manufacture of acti v ated carbon
(Dabrowski et al ., 2005; Streat et al ., 1995)
Raw material Carbon (%wt) Volatiles (%wt) Density (g/cm 3 ) Ash (%wt)
Wood 40–45 55–60 1.25–2.5 0.3–1.1
Lignin 35–40 58–60 2.5–3.33 –
Nutshells 40–45 55–60 0.71 –
Lignite 55–70 25–40 0.74–1 5–6
Coal 65–95 5–30 0.55–0.8 2–15
e Petroleum cok 70–85 15–20 0.74 0.5–0.7