Page 277 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

232 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

Fractal: An object or substance of irregular shape that may Isoelectric point: When a particle does not migrate toward
be difficult to define in terms of dimensions. either electrode in an electric field, it is said to be at
Fulvic acid: Similar to HAs except it is soluble at pH ¼ 1.0 its isoelectric point (Pilipovich et al., 1958).
and believed to be in true solution, vis-à-vis being Isotherm: Equilibrium relationship between an adsorbate
colloidal (Randtke, 1988, p. 43). (such as an organic compound) and an adsorbent
Functional groups: An ionic group attached to a bonding (such as activated carbon). In the case of NOM, the
site on a polymer molecule that ionizes. Examples of main interest relates to the capacity of a metal
such groups include: carboxyl ( COOH); amino hydroxide precipitate, for example, Al(OH) 3 as the
( NH 2 ); and sulfonic acids. Carboxyl groups ionize adsorbent. Two types of mathematical expressions
at pH > 4 (i.e., COOH þ H 2 O ! COO þ for isotherms are the Langmuir and the Freundlich
H 3 Oþ) and the amino group binds a proton at (see Chapter 14).
pH < 10 (i.e., NH 2 þ H 3 O þ! NH 3 þþ H 2 O). Jar test: A setup of six 1.5 L square jars each filled with 1.0 L
Gouy–Chapman double layer: An accounting for the of test water and arranged under a gang paddle
charge distribution in an electrical double layer, giv- stirring apparatus. A common use is to determine
ing the c o distribution with distance from the inter- coagulant dosage by applying a different dosage to
face. An exact treatment of the spherical double layer each jar with about 2 min rapid-mix at 300 rpm
is possible only by numerical techniques (see Loeb, followed by 10–15 min slow mix at about 10–20
1961). rpm, followed by about 20 min settling. The super-
Gram-equivalent weight: Atomic or molecular weight of natant is sampled for turbidity or other characteristic
an ion divided by its valency, for example, Cu 2þ ¼ of interest.
63.57=2 ¼ 31.79. Kinetics: Rate of reaction. Reaction orders are zero, first, and
Hydration: The ‘‘state’’ of a free metal ion that has been second. A second-order reaction is defined math-
complexed with water. In aqueous solution, all free ematically, dC=dt ¼ kC.
metal cations are complexed with water, that is, are Lennard-Jones 6-12 potential: As molecules approach one
hydrated (Stumm and Morgan, 1996, p. 258). another at molecular distances, that is, nanometers,
Humic acid: An organic acid insoluble at pH ¼ 1.0. another force, the Born repulsion, becomes signifi-
12
Humic substances: Typically, humic substances are divided cant and is given as w(Born) ¼ B=r . This, com-
into the more soluble FAs and the less soluble HAs. bined with the London force gives the net
12 6
The humic molecules are chemically complex; interaction, that is, w(r) ¼ B=r C L =r , which is
they are part aromatic and part aliphatic (Dempsey, called, commonly, the Lennard-Jones 6-12 potential.
1989, p. 2). The Born potential is repulsive and shows an expo-
Hydrolysis: Dissecting the word hydrolysis, it refers to nential decline with r; the London force is attractive
‘‘lysis,’’ a breaking apart, of something through the and shows an exponential increase. Adding the two
action of water. In aquatic chemistry the ‘‘hydrolysis functions, results in a ‘‘potential well,’’ which is a
of metal ions’’ is defined as a lysis of water itself by zone of adhesion.
the metal ion, not vice versa, for example, Mg 2þ þ Ligand: Ions or molecules that are attached to a central atom
H 2 O ! MgOH þ H (Gregory, 2006, p. 123). or ion as a part of a complex. The central species is
þ
þ
Illite: Illites are distinguished by the lack of interlayer swell- an electron acceptor and the ligand is an electron
ing. See also clay. donor.
Ionogenic group: Functional group attached to a surface that Log R: Log removal of a given constituent, defined,
has dissociable ion, for example, H ,Na , etc.
þ
þ
Ionic strength: The definition of ionic strength is (Alberty C(effluent)
and Silby, 1992, p. 246): Log R ¼ log
C(influent)

1 X In other words, suppose C(effluent) ¼ 0.01 cysts=L
2 1 2 2
i
2
1
2 2
I ¼ m i z ¼ m 1 z þ m 2 z þ (G9:2) and C(influent) ¼ 10 cysts=L. Then,
i

0:01 cysts=L
Log R ¼ log ¼ 3:0
where 10 cysts=L
I is the ionic strength (mol=kg solvent)
m i is the molal concentration of an ion, i,in The expression is, commonly, ‘‘3-log removal.’’
solution (mol i=kg solvent) London forces: A portion of the van der Waals interaction
z i is the valence of ion forces, also called ‘‘dispersion’’ interaction. The
potential energy of molecule separation is inversely
The summation pertains to all ions in solution, that proportional to the sixth power of their separation
is, all positive ions and all negative ions. (Shriver and Atkins, 1999, p. 55).