BTG Mutek PCD-05 Smart, Руководство по эксплуатации

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© BTG Operation Manual Mütek
TM
PCD-05, September 2017 13
II. Product description
2.1.2 Calculation of charges
Polyelectrolyte titration
For quantitative charge measurements of the sample, a
polyelectrolyte titration has to be conducted which uses
the streaming potential to identify the point of zero
charge (0 mV).
To this end, add an oppositely charged polyelectrolyte
of known charge level to the sample as a titrant.
The titrant charges neutralize existing charges of the
sample. Titration is stopped as soon as the point of zero
charge (0 mV) is reached.
The titrant consumption obtained in ml forms the basis
for further calculations.
Provided equal samples are titrated under identical con-
ditions, the consumed titrant volumes can be directly
compared. Normally, however, the charge level present
in aqueous samples is expressed in terms of the anionic
or cationic demand in eq/l.
Calculation of cationic/ anionic demand
The cationic or anionic demand [eq/l] of a sample is cal-
culated by the following formula:
C1: Concentration of titrant in [N] or [eq/l]
C2: Concentration of the titrated sample in [eq/l]
V1: Titrant consumption in [l]
V2: Sample volume to be titrated in [l]
Example:
10 ml filtrate of an anionic fiber suspension is pipetted
into the measuring cell of the Mütek™ PCD-05 and titra-
ted with a 0.001 N Poly-Dadmac solution until the point
of zero charge is reached. In the example, 5 ml cationic
polyelectrolyte (Poly-Dadmac) is required.
The cationic demand of the sample is the following:
0.0005 eq/l or 0.5 meq/l or 500 µeq/l
If the charge level is to be identified for an active subs-
tance (starch, wet strength agent) or for solids (pigment
slurry), the mass of the product should additionally be
included in the calculation to obtain the so-called speci-
fic charge density.
Calculation of the specific charge density
The specific charge density q [eq/g] is calculated by the
following formula:
V: Consumed titrant volume [l]
c: Titrant concentration [eq/l]
m: Solids of sample or its active substance [g]
q: Specific charge density [eq/g]
Example:
A 10 ml sample of a 0.1% Ti0
2
suspension contains
0.01 g solids at m = 0.01 g.
The consumption of cationic polyelectrolyte up to the
point of zero charge is 2.5 ml for a titrant concentration
of 0.001 N.
The specific charge density is the following:
250*10
-6
eq/g or 0.250 meq/g or 250 µeq/g
By multiplying the specific charge density in eq/g by the
Faraday's constant F = 96485 C/eq, the total charge in
C/g will be obtained.
C1 * V1
C2 =
V2
0.001 eq/l * 0.005 l
C2 = = 0.0005 eq/l
0.01 l
V * c
q =
m
0.0025 [l] * 0.001 [eq/l]
= 250 * 10
-6
[eq/g]
0.01 [g]
q =