1070-4272/02/7507-1166$27.00C2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 7, 2002, pp. 1166 !1169. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 7,
2002, pp. 1189!1192.
Original Russian Text Copyright + 2002 by Chernoberezhskii, Dyagileva, Atanesyan, Leshchenko.
AND POLYMERIC MATERIALS
Influence of the Kraft Lignin Concentration on the Efficiency
of Its Coagulation Recovery from Aqueous Electrolyte Solutions
Yu. M. Chernoberezhskii, A. B. Dyagileva, A. A. Atanesyan, and T. V. Leshchenko
St. Petersburg State Technological University of Plant Polymers, St. Petersburg, Russia
Received February 26, 2002
Abstract-The dependence of the aggregation stability of aqueous suspension of kraft lignin on its con-
centration in the system was studied spectrophotometrically in wide ranges of pH and sodium chloride con-
At present, the main procedure of production of
commercial cellulose is kraft cooking of wood [1, 2].
This procedure allows processing of virtually all types
of plant raw materials and production of cellulose
with high strength characteristics. In addition, kraft
cooking has a number of environmental and process
advantages. First, this process provides perfect regen-
eration of chemicals, allowing the use of wood com-
ponents passing into the cooking liquor as a source of
energy. Second, this process allows the most exhaus-
tive treatment of liquor-containing wastewater flows
with arrangement of local water-treatment systems
at the sites of formation of these concentrated flows.
This will decrease the load on the biological treatment
plant by preliminary removal of poorly soluble organ-
ic impurities and reduction of the color index of
wastewaters. These problems cannot be solved by
traditional procedures of biological treatment.
High color index and chemical oxygen demand
(COD) of this wastewater are caused by a significant
concentration of kraft lignin (KL), which is an aromat-
ic compound that is difficult to oxidize biochemically
at the wastewater treatment facilities existing at vir-
tually all paper and pulp plants. Therefore, develop-
ment of procedures of removal of KL from wastewater
is an urgent problem. Coagulation recovery of KL can
be one of such procedures.
Practically any procedure of wastewater treatment,
among them coagulation, includes separation of
a phase to be recovered from wastewater so as to
prevent secondary contamination of surface and under-
ground water. Therefore, decrease in the amount of
the resulting precipitates and their utilization can be
of practical interest.
The choice and substantiation of regimes for re-
covery of poorly soluble part of wastewater (KL)
require detailed studies in this field. The results re-
ported here present a part of complex studies of
colloid-chemical behavior of KL in aqueous systems.
In this work, the aggregation stability of the system
water3lignin3electrolyte was studied spectrophoto-
metrically in a wide range of KL and NaCl concentra-
tions and pH. Characteristics of KL, its colloid-chemi-
cal properties, and procedures of experiments with
[instant mixing] of components were described in
. The systems for studies with KL concentration
from 25 to 1000 mg l
were prepared from weighed
portions of KL by their dissolution in 0.1 M NaOH,
dilution with distilled water, and subsequent addition
of required amounts of HCl and NaCl. The efficiency
of coagulation recovery of KL was determined after
settling for 120 min from the residual KL concentra-
tion in the solution over the separated phase c
in the filtrate c
. Filtration was carried out through
a [blue band] filter. The residual concentration was
determined spectrophotometrically (l = 280 and
480 nm) on an SF-46 spectrophotometer from the op-
tical density of the solution alkalized to pH 11, using
the calibrating plot. The residual concentrations of
KL in the solution and filtrate were plotted vs. pH
of the system.
The pH dependences of the residual concentrations
of KL in the solution (Fig. 1a) and filtrate (Fig. 1b)
at ionic strength of 10
M are shown in Fig. 1. Fig-
ure 1a showes that at a KL concentration of 25 mg l
the solution is stable with respect to sedimentation
throughout the studied range of pH down to pH 1.5.