ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 10, pp. 1690!1695. + Pleiades Publishing, Inc., 2006.
Original Russian Text + L.A. Zemnukhova, O.V. Brovkina, N.A. Didenko, L.E. Kryukova, V.V. Bespalova, E.D. Shkorina, 2006, published in Zhurnal
Prikladnoi Khimii, 2006, Vol. 79, No. 10, pp. 1710 !1714.
AND POLYMERIC MATERIALS
Kinetics of Bleaching of Rice Straw and Husk
with Potassium Peroxoborate
L. A. Zemnukhova, O. V. Brovkina, N. A. Didenko, L. E. Kryukova,
V. V. Bespalova, and E. D. Shkorina
Institute of Chemistry, Far-Eastern Division, Russian Academy of Sciences, Vladivostok, Russia
Received March 23, 2006
Abstract-The kinetics of bleaching with potassium peroxoborate of waste from rice production (straw and
husk), untreated and treated with water, acid, and sodium hydroxide, was studied.
Production of husked rice groats involves forma-
tion of large-tonnage wastes. These wastes can be
a source for production of various types of products
for chemical, medical, food, textile, paper, construc-
tion, and other branches of industry . Rice straw
has long been used as a raw material for production of
the cellulose material . Development of environ-
mentally safe procedures for bleaching of lignocel-
lulose materials without using chlorine-containing
reagents is a topical problem .
This study proceeds with examination of wastes
from rice production and considers the possibility of
using potassium peroxoborate (PPB) for bleaching of
rice straw (RS) and husk (RH).
We chose for the study the RS and RH samples
prepared from rice of the Darii-8 strain cultivated
in Primorskii krai in 2002 . The straw was milled
to particles with a length of 335 cm, the husk was
fractionated, and particles with a size of no less than
2 mm were taken. The raw material was washed with
water and dried at 60oC. The content of inorganic and
organic components of the initial raw material has
been determined previously  and is as follows
(%): 12 and 88% for RS and 20 and 80%, respective-
ly, for RH.
As a bleaching agent we used PPB containing 20%
available oxygen O
whose synthesis is described in
. We studied the effect of PPB on the samples of
the initial raw materials and their residues after treat-
ment (extraction) with water, hydrochloric acid (1 N),
and sodium hydroxide (1 N) at the volume ratio sol-
id : liquid = 1 : 13, treatment duration of 1 h, and
temperature of 90oC. The residual raw materials after
the extraction of soluble substances were filtered off,
washed with water, and dried to constant weight at
60oC. The composition of the extracts was studied
in . The samples were bleached at the optimal
temperature of 95oC, with the concentration of PPB
varied from 6 to 12 g l
, and the process duration,
from 5 to 60 min.
The rate of PPB decomposition was estimated
from variation of the O
content in the solution, de-
termined by permanganatometric titration , and
was calculated from the ratio ln [c
is the initial concentration of O
in the solution,
) is the concentration of available oxy-
gen undecomposed by the time t. The rate constants
decomposition were evaluated from the rate
equation of a first-order reaction . The bleaching
power of PPB was estimated on a Specol device by
the procedure described in ; freshly calcined
magnesium oxide was used as reference. We anal-
yzed the spectrophotometric curves of the reflection
coefficient r in the wavelength range 4003700 nm.
The results are listed in Tables 1 and 2 and shown
in Figs. 13 4.
Initial (untreated) RS. The parameters of ther-
mal decomposition of aqueous solutions of PPB in