Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 12, pp. 2223−2229.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
M.O. Zhumanova, N. Usanboev, S.S. Namazov, B.M. Beglov, 2009, published in Khimicheskaya Promyshlennost’, 2009, Vol. 86,
No. 5, pp. 217−225.
TECHNOLOGY OF ORGANIC
AND INORGANIC CHEMISTRY
Oxidation of Brown Coal of Angren Deposit
with a Mixture of Nitric and Sulfuric Acids
M. O. Zhumanova, N. Usanboev, S. S. Namazov, and B. M. Beglov
Institute of General and Inorganic Chemistry, Uzbekistan Academy of Sciences, Uzbekistan
Received June 20, 2009
Oxidation of brown coal of Angren deposits by a mixture of nitric and sulfuric acids was
studied in respect of dependence on the concentration of nitric acid (5–30%), concentration of sulfuric
acid in nitric acid solution (2.5–20%), and temperature (40–80°C) at the process duration 2 h and the
ratio of coal : HNO
= 1 : 2. Optimal conditions of the process in terms of maximum yield of humic
acids and the minimum loss of nitrogen oxides were found.
Humic fertilizers and growth substances are of great
interest for agricultural production. They exhibit high
efﬁ ciency at the agrochemical cultivation of various
crops in any soil and climatic conditions. Only being used
together with mineral fertilizers they are able to provide
non-deﬁ cit balance, or even increase the humus content
in the soils of all soil types. At a high content of humus in
the soil the return from fertilizer increases 1.5–2.0 times.
Advance of these fertilizers consists also in the fact that
they decrease content of salts in the swamp-saline soil.
They are good soil conditioners, and thus enable the
creation of new fertile land. While helping to remove
heavy metals, oil, toxic substances and radionuclides
from the soil, they provide a recovery of technogenically
traumatized lands [1–6].
Best raw material for the humic fertilizers includes
manure, peat and the coal oxidized in natural conditions.
There is only poor reserve of manure in the country,
there is no turf, and the coal oxidized under natural
conditions also is available in small amount, from
Shargun coal deposit. Mining of this coal must be carried
out selectively, and is labor consuming. But Uzbekistan
has huge reserves of brown coal [7, 8]. At Angren ﬁ eld it
is produced in amount about 3 million tons per year. This
is not the unoxidized coal in natural conditions. Contents
of humic acids in this material is very low. The raw
material for production of solid humic fertilizers and plant
growth stimulants may only be a coal containing humic
acids above 45% . Therefore Angren coal should be
artiﬁ cially oxidized. The most suitable oxidizing agents
are oxygen and nitric acid. But the oxidation with oxygen
is difﬁ cult technologically. The process is conducted in an
autoclave at a temperature of 260–270°C and a pressure
of 70–100 atm . So it is best to use nitric acid, which
in the republic is quite enough, and the process of the
coal oxidation takes place at atmospheric pressure and
at low temperature.
In  was studied the process of oxidation of brown
coal from Angren deposits by nitric acid in dependence on
the acid concentration (10–40%), temperature (30–60°C),
duration (25–120 min), and the coal : acid weight ratio
(from 1 : 0.4 to 1 : 2). As shown, it is possible to increase
the content of humic acids in coal from 4.1% to 57.2% at
the oxidation with 40% HNO
at 40°C for 2 h at a weight
ratio of organic carbon to nitric acid monohydrate equal
to 1 : 2. But loss of nitrogen oxides (NO and NO
equals 9.2% of the organic part of the obtained product.
The patent  states that at the oxidation of brown
coal using a mixture of nitric and sulfuric acids the
process of converting the carbon-containing raw material
components into humic acids proceeds more efﬁ ciently
and formation of nitrogen oxides is precluded effectively.
Therefore we decided to check these data on an example
of the oxidation of brown coal from Angren deposits.