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ПОЛУЧЕНИЕ КАЛЬЦИЙ-МАГНИЕВЫХ ХЛОРАТОВ НА ОСНОВЕ ДОЛОМИТОВ
ИЗ МЕСТОРОЖДЕНИЯ ШОРСУ
З.А.Хамракулов, Х.А.Хамракулова, С.Тухтаев*, М.К.Аскарова*
OBTAINING OF CALCIUM-MAGNESIUM CHLORATES ON THE BASIS OF DOLOMITES OF SHORSU'S DEPOSIT
Z.A.Khamrakulov, Kh.A.Khamrakulova, S.Tukhtaev*, M.K.Askarova*
Ферганский политехнический институт, Республика Узбекистан, [email protected] *Институт общей и неорганической химии АН РУз, Ташкент, [email protected]
Представлены результаты исследования кинетики процесса конверсии раствора хлорида кальция и магния, полученного в результате разложения доломита соляной кислотой, с отделением нерастворимого остатка хлората натрия и без его отделения. Определены энергия активации процесса, последовательность и постоянная величина скорости реакции конверсии. Целесообразность конверсии установлена при 363 K с отделением остатка.
Ключевые слова: доломит, хлорид кальция, хлорат натрия, дефолианты, конверсия, степень конверсии, энергия активации
The paper provides the study results of kinetics process of conversion of calcium and magnesium chloride solution, obtained as a result of decomposition of dolomite with hydrochloric acid, with sodium chlorate without residue as well as with its residue. The activation energy of the process, order and constant of conversion reaction rate were determined. The expediency of conversion was set at 363 K with residue.
Keywords: dolomite, calcium chloride, sodium chlorate, defoliants, conversion, degree of the conversion, activation energy
In terms of cotton production and harvest Uzbekistan stays fifth in the world. Natural maturation process of the cotton crop, especially in Central Asia, one of the most northern cotton growing regions of the world, cotton production may take several weeks. Therefore, it is necessary to accelerate the process of crop ripening and plants' leaves pulling-down. This problem can be solved by defoliants applying.
The existing assortment of the defoliants recommended to application not to the full corresponds to the modern requirements shown by agriculture and members of public health services to chemical protection means of plants. Chlorate containing defoliants from the point of view of production and application are most low toxic and cheaper preparation.
Widely used in agriculture at Uzbekistan, magnesium chlorate defoliant contains in its composition 36% of active ingredients [1]. However, for the production of magnesium chlorate as 50% raw material, magnesium chloride (bischofite) is imported abroad being expansive for local industry. This leads to attraction of local defoliant production basing on local raw materials.
This urgent problem can be solved by using of decomposition products appeared in a process of hydrochloric acid affect on natural local dolomite taken as a raw material instead of imported bischofite.
The aim of this research is to obtain mixed calcium-magnesium chlorate defoliant by converting of calcium - magnesium chlorides solution obtained by decomposition of dolomite from of Fergana's "Shorsu" deposit by hydrochloric acid [2], with sodium chlorate.
A solution of calcium and magnesium chlorides, containing on average: 21.49% CaCl2, 15.50% MgCl2, 1.20% NaCl h 61.81% H2O and sodium chlorate manufactured byJC «Fergana'azot» was employed for the work.
For the purpose of obtaining of calcium-magnesium chlorate defoliant, the conversion process of chlorides of calcium and magnesium with sodium chlorate, depending on the temperature and duration of the process, was studied. The conversion was carried out at 323, 348 and 363 K and duration of the experiments 30, 60, 90 and 120 minutes without residue and with solution residue.
The process of the conversion was studied in a round bottom flask with 250 cm3 capacity, equipped with a stirrer. For the study, it was filled with 100 g of a solution of calcium and magnesium chlorides, derived from dolomite taken at "Shorsu" deposit, and an equivalent amount of sodium chlorate. The flask was placed in a thermostat at a predetermined temperature and its content was intensively stirred. After a certain time interval, the liquid phase was separated from the sediment and the corresponding chemical analysis of the sediment, on the content of chlorine - and chlorate-ions, sodium was conducted. The content of chlorate and chloride-ions was determined with the volumetric permanganatometric and argentometry methods [3,4], and the amount of sodium, calcium and magnesium was determined with atom-absorption spectrophotometer method [5]. After the first filtration step, the liquid phase was cooled up to 293 K, wherein the crystals of unreached portions of sodium chlorate fell. Further, a second filtering step was
conducted to separate the liquid phase from the crystals of sodium chlorate. The liquid phase was analyzed after the second filtration for the content of ClO3-, Cl-, Ca+2, Mg+2 and Na+ ions examination (fig. 1).
Time M, min 60
Fig.1. Influence of temperature and the time of process to degree of conversation of calcium and magnesium chlorides with sodium chlorate: 1 — for conversion without residue; 2 — for conversion with residue
The experimental data at figure 1 indicate that the degree of formation of calcium and magnesium chlorate from calcium and magnesium chlorides during the process without solution residue after 60 minutes at 323, 348 and 363 K are respectively 18.67, 30.26 and 42.11%, and after 90 minutes, respectively, 28.31, 41.11 and 55.68%. By increasing the duration of the conversion process up to 120 minutes, the increase of the degree of conversion varies slightly and at temperature mentioned above the degrees of conversion were 32.12, 45.62 and 58.93% respectively. The amounts of calcium and magnesium chlorates in the solution after conversion under the above mentioned temperatures and process duration of 60, 90 and 120 minutes were respectively 7.20, 11.66, 16.23%; 10.91, 15.84, 21.46% and 12.38, 17.58, 22.71%.
Studies of conversion of calcium and magnesium chlorides with sodium chlorate conducted without the solution residue showed that the maximum degree of conversion at 363 K for 120 minutes achieved only 58.93%, which is not high enough. To increase the degree of conversion, studies of calcium and magnesium chlorides conversion with sodium chlorate carried at solution residue were fulfilled.
In carrying out the conversion with the residue, the intensity of the process considerably accelerates, as demonstrated by the data in figure 1. Thus, at 323 K after 60, 90 and 120 minutes the degree of conversion increases by 1.30, 1.24 and 1.18 times. As a result of an increase in the temperature, the conversion process accelerates and the degree of the water removal increases. After the duration of the process of 60, 90 and 120 minutes at 348 K, the degree of conversion is increased by 1.51, 1.47 and 1.45 times, and at 363 K after 60, 90 and 120 minutes the degree of conversion reaches a maximum value, i.e. is increased by 1.43, 1.36 and 1.35 times. At a temperature of 363 K during 120 minutes, maximum degree of conversion of 79.27% is achieved. Conversion product contains: 40.5% E calcium and
magnesium chlorate; 7.5% E calcium and magnesium chloride; 1.3% sodium chloride, and the remaining being water.
For the conversion process, the order of reaction on kinetic equation (*) was determined [6]:
К =
2.303
lg:
C
(*)
(C -
with C0 h Ct respectively being concentration of calcium and magnesium chlorides in the initial stage of the conversion and for the past time interval (t); K - constant of the conversion speed.
According to the data achieved, the order of the process of calcium and magnesium chlorides conversion with sodium chlorate is of the first order. Evidence of this is that the constant of the conversion velocity, calculated using equation (*) based on experimental data, remains practically constant for each temperature within the first 120 minutes (fig.1). In addition, the rectilinear dependence of lg (Co-CT) on t attests the first reaction's order of the process of the conversion of calcium and magnesium chlorides with sodium chlorate (table 1).
Table 1
The constant of the velocity of interaction of calcium and magnesium chlorides with sodium chlorate in the conversion without residue and with residue
Time (т), Constant of the speed, (К-10-2, т-1)
minute 323 К 348 К 363 К
for conversion without residue
30 0.3504969 0.5462018 0.7922551
60 0.3443341 0.5998822 0.9100100
90 0.3693834 0.5874486 0.9029255
120 0.3225369 0.5069342 0.7403862
for conversion with residue
30 0.4299601 0.8759620 1.4730412
60 0.4643367 1.0220732 1.5308858
90 0.4809594 1.0258499 1.5604688
120 0.3986173 0.9066137 1.3115096
The reaction velocity's constant increases with temperature increasing (see fig. 1 and table 1) and its change depending on temperature is a subject to the Arrhenius law that is confirmed with the rectilinear graph dependence nature of lg K on 1/T.
The optimal parameters of mixed calcium and magnesium chlorate obtaining is the following the conversion of chlorides of calcium and magnesium with sodium chlorate at their molar ratio accordingly 1:2, during 120 minutes at 363 K temperature with the solution residue.
TSh. 88.16-34:2010. Жидкий хлорат магниевый дефолиант. Технические условия. Ташкент, «Узстандарт». 2010. 10 с.
Хамракулов З.А., Аскарова М.К., Тухтаев С. Получение раствора хлоридов кальция и магния из доломита. // Химическая промышленность. 2013. №2. С.70-78. ГОСТ 12257-77. Хлорат натрия технический. Технические условия. М.: Издательство стандартов, 1987. 19 с. Дорохова Е.Н., Прохорова Г.В. Аналитическая химия. Физико-химические методы анализа. М.: Высш. шк., 1991. 255 с.
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6. Оспанов Х.К. Физико-химические основы избирательного растворения минералов. М.: Недра, 1993. 175 с.
References
1. TSh. 88.16-34:2010. Zhidkii khlorat magnievyi defoliant. Tekhnicheskie usloviia [Liquid magnesium chlorate defoliant. Specifications]. Tashkent, "UZSTANDARD" Publ., 2010. 10 p.
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