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CHEMICAL SCIENCES
ADSORPTION OF SURFACE ACTIVE SUBSTANCES ON ORGANIC-INTERCALATED BENTONITES UNDER STATIC CONDITIONS Seytnazarova O.M.1, Kalbaev A.M.2, Mamataliev N.N.3, Abdikamalova A.B.4 (Republic of Uzbekistan) Email: Seytnazarova579@scientifictext.ru
1Seytnazarova Oksana Muratbaevna - Doctoral Student, DEPARTMENT OF GENERAL CHEMISTRY, TASHKENT STATE TECHNICAL UNIVERSITY NAMED AFTER ISLAM KARIMOV; 2Kalbaev Alisher Maksetbaevich - Master's Student, DEPARTMENT OF GENERAL AND OIL-GAS CHEMISTRY, NATIONAL UNIVERSITY OF UZBEKISTAN NAMED AFTER MIRZO ULUGBEK; 3Mamataliev Nozim Nimadzhonovich - Junior Researcher; 4Abdikamalova Aziza Bakhtiyarovna -PhD, Senior Researcher,
LABORATORY OF COLLOID CHEMISTRY, INSTITUTE OF GENERAL AND INORGANIC CHEMISTRY ACADEMY OF SCIENCES OF THE REPUBLIC OF UZBEKISTAN, TASHKENT, REPUBLIC OF UZBEKISTAN
Abstract: the results of a study of the adsorption characteristics of organobentonites in relation to organic dyes in the presence and without surfactants are presented. It was found that the surfactant impurity slightly reduces the sorption of anionic dyes on the Ch-KR adsorbent; however, with an increase in the sorption time, the sorption capacity increases, and the maximum degree of dye extraction reaches 70-90% for the concentration range of the impurity sulfonol 40-70 mg/l. The HDTMA-KR sample possesses higher adsorption capacities. As the results of studies have shown, an increase in the surfactant concentration of more than 160 mg/l negatively affects the degree of clarification of dye solutions, due to the binding of active surfactant ions by adsorption centers and overlapping the surface of the modified montmorillonite, restricts the access of large dye molecules. Keywords: organobentonite, adsorption, surfactant, sulfonol, dye, nonylphenol.
АДСОРБЦИЯ ПАВ НА ОРГАНИКА-ИНТЕРКАЛИРОВАННЫХ БЕНТОНИТАХ В СТАТИЧЕСКИХ УСЛОВИЯХ
1 2 3
Сейтназарова О.М. , Калбаев А.М. , Маматалиев Н.Н. , Абдикамалова А.Б.4 (Республика Узбекистан)
1Сейтназарова Оксана Муратбаевна - докторант, кафедра общей химии, Ташкентский государственный технический университет им. Ислама Каримова; 2Калбаев Алишер Максетбаевич - магистрант, кафедра общей и нефтегазовой химии, Национальный университет Узбекистана им. Мирзо Улугбека; 3Маматалиев Нозим Нимаджонович - младший научный сотрудник, 4Абдикамалова Азиза Бахтияровна - PhD, старший научный сотрудник, лаборатория коллоидной химии, Институт общей и неорганической химии Академия наук Республики Узбекистан, г. Ташкент, Республика Узбекистан
Аннотация: приведены результаты исследования адсорбционных характеристик органобентонитов по отношению к органическим красителям в присутствии и без ПАВ. Установлено, что примесь ПАВ несколько снижает сорбцию анионных красителей на адсорбенте Х-КР, однако с увеличением времени сорбции сорбционная емкость
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увеличивается, а максимальная степень извлечения красителя достигает 70-90% для интервала концентрации примесного сульфонола 40-70 мг/л. Более высокими адсорбционными способностями обладает образец ГДТМА-КР. Как показали результаты исследований увеличение концентрации ПАВ более 160 мг/л негативно влияет на степень осветления растворов красителей, за счет связывания активных ионов ПАВ адсорбционными центрами и перекрывая поверхность модифицированного монтмориллонита ограничивает доступ крупных молекул красителей. Ключевые слова: органобентонит, адсорбция, ПАВ, сульфонол, краситель, нонилфенола.
In 50-60 years of the last century, the production and mass use of new chemical compounds -synthetic surfactants began. Currently, surfactants differing in composition are widely used in everyday life and industrial production: in the preparation of lubricating fluids, anti-corrosion compounds, electrolytic coatings, in oil production, in mining flotation, to obtain fire-fighting foam, for dyeing and oiling textile fibers, as components of paint and varnish compositions and others [1, 2, 3]. In industrial wastewater, surfactants are in the form of soluble compounds. Some of them are distributed over the surface of the water film, and some of them settle and accumulate in bottom sediments and under anaerobic conditions they can become a source of secondary pollution of water bodies. The highest concentrations of synthetic surfactants are observed in wastewater from the processes of washing and washing various products, laundries, dyeing and finishing industries, car washes. Moreover, the composition of this wastewater includes anionic and nonionic surfactants, which are the most difficult to naturally biodegrade [4].
At present, granular activated carbon is widely used in the production cycle of the textile industry in installations for treating effluents from synthetic surfactants. The use of activated carbons is promising at the stages of wastewater treatment, with the content of synthetic surface active substances not exceeding 100-200 mg/l, and only in this case it is possible to achieve high cleaning results. However, the content of only anionic and nonionic surfactants has been found to vary widely both for the general runoff and for the dye shop runoff. After dyeing with reactive dyes, the textile material is exposed to a surfactant solution to remove the hydrolyzed dye, which also results in the formation of large amounts of dye and surfactant mixtures in the wastewater from the dye shop. Therefore, it is advisable to study the processes of adsorption of various surface active substances and their mixtures on organobentonites. In the experiments, the processes of adsorption from aqueous solutions of mixtures of nonionic (nonylphenol) and anionic (sulfonol) surface active substances in a wide range of concentrations and the effect on the adsorption of bright red 6B and bright blue 2B dyes on organobentonites were studied.
The choice of this Anionic surfactant is due to the use of anionic surfactant as a dispersant in an amount of up to 50% of technical forms of dispersed dyes. During the dyeing process, various wetting agents are also introduced into the dyeing container, which are usually nonionic surfactants [4]. For the study, aqueous solutions of sulfonol and nonylphenol were prepared in a mass ratio of 1:1 with a total concentration of 20 to 200 mg/l. Determination of the amount of adsorption on surface active substances was carried out by studying the dependence of electrical conductivity on the total concentration of surface active substances in solution. To measure the electrical conductivity of aqueous solutions of sulfonol, the method of direct conductometry was used [5]. The electrical conductivity of the solutions under study was measured using a Mettler Toledo conductometer at a temperature of 25 ± 1 °C. The setup was calibrated using a standard solution: Mettler Toledo Conductivity Standart 1413 mkCm/cm at 298 K. At 25 °C, the electrical conductivity of the standard solution was: x = 1403 mkCm/cm, which is the cell constant. Sulfonol adsorption was carried out in a static mode at a temperature of 25 °C. The method for studying adsorption from solutions is based on determining the concentration of the initial solution and determining the concentration of anionic surface active substances remaining in the solution after adsorption. For each solution, surface active substances with a volume of 50 cm3 were added to 0,05 g of adsorbent samples. After the onset of adsorption equilibrium (about 4-6 hours) according to the dependence с = f (C), using the method of boundary concentrations, the values of the equilibrium concentration of surface active substances were found. The amount of adsorption (A)
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was calculated as the ratio of the mass of the adsorbent to the change in the amount of adsorbate in the solution. According to the results of measuring the surface tension, depending on the concentration of solutions, surface active substances before and after adsorption on organobentonites HDTMA-KR and Ch-KR [6], adsorption isotherms were obtained, which are shown in Fig. 1.
Line I Linc2
Fig. 1. Isotherms of surfactant sorption on: 1) HDTMA-KR; 2) Ch-KR
As the curves of the adsorption isotherm diagram show, the studied organobentonites have a stepwise character. The sample HDTMA-KR possesses higher sorption characteristics. This is probably due to the nature of the modifier, the presence of a hydrophobic radical in it, which, after the introduction of the interlayer space, retains its structure and, at the same time, hydrophobizing the surface of montmorillonite, increases the adsorption of large micelles on them. In the initial sections of the curve, a sharp rise is observed, and then, starting from the equilibrium concentration values of 5 mg/l to 25 and 30 mg/l for HDTMA-KR and Ch-KR, respectively, a rectilinear section is observed with respect to the abscissa, which indicates the onset of adsorption equilibrium in the system Surface active substances + organobentonite. Then, a sharp rise is observed on the curves, which corresponds to the micelle concentrations of the formation of surface active substances, at which high adsorption values are observed in the adsorbent: adsorbate phase section. Consequently, the adsorption activity of organobentonites with respect to surface active substances, in addition to the nature of the adsorbent surface, is influenced by temperature, sorption time and the amount of surface active substances, i.e. achievement of critical micelle concentration values. At a concentration below the CCM, the adsorption isotherms of both adsorbents have a Langmuir character; the adsorption layer has a monomolecular layer with a horizontal adsorbate orientation. At concentrations of micelle formation, surface active substances, the value of adsorption increases sharply, resulting in the formation of a more complex polymolecular adsorption layer. The experimental data obtained on the study of adsorption of mixtures Anionic surface active substances and surface active substances on orgonobentonites HDTMA-KR and Ch-KR contributed to the establishment of quantitative characteristics of orgonophilic montmorillonites and the process of sorption in them: sorption time, sorption capacity and degree of extraction of surface active substances. The results of determining the sorption characteristics depending on the initial concentrations of adsorbates are given in table 1.
C, Mg/l
Table 1. Dependence of the characteristics of the sorption process on the initial concentration of surface active substances in solution (process conditions: temperature 25 ± 1 °C, pH=6.4, adsorbent consumption 2
g/l, process duration 6 hours)
Initial concentration of SAS, mg/l Adsorbent
HDTMA-KR Ch-KR
A, Mg/g SI*, % A, Mg/g SI*, %
25 0,48 96,1 0,41 82,1
50 0,54 54,8 0,56 56,1
75 0,62 41,3 0,65 43,3
100 0,71 35,5 0,74 37,1
125 0,76 30,4 0,77 30,8
150 1,18 40,3 1,01 34,1
175 0,91 26,1 0,84 24,1
200 1,02 25,5 0,96 24,1
At the same time, the influence of the pH values of the medium on the sorption parameters of organobentonite samples was studied. In fig. 2 shows the results of determining the amount of adsorption in a wide range of pH values of the medium. It was found that when the pH of the medium changes, the surface charge of montmorillonite, which is positive in an acidic medium, passes through the point of zero charge and becomes negative in a weakly acidic and alkaline medium. As it turned out, the amount of adsorption of nonionic surfactants on HDTMA-CR have stable values in the range of pH values from 3-8. However, a further change in pH completely destroys the adsorption equilibrium in the system of adsorbent-surface active substances. At pH values close to the point of zero charge, the surface active substances Anion has a low affinity for the OH-groups of the organobentonite surface. Consequently, under such conditions, the adsorption capacity of the HDTMA-KR and Ch-KR samples has a small stable value. A sharp increase in the amount of adsorption of anion surfactants on the Ch-CR is observed at pH 2<6, while adsorption increases very rapidly along with an increase in pH. This can be explained by the fact that at low currents of pH, adsorption occurs exclusively as a result of the interactions of hydrophobic parts, while with an increase in pH, ionic ones are also manifested along with this interaction. Considering that montmorillonite above the zero charge point has a positive charge, which increases with increasing pH, the affinity of surfactant anions will increase with increasing pH. The adsorption of nonionic surfactants can be attributed to its physical form, therefore, the interaction occurs mainly as a result of van der Waals forces. It is likely that the adsorbate molecules, i.e. surface active substances tend to be located on the surface in the form of chains. Due to this, part of the bond between the water molecules and the hydrophobic part of the molecules of the surface active substance is replaced by the surface active substance-surface active substance contacts formed, possibly, by the hydrophobic parts of the molecules of this substance and the adsorbent. Therefore, at the subsequent stages of adsorption, the predominance of the adsorbate-adsorbent interaction is enhanced. As the concentration of the surfactant increases, the transformation of the adsorption layer and a sharp increase in adsorption also increase. Further, the adsorption capacity of organobentonites in relation to dyes was investigated depending on the impurity surface active substances in the system. For research, an anionic dye active bright red 6B, which is widely used for dyeing cellulose fiber, was taken. The concentration of the dye before and after adsorption was established on the basis of photocalorimetric studies at a characteristic wavelength. It was found that the surface active substance impurity slightly reduces the sorption of anionic dyes on the Ch-KR adsorbent; however, with an increase in the sorption time, the sorption capacity increases, and the maximum degree of dye extraction reaches 70-90% for the concentration range of the impurity sulfonol 40-70 mg/l during more than 10 hours depending on the size of the dye molecules. As it turned out, for the onset of adsorption equilibrium in a system with a dye with a relatively large molecular size - bright red 6B, it takes a longer time (more than 10 h)
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compared to the bright blue 2B dye. At higher concentrations than CCM, the degree of clarification increases sharply for solutions of both dyes, due to an increase in their degree of extraction. Such a sharp change is probably due to the partial solubilization of large dye molecules between the hydrophobic radicals of the surface active substance and the adsorbent. Curves illustrating these changes are shown in Fig. 2.
20 40
C, Mg/1
3)
Fig. 2. Isotherms of adsorption of active bright red 6B on organobentonites: 1) HDTMA-KR; 2) Ch-KR, from a solution with an admixture of surface active substances in an amount: A) 100 mg/l; B) 160 mg/l
(corresponds to CCM)
As shown in the diagram, the HDTMA-KR sample has a higher adsorption capacity, which is clearly seen when the concentration of surfactants is increased to 160 mg/l. However, as shown by the research results, a further increase in the concentration of surface active substances negatively affects the degree of clarification of dye solutions. Probably, due to the binding of active ions, the surface active substances by adsorption centers and overlapping the surface of the modified montmorillonite restricts the access of large molecules of dyes bright red 6B and bright blue.
References / Список литературы
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3. Subbotkin L.D., Verbitskaya N.Yu. National Academy of Environmental Protection and Resort Construction. Wastewater treatment from surface-active substances by electroflotocoagulation method // Wastewater treatment from surfactants by electroflotocoagulation method / Construction and technogenic safety. -2011. №.38. [in Russian]
4. Vissarionova O.N., Voronchikhina L.I. Influence of mixtures of surfactants on the colloidal solubility of a dispersed // Modern science-intensive technologies, 2004. №5. Рp. 92-92 [in Russian].
5. Nechiporenko A.P, Physico-chemical (instrumental) methods of analysis. Electrochemical methods. Potentiometric and conductometric, 34 p. (ITMO, SPetersburg., 2013) [in Russian].
6. Seytnazarova O.M., Mamataliev N., Abdikamalova A.B., Ikhtiyarova G.A. Adsorption activity of organobentonite based on Krantau clay International journal of advanced Research in Science, Engineering and Technology Vol.7, Issue 12, December, 2020. Pp. 16164-16167.
