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AZ9RBAYCAN KIMYA JURNALI № 1 2018
UDC 661.183.666.972.16
SORPTION OF CATION-ACTIVE DYES ON MODIFIED BENTONITE
S.A.Mammadova, G.M.Heyderzade, A.I.Yagubov, N.V.Veliyeva, U.G.Osmanova
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
Received 27.04.2017
In the article Dash-Salakhly bentonite of Azerbaijan as a sorbent from aqueous solutions has been investigated. Physico-chemical characteristics of clays such as heat of wetting, capacity of exchange complex, humidity, porosity have been studied. For increasing adsorptive capacity of hydrophilic clay from aqueous solutions it was processed with cation-active surfactant. Optimum conditions were found out for adsorption, methylene blue, rhodamine G, methylene violet on obtained sorbent (dependence on time of contacting, on pH medium, and temperature). On the basis of experimental data we plotted isotherms of adsorption which conform to polymolecular adsorption. Obtained sorbent is recommended for purification of waste waters from cation-active dyes.
Keywords: hydrophilic nature, organobentonite, adsorption, isotherm of adsorption, X-ray data, methylene blue, rhodamine G, Dash-Salahly bentonite, IR spectra, kinetic curve.
Introduction
Production using chemical substances which in their turn are potential contaminants of reservoirs, led to the necessity of searching new and at the same time cheap sorbents of natural origin. Such type of sorbents are zeolite tuffs and clayish minerals. For the purification of waste waters from cation dyes the natural clayish minerals are successfully used as adsorbents. Clay which contains not less than 70% mineral of montmoril-lonite group can be called bentonite. Montmoril-lonite is a finely-dispersed layered aluminosilicate in which due to non-stoichiometric substitutions of cations, crystal lattice, excess negative charge appears which compensates exchange cations in interplanar space. This is due to a high hydro-philic behavior of a bentonite.
Since there are great deposits of bentonite clay (Dash-Salahly deposit of Gazakh region) in Azerbaijan we have taken this clay as a basis one. Bentonite clay of Dash-Salahly deposit contains 75-85% montmorillonite. In exchange complex of which cations of sodium, calcium and magnesium prevail.
One of the important chemical properties of sorbents which determine the application of these minerals in industry is their ability to interact with different media (lyophilic nature) or with water (hydrophilic nature). This property essentially determines the ways of using clays as sorbents.
Most of natural sorbents in natural condition have low sorption abilities (as it is known, mineral sorbents, in particular, clays in conside-
rable level of hydrophilic nature). That's why for increasing their adsorption capacity different activation methods are used, which can be conventionally divided in physical (heating, dispensing, screening and others) and chemical (processing with chemical reagents - acids, alkalies, salts and others) [1].
One of the most important colloidal-chemical characteristics of layered silicates is the presence of cation exchange ability in them. This property lies on the basis of a method of chemical modification of a surface of such sorbents by exchange reactions with organic cations. Modification with cation-active surfactants gives bentonite hydrophobic properties and increases its adsorption activity in relation to non-polar molecules. Functional groups which form dense hydrogen bonds are situated on the surface of these minerals. Retention of molecules of organic substances is mainly caused by dispersive interaction of them with surface atoms of adsorbent. During the interaction of clayish minerals with cation-active organic substances their surface properties considerably change. Large-sized organic cations occupy a part of ion-exchange places, cover large part of hydrophilic surface and thereby being hydro-phobic make the access of water molecule to hy-droxyls difficult [2].
Experimental part
Montmorillonite has a high cation exchange and adsorption properties. Primarily we studied physico-chemical characteristics of clay, which are given in the Table 1.
Table 1. Physico-chemical characteristics of bentonite clay
Specific weight, y, g/cm3 Heat of wetting, cal/g Capacity of exchange complex, mg-equ/100 g Humidity, w, % Porosity, p, %
2.31 12.3 93.7 7.9 54.59
In comparison with cation exchange forms of bentonites we have studied the obtained by us [4] organo-substituted bentonite as sorbents of anion- and cation-active dyes from aqueous solutions [3].
IR spectra of natural and processed octa-decylamineacetate bentonite clay have been taken on "Thermo scientific" of "Nicolet IS10". As the Figure 1 shows unlike natural one after processing of the studied sample with the salt of high long-chain amine absorption bands appear in the region of 2920-3200 cm-1 which are typical for adsorbed surfactants. Adsorption bands in 3200-3300 cm-1 are related to asymmetric valence and deformation vibrations of amine groups which form coordination bond with aprotic centers of sorbents surface. Adsorption bands in the region of 2800-3000 cm-1 belong to asymmetric and symmetric valence vibrations of CH2-group of an adsorbed surfactant. Intensity of absorption bands at 3620 cm-1, which belong to natural montmorillonite, is increased due to application on it a spectrum of
Fig. 1. IR spectra of natural (1) and hydrofobised bentonite (2).
It was established that a part of organic molecules which interact by ion exchange mechanism is firmly connected with a clayish mineral and is removed during dialysis, while sorbed part
of over capacity of exchange is easily desorbed.
By X-ray structural analysis it was shown (Figure 2), that not depending on saturation level of their exchange capacity octadecyl complexes of montmorillonite increases interpacket distance up to 20 A. This testifies that hydrocarbon chains of amine are situated parallel to a packet, overlap is observed even at over-equivalent sorption.
As a cation surfactant we used octadecyl-amineacetate (ODAA). Last was preliminarily triturated in ethyl alcohol till homogeneous mass, then washed, milled and sifted through sieve 0.2 mesh clay was added in the amount corresponding to its exchange complex (32.9 g ODAA for 100 g clay) [4]. Obtained modified clay - octadecylaminobentonite (ODAB) was dried on air and separated to fractions, passed through sieve of different sizes (0.2, 0.4, 0.6 mesh). As a result of the experiment we selected optimum size of fraction - 0.2 mesh.
Modified clay with selected size was studied for adsorption of rhodamine G (R G), methylene blue (MB) and methylene violet (MV) in ratio (1:50 ml) depending on time of contacting [5-7]. Time of contacting was determined after 15 min, 30 min, 2 hours, 3 hours, 4 hours of intensive contacting in apparatus for shaking Elpan Water Batlo shaker type 357. One sample was left to settle during a day. After interaction reaction samples were put into centrifuge for getting transparent solution necessary for the determination of optical density in photocolorimeter. It was established that adsorption equilibrium reaches on 1 hour contacting. Kinetic curve was given in Figure 3.
Dependence of adsorption on pH medium was studied in acidic (pH 2 and 4), alkali (pH 9 and 11) and neutral (pH 6, 7) media. Primary solution of a dye has a neutral pH. As a result of the experiment it was established that acidic and alkali media decrease adsorption level, i.e. the highest adsorption proceeds in neutral medium.
I
400 -300 -
200 -100 -
400 _ 300 _ 200 _ 100
Fig. 2. X-ray data of natural (1) and hydrophobised bentonite (2).
1
1 2 3 4 5 6
x, hour
Fig. 3. Kinetic curves of adsorption of 1 - rhodamine-G, 2 - methylene blue, 3 - methylene violet on ODAB.
At the same time we have studied the dependence of adsorption of shown dyes over modified bentonite on heating temperature. In this device the temperature in flasks was brought up to 40, 60 and 800С within 1 hour for shaking (water a bath shaker type) by heating water in a shaker. Then it was left to settle during 10 min, upper part of a solution was poured off, put into centrifuge to separate from suspension particles of adsorbent and optical density
was determined by photocalorimetric method. It was established that sorption capacity of or-gano-bentonite to studied dyes decreases with the increase of temperature. Optimum temperature was 200C.
According to the theory of polymolecular adsorption [8], its forces do not depend on temperature and consequently, with the increase of temperature to 60 C adsorption capacity for shown dyes decreases insignificantly.
12 3 4
Ceq, mol/l
Fig. 4. Isotherms of adsorption of rhodamine G (1), methylene blue (2), and methylene violet (3) on ODAB.
Considering determined optimum conditions the adsorption of three dyes - MB, rhodamine G, MV from solutions with different concentrations (100, 250, 500, 750, 1000, 1500, 2000 mg/l) was conducted. Sorbents were put into a shaker for an hour in ratio with aqueous phase 1:50. After centrifuging their optical density was determined. On the basis of the data we constructed isotherms of adsorption of dyes (Figure 4). As figure shows curves belong to polymolecular or potential adsorption. This adsorption is a pure physical adsorption. That's why we may say about existence of adsorption capacity on a surface of adsorbent which can be filled during adsorption of adsorbed molecules of adsorbate under the action of physical forces.
Conclusion
On the basis of experimental data it was established that ODAB on sorption capacity in relation to studied dyes 1.5-2 times prevails cation-substituted forms of bentonite. This sorbent can be recommended for sorption of cation-active dyes from waste waters of worsted-goods industry and dyeing houses which have a concentration up to 1000 mg/l.
References
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pri termodinamicheskom analize adsorbtcionnykh ravnovesii // Zhurn. fiz. himii. 1985. T. 59. № 11. S. 2764-2768.
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4. Evroziiskii patent № 028314. Sposob polucheniia organogliny / Mamedova S.A., Geidarzade G.M., Iagubov A.I., Nuriev A.N., Osmanova U.G., Is-mailova V.A. 2017.
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6. Mammadova S.A., Teymurova E.A., Muradova N.M., Yagubov A.I., Haydarzade G.M. Adsorption and colloidal-chemical characteristics of Dash-Salakhly natural bentonite and some monokation substituted forms at thermal treatment // European journal of Analytical and Appl. Chem. 2016. No 1. P. 23-28.
7. Iagubov A.I. Sorbtcionnaia ochistka stochnykh vod ot metilena golubogo na Fe(III)-bentonite, eksperimentalnye issledovaniia i modelirovanie // Kondensirovannye sredy i mezhfaznye granitcy. 2007. T. 9. № 2. S. 177-181.
8. Voiutckii S.S. Kurs kolloidnoi himii. M.: Himiia, 1964. 574 s.
KATiONAKTiV BOYALARIN BENTONiTiN SORBSiYASINDA iSTiFADOSi
S.A.Mamm3dova, G.M.Heydarzada, O.LYaqubov, N.V.Valiyeva, Ü.H.Osmanova
Azarbaycanin Da§-Salahli Bentonitinin sulu mahlullardan kationaktiv boyalann sorbsiyasinda sorbent kimi istifadasi tadqiq edilmi§dir. Gilin islanma istiliyi, yerdayi§ma kompleksinin hacmi, rütubatlilik, disperslik kimi fiziki-kimyavi xüsusiyyatlari öyranilmi§dir. Hidrofil gilin sulu mahlullarda sorbsiya xüsusiyyatini yüksaltmak ügün onlarin sathi-aktiv maddalarla modifikasiyasi aparilmi§dir. Alinmi§ sorbentda metilen abisinin rodamin G-nin, metilen banöv§ayinin sorbsiya §araiti öyranilmi§dir (mühitin pH-indan, temperaturdan, zamandan asililigi). Tacrübi naticalara asaslanaraq, polimolekulyar adsorbsiyaya cavab veran adsorbsiya izotermi qurulmu§dur. Tadqiq olunan sorbentin zulu mahlullarin kationaktiv boyalardan tamizlanmasinda taklif etmak olar.
Agar sözzr: hidrofillik, üzvi-bentonit, adsorbsiya, adsorbsiyanin izotermi, rentgenoqram, metilen abisi, rodamin G, Da§-Salahli bentoniti, iQ spektri, kinetik 3yri.
СОРБЦИЯ КАТИОНОАКТИВНЫХ КРАСИТЕЛЕЙ НА МОДИФИЦИРОВАННОМ БЕНТОНИТЕ
С.А.Мамедова, Г.М.Гейдарзаде, А.И.Ягубов, Н.В.Велиева, У.Г.Османова
Исследован Даш-Салахлинский бентонит Азербайджана в качестве сорбента из водных растворов. Изучены физико-химические характеристики глины, такие как теплота смачивания, объем обменного комплекса, влажность, пористость. Для увеличения адсорбционной способности гидрофильной глины из водных растворов она была подвергнута обработке катионоактивным ПАВ. Найдены оптимальные условия адсорбции метилена голубого, родамина G, метиленафиолетового на полученном сорбенте (зависимость от времени контактирования, от рН среды и температуры). На основе экспериментальных данных построены изотермы адсорбции, отвечающие полимолекулярной адсорбции. Полученный сорбент рекомендуется для очистки сточных вод от катионо-активных красителей.
Ключевые слова: гидрофильность, органобентонит, адсорбция, изотерма адсорбции, рентгенограмма, метилен голубой, родамин G, Даш-Салахлинский бентонит, ИК-спектры, кинетическая кривая.
