Lesichkov, V.

Mitev, D.

Obretenov, Tz.

English

Varna Medical University Press: Journals

CONCERNING M E T H Y L E N E B L U E SORPTION OVER ACID AND T H E R M A L L Y A C T I V I E D KAOLIN IN ULTRASOUND F I E L D D. Mitev, V. Lesichkov, Tz. Obretenov Native sorbents, under the form of filtering structures, are widely ap­plied in industry for rendering innocuous a variety of toxic substances in sewage waters, draining waters and the like. The rapid development of chemical industry in this country necessitates the undertaking of investi­gations for establishing the mostly effective utilization of the locally avail­able native sorbents. Thus, the inevitable pollution of water basins, still used as recipients of draining waters, would be avoided. Native sorbents occurring in nature have comparatively low sorptional capacity which entails systematic research to the end of rising it and accor­dingly, rendering them more effective. In previous works by the same authors (1, 2), certain conditions of methylene blue sorption over natural sor­bents from extensive beds located in Southern Bulgaria, namely, Dimitrov-grad and Kardjali, have been investigated. The method of activation of sorbents, the ultrasound treatment itself and the recording of sorption have been already described in the above cited works (1, 2). Acid or thermal activation of the sorbents results in a rise of their sorptional capacity towards methylene blue. Anyway, the latter increase is not to be considered as optimal. Hence, it is necessary to search for addi­tional methods of processing with the goal of securing additional activation. As a result of our studies it was established that acid and thermally aeti-vied sorbents, after being subjected to ultrasound treatment, furthermore augment their sorption capacity towards methylene blue. It is a well known fact that any medium subjected to ultrasound treatment undergoes a variety of intensive physico-chemical alterations. Along with pressure changes in the medium (from+3 atm to —3 atm) (2), from the equation л 2rcvpC it is possible also to estimate approximately the range of fluctuations of the particles within the medium treated with ultrasound A = 3 . 5 x l 0 - 6 cm, where p=3.3xl0 6 dyn/cm2 is the acoustic pressure within the medium, v =800 kHz is the frequency of ultrasound, p= 103 kg/m 3 — water density and c = 1.48 x10 s m/s — the diffusion rate of the ultrasound waves. Also, as regards the amplitude of acceleration of the particles, from the equation a 0=4 n 2 v 2 A, it results that a 0 =8.8xl0 8 cm/S 2. The physical and chemical processes taking place in the liquid under the effect of ultrasound are observed only in the presence therein of certain 2 Script* medlca 18 D. Mitev, V. Lesichkov, Tz. Obretenov acoustic parameters, corresponding to the apperance of the cavitational regimen, which, in general outline, appears to be the cause for all changes in the medium. High local temperatures, reaching up to several hundred degrees are produced in the pulsating resonances of the cavitational bubbles, depending on the nature of the gas (5, 6, 7, 8). T a b 1 е 1 Methylene-Blue Water Solutions' Sorption over Acid Activied Kaolin from the Village of Senovo, District of Razgrad in Kg/Kg Sorbent Ultrasound ^ ^ - ^ ^ parameters ^ ^ - ^ ^ ^ ^ ^ ^ Percent of НС1 2% 5% 10% 20% Control 22 kHz 4 W/cm 2 800 kHz 3 W/cm2 0.0130 0.0150 0.0162 0.0167 0.0184 0.0190 0.0163 0.0176 0.0185 0.0162 0.0173 0.0180 0.0160 0.0165 0.0172 "9/"9 0,0730 — " w V 20 %HCl Fig. 1 Methylene-Blue Water Solutions' Sorption over Thermally Activied Ultrasound^ parameters Temperature in °C 25° 75° 105° 125° 150° 175° Control 22 kHz 4 W/cm 2 800 kHz 3 W/cm2 0.013 0.014 0.015 0.018 0020 0.022 0019 0.021 0.023 0.019 0.021 0.024 0.019 0.021 0.025 0.019 0.021 0.025 Concerning Methylene Blue Sorpticn.. 19 In the opinion of Y . N. Frenkel (7), the presence of high electric ten-sions under conditions of cavitation leads to the occurrence of high energy particles (ionized and excitated molecules, ions, free radicals etc). According to some investigators (4, 9), upon occurrence of cavitation in the liquid treated with ultrasound, the chemical bonds are disrupted and the coagulational linkages in the molecular and supramolecular struc-tures as well. Thus, the physical essence of ultrasound treatment is practi-cally reduced to the formation in the medium investigated of cavitational bubbles, whose disruption creates enormous pressures with ensuing blast wave, high temperature, electric and photochemical phenomena. Al l this appears to be a powerful source for exerting influence and intensification of the physico-chemical processes. In the work submitted a description is made of the experimental re-sults of methylene blue water solutions sorption over acid and thermally activied kaolin from the bed in the village of Senovo, district of Razgrad, as well as of the results after ultrasound treatment. In Table 1 the experi-mental data are presented concerning the sorption of acid activied sorbent, graphically illustrated in Figure 1. Table 2 illustrates the data concerning the sorption of thermally activied sorbents, graphically presented in F i -gure 2. In both figures, the curve «k» represents the sorption capacity of the control samples (untreated with ultrasound), curve 1 — samples treated with ultrasound for 20 min at frequency 22 kHz and intensity 4 W/cm 2, and curve 2 — samples treated with ultrasound for 20 min at frequency 800 kHz and intensity 3 W/cm 2. It is evident from Fig. 1 that subsequent to ultrasound treatment, an increase occurs of the sorption capacity with 14% in relation to the control, subjected to acid activation with 2% HC1 for the samples treated with 800 kHz frequency, and with 10% for those treated with 22 kHz ultrasound frequency. The acid activied sample with 2% HC1 shows sorption capacity with 28% higher than that of the crude sorbent, the sample activied with 2% HC1 and subjected to ultrasound treatment with 800 kHz has46%,higher sorp-tion capacity than that of the crude sorbent, whereas in the sample subjected to ultrasound treatment with 22 kHz, the increase obtained amounts to 42 per cent. T a b l e 2 Kaolin from the Village of Senovo, District of Razgrad in Kg/kg Sorbent 200° 250° 300° 350° 400° 450° 500° 550° 600° 0.019 0.021 0.025 0.019 0.020 0.025 0.018 0.019 0.022 0.018 0.019 0.022 0.017 0.018 0.022 0.016 0.018 0.019 0.013 0.015 0.017 0.010 0.012 0.012 0.017 0.018 0.020 1 D. Mltev, V. Lesichkov, Tz. Obretenov It is obvious from Fig. 2 that thermally activied sorbents at tempera­ture ranging from 100 to 250° C, possess the highest sorption capacity. At identical temperature interval, the samples subjected to ultrasound treat-«91*3 0,026 -Ц — 1 ' I I .. 1 I 0 WO 200 300 400 500 600 Г С Fig. 2 ment with 800 kHz frequency display about 92% higher sorption capacity as compared to the crude sorbent, the samples treated with22 kHz — 62% and those subjected to thermal activation only — 46 per cent. R E F E R E N C E S 1. М и т е в , Д . , Ц в . О б р е т е н о в, В л. Л е с и ч к о в . Адсорбция на мети-леново синьо върху някои киселинно и термично активирани сорбенти в ултра­звуково поле (под печат) Годишни научни трудове на ВМИ — Варна. 2. О б р е т е н о в, Ц в . , Д . М и т е в , В л . Л е с и ч к о в . Относно сорбцията на метиленово синьо върху природни сорбенти в ултразвуково поле. (под печат) Трудове за юбилейната научна сесия на ВМИ — Варна. 3. Ф р е н к е л ь , Я. И. Ж. Ф. X., 14, 3, 303, 1940. 4. Э л ь п и н е р, И. Е. Ультразвук, Москва, 1963. 5. S m i t h , R. D. Phil. Mag., 19, 1147, 1935. 6. N a l t h i n g k, В. Е. , E . A. N е p p i r a s. Proc. Phys. Soc, 63, 8, 674, 1950. 7. N e p p i r a s , Е. А., В. E . N a l t h i n g k. Proc. Phys. Soc, 64, 387, 1951. 8. G r i f f 1 i n g, V. I . Chem. Phys., 20, 6, 939, 1957. 9. M a r l o e , E . A., W. A. W е у 1. Лрр/. P/i^., 21, 9, 937, 1950. Concerning Methylene Blue Sorption. 21 О СОРБЦИИ МЕТИЛЕНОВОЙ СИНИ НА КАОЛИНЕ ПОСЛЕ ЕГО КИСЛОТНОГО И ТЕРМИЧЕСКОГО АКТИВИРОВАНИЯ В УЛЬТРАЗВУКОВОМ ПОЛЕ Л. Митев, В л. Лесичков. Цв. Обретете Р Е З Ю М Е В работе приведены результаты изучения сорбции метиленовой сини из водных растворов в сорбенте Kg/Kg на активированном кислотой и термически каолине из с. Сеново, Разградското района. Активацию каолина кислотой проводили 2, 5, 10 и 20%-ной соляной кислотой, а термическую активацию — при 25, 75, 105, 125, 150, 175, 200, 250, 300, 350, 400, 450, 500, 550 и 600° С. Сорбцию производили в ультразвуковом поле следующей характеристики: 22 кгц и 4 вт/см 2 и 800 кгц и 3 вт/см 2. Полученные результаты представлены в двух таб­лицах и двух рксунак. Было установлено, что вследствие озвучивания получаетя повышение сорбционной способности в размере 14% при частоте ультразвука 800 кгц и 10% — при частоте 22 кгц по сравнению с контролем, активиро­ванным 2%-ной соляной кислотой. Активированная 2%-ной соляной кислотой проба обладала на 28% более высокой сорбционной способностью по сравнению с сырым сор­бентом, а в ультразвуковом поле при 800 кгц — на 46%, и при 22 кгц — на 42%. Наиболее высокой сорбционной способностью обладали термически активированные сорбенты в температурных границах от 100° до 250° С. В ультразвуковом поле при 800 кгц пробы обладали сорбционной способ­ностью, приблизительно на 92% превышающей таковую сырого сорбента, а в ультразвуковом поле при 22 кгц — на 62% выше, чем при сыром сор­бенте, и на 46% выше по сравнению с термически активированным. 

CONCERNING METHYLENE BLUE SORPTION OVER ACID AND THERMALLY ACTIVIED KAOLIN IN ULTRASOUND FIELD

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CONCERNING METHYLENE BLUE SORPTION OVER ACID AND THERMALLY ACTIVIED KAOLIN IN ULTRASOUND FIELD

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