УПРАВЛЕНИЕ И ОБРАЗОВАНИЕ MANAGEMENT AND EDUCATION TOM VII (3) 2011 VOL. VII (3) 2011 MODIFICATION OF ACTIVATED CARBONS WITH SILVER NANOPARTICLES IN ORDER TO IMPART THEM BIOCIDAL PROPERTIES Babken Balojan 1, Andrey Terekhov 1, Igor Chmutin 2, Marina Jarovaya 2, Tatyana Chudnova 1 МОДИФИКАЦИЯ НА АКТИВИРАНИ КАРБОНИ СЪС СРЕБЪРНИ НАНОЧАСТИЦИ Бабкен Балоян, Андрей Терехов, Игор Чмутин, Марина Яровая, Татяна Чуднова ABSTRACT:. The modification of birch and coconut activated carbons with silver nanoparticles to impart them biocidal properties was carried out. Kinetics of sorption of silver nanoparticles by activated carbons was studied. Influence of modification of activated carbons with silver nanoparticles on their sorption capacity towards ions of heavy metals (Pb 2+, Cu 2+ ) and oil products was investigated. Significant antibacterial effect of activated carbons modified with silver nanoparticles was observed. Key words: Activated carbons, silver nanoparticles, biocidal properties, sorption capacity. Introduction Quality and resources of potable water are actual problems of humanity. In the last decade bacterial contamination has become a particular threat which is related to the most spread and dangerous types of water pollutions. Therefore, the development of new and improvement of already known methods of antibacterial treatment of potable water seems to be a priority in the field of water purification. Natural sorbents including activated carbons (AC) are commonly used for purifying potable water of various pollutants. However, the coals have a number of important shortcomings such as the rapid contamination of the sorbent due to the swift growth of number of microorganisms in the sorbent [1]. This shortcoming can be eliminated by the impregnation of coals with silver salts which have biocidal properties. Silver ions are quickly washed away from the coal surface with water flow that does not allow using such sorbents safely for a sufficiently long time [2]. It requires using new highly effective agents of decontamination. Silver nanoparticles (SNP) could be one of such agents [3]. It has been observed that silver nanoparticles are much more efficient than all previously used forms of silver. SNP are universal, they are able to destroy more than 600 disease-causing viruses, bacteria and fungi. That is why no instance of adaptation of microorganisms to the effect of SNP has been found [1]. Experimental Activated charcoal branded BAU-MF (birch AC (BAC) produced in Russia) and BLC LO (coconut AC (CAC), produced in Sri Lanka) were used. The grain size of BAC was 1.0 3.6 mm, surface area was 464 m 2 /g and the grain size of CAC was 1.0 1.5 mm, surface area was 817 m 2 /g. Colloidal solution of SNP diluted by solvent branded AgBion-1 produced by Concern Nanoindustry [4] was used for impregnation of AC with silver nanoparticles. Its special feature was spherical form and silver nanoparticles size from 9 to 15 nm (see figure 1 (a) and (b)). It should be noted that modification of AC produced in Russia with certified SNP, which are not harmful to the human [5], was fulfilled for the first time. Modified AC were dried at elevated temperature, washed with various solvents to remove the surfactant and dried until complete removal of solvents. The concentration of SNP was determined with Shimadzu UV-1800 spectrophotometer by measuring the peak height of the plasmon resonance, which is observed for used silver nanoparticles at wavelengths of 420-440 nm. The concentration of ions of heavy metals was measured with Shimadzu A-6200 by the atomic absorption method and concentration of oil products in solutions was determined with Lyumex Fluorat-02-3M by the luminescence method. 222
Bactericidal activity of AC was determined by counting the total number of colonies formed by microorganisms in the nutrient medium at temperature of 37 0 С during 24 hours. Determination of fungicidal activity was realized by plate method marking of the test material onto lawns of five test cultures and by selfinfecting method at open and indoor air. Fig. 1. Histogram of the sizes (A) and electron micrograph (B) for silver nanoparticles in micellar solution AgBion Results & Discussion Kinetic curves of SNP sorption on BAC and CAC were obtained and kinetics of nanoparticles sorption has been described by the equation of pseudo-second order adsorption [6] (1) in the framework of Dubinin's adsorption theory (see figure 2(a)). The slope ratio of approximating straight lines obtained with the least-squares procedure allows calculating values of equilibrium sorption capacity for samples of CAC and BAC, which are 3.0 and 2.2 mg/g respectively. t а t = + 2 k q q e e 2. 1 (1) where: t is time, min; k 2 is constant; q e is equilibrium sorption capacity, mg/g; а is sorption capacity at current moment (t), mg/g. Studies of influence of modifying AC with SNP on sorption capacity of AC towards typical organic (oil products) and inorganic (heavy metals ions) pollutants of water were carried out. Solution of heavy metals ions (Pb 2+, Cu 2+ ) and solution of transformer oil were chosen as model solutions. The modification of AC with SNP maintains their sorption capacity determined on model substances. Equilibrium sorption capacity of AC for heavy metals ions (see figure 3c and 3d) and petroleum products (see figure 2(b)) was calculated. BAC had a greater sorption capacity than CAC (see table 1). Samples of crude and modified BAC and CAC with different concentrations of adsorbed nanoparticles were tested to determine biocidal activity. Microphotographs of three samples are presented in figure 4. Number of colonies of mesophilous aerobic and facultative anaerobic microorganisms was reduced by more than 96% 223
at the ratio of "water : AC" 40 : 1 at the concentration of SNP in the AC over 0.1 mg/g. Bactericidal activity of BAC was more pronounced (see figure 4). Table 1. Equilibrium sorption capacity of AC studied on model substances Sample name Equilibrium sorption capacity, mg/g Pb 2+ Cu 2+ Oil products BAC crude 4.00 4.00 3.03 BAC modified with SNP 4.00 3.13 4.00 CAC crude 3.13 1.79 2.00 CAC modified with SNP 3.23 1.64 2.04 Figure 2. Sorption kinetics of SNP (A) on crude activated carbons and of oil products (B) on crude and modified with SNP activated carbons 224
Figure 3. Sorption kinetics of Pb2+ (C) and Cu2+ (D) ions on crude and modified with SNP activated carbons Figure 4. Bactericidal activity of samples: (1) initial polluted water sample; (2) crude BAC sample, (3) sample of BAC modified with SNP with equilibrium sorption capacity of 1.2 mg/g. It has been ascertained that initial BAC was more resistant towards to fungi contamination than CAC. Modifying AC by SNP substantially enhanced its resistance towards infection with test-cultures. Deactivation of charcoal (washing with a tap water during 24 hours) does not decrease the fungicidal activity of the simple. Besides, modifying AC with SNP increases its stability towards microorganisms in indoor air. Conclusion The sorption activity of birch and coconut activated carbons towards silver nanoparticles has been studied. The significant bactericidal activity is observed at adsorption value of silver nanoparticles on activated carbon of higher than 0.1 mg/g. Negative influence of activated carbon modified with silver nanoparticles on sorption of Pb2+ and Cu2+ ions and oil products was not observed. The equilibrium capacity of crude and modified with silver nanoparticles activated carbons determined on model substances was calculated. 225
Acknowledgments We wish to thank M B Dmitrieva and The State Scientific and Research Institute of Restoration for the analysis of samples on the biocidal and fungicidal activity. References 1. Egorova E. M. 2006. Solutions of metal nanoparticles and their modified materials: properties and applications (in russian). Proc. Int. Sci. and pract. Conf. «Nanotechnologies to production 2005» (Frjazino), Moscow: Yanus-K, p. 26. 2. Egorova E. M. 2004. Solutions of metal nanoparticles (in russian). Biochemical synthesis and their application. Nanotechnics, 1 (15): 15-27. 3. The way of modifying the surface, 2002. Patent of Rus. Fed., 2182934. 4. The biocidal solution and a way of its preparation, 2007. Patent of Rus. Fed., 2333773. 5. Hotimchenko S. A., Gmoshinskij I. V., Kravchenko L. V., et. al., 2008. The Int. forum on nanotechnologies Rusnanotech 08, Moscow, 2 pp. 308-309. 6. Ho Y. S. and McKay G., 2000, Water Research, 34: 735-742. Prof. Ph.D. Babken Balojan E-mail: baloyan@uni-u.ru Andrey Terekhov E-mail: nil.ugresha@gmail.com Ph.D. Igor Chmutin Joint-Stock Company Concern "Nanoindustry", Nauchnyy passage, 20, build. 4, 117246, Moscow E-mail: tchmutin@mail.ru Ph.D. Marina Jarovaya Joint-Stock Company Concern "Nanoindustry", Nauchnyy passage, 20, build. 4, 117246, Moscow Ph.D. Tatyana Chudnova E-mail: nuch@uni-u.ru 226