MORPHOLOGY OF SURFACE, ADSORPTION PROPERTIES OF HUMIC ACID AND HUMINE FROM BROWN COALS

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1 MORPHOLOGY OF SURFACE, ADSORPTION PROPERTIES OF HUMIC ACID AND HUMINE FROM BROWN COALS S. Lugovskoy 1, I.P. Gainullina 2, I.M. Lokshina 2, А. Kharchenko 2, S.O. Karabaev 2 1 Ariel university center of Samaria, Ariel, Israel, svetlanalu@ariel.il 2 Kyrgyz Russian Slavonic university, Kyrgyzstan, karabaev_s@mail.ru Key words: Humic acid, humine, morphology of surface, IR-spectra, X-ray analysis, ash content, moist, element composition, monomolecular adsorption, volumetric filling of micropores of adsorbent Resume Morphology of surface of humic acid and humine samples, extracted from Kara-Keche coals was researched. Comparable analysis of IR-spectra, X-ray analysis, element composition, ash content, moist of analytical samples of humic acid and humine from Kara-Keche coals was made. Mechanism of adsorption of urea from water solutions on humine and humic acid was suggested. Introduction Supramolecular native dispersal systems such as humic acid and non hydrolyzed organic compounds (humine) extracted from brown coals are of great interest. It was established a stimulation influence of humic acid on growth and development of plants and improvement of their stability to unfavorable conditions of environment [1]. Due to sorption properties humic acid and humine bind radio nuclides, ions of heavy metals. Catalysis properties of these substances promote decay of pesticides, accelerate processes of detoxication of plants and living organisms. Searching of cheap adsorbents and production of new compositional materials on the base of native materials are actual problems of physical chemistry of surface phenomenon and dispersal systems. Decision of these problems ensures possibility of non fuel use of low calorie brown coals. Results of Scanning electronic microscopy, X-ray analysis, IR-spectra, element composition of humic acid and humine from Kara-Keche coals are presented in the article. Comparison of surface morphology and analysis of adsorption properties of researched simples of adsorbents relatively urea are carried out. Results and discussion Two products, extracted from brown coals are objects of research, namely: 1) Humic acid (HA), extracted from analytical test of brown coals of Kara-Keche deposit, (Kyrgyzstan) using method of Orlov [1] (selection from main seam of 2008 year). Particles of powder for analysis were about 60 meshes (0,25 mm); 2) Humine (HU) the rest of Kara-Keche coals, non soluble in acids and alkali, consists of non hydrolytic organic substances. Dark-colored powder of humine had the sizes of particles about 60 meshes. 1-54

2 Morphology of surface of humine and humic acid samples was researched by Scanning electronic microscope of JEOL company (Japan Electron Optics Laboratory) JSM 6510 using secondary electrons detector (SEI) and detector of reflected electrons (BEC). Suitable photographs are presented on the Fig. 1. Surface of HA х200 (SEI) Surface of HU х200 (SEI) Surface of HA х1500 (SEI) Surface of HU х1500 (SEI) Surface of HA х200 (BEC) Surface of HU х1100 (BEC) 1-55

3 Fig.1 Photographs of humic acid and humine surfaces, extracted from Kara-Keche coals As seen from Fig.1 (detector BEC), particles of humic acid have pseudocrystalline form. They are grains of different dimensions as much as 100μm. Surface of humic acid is plane, without pores, capillary, roughness. But humine unlike humic acid have particles of nonregular, fragmental form with dimensions as much as 100 μm. Moreover there are particles with porous surface. Maximal dimension of pores reaches 200 nanometers. As seen from Fig.1 (detector BEC), surfaces of humic acid and humine have homogeneous grey color with small light components. These components probably are more oxidized fragments in the structure of researched substance or zones with increased maintenance of ashes elements. On a level with Scanning electronic microscopy of humic acid and humine the IR-spectra of these substances were measured on IR- Furie spectrometer Varian in the spectral range of сm -1 in standard KBr based tablets. 1-56

4 Fig.2 IR spectra of humic acid and humine from Kara-Keche coal As seen from Fig.2, distinctive bands of absorption are observed. This is evidence of multi functionality of these compounds. Quantitative valuation of functional groups content was made by ratio of optical densities of adsorption bands of oxygen containing groups to the optical densities corresponding to aromatic poly conjugated systems (1600sm -1 ) and aliphatic substitutes at 2920 cm -1. Calculation of structure parameters of humic acid is shown in table 1. Table 1 Correlation of optical densities of absorption at the definite wave length on the base of IR-spectroscopy data Correlation of optical dencities Humic acid Humine А О-Н 3400 /А С=С ,56 0,45 А С=О 1720 /А С=С ,74 0,57 А С-О 1225 /А С=С ,88 0,86 А Слк 2920 /А С=С ,62 0,55 А О-Н 3400 /А alk ,90 0,82 А С=О 1720 /А alk ,20 1,04 А С-О 1225 /А alk ,41 1,56 Correlation of optical densities of absorption bands of functional oxygen containing groups and alkyls substitutes to aromatic fragments showed prevalence of the latter over alkyls (D 2920 /D 1610 ). Humic acid contains more alkyl substitutes than humine. Comparative amount of hydroxyl groups (D 3400 /D 1600 ) in humic acid and humine is not high. It prevails in humic acid. Humic acid contains more carboxyl groups (D 1720 /D 1610 ) than humane. As seen from table 1 carboxyl groups prevail over alkyl substitutes in HA and HU. Ratio D 1720 /D 2920 for both samples more than 1. Data show the number of oxygencontaining groups of all types more than number of aliphatic C-H bonds. Notice, IR-spectra of humic acid and humin are enough similar. Both samples have the main characteristic maximum of absorption for humic substances. Distinctions are observed mainly in various intensity, prevalence of oxygencontaining groups in humic acid, displacement of absorption bonds. It can be explained by intermolecular interactions in amorphous regions and complexes formation. It was established humane contains more aromatic fragments. Reducing of alkyl substitutes is typical for both samples. X-ray analysis of humine and humic acid was made by difractometer Panalytical X Pert Pro (Philips) at the wave length λ=0.154 nm. 1-57

5 Humine Humic acid Fig.3 X-ray analysis of humine and humic acid from Kara-Keche coals As seen from fig.3 X-ray spectrums have the view of broad line (halo). It is typical for amorphous materials. Peaks in humine samples testify existence of structural formations. X ray analysis discovered presence of α-graphite in humine. The moisture, ash content and element composition of humic acid and humine from Kara-Keche coals were defined using the methods described in [2,3]. The results of measurements are presented in tabl. 2 and 3. As seen from tables 2 and 3 humine in comparison with humic acid contains more moisture, ash, carbon (re-calculation on anhydrous and ashless mass) and practically don t has nitrogen. At the same time humic acid in comparison with humin is more oxidized (re-calculation on anhydrous and ashless mass). Table 2 Moisture, ash content and element composition of analytical samples of humine and humic acid from Kara-Keche coals Analytical sample С,% H,% S,% N, % О,% a W,% a A,% Humic acid 60,60 3,44 1,04 0,94 19,65 3,63 10,70 Humine 56,8 3,66 0,93 0,00 10,74 7,35 20,52 Table 3 Element composition, atomic relations for humic acid and humane from Kara-Keche coals in recalculation on anhydrous and ashless mass Anhydrous and ashless H O mass of sample С,% H,% S,% N,% О,% C C Humic acid 70,90 3,56 1,22 1,10 23,22 0,60 0,25 Humine 78,75 3,94 1,29 0,00 16,02 0,60 0,15 Notice, distinctions between humine and humic acid from Kara-Keche coals in element composition, IR-spectrum, scanning electronic microscopy also reflect in Van-Krevelen H O diagrams, dependence of atomic relations : (tabl.3). The comparative analysis of Van- C C 1-58

6 Krevelen diagrams for our samples and humic substances, extracted from other sources [4] allow us an assumption that the studied samples correspond to the complex of typical signs of a molecular ensemble of humic acid (humin) with maximal contents of aromatic carbon. Presence in researching samples of polycondensed structures, theirs high hydrophobic properties, ash content, oxidizing and less pore filler of humic acid in comparison with humine allow to suppose the differences of theirs adsorption properties. In connection with this isothermal adsorption of urea from water solutions on humic acid and humine, accordingly, was researched. For this aim shots of adsorbent with mass 0.05 g were put in 5 twenty milliliters bottles with tighten up lids. 10 ml of researched concentrations of urea solutions were added in each bottle. Solutions with adsorbent were placed on a rotary shaker for mixing at 80 rotations in minute during hour. After that the suspension was settled for 24 hours. After twenty-for hours and establishment of heterogeneous equilibrium phases were separated by two multiple filtration. Initial separation was made by filter paper. Final separation was made by syringe filter with diameter of pore 0,2 mkm. Concentration of water solution of urea till and after adsorption was determined by liquid chromatograph JASCO-HPLC. Chromatographic column (length 25 sm; diameter 4,6 sm), filling by sorbent with grains dimensions about 5 mkm was used. Acetonitrile and water in ratio 1:1 were used as moved phase. Spectrophotometrical UF-detector was used for measuring at the wave length 200 nm. Quantity of substance, molecular adsorbed from solutions was determined by equation [5]: ( c 0 ce V a 1000, m) where c 0 и c e initial and equilibrium concentrations of adsorbate, M; V volume of adsorbed solution, l; m quantity of adsorbent, gr.; 1000 coefficient, transferring unit of measurement of adsorption in mmol/g. Dependences of adsorption from concentration of adsorbate are presented on Fig.4. C 0 ( M ) C HU e (M ) C HA e (M ) a HU ( mmol / g) a HA ( mmol / g) 0,006 0,004 0,004 0,40 0,40 0,021 0,011 0,014 2,00 1,

7 0,064 0,035 0,047 5,80 3,40 0,164 0,088 0,135 15,20 5,80 Fig.4 Isotherms of adsorption of urea from water solutions on humic acid and humine at K: 1) adsorbent humic acid from Kara-Keche coals; 2) adsorbent humine from Kara- HU Keche coals; C - molar concentration of urea in water solution till adsorption; C 0 e ( molar concentration of urea in water solution after adsorption on humine (humic acid); a HA ) value of adsorption on humine (humic acid) HA C e ) a HU ( As seen from Fig.4 in comparable conditions humine from Kara-Keche coals is more effective adsorbent of urea than humic acid from Kara-Keche coals. Isotherms of adsorption of urea on humane and humic acid are distinguished. It is possible, the mechanism of adsorption of urea from water solutions on humic acid and humin, accordingly is different. In this connection data of Fig.4 were analyzed within the frames of monomolecular theory of adsorption, poly molecular theory of adsorption, and theory of volumetric filling of micro pores of adsorbent [5]. Final results of research were presented on the Fig. 5. Humine water solution of urea Volumetric filling of micro pores of adsorbent Dubinin-Radushkevich equation: ln a ln a B 1 C s =19,98 M T ln( c e / c s ) =8442,7 Humic acid water solution of urea T B 1 =1,15 k corr = 0,99 Monomolecular adsorption Langmure equation: сe 1 ce K a 1-60

8 = 9,52 К=11,7 k corr = 0,99 Fig.5 Adsorption of urea on humic acid and humine in coordinates of Langmure and Dubinin-Radushkevich equations High coefficients of correlation of linear dependences, presented on Fig.5 in coordinates of fundamental equation of adsorption make it possible to come to a conclusion about volumetric filling of micro pores of humine with urea and monomolecular adsorption of urea on humic acid from water solution. In such away adsorption ability of humine exceeds adsorption ability of humic acid so as HU HA a a. It is important the result of realized examination corresponds to the determined morphology of surface of researched adsorbents, extracted from Kara-Keche coals. Literature 1. Orlov D.C. Chemistry of soils. Moscow: Moscow State university, p. 2. Avdeeva А.А., Beloselsky B.C., Krasnov M.N. Control of fuel on electrostations.- Мoscow: Energy, p. 3. Klimova V.A. Basic micromethods of analysis of organic compounds. Moscow: Chemistry, p. 4. Perminova I.V. Analysis, classification and prediction of humic acid properties / Thesis for a doctor`s degree submission. Moscow: Moscow State university, p. 5. Frolov U.G. Manual of colloid chemistry. Surface phenomenon and dispersoid. - Moscow: Chemistry, p. 1-61

ADSORPTION OF HEAVY METAL IONS FROM AQUEOUS SOLUTIONS ON CARBON SORBENTS SELECTED FROM BROWN COAL

ADSORPTION OF HEAVY METAL IONS FROM AQUEOUS SOLUTIONS ON CARBON SORBENTS SELECTED FROM BROWN COAL Karabaev S. 1,2,a, Gainullina I. 1,2, Lokshina I. 1, Djunushalieva A. 1, Lugovskoy S. 3,b 1 Kyrgyz national