Odessa I.I. Mechnikov National University,

Pastera st. 27, 65026 Odessa, Ukraine

Lead isolation from its salt diluted solutions can be carried out by lead precipitation particles surface as slightly soluble hydroxide, hydrophobization of by appropriate surfactant (collector) and following hydrophobizated particles flotation. The information about the mechanism of surfactant interaction with lead hydroxide is necessary for efficient prognosis of surfactants action as flotation collectors of lead in lead hydroxide form.

The regularities of potassium alkyl carboxylates adsorption by fresh-precipitated lead hydroxide have been studied and are stated in this work.

It has been stated that isotherms of potassium decyl- (CH3(CH2)8COOK), dodecyl- (CH3(CH2)10COOK), and tetradecyl- (CH3(CH2)12COOK) carboxylates adsorption by lead hydroxide have a form close to one of S-type isotherms by Jiles classification, i.e. correspond to polymolecular adsorption.

The temperature increase from 25 to 45° C slightly increases the adsorption (it shows mainly chemical character of adsorption), however practically doesn‘t change the form of adsorption isotherms.

For small equilibrium concentrations the isotherms are characterized by linear dependence of adsorption from surfactant equilibrium concentration. It allowed to use Langmir equation to describe the initial part of the isotherms.

Cp/A = 1/(A ¥ b)+ Cp/ A ¥.

According to the obtained data the free energy of Gibbs DGo = -RTlnK, enthalpy DHo = RT2(dlnK/dT) and entropy DSo = (DHo - DGo)/T have been calculated.

It has been shown that potassium alkyl carboxylates adsorption was accompanied by considerable decrease of system free energy, whereas the DGo value increases with temperature increase and decreases with adsorbate

hydrocarbon radical length increase. The DHo values are positive and small, that indicates the chemical character of adsorption; DSo values are positive and sufficiently great, that is associated with water molecules displacement by surfactant molecules from adsorption layer and desolvation of adsorbate polar groups.

The adsorption monolayer capacities found from adsorption isotherms decrease with potassium alkyl carboxylate hydrocarbon radical length increase. It allows to suppose that the adsorption mechanism is connected with lead hydroxide surface structure and with the association of adsorbate molecules the adsorption of which in adsorbent pores is difficult because of steric causes.

It can be supposed that adsorbates - potassium alkyl carboxylates – form coordination bonds with lead ion on the one hand and hydrogen bonds with hydroxy groups of adsorbent (lead hydroxide) on the other hand. The first adsorption layer is, in our opinion, formed owing to the formation of the hydrogen bond between adsorbate carboxy groups and adsorbent surface groups.

The second adsorption layer is formed owing to the hydrophobic interactions. The lead hydroxide colloid particles micelle structure in the presence of sufficiently great (necessary for their flotation) amounts of potassium alkyl carboxylates evidently corresponds to formula:

ím[Pb(OH)2]nRCOO-(n-x)K+ýx-xK+

Institute for Sorption and Endoecology Problems, Ukrainian National Academy of Sciences, General Naymov st. 13, 03680 Kiev, Ukraine

Designed in Institute of Sorption and Endoecology Problems amorphous granulated modified titanium and zirconium phosphates differ from crystalline types of phosphates. Due to the optimal size of granules and developed porosity they can be utilized in sorption columns with low hydrodynamic drag force, that uncloses perspectives of building on the basis of these ion exchangers of effective sorption technologies of extraction, concentrating and high effective purification of materials [1,2].

The literary data testify that the real exchange capacities of amorphous titanium and zirconium phosphates do not exceed half from the theoretically calculated quantities.

In the present work we have made the attempt to increase ion-exchange capacity and porosity of amorphous titanium and zirconium phosphates for score of introduction in working reagents mixture of tervalent metals (Al3+, Fe3+) salt solutions. It was supposed, that the tervalent metal cations will play a role of template-cations, linking part of phosphate groups of ion exchangers during their synthesis. When washing of such phosphate hydrogels the tervalent cations - templates should be washed from gel in solution, owing to what the part of free phosphate groups, bounded with titanium and zirconium should be higher, than for ion-exchangers, obtained by an ordinary method. It is possible to suggest, that the ion-exchangers of such type will show increased ion-exchange capacity relatively to three-valent ions – templates, and also towards uranium ions, showing high affinity to phosphate ligands [3]. We have comprehensively investigated a uranium sorption from water solutions of uranyl acetate UO2 (CH3COO)2·2Н2О by the modified with Al3+ or Fe3+ ions hydrogenous and potassium forms of TiP and ZrP. The kinetics of uranium uptake by all samples testifies to two-stage character of sorption process: a

rapid first stage, during which sorb more than 85 % of uranium and time-lagged second stage when 15 % of stayed uranium are extracted.

The isotherms of uranium sorption by modified TiP and ZrP, testify that sorption capacity of ion exchangers in the hydrogenous form is much higher than one in the potassium form as a result of uranyl ions high affinity to a ion exchangers surface.

Thus, the titanium and zirconium phosphates in the hydrogenous form, modified with Al3+ or Fe3+ ions in the process of gelation are characterized by heightened values of specific surface.

These sorbents show high ion-exchange capacity up to 1,7 meq/g (229,5mg/g) relatively to uranil ions. Ion exchange capacity weakly depends from рН in a broad enough interval.

Therefore it is possible to think, that the designed sorbents are quite perspective for purification of underground, artesian 15, and also utilized waters of Atomic Power Plants 16 from uranium, transuranium elements. Actinides can be concentrated for analytical definition purposes from acid complicate composition solutions too.

References

1. V.V. Strelko, Chemistry in Environmental Protection, Naukova Dumka, Kiev, 1982, P. 179.

2. A.I. Bortun, V.V. Strelko, Proc.IV th Int. Conf. on Fundamentals of Adsorption. - (Kyoto, May 17-22 1992).- Kyoto, 1992.- P.59-65.

3. C.B. Amphlett. Inorganic Ion Exchangers, Elsevier, New York ,1964, P.188.

Department of Chemistry, Lviv Ivan Franko National University, Ukraine

Production of metal oxide powders and sphere of their application have been expanding on the regular basis. The significant number of disperse oxides are used for obtaining composite materials with the required set of properties. Even distribution of particles of highly dispersed powders in disperse medium is among one of the problems that occur at producing such materials.

The issues of securing a homogenous coagulation structure of disperse systems and preserving parameters of molding mixtures that are used in technological processes of producing materials are being discussed in the report. Coagulation structure of dispersed systems is formed a result of such physical-chemical phenomena as wetting, redispersion and powder particles stabilization. The degree of development of these physical-chemical phenomena in the systems that are obtained by mixing powders of fluid disperse media is determined by balanced action of the relevant factors. Namely, for wetting it’s balance of specific surface energies; for redispersion – it is balance of external forces and forces of interparticle interaction; for stabilization – it is balance of long-range surface forces.

The analysis of surface force and interparticle force balance has demonstrated that aggregation index in dispersed systems where the size of particles is less than 10 mkm has values higher than 1. In this situation the conditions for partial redispersion of metal oxides are created. The report contains results of researching redispersion of powders of aluminum, titanium and silicone oxides in solutions and at SAS of different nature. The factors that have the biggest impact on the degree of redispersion have been determined.

Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland

Among numerous silica gels the wide-pore gels are especially useful as adsorbents because of their high degree of chemical purity, homogeneity and mechanical resistance. Water similarly as other liquids (n-butanol, benzene, n-octane) adsorbed on solid surfaces, especially on silica gel surfaces, induces the changes of physicochemical properties of interface. Owing to interactions of active centers change of the properties of adsorption layers in comparison to those of bulk liquid. Water also changes the physicochemical properties of silica gel surface which is due to the blocking of active centers by molecules.

The measurements of thermodesorption of the liquid were made in quasi-isothermal conditions. As a result of performed desorption measurements the Q-TG and Q-DTG curves as a function of temperature and time were obtained. On the basis of above curves the adsorption properties and porosity of tested silica materials in relation to individual liquids were studied. For precise determination of inflection points on Q-TG curves the Q-DTG curves registered as a function of temperature and time were utilized. The measurements were performed on the following silica materials: wide-pore Si-100 silica gel, 2MCVD silica and Tullanox 500 (T-500 silica). In experiments the water, n-butanol, benzene and n-octane liquids have been used. The adsorption and porosity properties of tested silica materials were also calculated from measurements of low-temperature adsorption of gas nitrogen at temperature of liquid nitrogen using Sorptomatic 1800 apparatus (Carlo Erba Milano, Italy). The Q-1500 derivatograph (MOM Hungary) consisting of furnace, controlling system (permitting to keep the constant rate of heating of the sample) and registrator was used in our experiments. This apparatus was connected via interface with computer equipped appropriate Derivat program serving to registration of mass loss Q-TG and differential Q-DTG curves in

relation to temperature and time. Before the measurement, the samples of tested materials were dried at 200° C in order to remove water from their surface and then were saturated with vapors of selected liquids in vacuum desiccator at p/po = 1. The prepared samples were placed in platinum crucible and then the measurements of programmed thermodsorption were started. The samples were heated with the rate of 6 o/min (program II) at balance sensitivity equal to 200 mg. During the measurements the mass loss Q-TG curves were registered as a function of temperature or time.

For calculation of number of statistical monolayers of the liquid, number of hydroxyl groups and coverage degree of the surface of tested silica materials we utilized the values of specific surface area of the samples calculated on the basis of BET adsorption isotherm. The values of specific surface area are contained in the range 300-500 m2/g. Such values of specific area are typical for wide-pore adsorbents. Mean pore radii and pore volume are typical for mesopores. On the basis of thermodesorption measurements the adsorption capacity of samples, number of statistical monolayers of individual liquids adsorbed on the surface, volume of mesopores, number of surface hydroxyl groups and surface coverage degree have been calculated and correlated with analogous one from sorptometric method. The values of mesopore volume calculated from thermodesorption of individual liquids from the surface of tested samples and those calculated on the basis of the BET adsorption isotherms are comparable.

Institute of Colloid Chemistry and Chemistry of Water, Ukrainian National Academy of Sciences, Vernadsky avenue 42, 03680 Kyiv, Ukraine

In the removal of metal ions from dilute solutions, the most efficient and selective are the inorganic materials with adsorption ability essentially determined by ion-exchange and chemical interactions, in particular, the formation of complexes. Phosphates of alkali earth metals are efficient for the sorption of heavy metal ions. Among these phosphates, the hydroxyapatite Ca10(PO4)6(OH)2 is the most stable material.

The studies were performed with two samples: (HAP‑1), the synthetic hydroxyapatite for which the structural formula is presented above; and (HAP‑2), the two-phase system which consists of the hydroxyapatite (70 %) and tricalcium phosphate (30 %). The porous structure of the samples was studied by microbalance adsorption of water and hexane vapours; the results are summarised in the Table below. It is seen from the Table that the adsorbents are mesoporous, therefore no restrictions should be expected in the diffusion of adsorbed ions.

Table. Specific area (S) and capacity of arbitrary monolayer (am) with respect to hexane and water; effective pore radius (ref) and Ca:P ratio of hydroxyapatite

Sorbent

am, mmol/g

S, m2/g

ref, nm

Ca:P

n‑C6H14

H2O

n‑C6H14

H2O

HAP‑1

0.28

1.21

84

78

2−3.8

1.66

HAP‑2

0.183

0.49

55

32

2(a),

3.5−4.5(b)

1.61

(a),(b)−two maximums of effective pore radius distribution

The sorbents were studied with respect to the removal of heavy metal ions Cd2+, Ni2+, Co2+, Zn2+ in static conditions from diluted water solutions in the concentration range 100−4000mg/dm3. While the specific area of HAP‑1 is higher than that of HAP‑2, the sorption activity of the latter with respect to heavy metals is higher. However, HAP‑2 is less chemically stable; therefore, the studies and application of HAP‑1 is more promising.

The sorption of heavy metals at both samples is decreasing in the series Zn>Co>Ni>Cd. The sorption isotherms are of the Langmuir type. From the sorption isotherms in the Henry region the distribution coefficients were calculated, which were found to be as large as 104, indicating the high selectivity of the sorbent with respect to the studied ions.

To elucidate possible mechanisms of sorption at the studied sorbents, the pH values of equilibrium solutions and the amount of Ca2+ ions desorbed into the solution were measured. The pH value corresponding to the precipitate formation of hydroxides of the metals studied was higher than the pH value of initial and equilibrium solutions, therefore the formation of heavy metal hydroxides at the HAP surface cannot take place. The transfer of Ca2+ ions instead of Zn2+ ions into the equilibrium solution indicates that the sorption is determined by the ion exchange mechanism. However, for the systems Co‑, Ni‑, and Cd‑HAP the non-equivalence between the amount of sorbed heavy metal ions and the Ca2+ ions displaced to the solution was observed. This suggests that another sorption mechanism also exists, namely the formation of complexes with the phosphate groups. This mechanism was found for sorption of heavy metal ions at inorganic sorbents modified by condensed polyphosphates [1].

To summarise, the synthetic hydroxyapatite can be regarded as the promising material for the removal of heavy metal ions from diluted solutions. This suggests its applicability for the cleaning of galvanic industrial waters.

References

1. Yu.I. Tarasevich, G.M. Klimova, Applied Clay Sci. 19 (2001) 95.

Department of Physicochemistry of Solid Surface, Faculty of Chemistry,

Maria Curie-Sklodowska University,

Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland

In the past decade great interest in properties of a new generation of the molecular sieve surfaces was observed. It results from cognitive aspects and their application as adsorbents and catalysts. In the early ninties a new method of production of micro- and macroporous catalytic materials (e.g. MCM-41 molecular sieves) with a definite pore shape were introduced. It is so-called the Zebedde method (zeolities evolutionary de novo design) using template, i.e. organic molecule compounds carrying out the functions of patterns. A porous structure of synthetic zeolite from inorganic gel forms around the organic molecule. Template uses largely alkalies and other organic compounds, e.g. 2-metylcyclohexamine and/or alkyltrimethyl-ammonium bromides. When the synthesis is over, the above compounds are removed by burning from the sample. It is a result of the regular net of empty places in the zeolite grains. So far, the techniques of porous structure zeolites production have been of empirical character using the method of tests and errors. The Zebedde method makes it possible to project such porous materials which are indispensable in a given catalytic reaction. The MCM-41 molecular sieves are easy to synthesize and can be modified by different heteroatoms such as galium. The Zebedde method has already been used to obtain catalysts of practical application in the process of ethylene and propylene production from methanol. It is very essential in this process, that the size of the catalyst pores cannot be very large, because such compounds as benzene and naphthalene could be formed. The MCM-41 molecular sieves possess a compact chemical construction and exact pore size and structure. Moreover, they have unique

adsorption, catalytic and ion exchange properties which decide about various possibilities of their application in many spheres of life.

Application of adsorbents and/or catalysts require knowledge of many surface physicochemical parameters, mainly their adsorption properties and porosity as well as selectivity, catalytic activity and properties of the surface active sites. For estimation of their nature, quality, localization and energy of active centers (Levis and/or Brönsted acid type) adsorption and microcalorimetric methods are most frequently used. Lately, a special thermal analysis technique has been succesfully adopted to study the liquid/solid systems, especially for characterization of the heterogeneous properties of materials. The effects taking place during thermodesorption of liquids from solid samples were registered and used in the practical calculation of the physicochemical parameters. During the thermodesorption process of adsorbed liquid films from solid surfaces the physical bonds (first of all hydrogen bonds, which are 10 times weaker than the chemical ones) are disrupted. The experimental results obtained so far showed that the simple thermogravimetry method of programmed thermodesorption of liquids from material surfaces in quasi-isothermal condition could be applied to study the adsorbed liquid films on the MCM-41 surfaces and its heterogeneous properties.

The studies were made using Na+[Si/Al] MCM-41-10 and Na+[Si/Al] MCM-41-20 molecular sieves. In the studies of liquids thermodesorption process the samples were prepared as follows. To obtain a desirable thickness of the liquid adsorption films on the surfaces, the samples were wetted with liquids to complete saturation and/or vacuum dessicator where the relative liquid vapor pressure p/po was 1. Measurements of programmed thermodesorption of the polar and apolar liquids from the molecular sieve samples under the quasi-isothermal conditions were made using the simultaneous derivatograph Q-1500D (MOM, Budapest, Hungary). The Derivatograph Q-1500D was connected with computer, via the interface, equipped with a suitable Derivat program to register the sample mass loss Q-TG curves as a function of temperature and time and to determine Q-DTG curves with respect to temperature and time as well as to integrate corresponding areas on the differential thermal analysis DTA curves during the classical measurements. The sample mass loss Q-TG and the differential Q-DTG curves in relation to temperature and time were registered and printed using a special platinum crucible and the computer system.

The porosity of molecular sieves MCM-41 were estimated by means of nitrogen adsorption at 77.35 K, with BET and BJH equations employed using sorptomat apparatus type ASAP 2010 V.2.00A (Micrometrics, Inc., USA).