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The surfaces of natural (NZ) and zeolite/iron oxyhydroxide composite (ZFe) samples were analysed by means of inverse gas chromatography (IGC) using the adsorption data of organic non-polar and polar probes, in the infinite and finite-dilution regimes, in the temperature range 483–513 K. The dispersive components of the free energy of adsorption, γS, determined by the Gray method, decreased with increasing temperature for both zeolites. The specific interactions were characterised by the specific free adsorption energy change, ΔGa S, the specific enthalpy change of adsorption, ΔHa S, as well as the donor and acceptor interaction parameters (KA, KD) and the basic character of the NZ and ZFe was evidenced. The adsorption isotherms of n-hexane, benzene, chloroform and tetrahydrofuran (THF) were determined under finite surface coverage and used to estimate the specific surface area and the adsorption energy distribution. The adsorption capacity of the ZFe was higher than for NZ for all the investigated adsorbates. The specific surface areas and pore size distributions were also determined using nitrogen adsorption–desorption isotherms, i.e., the BET method. It was observed that the nature of the adsorbate and the properties of the solid surface of the initial and modified samples governed the uptake of adsorbates.

Synthetic hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is very similar to the inorganic part of the bones and teeth of mammals. It is a well-known biomaterial with good biocompatibility, osteoconductivity and bioactivity. Nifuroxazide (C12H9N3O5, NFX) is a broad-spectrum antibacterial drug and poorly soluble in water. In order to increase the solubility of NFX, nano-sized HAp powder and raw NFX drug were mixed giving, as a result, a HAp/NFX conjugate. Characterization of the raw materials and the obtained conjugate confirmed the integration of NFX on the HAp surface. An in vitro study of drug release in simulated stomach acid and intestinal fluid showed a much faster release of NFX from HAp surface than those of the raw drug. The HAp/NFX conjugate showed excellent inhibitory effects against Gram-positive bacterium Staphylococcus aureus, Gram-negative bacterium Escherichia coli and yeast Candida albicans, proving the nano-sized HAp powder as a promising drug carrier.

In order to improve the mechanical properties of paper, 1, 3 and 5 wt.% of sepiolite were dispersed in a poly(vinyl butyral) (PVB) matrix and coated onto the surface of schrenz (110 g m-2). Deagglomerated sepiolite nanofibers in PVB matrix on paper surface were observed by scanning electronic microscopy. The glass transition temperature of schrenz with PVB/sepiolite coatings was not changed with increasing content of sepiolite. Two different methods were used to evaluate the mechanical properties of the paper sample reinforced with PVB/sepiolite nanocomposites: tensile testing and nanoindentation. The values of breaking force and tensile energy absorption of the reinforced paper samples obtained by tensile testing were increased by up 10 %. The values of the reduced elastic modulus and hardness obtained by nanoindentation were increased by up to 78 %. The best improvement of the mechanical properties was shown by the paper sample coated with PVB/3 wt.% sepiolite nanocomposite. [Projekat Ministarstva nauke Republike Srbije, br. III 45019]

sorption of Ni2+ on the sepiolite functionalized by covalent grafting of N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt, MSEAS, was studied in batch experiments as a function of the initial metal concentration, the equilibration time, pH value, and temperature. The modification of sepiolite resulted in an enhanced Ni2+ retention with a capacity of 0.261 mmol/g at 298 K. The retention of Ni2+ ions occurred dominantly by specific sorption and exchange of Mg2+ ions from the sepiolite structure. The sorption process followed pseudo-second-order kinetics. The sorption equilibrium results were best described by the non-linear form of the Langmuir Sorption Equation. The values of the thermodynamic parameters (enthalpy, free energy and entropy) were calculated from temperature dependent sorption isotherms and these values showed that the sorption of Ni2+ onto modified sepiolite was endothermic. [Projekat Ministarstva nauke Republike Srbije, br. III 45019 i FP7 NANOTECH FTM No. 245916]

Natural sepiolite from Andrici (Serbia) was functionalized by covalent grafting of N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt to the Si-OH sepiolite groups. The functionalized material, MSEAS, was characterized by determination of phase composition by X-ray diffraction (XRD) analysis, analysis of morphological characteristics by scanning electron microscopy (SEM), using Fourier transform infrared (FTIR) spectroscopy, differential thermal analyses (DTA), determination of specific surface areas and pore size distribution using B.E.T. method and point of zero charge (pHpzc) determination. The crystal structure of sepiolite does not change significantly upon surface modification. FT-IR and DTA analysis confirmed that the modified sample maintained the basic structure of sepiolite and also the presence of organic groups in functionalized sepiolite sample. The point of zero charge of MSEAS in KNO3 solutions of different concentrations determination by the batch technique from was at pH 7.0 ± 0.1. [Projekat Ministarstva nauke Republike Srbije, br. III 45019, and FP7 NANOTECH FTM No. 245916]

The photocatalytic efficiency of the recently synthesized TiO2 powder, named P160, of the degradation of dye Dye C.I. Reactive orange 16 in natural and artificial seawater was investigated in comparison to its efficiency in deionized water and the efficiency of a standard TiO2 powder Degusa P25. It was shown that the photocatalytic efficiency of P160 was slightly higher than that of P25, probably due to slightly higher specific surface area, higher pore volume and larger pores of the powder P160. The efficiency of both photocatalysts in natural and artificial seawater was significantly lower than that in deionized water. The overall rate of dye degradation for both types of photocatalysts is litle higher in artificial seawater than in natural seawater, which shows the influence of organic compounds naturally present in seawater on the photocatalysts activity. A saturation Langmuir-type relationship between the initial degradation rate and the initial dye concentration indicates that the adsorption plays a role in the photocatalytic reaction. The photodegradation rate constant k, which represents the maximum reaction rate, has similar values for P25 and P160 in all types of water due to the similar properties of the photocatalysts. [Projekat Ministarstva nauke Republike Srbije, br III 45019]

The sorption of inorganic arsenic species, As(III) and As(V), from water by sepiolite modified with hydrated iron(III) oxide was investigated at 25 °C through batch studies. The influence of the initial pH value, the initial As concentrations, the contact time and types of water on the sorption capacity was investigated. Two types of water were used, deionized and groundwater. The maximal sorption capacity for As(III) from deionized water was observed at initial and final pH value 7.0, while the bonding of As(V) was observed to be almost pH independent for pH value in the range from 2.0 to 7.0, and the significant decrease in the sorption capacity was observed at pH values above 7.0. The sorption capacity at initial pH 7.0 was about 10 mg gˉ1 for As(III) and 4.2 mg gˉ1 for As(V) in deionized water. The capacity in groundwater was decreased by 40 % for As(III) and by 20 % for As(V). The Langmuir model and pseudo-second order kinetic model revealed good agreement with the experimental results. The results show that Fe(III)-modified sepiolite exhibits significant affinity for arsenic removal and it has a potential for the application in water purification processes. [Projekat Ministarstva nauke Republike Srbije, br. III 45019, III 43009 i TR 37010]

The photocatalytic degradation of synthetic textile dye CI Basic Yellow 28 (BY28) in water, using recently synthesized P160 TiO2 based catalyst, under Osram ultra-vitalux® lamp (300 W) light, was studied. The effect of the operational parameters such as initial concentration of catalyst, initial dye concentration and pH was studied. Salt effect was also investigated (NaCl, Na2CO3, Na2SO4, NaNO3). It was found that the optimal concentration of catalyst is 2.0 g L-1. A pseudo first-order kinetic model was illustrated using the Langmuir-Hinshelwood mechanism, and the adsorption equilibrium constant and the rate constant of the surface reaction were calculated (KBY = 6.126 L mg-1 and kC = 0.272 mg L-1 min-1, respectively). The photodegradation rate was higher in weak acidic than in high acidic and alkaline conditions. The presence of CO32- ions increases the photodegradation rate while Cl-, SO42- and NO3-ions decreases the reaction rate. The rate of photodegradation of BY28 was measured using UV-Vis spectroscopy. [Projekat Ministarstva nauke Republike Srbije, br. III 45019 and br. 172013.]

In order to obtain multifunctional materials with good biocompatibility and antimicrobial effect, hydroxyapatite (HAp) doped with Zn2+ was synthesized by hydrothermal method. Powders with different content of zinc ions were synthesized and compared with undoped HAp to investigation of Zn2+ ion influence on the antimicrobial activity of HAp. Analyses of undoped and Zn2+-doped powders before and after thermal treatment at 1200ºC were performed by SEM and XRD. Antimicrobial effects of powders were examined in relation to Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans in liquid medium. The results showed that the obtained powders have good antimicrobial activity, but higher antimicrobial activities of powders doped with Zn2+ were observed after annealing at 1200°C. For powders annealed at 1200°C in vitro biocompatibility tests MTT and DET with MRC-5 fibroblast cells in liquid medium were carried out. Based on MTT and DET tests it was shown that powders do not have a significant cytotoxic effect, which was confirmed by SEM analysis of MRC-5 fibroblast cells after theirs in vitro contact with powders. [Projekat Ministarstva nauke Republike Srbije, br. III 45019 and FP7-REGPOT-2009-1 NANOTECH FTM]

Three cordierite-type gels were prepared from an aqueous solution of Mg(NO3)2, a boehmite sol and silica sols of very small particle sizes. The effect of varying the silica particle size on the crystallization and densification behaviour was studied. Phase development was examined by thermal analysis and X-ray diffraction, while the densification behaviour was characterized by measuring the linear shrinkage of pellets. The activation energy of densification by viscous flow was determined using the Franckel model for non-isothermal conditions and a constant heating rate. The results show that spinel crystallizes from the colloidal gels prior to cristobalite, and their reaction gives -cordierite, which is specific for three-phase gels. Decreasing the silica particles size lowers the cristobalite crystallization temperature and the -cordierite formation temperature. The activation energy of densification by viscous flow is lower and the densification more efficient, the smaller the silica particles are.

In this paper the results of an examination of the surface roughness and morphology dependence of silver thin films up to 100 nm thick deposited on a microscope glass on the deposition rate and on the deposition time are presented. It was found that, for a constant deposition rate, the surface roughness exhibits minimum at a certain layer thickness. This coincides with the turning point when the influence of the substrate surface on the deposition process becomes negligible, i.e., to the change in the nature of the system substrate/deposit from Ag/glass to Ag/Ag. For a constant layer thickness, sthe surface roughness minimum, achieved at a certain deposition rate, coincides to the turning point when the average free path for vertical adatom mobility becomes zero.

The role of defects on a substrate surface during the initial stages of nucleation and growth ofAg deposited electrochemically and physically on highly oriented pyrolytic graphite (HOPG) has been observed ex situ by scanning tunneling microscopy (STM). The silver was electrodeposited under current controlled electrochemical conditions at 26μA/cm2, which corresponded to a deposition rate of 0.1 monolayers (ML) per second. For comparison, physical deposition of Ag on HOPG was performed by DC Ar + ion sputtering, at the same deposition rate and for the same deposition times. In both cases, Ag grows in an island growth mode, but the distribution of the islands appears to be quite different. In physical deposition, the Ag islands are almost homogeneously distributed over the substrate surface and a slight accumulation of islands on steps does not contribut e significantly to the overallmorphology. This indicates the crucial role of point defects on the substrate in the initial stages of nucleation. In electrochemical deposition, more line d defects are observed after a flow of current, andtheir role in the beginning of the nucleat ion is more pronounced. Lined defects are responsible for the string-like shaped domains of deposited atoms. Also, the existence of string-like shaped nucleation exclusion zones is indicated. The problem of the formation of nucleation exclusion zones,which appear only in electrochemical deposition, has been reconsidered and a new explanaton of their formation is given. A mathematical model for the calculation of the radius of the nucleati on exclusion zone has been developed.