Gerhard Rychlicki

Nicolaus Copernicus University, Toruń, Kujawsko-Pomorskie, Poland

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Publications (65)145.91 Total impact

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    ABSTRACT: A series of hydrosilated stationary phases were compared with respect to their hydrophilic–hydrophobic properties. The stationary phases were also compared to the bare silica gel used for this synthesis. The investigations were done using microcalorimetric measurements of methanol and acetonitrile heats of immersion. Because these stationary phases are used in both the reversed-phase and aqueous normal phase modes of liquid chromatography, the excess isotherm of water from acetonitrile solution was measured.From the materials tested the highest polarity was exhibited by the silica hydride and the bare silica. The Diamond Hydride is less polar. The highest hydrophobicity is exhibited by the hydrosilated stationary phase which contains bonded octadecyl ligands.
    Journal of Colloid and Interface Science 01/2014; 416:161–166. · 3.55 Impact Factor
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    ABSTRACT: This paper presents the numerical analysis of spherical carbon adsorbents produced by the single-step steam pyrolysis of a polystyrene-divinylbenzene resin. The porous structure of the materials produced this way was easily controlled by varying such factors as the carbonization temperature, atmosphere or the heating rate, allowing carbonaceous materials to have a controlled microporous structure. Due to their unique properties, the obtained adsorbents can be considered applicable in various processes in technology and environmental protection. The fast multivariant fitting procedure with the new adsorption numerical models of the LBET class was used for the analysis of the microporous structure. The computer calculations using the LBET class models with the fast multivariant identification procedure were carried out with the application of the nitrogen (77.15 K) adsorption isotherms.
    Applied Surface Science 10/2012; 259:13–20. · 2.54 Impact Factor
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    ABSTRACT: We studied the thermodynamics of benzene adsorption on a series of oxidized closed-ended multiwalled carbon nanotubes at 298 K. Combined experimental and simulation results showed the significant effect of the surface heterogeneity on the benzene adsorption enthalpy and entropy at low surface coverages. For oxidized carbon nanotubes and low benzene uptakes, the differential entropy of the adsorbed phase is close to the differential entropy of solid benzene. Therefore, benzene molecules interacting with surface heterogeneities are ordered in quasi-solid structures at 298 K. At higher surface coverages, the ordering and packing of benzene molecules is liquid-like.
    Chemical Physics Letters 06/2012; 538:93–98. · 2.15 Impact Factor
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    ABSTRACT: The calorimetric measurements of methanol and hexane heats of immersion were carried out on different silica gels. Based on the difference in immersion heats, a methodology for the determination of the number of silanols on the surface is presented. The calculated concentration of residual silanols on the silica gel surface agreed with data found in the literature. The proposed methodology, based on a calculation of possible hydrogen bond formation, was also tested on the series of bonded stationary phases with different coverage densities. A very good correlation between the calculated number of accessible residual silanols and the coverage density of bonded ligands was observed.
    Journal of Chromatography A 09/2011; 1232:43-6. · 4.61 Impact Factor
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    Bogusław Buszewski, Szymon Bocian, Gerhard Rychlicki
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    ABSTRACT: A detailed description of the stationary-bonded phase surface in reversed-phase liquid chromatography (RPLC) is a topic of great interest in separation sciences. For this purpose, the thermal effects connected with solvent adsorption on the series of octadecyl stationary-bonded phases were investigated. Microcalorimetric study of organic solvent heat of immersion of the stationary-phase and chromatographic measurements of the silanol activity were executed. Good correlation between the heat of immersion of different solvents and the residual silanol activity obtained from chromatographic tests of various stationary phases are observed. The present data suggest that measurement of solvent adsorption heat governed by polar interaction with residual silanols may be a useful tool for the determination of silanol activity and surface topography. The present methodology allows determining the access of the solvent molecules to the residual silanols on the chemically bonded phase surface based on silica gel.
    Journal of Separation Science 03/2011; 34(7):773-9. · 2.59 Impact Factor
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    ABSTRACT: A simple method of preparation of new high surface area spherical carbon adsorbents is presented. The phosphoric acid activation upon hydrothermally formed spherules was employed to produce carbons having controlled high specific surface area (over 2100m(2)/g), large volumes of pores (1.2cm(3)/g), and high acidity. Prepared from sucrose materials show high adsorption capacities (i.e. 220mg/g(C)) toward paracetamol. It is proved that for these materials the contents of surface phosphorus are responsible for the reversibility of drug adsorption/release process.
    Journal of Colloid and Interface Science 02/2011; 354(2):891-4. · 3.55 Impact Factor
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    ABSTRACT: A detailed, molecular-level description of the sorption mechanism in reversed-phase liquid chromatography is of great interest to analytical chemists. For this purpose, solvent adsorption in the octadecyl stationary bonded phase was investigated. Preferential adsorption of solvents from an acetonitrile-water and methanol-water mobile phase was measured on a series of non-end-capped octadecyl bonded phases with different coverage densities of bonded ligands using the minor disturbance method. For a comparison, a microcalorimetric study of organic solvent adsorption on the stationary phase was executed. The results from the excess isotherm measurement agree well with the experimental measurement of the heat of immersion of the bonded stationary phases by the test solvents. The microcalorimetric measurement is another method for determination of solvation processes of the stationary phases. Changes of the heat of immersion provide information about the surface accessibility for interaction with solvent molecules. The increase of the stationary phase coverage density reduces the free space between bonded chains and penetration of solvent between organic chains.
    Journal of Colloid and Interface Science 09/2010; 349(2):620-5. · 3.55 Impact Factor
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    ABSTRACT: Using the combined techniques of molecular simulation, simple analytical modeling, and adsorption calorimetry, we propose new models describing adsorption onto closed carbon nanotubes. The models are capable of describing the adsorption isotherms and calorimetric enthalpy of carbon tetrachloride adsorption measured on three different closed carbon nanotubes. It is shown that the assumption of the presence of two types of surface centers (high- and low-energy centers) on external tube surfaces is sufficient to describe experimental adsorption and calorimetric enthalpy data.
    Journal of Colloid and Interface Science 09/2010; 349(1):321-30. · 3.55 Impact Factor
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    Marek Winiewski, Gerhard Rychlicki, Andrzej Arcimowicz
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    ABSTRACT: a b s t r a c t The enthalpy of immersion of closed-end carbon nanotubes in a series of organic liquids has been mea-sured. The enthalpy was found to be linear function of the dipole moments. From the slope of the lines the average electrostatic field strength of the surface was calculated. This value increases with the decrease in tube radius. The curved aromatic fragments of C 24 H 12 have been employed as models of car-bon nanotubes (n, 0), where n varies from 30 up to 180. Theoretical results indicate that the reactivity indices also depend strongly on the surface curvature being linearly correlated with the surface electro-static field strength.
    Chemical Physics Letters 01/2010; 485(4). · 2.15 Impact Factor
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    ABSTRACT: A series of commercial unmodified and modified activated carbons was studied. The surface chemical composition was characterized using X-ray photoelectron spectroscopy and Boehm titration methods. Data on p-nitrophenol (pnp) adsorption isotherms determined under real oxic and anoxic conditions (at 310 K) are presented and described using bimodal Langmuir and lattice density functional theory models. The applicability of the pnp molecule for determination of surface area using adsorption from solution data is discussed. It is shown that under anoxic conditions adsorption and relative enthalpy of this process depend on the value of BET apparent surface area and DA micropore volumes. The differences between adsorption levels under both conditions increase with rise in solute equilibrium concentration. Moreover, the average difference between adsorption values under both conditions increases and next decreases with rise in the concentration of surface acidic groups. Applying quantum chemical calculations, we show that under anoxic conditions the influence of surface oxygen groups on pnp adsorption is small, whereas under oxic conditions the reverse situation is observed. Obtained theoretical results show very good correspondence to the experimental data and the origin of the relationships observed experimentally is explained and discussed.
    Journal of Colloid and Interface Science 05/2008; 320(1):40-51. · 3.55 Impact Factor
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    ABSTRACT: The purpose of the current study is to present the state of art in the field of analytical description of water sorption on carbons. We discuss the most important and promising models proposed recently (for example by Mahle; Talu and Meunier; and Malakhov and Volkov) as well as some older theoretical models inspired by the pioneering ideas proposed in the papers of Dubinin, Serpinsky, Barton, D'Arcy, Watt, Do and Do and others. The applicability, advantages, and defects of all these analytical formulas are pointed out and some new approaches in this field are presented. The special attention is paid to the finite adsorption space and the possible involvement of partial chemisorption, i.e. the existence of various types of the hydrophilic centres. Since the calculation of isosteric enthalpy from an adsorption equation, and the comparison of theoretical enthalpy plot with the values measured calorimetrically, is the fundamental condition for the verification of the correctness of an adsorption model, for all considered models we show the corresponding adsorption enthalpy equations. The validity of all mentioned above models is verified for the data measured for five water-activated carbon systems. Finally, a summary of obtained results and some perspectives and suggestions for the description of experimental data are presented. From the analysis of experimental data it is seen that developed recently- the heterogeneous Do and Do model is probably the most successful for the simultaneous description of water adsorption and enthalpy of adsorption results.
    Advances in Colloid and Interface Science 04/2008; 137(2):82-143. · 6.17 Impact Factor
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    Adsorption Science & Technology - ADSORPT SCI TECHNOL. 01/2008; 26(6):407-413.
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    ABSTRACT: A plausible model for the structure of non-graphitizing carbon is one which consists of curved, fullerene-like fragments grouped together in a random arrangement. Although this model was proposed several years ago, there have been no attempts to calculate the properties of such a structure. Here, we determine the density, pore size distribution and adsorption properties of a model porous carbon constructed from fullerene-like elements. Using the method proposed recently by Bhattacharya and Gubbins (BG), which was tested in this study for ideal and defective carbon slits, the pore size distributions (PSDs) of the initial model and two related carbon models are calculated. The obtained PSD curves show that two structures are micro-mesoporous (with different ratio of micro/mesopores) and the third is strictly microporous. Using the grand canonical Monte Carlo (GCMC) method, adsorption isotherms of Ar (87 K) are simulated for all the structures. Finally PSD curves are calculated using the Horvath-Kawazoe, non-local density functional theory (NLDFT), Nguyen and Do, and Barrett-Joyner-Halenda (BJH) approaches, and compared with those predicted by the BG method. This is the first study in which different methods of calculation of PSDs for carbons from adsorption data can be really verified, since absolute (i.e. true) PSDs are obtained using the BG method. This is also the first study reporting the results of computer simulations of adsorption on fullerene-like carbon models.
    Physical Chemistry Chemical Physics 12/2007; 9(44):5919-27. · 4.20 Impact Factor
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    ABSTRACT: We present the results of benzene adsorption at the acidic pH level determined on the series of chemically modified activated carbons and at three temperatures. The influence of carbon surface chemical composition on benzene adsorption is discussed. It is shown that the decrease in the pH level from 7 up to 1.5 increases benzene adsorption and the only exception is carbon modified with gaseous ammonia. Basing on the results of current work and those published previously (for phenol, paracetamol, acetanilide and aniline) and using the results of quantum chemistry calculations (DFT, Gaussian 98) we show, that the value of the energy of interaction with unit positive charge is crucial during the analysis of the influence of pH level on adsorption. Obtained results allow to predict the changes in adsorption of aromatics on carbons with the decrease in the pH level.
    Applied Surface Science 01/2007; 253(8):4006-4009. · 2.54 Impact Factor
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    ABSTRACT: In this study, we develop the equation describing the enthalpy of adsorption corresponding to the cooperative multimolecular sorption approach proposed by Malakhov and Volkov. For different shapes of adsorption isotherms plotted from this model (and analyzed by Rutherford and Coons), we generated the corresponding enthalpy of adsorption curves. We also discuss other enthalpy plot shapes predicted by the CMMS. The new relations are verified for simultaneous description of SO2 adsorption data, and enthalpy of sorption, measured on graphitized carbon black and on activated carbon. Finally, we apply the CMMS model to description of adsorption data of SO2 measured on the series of modified activated carbons. The porosity of adsorbents was characterized via description of low-temperature N2 isotherms applying the method of Nguyen and Do. Oxygen content in carbons was measured applying the elemental analysis. From the results of the correlations between the parameters of the CMMS and elemental analysis data, it is concluded that the interaction between SO2 molecules and carbon surface oxygen groups is crucial during adsorption of this adsorbate. Our results explain and summarize up the conclusions concerning the effect of carbon surface nitrogen functionalities on SO2 sorption mechanism presented by other authors. Finally, we conclude that the CMMS approach can be successfully applied to the description of this process.
    Langmuir 09/2006; 22(16):6887-92. · 4.38 Impact Factor
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    Artur P Terzyk, Piotr A Gauden, Gerhard Rychlicki
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    ABSTRACT: Based on the series of benzene adsorption and related enthalpy of adsorption data measured on porous carbons that possess various porous structures, we show that the creation of a solidlike structure in pores depends on the average pore diameter of an adsorbent. Taking into account the solidlike adsorbed phase in the thermodynamic description of the adsorption process via the formalism of the theory of volume filling of micropores (TVFM) leads to very good agreement between the data measured experimentally and those calculated from TVFM. Finally we show that the boundary between solidlike and liquidlike structures of benzene molecules in carbon pores is located around the average pore diameter, close to ca. 2.1-2.4 nm.
    Journal of Colloid and Interface Science 07/2006; 298(1):66-73. · 3.55 Impact Factor
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    ABSTRACT: The chemical character, geometry, and architecture of chemically formed surface layers determine interactions between stationary phase, analyte, and mobile phase, and therefore the retention mechanisms (partitioning, adsorption, ion exchange, steric exclusion) of separated analytes. These interactions also depend on the structure and chemical character of the solutes and the composition of the mobile phase. High-molecular-weight fullerenes (C60 and C70) and water-soluble selenium-containing peptides (833 and 2607 Da) were used for the evaluation of laboratory-prepared octadecyl stationary phases with high and low coverage density before and after end-capping. The aim of this work was to study differences in surface coverage density and homogeneity and conformational changes of chemically bonded moieties and the influence of these parameters on the separation of mixtures of selenopeptides and fullerenes with significantly different molecular masses. A topographical model of the chemically modified stationary surface is presented.
    Journal of Separation Science 05/2006; 29(6):829-36. · 2.59 Impact Factor
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    ABSTRACT: We present two very simple models of adsorption in cylindrical pores. It is assumed that a layer-by-layer mechanism occurs similarly to that in the BET theory. The major assumption is that in the pores having an adsorption space with cylindrical geometry, the surface area of the upper surface (in comparison with the bottom surface) should be diminished in proportion to the radii of a cylinder. Two cases are considered: the adsorbate-adsorbate interactions are neglected or they are taken into account according to the lattice model developed by Fowler and Guggenheim. It is shown that the data simulated by Ohba and Kaneko for adsorption of nitrogen in the internal space of carbon nanotubes are successfully described by our models. On the basis of the fitted data we show that the relation between the monolayer capacity in cylindrical pores and on flat surfaces is in excellent agreement with the equation developed recently by Salmas and Androutsopoulos. Moreover, our models are verified for two sets of experimental data reported by Kaneko et al. We obtain excellent agreement between the values of the pore diameters calculated by us and suggested by these authors (from HRTEM, the GCMC simulations, and the IDBdB model). It is concluded that proposed simple and fast models can be applied as a first approximation to the estimation of the internal nanotube diameters if they do not exceed ca. 5 nm and are slightly dispersed.
    Journal of Colloid and Interface Science 04/2006; 295(2):310-7. · 3.55 Impact Factor
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    ABSTRACT: The paper investigates the changes in porosity (i.e., in the accessible adsorption capacity of carbonaceous adsorbents for pollutants during filter bed maturation) of three activated carbons applied in a filter bed pilot operation. The results of this investigation may help to reduce operating costs, increase granular activated carbon bed life, maximize the useful life of biofilters, and understand the mechanism of water purification by carbon adsorbents. The analysis of the pore structure was limited to the first year of service of the beds, since this was when the largest decrease in the available pore capacity occurred. Low-temperature nitrogen adsorption isotherms were used to evaluate the structural parameters and pore size distributions (PSDs) of carbon samples (virgin (reference) and mature adsorbents for different periods of water treatment) on the basis of the Nguyen and Do (ND) method and density functional theory (DFT). These results were compared with small-angle X-ray scattering (SAXS) investigations (PSDs calculated by Glatter's indirect transformation method (ITP)). The results show that in general, the ND and ITP methods lead to almost the same qualitative distribution curve behavior. Moreover, the enthalpy of immersion in water, mercury porosimetry, densities (true and apparent), and the analysis of ash are reported and compared to explain the decrease in adsorptive capacity of the carbons investigated. On the other hand, the efficacy of TOC (total organic carbon, i.e., a quantity describing the complex matrix of organic material present in natural waters) removal and the bacteria count were analyzed to explain the role of adsorption in the elimination of contaminants from water. Finally, a mechanism of organic matter removal was suggested on the basis of the above-mentioned experimental data and compared with mechanisms reported by other authors.
    Journal of Colloid and Interface Science 04/2006; 295(2):327-47. · 3.55 Impact Factor
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    ABSTRACT: The efficiency of multi-walled carbon nanotubes (MWNTs) and traditional activated carbons for benzene adsorption is studied. Ben-zene adsorption isotherms and the related values of the calorimetric adsorption enthalpy at 298 K are used to calculate the entropy and the state of the adsorbed molecules. The analysis of the experimental data leads to the conclusion that both thermodynamic functions are related to the kind of porosity present in the studied materials. Our results also show that in the case of MWNTs the adsorption between the tubes is a very important effect which determines the mechanism of this process.
    Chemical Physics Letters 03/2006; 421(4). · 2.15 Impact Factor

Publication Stats

308 Citations
145.91 Total Impact Points

Institutions

  • 1991–2014
    • Nicolaus Copernicus University
      • • Faculty of Chemistry
      • • Department of Drugs Chemistry
      • • Department of Environmental Chemistry and Bioanalytics
      Toruń, Kujawsko-Pomorskie, Poland
  • 2004–2006
    • Academy of Humanities & Economics in Lódz
      Łódź, Łódź Voivodeship, Poland
  • 2004–2005
    • Chiba University
      • Department of Chemistry
      Chiba-shi, Chiba-ken, Japan