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1

Surface properties of the doped silica hydrophobic coatings deposited on plasma activated glass supports

Chodkowski Michał, Terpiłowski Konrad, Goncharuk Olena

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 6

1450--1459

EN

The paper discusses preparation and characteristics of silica hydrophobic layers deposited on the plasma-modified glass supports. The surfaces were investigated using wettability measurements, profilometry, photoacoustic and infrared spectroscopy, X-ray photoelectron spectroscopy as well as scanning electron microscopy. The wettability measurements showed that the obtained surfaces are hydrophobic – the water contact angle was in the range of 140-150 degrees. The photoacoustic and infrared spectroscopy as well as X-ray photoelectron spectroscopy disclosed the surface compositions, particularly that of the hydrophobic alkyl groups deposited on them. They were methyl groups introduced during hydrophobization by hexamethyldisilazane. In addition, it was found that the number of groups on the surface depends on the kind of plasma by which the supports were activated. The optical profilometer showed differences in the surface roughness which affects their hydrophobicity. Moreover, the surface free energies were determined using the contact angle hysteresis method. They disclosed differences in each surface, depending on the way of supports activation. The largest hydrophobicity was obtained on the layer deposited on the support activated by the argon plasma. However, support activation by the air plasma resulted in a decrease of hydrophobicity compared to that of the non-activated surface.

2

Wpływ chemii powierzchni węgli aktywnych na adsorpcję kwasu 2,4-dichlorofenoksyoctowego

Kuśmierek K., Świątkowski A.

Inżynieria i Ochrona Środowiska

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2016

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T. 19, nr 2

255--263

EN

The aim of this study was to investigate the effect of surface chemistry of the activated carbons on the adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D). The 2,4-D was adsorbed on non-modified Norit R3-ex activated carbon (AC-NM) as well as on activated carbons modified by oxidation with concentrated nitric acid (AC-HNO3) and by heat treatment in ammonia at 900°C (AC-NH3). Adsorption isotherms of the 2,4-D on the activated carbons were analyzed using the Freundlich, Langmuir and Langmuir-Freundlich models. The Langmuir equation was slightly better fitted to the experimental data with the correlation coefficients better than 0.99. The values of the Langmuir maximum adsorption capacity (qm) were 2.945, 2.740 and 3.297 mmol/g for the AC-NM, AC-HNO3 and AC-NH3 activated carbons, respectively. The adsorption capacity of the activated carbons increased in the order: AC-HNO3 < AC-NM < AC-NH3. The best adsorbent was activated carbon with basic properties, while the worst adsorption properties were observed for the activated carbon with acidic properties. The acid treatment of activated carbon produced a large number of oxygen-containing functional groups on the carbon surface as it increases its acidic property and, in consequence, reduces the adsorption of the 2,4-D. The treatment of activated carbon with ammonia at high temperature leads to the formation of nitrogen-containing groups. The basic properties of the carbon surface enhance the interaction between activated carbon and acid molecules (dipole-dipole, H-bonding, covalent bonding) causing the increased adsorption of the 2,4-D from water. The effect of pH on the adsorption of 2,4-D onto activated carbons was also studied. The adsorption of the 2,4-D was almost constant at the pH range of 2.0-2.6 and decreased with the further increasing in the pH. The solution pH determines the adsorbent charge and the protonation or dissociation of the adsorbate. The pKa of 2,4-D is 2.8, and at a pH greater than the pKa value, the herbicide existed predominantly in anionic forms. As the pH increased, the degree of dissociation of 2,4-D increased, thereby making it more negatively charged. The values of the point of zero charge (pHPZC) were 6.10, 3.35 and 7.85 for the AC-NM, AC-HNO3 and AC-NH3 activated carbons, respectively. At pH of less than the pHPZC, the surface of the carbon had a net positive charge; at a pH greater than pHPZC, the surface had a net negative charge. The large reduction in the 2,4-dichlorophenoxyacetic acid adsorption at highly basic conditions can be attributed to the electrostatic repulsion between the negatively charged activated carbons and the dissociated 2,4-D molecules. The experimental results demonstrate that the surface chemistry of the activated carbons affects significantly the adsorption of the 2,4-D and should be taken into account when choosing an adsorbent for the removal of the herbicide from water.

PL

Celem pracy było zbadanie wpływu chemii powierzchni węgli aktywnych na adsorpcję kwasu 2,4-dichlorofenoksyoctowego (2,4-D) z wody. Adsorpcję prowadzono na węglu Norit R3-ex o niemodyfikowanej powierzchni (AC-NM), na węglu utlenionym stężonym kwasem azotowym(V) (AC-HNO₃) oraz węglu wygrzewanym w amoniaku w temperaturze 900°C (AC-NH₃). Do opisu adsorpcji zastosowano równania Freundlicha, Langmuira i Langmuira-Freundlicha. Pojemność adsorpcyjna badanych węgli wzrastała w kolejności AC-HNO₃<3. Najlepszym adsorbentem okazał się węgiel aktywny o zasadowym charakterze (AC-NH₃), najgorsze właściwości adsorpcyjne zaobserwowano dla węgla aktywnego o kwaśnych właściwościach (AC-HNO₃). Zbadano również wpływ pH na adsorpcję 2,4-D z wody. Adsorpcja zmniejszała się wraz ze wzrostem pH roztworu, spadek ten był skorelowany z właściwościami kwasowo-zasadowymi powierzchni adsorbentów. Wyniki pokazały, że chemia powierzchni węgli aktywnych jest ważnym czynnikiem wpływającym na adsorpcję 2,4-D z wody i powinna być brana pod uwagę przy wyborze adsorbentu do usuwania herbicydu z wody w celu zmaksymalizowania skuteczności procesu oczyszczania.

3

Effect of oxidation roasting on ilmenite flotation

Mehdilo A., Irannajad M., Rezai B.

Physicochemical Problems of Mineral Processing

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2014

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Vol. 50, iss. 2

493--505

EN

In this study, the oxidation roasting was used to modify the ilmenite chemistry to improve the collector adsorption and ilmenite flotation behavior. The results indicated that the increase of the roasting temperature up to 600 ºC increased the ilmenite flotation recovery. The maximum collector adsorption density occurred on ilmenite roasted at 600 °C which resulted in the increase of ilmenite flotation recovery from 73.5% to 91% at pH 6.3. This improvement was attributed to a greater conversion of Fe2+ to Fe3+ ions and significant decrease in the zeta potential of ilmenite. At the roasting temperatures of 750 °C and 950 °C, ilmenite was converted to rutile and some trivalent iron containing phases such as hematite and pseudobrookite. Under these conditions, the collector adsorption and hence ilmenite flotation improved, however the flotation recovery decreased after the roasting at 950 °C.

4

Synthesis and preliminary characterization of 2-line ferrihydrite containing different amounts of Si

Pieczara G., Rzepa G.

Geology, Geophysics and Environment

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2012

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Vol. 38, no. 4

517--518

EN

Ferrihydrite (Fe5HO8 • 4H2O) is the reddish-brown, nearly amorphous hydrous ferric oxyhydroxide mineral with variable composition, widespread in various near-surface environments. Being thermodynamically unstable, it transforms with time into goethite (a-FeOOH) or hematite (a-Fe2O3). Due to its low crystallinity and high surface area, ferrihydrite is highly reactive and plays, through coprecipitation and adsorption reactions, an essential role in e.g. geochemical cycling of various trace elements and capturing of contaminants from streams and groundwater in such environments as ironladen springs, mine wastes and acid mine drainage. The environmental importance is one of the main reasons for numerous studies on ferrihydrite properties which have been carried out recently. These studies have been dealing with, among others, solubility, thermodynamic features, surface chemistry, sorption and catalytic properties etc. However, in the majority of experimental works synthetic ferrihydrite analogues with chemical composition close to ideal have been applied. Such approach might cause oversimplification, because ferrihydrite always contain substantial amounts of admixtures, with Si, C, P, As, Ca, Al being probably most common. One of the most important and the most common impurity is Si, which in the form of silicate ion has strong affinity for a hydrous ferric oxyhydroxide surface. An association of ferrihydrite with Si not only retards the rate of its transformation to the stable phases (goethite or hematite), but also seriously affects e.g. surface chemistry. Although Si-ferrihydrite was successfully synthesized in several studies, relatively little is known about its properties. The aim of this work was to fill that gap. Ferrihydrite samples having different Si/Fe molar ratios: 0.00, 0.05, 0.10, 0.20, 0.25, 0.50, 0.75, 1.00, and 1.50, were obtained by reaction of Fe2(SO4)3 with NaOH in the presence of Na2Si03 at pH 8.2. The precipitates were incubated for four days at room temperature, then the suspensions were dialyzed to remove an excess of salt, and finally freezedried. The products were characterized using a variety of analytical techniques, including X-ray powder diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and Raman spectroscopy. The X-ray pattern of pure ferrihydrite reveals two asymmetric broad bands with maxima at 2.55 A and 1.50 A, characteristic for 2-line ferrihydrite. With increasing Si/Fe molar ratio, shifting in position of the first (ca. 35°20) peak towards lower angles (up to ca. 29°20) was observed. Gradual broadening of the peak and declining its asymmetry were noticed as well. Both the position and the shape of the second band did not shift at the same time. These features indicate reducing crystallinity and lowering grain size of Si-ferrihydrite in comparison to those for the pure ferrihydrite. Infrared spectrum of the pure (Si-free) ferrihydrite shows a broad band at ca. 400 cm"1, with a shoulder at 600 cm"1, attributable to Fe-0 stretching vibrations. Distinct bands at 1635 cm"1 and 3400 cm"1, related to OH stretching, are apparent as well. The presence of small peaks at 975 cm" , 1055 cm" and 1125 cm" is probably an effect of sulfate complex formation on the ferrihydrite surface. Increasing Si concentration strongly affects infrared spectra of ferrihydrite: additional intensive band at ca. 990 cm" (Si-0 stretching) appears and is getting stronger with increasing Si/Fe ratio. The position of this band is shifted slightly towards higher wavenumbers (up to 1003 cm"1) at higher-Si-ferrihydrite spectra. At the same time, ~ 600 cm"1 shoulder and sulfate peaks disappear. Results of Raman spectroscopy are in general consistent with those of FTIR and gave more specific information about the band at ca. 400 cm"1, which is quite indistinct on infrared spectra and attributed to Fe-OH unsymmetrical-stretching vibrations. The band is getting broader and is slightly shifted to higher wavenumbers with increasing Si/Fe ratio but its intensity decreases drastically for the highest-Si samples (Si/Fe > 0.75). At the same time, characteristic 720 cm"1 peak and ca. 500 cm"1 shoulder become hardly visible and the spectra are getting dominated by broad but intensive band of ca. 1500-1700 cm"1, typical for amorphous silica. Additionally, sharp peak at 980 cm"1 present on lower-Si spectra is probably an effect of relic sulfate ion adsorption onto ferrihydrite surface. Preliminary results indicate that silicate ions not only cause decreasing crystallinity and retard ferrihydrite transformation but also strongly affect its surface properties. To verify this hypothesis and to enhance characteristics of Si-ferrihydrite, additional analyses are planned, including solubility, surface area and pHPZC determinations, thermal analyses and electron microscopy. Sorption/desorption studies involving cations and anions binding are planned as well.

5

XPS study of air exposed copper phthalocyanine ultra-thin films deposited on Si(111) native substrates

Krzywiecki M., Grządziel L., Ottaviano L., Parisse P., Santucci S., Szuber J.

Materials Science Poland

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2008

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Vol. 26, No. 2

287--294

EN

Results are presented of XPS characterization of ultra-thin copper phthalocyanine (CuPc) (16 nm- QCM controlled) films thermally deposited under UHV conditions on p- and n- type Si(111) substrates covered by native oxide. Our attempt has been focused on comparative studies of thin films in terms of the stability and durability of CuPc layers after one year of aging in ambient atmosphere. The impact of the type of the substrate doping was also explored. Our results clearly prove that CuPc layers are chemically stable and durable after one year exposure to air. We also demonstrate the existence of the substrate doping impact on the CuPc ultra-thin film what might be caused by dipole effects.

6

The chlorinated synthetic diamond surface interaction with C-nucleophiles

Korolkov V.V., Tarasevich B.N., Kulakova I.I., Lisichkin G.V.

Inżynieria Biomateriałów

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2006

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R. 9, nr 56-57

16-19

EN

Several reactions of C-nucleophiles with the chlorinated surface of two types of diamond were implemented. Detonating nanodiamond "UDA-SF" and synthetic diamond "DALAN" have been employed in the above procedures. The incorporation of butyl and nitrile groups has been achieved. However the incorporating of phenyl groups via reaction with PhLi is still a problem. For the first time NMR-H1 spectroscopy of suspension was used for elucidating structure of grafting compounds was proposed.

7

Adhesion, growth and differentiation markers in human osteoblast-like cells cultured on surface-modified metallic materials designer for bone implants

Bacakova L., Kabatova J., Lisa V., Stary V., Fencl J.

Inżynieria Biomateriałów

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2006

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R. 9, nr 58-60

1-3

EN

A series of metallic materials with different surface treatments were prepared: pure machined titanium (T), titanium polished by diamond paste (TL), machined Ti6Al4V alloy (TS), Ti6Al4V alloy polished by diamond paste (TSL), Ti5Al2.5Fe alloy treated by electro-erosion (A) and Ti5Al2.5Fe plasma-sprayed with Ti (PL). The materials were seeded with human osteoblast-like cells MG 63. One day after seeding, the highest cell numbers were obtained on the samples of medium surface roughness (T and TS; Ra 0.63-0.30 um and 0.89-0.57 um, respectively). From day 1 to 4, the cell proliferation was the quickest on the samples with the lowest surface roughness (TL and TSL; Ra 0.17-0.13 for both materials). The cells on TL also contained the highest concentration of integrin adhesion molecules with alpha V chain, i.e. receptors for vitronectin and fibronectin. One day 8 after seeding, the cell on all metallic samples as well as tissue culture polystyrene reached similar population densities. The cells on electro-eroded Ti5Al2.5Fe (samples A; Ra 15.27-0.74 um) contained the highest concentration of osteocalcin and osteopontin, i.e. markers of osteoblastic differentiation. Thus, the latter newly developed material could be considered as promising for construction of bone implants well anchored in the surrounding bone tissue.

8

Supramolecular organization of adsorbed collagen layers on polymer substrata: effect of time and substratum surface chemistry

Pamuła E., Cupere V. de, Rouxhet P. G., Dufrene Y. F.

Inżynieria Biomateriałów

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2001

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R. 4, nr 17-19

83-84

9

Badania właściwości powierzchniowych adsorbentów węglowych za pomocą spektroskopii w podczerwieni i termograwimetrii

Burakiewicz-Mortka W., Choma J., Jaroniec M.

Biuletyn Wojskowej Akademii Technicznej

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2000

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Vol. 49, nr 8

5-17

PL

Adsorbenty węglowe (węgle aktywne i sadze) utleniano za pomocą roztworów nadtlenku wodoru, kwasu nadchlorowego i kwasu azotowego. Chemiczne zmiany zachodzące na powierzchni węglowej na skutek procesu utleniania śledzono za pomocą spektroskopii w podczerwieni i wysokorozdzielczej termograwimetrii. Stwierdzono powstawanie na powierzchni węglowej różnych tlenowych grup funkcyjnych o zróżnicowanej trwałości termicznej. Największe zmiany właściwości powierzchniowych zaobserwowano dla węgli aktywnych i sadzy utlenianych w drastycznych warunkach tj. za pomocą stężonego kwasu azotowego w temperaturze wrzenia.

EN

Carbon adsorbents (active carbons and soot) were oxidized by using solutions of hydrogen peroxide, perloric acid and nitric acid. Chemical changes occurring on the carbon surface during oxidation process were monitored by the FTIR spectroscopy and high-resolution thermogravimetry. It was shown that various oxygen groups of different thermal stability were formed on the carbon surface. The greatest changes of surface properties were observed for active carbons and soots oxidized under drastic conditions, e.g., using concentrated nitric acid at its boiling temperature.

10

Structural and surface properties of active carbons oxidized with nitric acid at high temperature

Choma J., Jaroniec M., Burakiewicz-Mortka W., Klinik J., Olejniczak K.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 5

860-868

EN

The effect of oxidation of active carbons with nitric acid at the boiling temperature on their structural and surface properties was analyzed by nitrogen and water vapor adsorption data. Adsorption isotherms on unmodified and oxidized active carbons were measured at 77 K for nitrogen and 298 K for water vapor. This oxidation of active carbons led to farmation of a significant amount of oxygen acidic group on their surface. Simultaneously this oxidation led to a considerable degradation of the porous structure, which is menifested by decreasing: the total surface area, the micropore volume, and the external surface area of mesopores. However, adsorption of water vapor on oxidized active carbons under low and moderate pressures is considerably greater than on unmodified carbons.