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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.

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Zmiany chemii powierzchni węgla aktywnego WD-extra po regeneracji reagentem Fentona zastosowanego do adsorpcji zieleni naftolowej B

Bezak-Mazur E., Adamczyk D.

Rocznik Ochrona Środowiska

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2013

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Tom 15, cz. 1

966--988

EN

This paper describes the process of adsorption of selected acid dye such as naphthol green B on virgin and regenerated commercial activated carbon WD-extra (Gryfskand). Fenton's reagent regeneration was carried out five times. In the case of virgin activated carbon adsorption value was 130 mg/g, and for the regenerated it has ranged from 38 mg/g to 71 mg/g At the same time the weight loss was controlled, which after five regenerations equal almost 23%. Sorption capacity of activated carbon was controlled with an iodine adsorption numebr in accordance to the PN-83 C-97555.04. It was noted that with the times of regeneration iodine number decreased slightly. In experiment the concentration of acidic and basic functional groups on the surface of the activated carbon was measured by Boehm method. According to the results it can be concluded that regeneration by Fenton's reagent increases the content of acid groups and reduce the basic groups. Amount of acid groups increased to 4.625 mmol/g, and the basic groups has decreased to 0.9375 mmol/g.

3

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.

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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.

5

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

6

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.