Adsorpcja monopodstawionych fenoli na węglach aktywnych o zróżnicowanym charakterze chemicznym powierzchni

• Autorzy: Lorenc-Grabowska E. , Gryglewicz G.

Warianty tytułu

EN

Adsorption of monosubstituted phenols onto activated carbons with different surface characteristics

• Języki publikacji: PL

Abstrakty

PL

W pracy zbadano wpływ charakteru chemicznego powierzchni węgla aktywnego na adsorpcję wybranych monopodstawionych fenoli. Wyjściowy węgiel aktywny CWZ 22 poddano demineralizacji, działaniu nadtlenku wodoru, amoniaku i wygrzewaniu w wysokiej temperaturze w atmosferze inertnej. Otrzymane węgle różniły się zawartością kwasowych i zasadowych grup funkcyjnych i wartością pHPZC. Procesy modyfikacji nie wpłynęły zasadniczo na strukturę porowatą węgli aktywnych. Adsorpcję 2-chlorofenolu (OCF), 4-chlorofenolu (PCF) i 4-nitrofenolu (PNF) przeprowadzono w warunkach statycznych. Czasy osiągania stanu równowagi rosły w kierunku OCF < PCF < PNF. Wyznaczone nadmiarowe izotermy adsorpcji interpretowano, opierając się na modelu Freundlicha i Langmuira. Wykazano, że do stężenia równowagowego około 125 mg/dm³ równanie Langmuira lepiej opisuje adsorpcję fenoli niż równanie Freundlicha. Węgiel aktywny po wygrzewaniu w temperaturze 800°C w atmosferze azotu charakteryzował się największą pojemnością sorpcyjną względem badanych monopodstawionych fenoli. Obróbka termiczna w podanych warunkach spowodowała wyraźny wzrost wartości pHPZC i zmniejszenie zawartości powierzchniowych tlenowych grup kwasowych.

EN

The effect of the carbon surface chemistry on the adsorption of 2-chlorophenol (OCF), 4-chlorophenol (OCP) and 4-nitrophenol (PNP) has been studied. To obtain a series of activated carbons with different content of acidic and basic functionalities and pHPZC value, the initial activated carbon CWZ 22 was subjected to the demineralization with inorganic acids (CWZ dem), the treatment with 20% hydrogen peroxide (CWZ H2O2), the treatment with ammonia at 450°C (CWZ NH3), and heat treatment in an inert atmosphere at 800°C (CWZ N2). For the obtained carbons, pHPZC ranged from 5.85 to 10.08 and increased in the following direction: CWZ H2O2 < CWZ dem < CWZ 22 < CWZ NH3 < CWZ N2. The applied treatments changed insignificantly the porous structure of the activated carbon. The adsorption process of selected monosubstituted phenols was carried out in static conditions, maintaining solution pH below pKa of a given adsorbate. The equilibrium time of adsorption process of phenols increased in the direction: OCF < PCF < PNF. For CWZ NH3 and CWZ N2 carbons the equilibrium time was the shortest whereas the longest time was required in the case of CWZ H2O2. The adsorption of phenols on the tested activated carbons proceeded relatively fast. Around 50% of the maximum sorption capacity was attained after 1 h of the process. The Langmuir and Freundlich models were applied to interpret the adsorption isotherm data. It was found that up to around 125 mg/dm³ of the equilibrium concentration, the Langmuir model better describes the adsorption system than the Freundlich equation. In this range of concentrations the extent of adsorption decreased with increasing the adsorbate solubility. For studied activated carbons, except for CWZ H2O2, the calculated surface monolayer coverage by adsorbate molecules is higher than 0.7. The obtained results suggest that the multilayer adsorption was probably responsible for a rapid increase in the adsorbed amount that was observed at higher equilibrium concentrations. The activated carbon heated under nitrogen flow at high temperature showed the highest adsorption capacity toward monosubstituted phenols. Heat treatment of initial activated carbon led to a marked increase in the pHPZC value and a decrease in the acidic groups content. The oxidation of CWZ 22 resulted in a increase in the oxygen surface functionalities and as a result, CWZ H2O2 was characterized by the lowest efficiency in the removal of phenols from aqueous solution.

Słowa kluczowe

PL

węgiel aktywny; modyfikacja powierzchni; adsorpcja; pochodne fenolu

EN

activated carbon; surface modification; adsorption; phenols

• Wydawca: Wydawnictwo Politechniki Częstochowskiej
• Czasopismo: Inżynieria i Ochrona Środowiska
• Rocznik: 2006
• Tom: T. 9, nr 2
• Strony: 173--184
• Opis fizyczny: Bibliogr. 21 poz.

Twórcy

autor

Lorenc-Grabowska E.

autor

Gryglewicz G.

• Politechnika Wrocławska, Wydział Chemiczny, Zakład Materiałów Polimerowych i Węglowych, ul. Gdańska 7/9, 50-344 Wrocław

Bibliografia

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