Browsing by Author "Fathy, Nady"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Activated carbon xerogel-chitosan composite materials for catalytic wet peroxide oxidation under intensified process conditionsPublication . Pinho, Maria; Silva, Adrián; Fathy, Nady; Attia, Amina; Gomes, Helder; Faria, JoaquimDifferent activated carbon xerogels (ACX) and ACX–chitosan composite materials were tested for the removal of the azo dye Orange II (OII) in aqueous solutions, either by pure adsorption or by catalytic wet peroxide oxidation (CWPO). The ACX materials were produced by activation of an organic resorcinol formaldehyde xerogel (RFX), considering different activation procedures: chemical impregnation with H3PO4 at 773 K (ACX-P), chemical impregnation with monoethanolamine at 773 K (ACX–MEA) and alkali activation with KOH at 1073 K using a 1:1 mass ratio of KOH/RFX (ACX-K). The ACX–chitosan composites were produced by oxidation of ACX with oxalic acid followed by treatment with chitosan gel. During screening studies in adsorption and CWPO tests, the composites ACX-K–chitosan and ACX-P–chitosan revealed the best performances among all the tested materials, namely OII removals between 69 and 73% were respectively obtained in CWPO after 150 min (pH 3.0, T = 323 K, material load of 0.2 g L-1, OII concentration of 100 mg L-1 and hydrogen peroxide concentration of 1.18 g L-1). In process intensification conditions, the CWPO process performance increased remarkably when using the ACX-P–chitosan composite. Complete OII removal in 90 min and a TOC removal of 55% in 24 h was achieved by CWPO, while less than 10% of OII was removed by pure adsorption (pH 3.5, T = 353 K, material load of 2.5 g L-1, OII concentration of 4.5 g L-1 and, in CWPO, hydrogen peroxide concentration of 25 g L-1). The superior performance of the ACX–chitosan composite at intensified process conditions was more likely related with the high pollutant/catalyst ratio, which favors a more controllable H2O2 decomposition near the adsorbed pollutant species, thus avoiding parallel parasite reactions involving hydroxyl radicals and leading to a consequent higher efficiency of its usage. These conditions are of major interest in the treatment of highly polluted waste waters.
- Activated carbon xerogels for the removal of azo dyes by adsorption and catalytic wet peroxide oxidationPublication . Ribeiro, Rui; Fathy, Nady; Silva, Adrián; Faria, Joaquim; Gomes, Helder
- Activated carbon xerogels for the removal of the anionic azo dyes Orange II and Chromotrope 2R by adsorption and catalytic wet peroxide oxidationPublication . Ribeiro, Rui; Fathy, Nady; Attia, Amina; Silva, Adrián; Faria, Joaquim; Gomes, HelderActivated carbon xerogels (ACXs) were tested for the removal of azo dyes in aqueous solutions, either by adsorption or by catalytic wet peroxide oxidation (CWPO). Two azo dyes, Orange II (OII) and Chromotrope 2R (C2R), were chosen as model pollutants. The ACXs were produced by activation of an organic resorcinol–formaldehyde xerogel (RFX). Three different activation procedures were carried out producing five distinct ACXs: steam at 1073 K (ACX-S), chemical impregnation with H3PO4 at 773 K (ACX-P) and alkali activation with dry KOH at 973 K (ACX-K), using three different mass ratios of KOH/RFX, namely 1:1 (ACX-K1), 2:1 (ACX-K2) and 4:1 (ACX-K4). The results obtained in the adsorption experiments carried out at pH = 3, T = 303 K, adsorbent load of 0.1 g L 1 and azo dye concentration of 100 mg L 1 show that the interaction between the carbon materials and the anionic dyes is enhanced with the basicity of the carbon surfaces. ACX-K materials, the carbon materials with higher basicity amongst those prepared, exhibit high adsorption performances for the removal of both dyes, namely from over 215 mg g 1 (for adsorption of C2R on ACX-K2 after 150 min) up to 499 mg g 1 (for adsorption of OII on ACX-K4 at the same period of time). Furthermore, with ACX-K materials in CWPO (i.e., using H2O2) increments in the removal of C2R as high as 33%, 24% and 20%, in comparison to the removals obtained by adsorption, where obtained when ACX-K1, ACX-K2 and ACX-K4 were respectively tested at 303 K. Increasing the operating temperature (T = 323 K), the removal increments achieved by CWPO, compared to the removals obtained by adsorption at the same temperature, increase 67%, 59% and 49%, when ACX-K1, ACX-K2 and ACX-K4 were respectively tested. Recycling studies with ACX-K1 puts in evidence the high stability of this catalyst in CWPO, since it was observed, after a first reaction run, that the catalytic activity of this material is not affected by its successive reuse. Increasing the operating temperature (T = 323 K) and the adsorbent load (0.5 g L 1), ACX-K4 is able to completely remove the C2R content by adsorption. In the case of ACX-K1 and ACX-K2, adsorption removals over 97% of the C2R content are attainable.
- Materiais de carbono como catalisadores no processo de oxidação catalítica com peróxido de hidrogénioPublication . Ribeiro, Rui; Fathy, Nady; Attia, Amina; Silva, Adrián; Faria, Joaquim; Gomes, HelderOs materiais de carbono, e em particular os carvões ativados, têm sido explorados como catalisadores no processo de oxidação catalítica com peróxido de hidrogénio (CWPO – Catalytic Wet Peroxide Oxidation) para a degradação de poluentes orgânicos [1]. O mecanismo do processo envolve a decomposição do peróxido de hidrogénio em radicais hidroxilo, espécies oxidantes muito reativas, responsáveis pela degradação dos poluentes. Resultados recentes comprovam a adequabilidade dos carvões ativados para a degradação de corantes azo [2, 3] e de compostos fenólicos [4], sendo a sua atividade justificada pela presença de grupos funcionais específicos ou pela presença de espécies inorgânicas na sua composição. Neste trabalho procurou-se avaliar a atividade catalítica de outras estruturas de carbono, nomeadamente xerogéis de carbono ativados e nanotubos de carbono de paredes múltiplas (MWCNT – Multi-walled Carbon Nanotubes), utilizando como poluentes modelo corantes azo, Orange II (OII) e Chromotrope 2R (C2R), e compostos nitrofenólicos, como por exemplo o 2-nitrofenol.
- Orange II removal by catalytic wet peroxide oxidation using activated carbon xerogelsPublication . Pinho, Maria; Silva, Adrián; Fathy, Nady; Attia, Amina; Gomes, Helder; Faria, JoaquimOrange II is a synthetic dye widely employed in the textile industry and responsible for serious environrnentaI cancerns. Dyes like this urge the development af new technologies for the treatment af wastewaters generated in this industrial activity. Those include catalytic wet peroxide oxidation (CWPO), which is an advanced oxidation process (AOP) based on the generation of hydroxyl radicais (I-lO·) from hydrogen peroxide with tlle aid ofa suitable catalysl [I].