Degradation of organic pollutants by catalytic wet peroxide oxidation using carbon materials

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The role of activated carbons functionalized with thiol and sulfonic acid groups in catalytic wet peroxide oxidation

Publication . Gomes, Helder; Miranda, Sandra; Sampaio, Maria; Figueiredo, José; Silva, Adrián; Faria, Joaquim

Norit ROX 0.8 commercial activated carbon was subjected to liquid phase treatments with sulfuric acid at different concentrations (5-18 M) and temperatures (353 and 423 K), to generate different amounts (760-1000 mu mol g(-1)) of sulfur groups (thiol and sulfonic acid), with varying surface acidity. The prepared materials were chemically characterized by the determination of the point of zero charge (2.0-5.8) and by mass titration, temperature programmed desorption and X-ray photoelectron spectroscopy, to evaluate the nature and concentration of acidic surface functionalities. The materials were tested as catalysts in the catalytic wet peroxide oxidation of aqueous solutions of the acid dye Chromotrope 2R. A correlation between the surface acidic strength and the efficiency for dye removal from solution was found, which was ascribed both to adsorption and to reaction. In general, dye removal by adsorption is increased when using adsorbents with lower acidic character, due to enhanced electrostatic attraction between the acid dye and the catalyst surface. In addition, the introduction of sulfur containing groups promotes the decomposition of hydrogen peroxide, leading to increased production of hydroxyl radicals close to the pollutant and subsequent improved dye degradation.

2011Journal article

Restricted access

Nanotubos e grafeno: os primos mais jovens na família do carbono!

Publication . Pastrana-Martínez, Luisa; Morales-Torres, Sergio; Gomes, Helder; Silva, Adrián

O carbono é o sexto elemento mais abundante do universo, encontrando-se presente tanto na forma orgânica, como em materiais inorgânicos. Além das três formas alotrópicas que ocorrem naturalmente (carbono amorfo, grafite e diamante), podem ser também sintetizadas estruturas de carbono com dimensões nanométricas. Nos últimos anos foram descobertas e caracterizadas novas e interessantes nanoestruturas de carbono, incluindo os nanotubos de carbono e o grafeno. Este breve artigo faz uma resenha sobre os métodos de síntese e caracterização destes dois materiais, aludindo a algumas das suas propriedades mais extraordinárias, bem como às suas aplicações mais recentes e de maior impacto em diversos domínios da ciência e da tecnologia, permitindo, de uma forma simples, introduzir os leitores menos familiarizados com o tema no fascinante mundo destas duas nanoestruturas de carbono.

2013Journal article

Open access

Development of glycerol-based carbon materials for environmental catalytic applications in advanced oxidation processes

Publication . Gomes, Helder; Ribeiro, Rui; Silva, Adrián; Pinho, Teresa; Figueiredo, José; Faria, Joaquim

A glycerol-based carbon material was initially produced by partial carbonization of glycerol with sulphuric acid followed by calcination under inert atmosphere. This material, characterized by high thermal stability, low ash content, non-porous structure and basic character, was further activated in air atmosphere at different temperatures (from 150 to 350 oC), resulting in materials with less basic character, due to the incorporation of oxygenated surface groups, and to a notorious evolution of the porosity. These metal-free carbon materials are highly active catalysts for environmental applications, more specifically for the catalytic wet peroxide oxidation process, when the surface chemistry and textural properties are properly tuned. Effective catalytic degradation of 2-nitrophenol was achieved with the material treated under air atmosphere at 300 ºC, opening a window of opportunity for the valorisation of crude glycerol by-products and the production of value-added materials.

2013Conference object

Open access

Carbon-based materials as catalysts in advanced oxidation processes for water treatment

Publication . Silva, Adrián; Romanos, George; Gomes, Helder; Pastrana-Martínez, Luisa; Morales-Torres, Sergio; Likodimos, Vlassis; Figueiredo, José; Faria, Joaquim; Falaras, Polycarpos

Limited access to clean water is one of the major problems afflicting mankind. Water scarcity is an immediate consequence of population growth, agricultural and industrial expansion, and is on the verge of a criticai point in several zones of the globe. This ca\1s for the research and development of new efficient water purification technologies, preferably of low cost and low energy consumption, as we\1 as minimizing the use of chemicals and their impact on the environrnent.

2012Conference object

Open access

Carbon nanotubes: a suitable material for catalytic wet peroxide oxidation of organic pollutants?

Publication . Ribeiro, Rui; Silva, Adrián; Faria, Joaquim; Gomes, Helder

Carbon materials, such as activated carbons (AC), graphite and activated carbon xerogels, have been explored as metal-free catalysts for the catalytic wet peroxide oxidation (CWPO) of bio-refractory organic compounds, such as azo dyes and phenolic compounds [1-3]. At the same time, the application of carbon nanomaterials in catalysis, such as carbon nanotubes (CNT), has grown exponentially [4]. In the present work, commercial multiwalled carbon nanotubes (MWNT) were used in the CWPO of 2-nitrophenol and its activity compared to a commercial AC, used as received and after chemical modifications.

2012Conference object

Open access