Activated carbon prepared by physical activation of olive stones for the removal of NO2 at ambient temperature

International audienceActivated carbon was prepared from olive stones by physical activation using water vapor at 750°C. Textural, morphology and surface chemistry characterizations were achieved (nitrogen adsorption, SEM, FTIR and TPD–MS). NO2 adsorption was performed for different inlet gas compositions and temperatures. NO2 may adsorb directly on the oxygenated surface groups, and can also be reduced to NO. Therefore, a second NO2 molecule adsorbs on the oxygen left on the carbon surface. TPD performed after NO2 adsorption showed the presence of various surface groups. The adsorption capacity was about 131mg/g, which is higher than with several activated carbon prepared from classical lignocellulosic biomass. NO2 reduction into NO decreased with increasing the inlet oxygen concentration. In contrast, a slight decrease in the NO2 adsorption capacity was observed with increasing temperature. It seems that the activated carbons prepared from olive stones by steam activation could be used as efficient adsorbents for NO2 removal

Factors Influencing NO2 Adsorption/Reduction on Microporous Activated Carbon: Porosity vs. Surface Chemistry

The textural properties and surface chemistry of different activated carbons, prepared by the chemical activation of olive stones, have been investigated in order to gain insight on the NO2 adsorption mechanism. The parent chemical activated carbon was prepared by the impregnation of olive stones in phosphoric acid followed by thermal carbonization. Then, the textural properties and surface chemistry were modified by chemical treatments including nitric acid, sodium hydroxide and/or a thermal treatment at 900 °C. The main properties of the parent and modified activated carbons were analyzed by N2-adsorption, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques, in order to enlighten the modifications issued from the chemical and thermal treatments. The NO2 adsorption capacities of the different activated carbons were measured in fixed bed experiments under 500 ppmv NO2 concentrations at room temperature. Temperature programmed desorption (TPD) was applied after adsorption tests in order to quantify the amount of the physisorbed and chemisorbed NO2. The obtained results showed that the development of microporosity, the presence of oxygen-free sites, and the presence of basic surface groups are key factors for the efficient adsorption of NO2

CO₂ and CH₄ Adsorption Behavior of Biomass-Based Activated Carbons

The aim of the present work is to study the effect of different activation methods for the production of a biomass-based activated carbon on the CO 2 and CH 4 adsorption. The influence of the activation method on the adsorption uptake was studied using three activated carbons obtained by different activation methods (H 3 PO 4 chemical activation and H 2 O and CO 2 physical activation) of olive stones. Methane and carbon dioxide pure gas adsorption experiments were carried out at two working temperatures (303.15 and 323.15 K). The influence of the activation method on the adsorption uptake was studied in terms of both textural properties and surface chemistry. For the three adsorbents, the CO 2 adsorption was more important than that of CH 4 . The chemically-activated carbon presented a higher specific surface area and micropore volume, which led to a higher adsorption capacity of both CO 2 and CH 4 . For methane adsorption, the presence of mesopores facilitated the diffusion of the gas molecules into the micropores. In the case of carbon dioxide adsorption, the presence of more oxygen groups on the water vapor-activated carbon enhanced its adsorption capacity

The Potential of Activated Carbon Made of Agro-Industrial Residues in NOx Immissions Abatement

The treatment of NOx from automotive gas exhaust has been widely studied, however the presence of low concentrations of NOx in confined areas is still under investigation. As an example, the concentration of NO2 can approximate 0.15 ppmv inside vehicles when people are driving on highways. This interior pollution becomes an environmental problem and a health problem. In the present work, the abatement of NO2 immission is studied at room temperature. Three activated carbons (ACs) prepared by physical (CO2 or H2O) or chemical activation (H3PO4) are tested as adsorbents. The novelty of this work consists in studying the adsorption of NO2 at low concentrations that approach real life immission concentrations and is experimentally realizable. The ACs present different structural and textural properties as well as functional surface groups, which induce different affinities with NO2. The AC prepared using water vapor activation presents the best adsorption capacity, which may originate from a more basic surface. The presence of a mesoporosity may also influence the diffusion of NO2 inside the carbon matrix. The high reduction activity of the AC prepared from H3PO4 activation is explained by the important concentration of acidic groups on its surface