Adsorption of NO on Co-ZSM-5 leads to formation of dinitrosyls at 1895 cm~1 and Co2`(NO) 2 [l s (NO) at 1812 cm~1], Co3`ÈNO linear species [l(NO) at 1950 and 1937 cm~1] and NO`occupying cationic l as (NO) zeolite positions [l(NO) at 2133 cm~1]. The NO`and Co3`ÈNO species are of low stability and can be removed by evacuation at ambient temperature. The species start to decompose at 200 ¡C, thus Co2`(NO) 2 forming Co2`ÈNO compounds [l(NO) at 1857 cm~1]. The latter are stable up to 350 ¡C. Water strongly suppresses the formation of NO`and Co3`ÈNO. Its e †ect on the dinitrosyls is, however, weaker Co2`(NO) 2 and even small amounts of water favour the formation of species. The dinitrosyls of Co2`do not Co2`(NO) 2 react with oxygen at ambient temperature but are oxidized in an atmosphere above 100 ¡C. However, they O 2 react easily with a mixture forming surface nitrates as Ðnal products. This process is almost NO ] O 2 una †ected by water. The species start to interact with ethane at 100 ¡C and water has been Co2`(NO) 2 detected as a reaction product. These results account for the (although low) activity of Co-ZSM-5 in the reduction of NO in the absence of oxygen. The only stable species formed in a atmosphere are NO ] O 2 di †erent kinds of surface nitrates (observed in the 1650È1500 cm~1 region). The latter start to interact with ethane at 100 ¡C and nitriles are suggested as interaction intermediates. The role of di †erent surface species and the e †ect of the reactants and reaction products on the SCR of NO over Co-ZSM-5 are discussed.

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The goal of this study was to investigate the preparation of low-cost activated carbons from bean pods waste and to explore their potential application to the removal of heavy metals from aqueous solutions. Conventional physical (water vapor) activation was used for synthesizing the adsorbent. The obtained carbon was employed for the removal of As (III) and Mn (II) from aqueous solutions at different initial concentrations and pH values. Adsorption for both ions follows Langmuir-type isotherm, the maximum loading capacities for arsenic (III) and Mn (II) ions being 1.01 and 23.4 mg g-1 , respectively. According to the experimental data, it can be inferred that the basic character of the surface, i.e. the high content of basic groups favors adsorption of ions. Arsenic adsorption capacity on the carbon obtained from agricultural waste was found to be similar to more expensive commercial carbons showing high adsorption capability. As regards manganese adsorption, herein obtained carbon presented higher uptake than that of activated carbons reported in the literature.

The preparation of activated carbons from bean pods waste by chemical (K(2)CO(3)) and physical (water vapor) activation was investigated. The carbon prepared by chemical activation presented a more developed porous structure (surface area 1580 m(2) g(-1) and pore volume 0.809 cm(3) g(-1)) than the one obtained by water vapor activation (258 m(2) g(-1) and 0.206 cm(3) g(-1)). These carbons were explored as adsorbents for the adsorption of naphthalene from water solutions at low concentration and room temperature and their properties are compared with those of commercial activated carbons. Naphthalene adsorption on the carbons obtained from agricultural waste was stronger than that of carbon adsorbents reported in the literature. This seems to be due to the presence of large amounts of basic groups on the bean-pod-based carbons. The adsorption capacity evaluated from Freundlich equation was found to depend on both the textural and chemical properties of the carbons. Naphthalene uptake on biomass-derived carbons was 300 and 85 mg g(-1) for the carbon prepared by chemical and physical activation, respectively. Moreover, when the uptake is normalized per unit area of adsorbent, the least porous carbon displays enhanced naphthalene removal. The results suggest an important role of the carbon composition including mineral matter in naphthalene retention. This issue remains under investigation.

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