RESUMO
Hexavalent chromium (Cr(VI)) is a highly mobile cancerogenic and teratogenic heavy metal ion. Among the varied technologies applied today to address chromium water pollution, photocatalysis offers a rapid reduction of Cr(VI) to the less toxic Cr(III). In contrast to classic photocatalysts, Metal-Organic frameworks (MOFs) are porous semiconductors that can couple the Cr(VI) to Cr(III) photoreduction to the chromium species immobilization. In this minireview, we wish to discuss and analyze the state-of-the-art of MOFs for Cr(VI) detoxification and contextualizing it to the most recent advances and strategies of MOFs for photocatalysis purposes. The minireview has been structured in three sections: (i) a detailed discussion of the specific experimental techniques employed to characterize MOF photocatalysts, (ii) a description and identification of the key characteristics of MOFs for Cr(VI) photoreduction, and (iii) an outlook and perspective section in order to identify future trends.
RESUMO
Synthesis of activated carbon (AC) from sawdust of Algarroba wood was performed as a function of the temperature under CO(2) and N(2) flow. Characterization was performed by adsorption-desorption N(2) isotherms, FTIR, XPS and SEM. Functional acid or basic groups were detected on the surface of AC. For both studied atmospheres, the maximum value of surface area was obtained at 800°C. A monotonic correlation between temperature and mean pore diameter was detected being the higher the activation temperature the lower the mean pore width of AC. Ultramicroporous AC with pore diameters of 6.7 Å and 5.3 Å were obtained at 900°C under CO(2) and N(2) flow, respectively. It can be concluded that pore diameter and the functionalization of the AC surface can be controlled easily controlling the temperature of activation, independently of the gas atmosphere. The present results suggest that waste biomass is a potential source for the synthesis of carbon materials with potential novel applications.