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We showed the effect of commensurate confinement in the pores of nanoporous carbons in the conversion of visible light into a chemical reaction. By using a series of nanoporous carbons with a controlled distribution of pore sizes obtained from a gradual activation under moderate conditions, we have demonstrated the superior conversion of light in the constrained pore space of the carbons compared to values in solution. Besides a more efficient conversion of light, nanopore confinement resulted in a 100–200 nm redshift in the wavelength onset of the photochemical reaction. The visible light activity was boosted in pores which sizes match the dimensions of the confined compound. We attribute this to the enhanced splitting and charge separation of the photogenerated species in the nanopores, due to the proximity of the charge carriers and the adsorbed molecules.

We showed the effect of commensurate confinement in the pores of nanoporous carbons in the conversion of visible light into a chemical reaction. By using a series of nanoporous carbons with a controlled distribution of pore sizes obtained from a gradual activation under moderate conditions, we have demonstrated the superior conversion of light in the constrained pore space of the carbons compared to values in solution. Besides a more efficient conversion of light, nanopore confinement resulted in a 100–200 nm redshift in the wavelength onset of the photochemical reaction. The visible light activity was boosted in pores which sizes match the dimensions of the confined compound. We attribute this to the enhanced splitting and charge separation of the photogenerated species in the nanopores, due to the proximity of the charge carriers and the adsorbed molecules.

We have explored the impact of the incorporation of nanoporous carbons as additives to tungsten oxide on the photocatalytic degradation of two recalcitrant pollutants: rhodamine B (RhB) and phenol, under simulated solar light. For this purpose, WO3/carbon mixtures were prepared using three carbon materials with different properties (in terms of porosity, structural order and surface chemistry). Despite the low carbon content used (2 wt.%), a significant increase in the photocatalytic performance of the semiconductor was observed for all the catalysts. Moreover, the influence of the carbon additive on the performance of the photocatalysts was found to be very different for the two pollutants. Carbon additives of hydrophobic nature increased the photodegradation yield of phenol compared to bare WO3, likely due to the higher affinity and stronger interactions of phenol molecules toward basic nanoporous carbons. Oppositely, the use of acidic carbon additives led to higher RhB conversions due to increased acidity of the WO3/carbon mixtures and the stronger affinity of the pollutant for acidic catalyst’s surfaces. As a result, the photooxidation of RhB is favored by means of a coupled (photosensitized and photocatalytic) degradation mechanism. All these results highlight the importance of favoring the interactions of the pollutant with the catalyst’s surface through a detailed design of the features of the photocatalyst.

The diffusion properties of aggregates of amphiphilic molecules (e.g. micelles, microemulsion) are discussed. The interaction of these organized assemblies with water sparingly soluble organic compounds and ions and the consequent influence on the transport of these species is examined as well as their effect on the transfer of solutes through a membrane.

The diffusion properties of aggregates of amphiphilic molecules (e.g. micelles, microemulsion) are discussed. The interaction of these organized assemblies with water sparingly soluble organic compounds and ions and the consequent influence on the transport of these species is examined as well as their effect on the transfer of solutes through a membrane.

Hematite particles with controlled size and shape (cubic, spherical and ovoidal, with size range from hundreds nm to µm) were produced by modulating the conditions of synthesis and were characterized by different techniques (XRD spectroscopy, scanning electron microscopy, BET analysis, dynamic light scattering, UV-vis spectroscopy). The photoactivity of the synthesized hematite particles was tested towards the degradation of phenol under photo-Fenton conditions, obtaining optimal results in the pH range 3-4. Although the smaller particles have a larger contact interface between the solid and the solution, no obvious relationship was found between size and photoactivity. A possible explanation is that the smallest particles tested showed an important radiation scattering, which would interfere with radiation absorption and, therefore, with photoactivity. In contrast, the most photoactive samples were those showing the highest concentrations of leached iron. This issue would imply that photoactivity may be related to partial dissolution of hematite with formation of Fe(II) and of photo-active Fe(III) species, which activate the classic photo-Fenton process. Anyway, leached Fe was limited to the µg L-1 range that is safely far from the mg L-1 limits for wastewater.

The diffusion properties of aggregates of amphiphilic molecules (e.g. micelles, microemulsion) are discussed. The interaction of these organized assemblies with water sparingly soluble organic compounds and ions and the consequent influence on the transport of these species is examined as well as their effect on the transfer of solutes through a membrane.

The diffusion properties of aggregates of amphiphilic molecules (e.g. micelles, microemulsion) are discussed. The interaction of these organized assemblies with water sparingly soluble organic compounds and ions and the consequent influence on the transport of these species is examined as well as their effect on the transfer of solutes through a membrane.

We showed the effect of commensurate confinement in the pores of nanoporous carbons in the conversion of visible light into a chemical reaction. By using a series of nanoporous carbons with a controlled distribution of pore sizes obtained from a gradual activation under moderate conditions, we have demonstrated the superior conversion of light in the constrained pore space of the carbons compared to values in solution. Besides a more efficient conversion of light, nanopore confinement resulted in a 100–200 nm redshift in the wavelength onset of the photochemical reaction. The visible light activity was boosted in pores which sizes match the dimensions of the confined compound. We attribute this to the enhanced splitting and charge separation of the photogenerated species in the nanopores, due to the proximity of the charge carriers and the adsorbed molecules.

This work provides an experimental evidence of the photoinduced generation of radical species upon UV irradiation of aqueous suspensions of carbon materials with varied textural, structural and chemical composition. The use of a powerful spectroscopic tool as spin trapping electron spin resonance (ESR) has allowed to detect and identify these radicals (among which are hydroxyl, superoxide and other organic radicals), which are the basis of the so-called Advanced Oxidation Processes. Our results demonstrate the ability of carbon materials – including activated carbons – to interact with UV light, and also to generate highly reactive species capable of promoting the photooxidation of an aromatic pollutant. Moreover, for some of the carbons the concentration of radicals was higher than that detected for titania powders. Although the photogeneration of radicals upon irradiation is a well-known process for inorganic semiconductors such as titanium oxide or zinc oxide, our results demonstrate a similar behavior on carbon materials in the absence of semiconductor additives.

This work demonstrates the ability of ash-free activated carbons to interact with UV light to promote the photooxidation of phenol in solution through the formation of radical species. Our results show that in the absence of inorganic impurities or semiconductor additives, the photodegradation efficiency of the studied activated carbons has to be ascribed to the carbon matrix itself. Hydroxyl radicals have been detected by spin trapping electron spin resonance spectroscopy upon UV irradiation of the activated carbon suspensions in aqueous solution. Although the ability to photogenerate radicals upon irradiation is well known in inorganic semiconductors (such as titanium dioxide) or carbon/semiconductor composites, we herein demonstrate the capacity of the carbon matrix alone to interact with UV light, generating reactive species that would be responsible for the observed photoinduced reaction using carbons alone in the absence of semiconductor additives. Thus, the conventional interpretation of the enhanced photodegradation efficiency of carbon/semiconductor photocatalysts -so far attributed to synergistic and confinement effects, and minimized surface recombination of the charge carriers- should be reconsidered to account for the radicals photogenerated when the carbons are exposed to UV light.