Enhancement of adsorptive chemical filters via titania photocatalysts to remove vapor-phase toluene and isopropanol

Integrated adsorption and photocatalytic degradation of volatile organic compounds (VOCs) using carbon-based nanocomposites: A critical review

Volatile organic compounds (VOCs) are harmful for human and surrounding ecosystem, and a great number of VOC abatement technologies have been developed during the past few decades. However, the single method has some problems such as high energy consumption, unfriendly environment, and low removal efficiency. Recently, the integration of adsorption and photocatalytic degradation of VOCs is considered as a promising one. Carbon material, with large surface area, high adsorption capacity, and fast electron transfer ability, is widely used in integrated adsorptive-photocatalytic removal of VOCs. It is thus crucial to digest and summarize recent research advances in carbon-based nanocomposites as the adsorbent-photocatalyst for VOC removal. To satisfy this need, this work provides a critical review of the related literature with focuses on: (1) the advantages and disadvantages of various carbon-based nanocomposites for the applications of VOC adsorption and photocatalytic degradation; (2) models and mechanisms of adsorptive-photocatalytic removal of VOCs according to the material properties; and (3) major factors controlling adsorption-photocatalysis processes of VOCs. The review is aimed to establish the "structure-property-application" relationships for the development of innovative carbon-supported nanocomposites and to promote future research on the integrated adsorptive and photocatalytic removal of VOCs.

Synergetic effect between adsorption and photodegradation on nanostructured TiO2/activated carbon fiber felt porous composites for toluene removal

The low quantum efficiency and limited adsorption efficiency of TiO₂ makes it only fit for the removal of VOCs with low concentrations. Herein, we for the first time fabricated nanostructured TiO₂/activated carbon fiber felt (TiO₂/ACFF) porous composites by the in situ deposition of TiO₂ microspheres on the carbon fibers in ACFF. Interestingly, the TiO₂ microspheres exhibit hierarchical nanostructures constructed by nanocrystals as building blocks. The TiO₂/ACFF porous composites possess excellent adsorption and photodegradation properties for toluene because of the synergetic effects between the nanostructured TiO₂ and ACFF. The adsorption efficiencies of the TiO₂/ACFF porous composites reach approximately 98% at the toluene concentration (<1150ppm) and approximately 77% even at the high concentration of 6900ppm. Moreover, the ACFF in the TiO₂/ACFF porous composites significantly enhances photocatalytic property for toluene by hindering the recombination of electron-hole pairs, reducing the TiO₂ band gap energy (E_g) to 2.95eV and accelerating toluene adsorption. At the toluene concentrations of 230ppm and 460ppm, the photocatalytic oxidation efficiency of toluene into CO₂ arrives at 100% and 81.5%, respectively. Therefore, the TiO₂/ACFF porous composites with synergetic adsorption and photocatalytic activities have great potentials for toluene removal.

Portable photocatalytic air cleaners: efficiencies and by-product generation

Portable photocatalytic air cleaners were investigated in 24 and 48 m(3) emission test chambers with regard to efficiency and by-product generation. For this purpose, formaldehyde, decane, 1,2-dichlorobenzene, toluene, α-pinene and heptanal were doped at sub-ppm concentration levels into the chambers individually and in mixtures. By way of specified test protocols, efficiencies could be distinguished but were strongly dependant on the choice of test compounds, especially on whether single or multi compound dosing was used, and on long-term effects. Initial clean air delivery rates (CADRs) up to 137 m(3)/h were measured. Typical by-products were found in significant concentrations. The main ones were formaldehyde up to 50 ppb (62 μg/m(3)) and acetone up to 80 ppb (190 μg/m(3)). Other aldehydes were also found, but at smaller levels. The detection of chloroacetone, a strong irritating compound, at concentrations up to 15 ppb (57 μg/m(3)) strengthens the importance of such investigations especially in cases were chloro-organic compounds are involved.

Functionalized Activated Carbon Derived from Biomass for Photocatalysis Applications Perspective

This review highlighted the developments of safe, effective, economic, and environmental friendly catalytic technologies to transform lignocellulosic biomass into the activated carbon (AC). In the photocatalysis applications, this AC can further be used as a support material. The limits of AC productions raised by energy assumption and product selectivity have been uplifted to develop sustainable carbon of the synthesis process, where catalytic conversion is accounted. The catalytic treatment corresponding to mild condition provided a bulk, mesoporous, and nanostructure AC materials. These characteristics of AC materials are necessary for the low energy and efficient photocatalytic system. Due to the excellent oxidizing characteristics, cheapness, and long-term stability, semiconductor materials have been used immensely in photocatalytic reactors. However, in practical, such conductors lead to problems with the separation steps and loss of photocatalytic activity. Therefore, proper attention has been given to develop supported semiconductor catalysts and certain matrixes of carbon materials such as carbon nanotubes, carbon microspheres, carbon nanofibers, carbon black, and activated carbons have been recently considered and reported. AC has been reported as a potential support in photocatalytic systems because it improves the transfer rate of the interface charge and lowers the recombination rate of holes and electrons.