Search

Removal of bio-recalcitrant and toxic compounds from wastewaters has been a major objective of industrial manufacturers for a few years. Due to the potential risk toward public health, regulations are becoming increasingly strict and classical treatments like biological treatments are not efficient. Other techniques such as incineration, oxidation or adsorption provide higher levels of removal but with a high energy and capital cost. A coupled process involving adsorption and oxidation is studied. Four adsorbents are tested and compared according to two objectives, their adsorption capacity and their capability to decompose ozone into powerful hydroxyl radicals. Two model compounds were chosen: 2,4-dichlorophenol and nitrobenzene. Experimental results allow comparing coupled process with results obtained during ozonation alone. Zeolite (Faujasite Y) gave disappointing results in term of both adsorption kinetics and ozone decomposition. On the contrary, activated carbons showed fast adsorptions and important capabilites to decompose ozone into radicals, almost in nitrobenzene experiments. S-23 activated carbon proved to be the most interesting adsorbent for better mechanical and chemical stabilities over time. Sequential adsorption/ozonation experiments were conducted, showing a strong loss of adsorption efficiency after the first operation, but the positive point is that the adsorption capacity remains almost constant during further cycles. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Chemical Engineering is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

New titanium dioxide (TiO2) based catalysts were prepared by impregnating commercial zeolites in pellets form using a sol–gel technique. Characterization was done with chemical analysis, X-Ray diffraction, scanning electron microscopy, and BET measurements, together with volatile organic compounds (VOC) adsorption equilibrium experiments. TiO2 happened to fix on the inert binder leading to a close intimacy of mixing with the zeolites crystallites, without significant modification of support properties. A diffusion cell was used to produce dilute polluted air streams for dynamic experiments, in which adsorption and photodegradation phases were alternatively carried out. Regeneration of adsorbent was evaluated regarding experimental conditions. Through a comparison with the results obtained on impregnated mesoporous borosilicate beads, it was clarified that zeolite supports had no effect on 1-butanol (BuOH) photooxidation mechanisms. Yet, evidence for mass transfer limitation was found, and attributed to intracrystalline diffusion in zeolites. [Copyright &y& Elsevier]