Comparison of Activated Carbon and Hydrophobic Zeolite Efficiencies in 2,4-Dichlorophenol Advanced Ozonation

Abstract

This study aims at comparing the removal of 2,4-dichlorophenol (2,4-DCP) by 3 methods; adsorption using hydrophobic zeolite (faujasite) or activated carbon (S-23 and L-27), conventional ozonation and hybrid adsorption/ozonation treatment. On the one hand, the three materials correctly adsorb 2,4-DCP; however the adsorption kinetics using zeolite is very low. On the other hand, ozonation totally removes 2,4-DCP after 1 h experiment and the simultaneous combination of adsorbent and ozone does not change the 2,4-DCP degradation. But, though ozonation and hybrid process appear to be equivalent for 2,4-DCP removal, activated carbons are able to decompose ozone and to improve chemical oxygen demand (COD) removal, whereas the zeolite does not show this catalytic effect. Similar results were also observed in a former study with nitrobenzene. Adsorbent degradation is evaluated by Brunauer, Emmet and Teller (BET) and differential thermogravimetric (DTG) analysis, which evidence that Faujasite and S-23 activated carbon are resistant to ozone exposure whereas the pore volume and the surface area of L-27 activated carbon decrease during ozonation.

Low-cost activated carbon for adsorption and heterogeneous ozonation of phenolic wastewater

“…In addition, an acidification of the medium is also noted, the pH decreasing from 5.3 to 3.1 and from 5.3 to 1.7 for single ozonation and catalytic ozonation, respectively, confirming the generation of acidic species. With bpAC, this pH decrease could be (i) due to the degradation of bpAC surface by ozone attack [14,53] and also (ii) due to the consequence of the leaching of residual phosphoric acid contained inside the pores even though it has been carefully rinsed.…”

“…The second explanation for the stronger decrease in TOC when bpAC is added is an oxidation of the molecules by the radical route. Indeed, it is known that molecular ozone can generate free radicals in contact with solids such as activated carbon [14][15][16]. As these species are much more reactive than ozone and non-selective, they are able to attack compounds refractory to molecular ozone.…”

“…Nervertheless, oxidation processes with ozone can be improved by adding an adsorbent in the process. Several studies have dealt with the interest of catalytic ozonation in presence of zeolite or activated carbon (AC) for the last two decades [9][10][11][12][13][14][15][16][17][18]. This coupling generates the production of non-selective radicals such as hydroxyl radicals which have a higher oxidation potential than molecular ozone.…”

“…This coupling generates the production of non-selective radicals such as hydroxyl radicals which have a higher oxidation potential than molecular ozone. The heterogeneous catalytic ozonation in the presence of activated carbon was reported to be more efficient than molecular ozonation particularly for the treatment of effluents containing compounds with low biodegradability [9,[14][15][16][17]19]. In all these papers, the reaction kinetics was enhanced due to the decomposition of ozone on the surface of the activated carbon into powerful non-selective free radicals: HO • and O 2 -• .…”

Modelling of succinic acid heterogeneous catalytic ozonation on metallic foam

“…However, only a few articles have assessed catalytic ozonation at semi-industrial or industrial scales. Most laboratory studies are performed on powder form catalysts poured in stirred vessels [9][10][11], and few of them optimize the operating conditions from a process standpoint [12]. Several patented processes based on heterogeneous catalytic ozonation, with a powder catalyst operating in slurry-type reactor [13][14][15] or with pellets operating in a trickle-bed-type reactor, have also been reported [16][17][18][19].…”