Industrial Petrochemical Wastewater Treatment By Ozonation in the Presence of Alumino Silica Materials in a Gas Liquid Solid Reactor
Title:
Industrial petrochemical wastewater treatment by ozonation in the presence of alumino‑silica materials in a gas‑liquid‑solid reactor.
Wael Aboussaoud(a,b), Marie-Hélène Manero(a,b), Jean‑Stéphane Pic(c), Hubert Debellefontaine(c), Ping Zeng(d,e) and Yonghui Song(d,e)
(a) Université de Toulouse ; INPT, UPS ; Laboratoire de Génie Chimique ; 4, Allée Emile Monso, F-31432 Toulouse, France.
(b) Laboratoire de Génie Chimique (UMR CNRS 5503); F‑31432 Toulouse, France.
(c) Université de Toulouse – LISBP – Laboratoire d’Ingénierie des Systèmes Biologiques et des Procédés (UMR CNRS 5504/INRA 792) – INSA de Toulouse – 135 avenue de Rangueil – 31077 Toulouse Cedex 4 – France.
(d) Department of Urban Water Environmental Research, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
(e) State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Keywords:
Ozonation, adsorption, alumino‑silica materials, petrochemical wastewater, gas‑liquid‑solid reactor.
Presentation form:
Oral presentation if possible, if not, a poster
Group/Topic:
Novel G-L and G-L-S reaction pathways for sustainable energy and environment
Abstract:
This work aims to study the efficiency of ozonation in the presence of alumino‑silica materials as an advanced oxidation process for the degradation of refractory organic compounds from a real petrochemical wastewater. The selection of the material and the reactor configuration are key parameters governing the efficiency of this kind of processes. Three types of zeolites (Faujasite-Y, Mordenite and ZSM-5) and one g‑alumina were selected because of their physical and chemical resistance to ozone and were used in powder form. Their effect on TOC removal was evaluated under the same ozonation conditions (QG = 31 L/h, [O3]G,E = 60 g/Nm3, T = 35°C) using a 1 L semi-batch slurry reactor for the treatment of a petrochemical wastewater with an initial TOC concentration of 180 mg/L.
In order to understand this gas-liquid-solid system, the binary interactions between ozone, the materials and the effluent were studied separately. First, the adsorption kinetics and capacities of the materials were evaluated. The best results in terms of adsorption capacity were obtained with Faujasite‑Y followed by Mordenite because of its large pores diameter and important pore volumes comparing to the ZSM‑5 which is characterised by small pores (Figure 1). Despite its large pores and an important porous volume, g‑alumina did not show any interesting adsorption potential, probably due to its hydrophilic character. The adsorption kinetics were very fast in the case of all materials tested; the adsorption equilibrium was reached in less than 15 minutes contact time (Figure 2). This behaviour indicates that there is no limitation by external mass transfer when these materials were used in a powder form. Moreover no difference was noticed between the different materialsdespite the difference in their pore sizes. This indicates that the potential limitation by internal diffusion could not be observed through these experiments.
Then, the effect of the materials on ozone decomposition was studied. Ozone decomposition to radical species (such as HO°) is favourable to make an advanced oxidation process because, unlike ozone, these species react unselectively and more rapidly with organics. The reaction of ozone decomposition was considered to follow a first order kinetics the constant of which was calculated through mass balances (Aboussaoud et al., 2014). Neither the zeolites nor g‑alumina do enhance ozone decomposition in water in the experimental conditions of the study (Figure 3).
In terms of TOC removal, single ozonation leads to remove 58% of the initial TOC after 6 hours treatment (Figure 4). An apparent zero order kinetics is observed, suggesting that the process is controlled by ozone mass transfer. Yet, this is not the case since from the beginning of the experiment ozone was accumulated in the liquid phase until a plateau was observed, which confirms that the oxidation is not limited by ozone transfer from the gas to the liquid phase.
During the experiments of ozonation in the presence of materials, a beneficial effect was observed; the best results were obtained in the case of g‑alumina and ZSM‑5 with more than 80% of the initial TOC removed after 6 hours of treatment, compared to 77% in the case of Faujasite‑Y and 68% in the case of Mordenite (Figure 4).
In order to understand the origin of the beneficial effect observed when the materials were used, the evolution on TOC removal over time during the experiments of single adsorption, single ozonation and ozonation in presence of materials were compared (Figure 5). In the case of FaujasiteY and Mordenite (Figure 5 A and B), it is obvious that the phenomena that occurred during the first minutes of ozonation treatment in the presence of materials was a fast adsorption step of some pollutants initially contained in the effluent, then the oxidation of the non-adsorbed pollutants took place. The TOC removed by ozonation in the presence of materials was similar to the TOC removed by single adsorption added to the TOC removed by single ozonation.
However, in the case of g‑alumina and ZSM‑5 (Figure 5 C and D), most of the pollutants initially contained in the effluent were not adsorbed, but at the same time, the use of these materials during ozonation clearly enhanced TOC removal. The TOC removed during ozonation in the presence of material is higher than the TOC removed by single adsorption added to TOC removed by single ozonation, indicating the synergy effect of these materials.
Our previous studies realised with a synthetic phenolic effluent (Aboussaoud et al. 2014, Vittenet et al. 2014) show that the phenomenon occurring when using these materials is rather progressive adsorption of some specific oxidation by‑products characterised by a hydrophilic or hydrophobic character compatible with the hydrophobicity of the material used, and that molecular ozone alone ensures oxidation, suggesting the absence of catalytic activity of the materials towards ozone decomposition into radicals. This leads to a better efficiency of the oxidation reaction and thus to a reduction in ozone consumption.
Acknowledgements:
The authors acknowledge the French National Agency for Research (ANR) for supporting this study through the convention ANR ECOTECH 2010 project PETZECO (1081C0230/ANR-10-ECOT-011-03) and the Sino-French international Scientific and Technological Cooperation Project for petrochemical & pharmaceutical industrial water conservation and reduction technical cooperative research (2010DFB90590).
Figure 1 Adsorption equilibrium isotherms onto the materials. [TOC]0 = 180 mg/L, pH0 = 3, T = 35°C.
Figure 2 Adsorption kinetics onto powder materials. VL = 1 L, T = 35°C, QN2 = 31 L/h, [TOC]0 = 180 mg/L, [material] = 5 g/L, pH0 = 3.
Figure 3 Evolution of ozone decomposition kinetic constant (kc) as a function of the material concentration. [O3]G,E = 30 g/Nm3, QG = 30 L/h, pH = 7, VL = 2 L, T = 25°C.
Figure 4 TOC removal evolution during single ozonation and ozonation in the presence of materials. [O3]G,E = 60 g/Nm3, QG = 31 L/h, [TOC]0 = 180 mg/L, [material] = 5 g/L, VL = 1 L, T = 35°C, pH0 = 3.
Figure 5 Comparaison of TOC removal evolution during single ozonation, single adsorption and ozonation in presence of Faujasite‑Y (A), Mordenite (B), ZSM‑5 (C) and g‑alumina (D). [O3]G,E = 60 g/Nm3, QG = 31 L/h, [TOC]0 = 180 mg/L, [material] = 5 g/L, VL = 1 L, T = 35°C, pH0 = 3.
References:
Aboussaoud W., Manero M.H., Pic J.S. and Debellefontaine H., Combined Ozonation Using Alumino‑Silica Materials for the Removal of 2,4‑dimethylphenol from Water, Ozone: Science & Engineering, 36 (2014) 221-228.
Vittenet J., Aboussaoud W., Mendret J., Pic J.S., Debellefontaine H., Lesage N., Faucher K., Manero M.H., Thibault-Starzyk F., Leclerc H., Galarneau A., Brosillon S., Catalytic ozonation with g-Al2O3 to enhance the degradation of refractory organics in water, Applied. Catalysis. A: General. (2014) http://dx.doi.org/10.1016/j.apcata.2014.10.037