Mass Transfer in VOC Adsorption on Zeolite : Experimental and Theoretical Breakthrough Curves

From experimental results of adsorption of volatile organic compounds (VOCs) on zeolite, we propose simulations of the breakthrough curves based on the Linear Driving Force model. Experiments were run on fixed beds of hydrophobic commercial zeolites. Pollutants chosen are from several chemical classes with different polarities. A good agreement between experimental and numerical results is found when an adjustable value of the internal mass-transfer coefficient is used. A constant value of effective diffusivity is found independent of the nature and the amount of VOCs adsorbed. A relation linking intrapellet mass-transfer coefficient and equilibrium constant is proposed, including the average effective diffusivity, to make predictions of breakthrough curves for any kind of volatile organic pollutant in gaseous effluent

TRAITEMENT DES COMPOSES ORGANIQUES VOLATILS (COV) PAR ADSORPTION SUR ZEOLITHE. ETUDE DU COUPLAGE ABSORPTION/ADSORPTION APPLIQUE AU TRAITEMENT DE L'AIR

TOULOUSE-INSA (315552106) / SudocSudocFranceF

Modelling of a falling thin film deposited photocatalytic step reactor for water purification: Pesticide treatment

International audiencePhotocatalysis is a process that can mineralize organic pollutants such as pesticides released from agricultural activities. In this work we study the modelling of photocatalytic degradation of metolachlor and chlortoluron in a falling film closed loop step photoreactor. TiO2 was coated on fiber which was deposited on the steps. The modelling was done by introducing an equivalent intermediate (EI) formed by the photo-oxidation of the initial compound to reproduce, partially, the competitive effect of the unknown by-products. The results obtained are satisfactory for describing the degradation kinetics but need improvement for the description of the mineralization. The model was used to simulate the degradation and the mineralization of a commercial pesticide solution (chlortoluron). The fitting gives interesting results but the description of the chemical pathway has to be refined

Photocatalytic degradation of a triazole pesticide, cyproconazole, in water

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Removal of antibiotics by an integrated process coupling photocatalysis and biological treatment - Case of tetracycline and tylosin

International audienceMuch attention has been recently devoted to the fate of pharmaceutically active compounds such as antibiotics in soil and water. Among them, tetracycline (TC) and tylosin (TYL) antibiotics were shown to be poorly biodegradable and toxic for microorganisms. The question of their fate in the environment has to be clearly identified in order to prevent any environmental contamination and to avoid generating antibioresistant strains. Hybrid processes involving a physico-chemical pre-treatment like photocatalysis coupled to a biological treatment have been considered for their removal. Prior to a biological treatment, pre-treatment of both antibiotics by photocatalysis was considered in this work. To ensure a significant residual organic content for the biological treatment, an irradiation time of 2 h was considered. A decrease of the residual amount of antibiotics contained in the irradiated solutions was recorded, which can be related to an "inherent" biodegradation since these residual concentrations were below their inhibitory thresholds, 18 and 9 mg l −1 for TC and TYL. The absence of biodegradability of TC by-products was noted because of their toxicity (EC 50 < 1%) while TYL by-products showed a significant biodegradability (56% COD decrease). TYL toxicity decreased from highly toxic (EC 50 < 1%) initially to toxic (EC 50 = 36%) after irradiation

Ozonation using hollow fiber contactor technology and its perspectives for micropollutants removal in water: A review

Membrane contactor is a device generally used for the removal or the absorption of a gas into another fluid. The membrane acts as a barrier between the two phases and mass transfer occurs by diffusion and not by dispersion. This article is a review of the application of membrane contactor technology for ozonation applied to water treatment. The challenge of removing micropollutants is also discussed. In the first part, the ozonation process is mentioned, in particular chemical reactions induced by ozone and its advantages and disadvantages. In the second part, generalities on membrane contactor technology using hollow fibers are presented. Then, the benefit of using a membrane contactor for the elimination of micropollutants is shown through a critical analysis of the influence of several parameters on the ozonation efficiency. The impact of the membrane material is also highlighted. Finally, several modeling approaches are presented as a tool for a better understanding of the phenomena occurring in the contactor and a possible optimization of this process

Urban wastewater reuse using a coupling between nanofiltration and ozonation: Techno-economic assessment

International audienceCombination of nanofiltration and ozonation was investigated for the treatment of urban wastewater. First objective was to demonstrate that nanofiltration can be used instead of reverse osmosis as it enables good rejection rates with reduced cost because of lower operating and maintenance costs. In this way, this paper presents an economic and technical evaluation of the proposed coupling where ozonation is used to treat retentates from nanofiltration. Reverse Osmosis System Analysis (ROSA) software was applied to simulate the filtration design. The effect of membrane choice on specific energy consumption, capital, operation and maintenance costs and scaling potential was investigated. It was demonstrated that using nanofiltration instead of reverse osmosis enable cost saving of 35 k$/year for 125 m(3)/h. Second objective was to evaluate the impact of the treatment of retentates by ozonation on the global cost. It was highlighted that the coupling would be an acceptable solution from an economic point of view for wastewater reuse. The possible reuse of both permeate and concentrate enable an operating cost saving of 15.4 k$/year for 125 m(3)/h. An optimum recovery rate of 80% was found for which cost of membrane process is balanced by a decrease in the cost of ozonation. (C) 2019 Institution of Chemical Engineer

Photocatalytic degradation of a phenylurea, chlortoluron, in water using an industrial titanium dioxide coated media

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Photocatalysis as a pre-treatment prior to a biological degradation of cyproconazole

International audienceThe feasibility of coupling photocatalysis and a biological treatment (Pseudomonas fluorescens) to remove a fungicide, cyproconazole, in pure water was examined. Photocatalytic elimination of 85 10 −3 g L −1 cyproconazole was almost complete after 500minutes irradiation. In view of a subsequent biological treatment, the residual organic content should be significant and hence 255minutes irradiation time was chosen, leading to 85.8% elimination yield, 38.5% mineralisation and 51.6% oxidation. COD on TOC ratio decreased during photocatalysis indicating a favourable trend, which however was not confirmed by a decrease of the toxicity, since the EC 50 values were 61% and 64% initially and after 255minutes irradiation. In addition, the presence of by-products from photocatalysis after P. fluorescens culture, showing their non-biodegradability, was also in disfavour of a coupling of the two operations. Therefore in the considered experimental conditions, photocatalysis prior to biological treatment with P. fluorescens is not really relevant to treat water containing cyproconazole

Influence of ionic strength in the adsorption and during photocatalysis of reactive black 5 azo dye on TiO2 coated on non woven paper with SiO2 as a binder

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