Combinação de adsorção por carvão ativado com Processo Oxidativo Avançado (POA) para tratamento de efluentes contendo fenol

L'adsorption sur charbon actif est une technique relativement répandue de post-traitement des effluents aqueux. Cependant il ne s'agit pas d'un traitement ultime, puisque les polluants restent concentrés sur la surface solide. Des techniques de régénération doivent donc être mises en œuvre. C'est dans ce contexte qu'ont été étudiés ici les procédés d'oxydation avancée Fenton et photo-Fenton, dont l'efficacité est reconnue pour éliminer la pollution organique. Plus précisément, l'objet de cette thèse est l'étude sur plusieurs cycles consécutifs de l'adsorption du phénol sur charbon actif et de la régénération in-situ de l'adsorbant par oxydation (photo)Fenton. Deux charbons actifs différents ont été étudiés : le premier à la fois micro et mésoporeux (PICA L27) et le second essentiellement microporeux (PICA S23). Deux séries d'expériences ont été ainsi réalisées : 1) d'abord en réacteur agité (adsorption et oxydation en mode batch), 2) puis dans des conditions plus proches du procédé réel, avec une adsorption continue en lit fixe, suivie de l'oxydation batch par recirculation du réactif Fenton au travers du lit saturé. Dans le premier cas, les effets de la concentration en Fe2+ et en H2O2 ont été analysés, montrant que les conditions optimales pour l'oxydation homogène du phénol (sans charbon) ne sont pas les meilleures pour la régénération du charbon saturé par le polluant : une réduction continue de la capacité d'adsorption du L27, de 100% à 23%, est observée après 3 oxydations, en raison de la consommation du charbon et de la diminution de sa surface spécifique. Par contre, une concentration plus élevée de Fe2+ et plus faible de H2O2 (2 fois la stœchiométrie) permettent de retrouver 50% de la capacité initiale d'adsorption pendant au moins 4 cycles consécutifs. Comme il a été vu dans des études précédentes utilisant l'oxydation à l'air (sous température et pression), l'efficacité de régénération est aussi bien plus faible pour le S23 (autour de 20%). Des résultats similaires ont été obtenus sur le réacteur à lit fixe avec recirculation. Durant l'oxydation, le taux de conversion du Carbone Organique Total en phase liquide a atteint à chaque fois une valeur limite, probablement du fait de la formation de complexes entre le fer et les acides carboxyliques produits. L'utilisation de l'irradiation UV, qui est connue pour décomposer ces complexes, a conduit à une minéralisation quasi-totale et a amélioré l'efficacité de régénération du charbon, jusqu'à 56% de la capacité initiale après 2 cycles (contre 40% pour l'oxydation Fenton simple). ABSTRACT : Adsorption on activated carbon (AC) is a technique extensively applied for wastewater treatment. However adsorption alone is not an ultimate solution, since the pollutants are just immobilized on the carbon surface. There is thus a need for efficient regeneration techniques. In this context, Fenton and photo-Fenton oxidations, which are promising technologies to destroy organic pollution, have been tested to regenerate the AC. The purposes of this study are the adsorption of phenol on activated carbons and the consecutive in-situ regeneration of carbon by (photo-) Fenton oxidation. Two different operations have been carried out: 1) batch procedure in order to investigate the influence of Fe2+ and H2O2 concentrations; 2) continuous fixed bed adsorption, followed by a batch circulation of the Fenton’s reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (PICA L27) and an only microporous one (PICA S23). In the batch reactor the best conditions found for pollutant mineralization in the homogeneous Fenton system are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ and lower concentration of H2O2 (2 times the stoechiometry) lead to a 50% recovery of the initial adsorption capacity during at least 4 consecutive cycles for L27, while about 20% for S23. In the consecutive continuous adsorption/batch Fenton oxidation process, the regeneration efficiency reaches 30% to 40% for L27 after two cycles whatever the feed concentration and less than 10% for S23. A photo-Fenton test performed on L27 shows almost complete mineralization (contrary to dark Fenton) and further improves recovery of AC adsorption capacity although not complete (56% after two cycles)

Regeneration of activated carbon by fenton and photofenton oxidation for the treatment of phenol wastewater

Advanced Oxidation Processes have emerged as promising technologies for the recovery of carbons saturated with aromatic molecules, owing to their potency to degrade a wide range of organic pollutants by the generation of very reactive and non selective free hydroxyl radicals. The purpose of this work is to study the adsorption of phenol on activated carbons (ACs) and the consecutive in-situ regeneration of carbon by Fenton oxidation. Two different processes have been carried out: - the first one is based on a complete batch system in order to investigate the influence of Fe2+ and H2O2 concentrations; - the second one consists in a continuous fixed bed adsorption, followed by a batch circulation of the Fenton’s reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (L27) and an only microporous one (S23). In the batch reactor containing a 1 g/L phenol solution, the optimal conditions found for pollutant mineralization in the homogeneous Fenton system (Fe2+ = 10 mmol/L, [H2O2] = 1000 mmol/L, corresponding to 6.5 times the stoechiometric amount for complete mineralization) are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 from 100% to 23% is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ (20 mmol/L) and lower concentration of H2O2 (2 times the stoechiometry) lead to a 50% recovery of the initial adsorption capacity during at least 4 consecutive cycles for L27, while about 20% or less for S23. In the consecutive continuous adsorption/batch oxidation process, the regeneration efficiency reaches 30% to 40% for L27 after two cycles whatever the feed concentration (0.1 g/L or 1 g/L of phenol) and less than 10% for S23 (0.1 g/L of phenol). During oxidation step, Total Organic Carbon removal is found to reach a limit, probably due to the formation of Fe3+/organic acid complex, hindering Fe2+ regeneration. Such complexes are stable in usual Fenton conditions, but can be destroyed by UV radiation. A photo-Fenton test performed on L27 indeed shows almost complete mineralization and improved recovery of AC adsorption capacity although not complete (56% after two cycles)

Combinação de adsorção por carvão ativado com Processo Oxidativo Avançado (POA) para tratamento de efluentes contendo fenol

L'adsorption sur charbon actif est une technique relativement répandue de post-traitement des effluents aqueux. Cependant il ne s'agit pas d'un traitement ultime, puisque les polluants restent concentrés sur la surface solide. Des techniques de régénération doivent donc être mises en œuvre. C'est dans ce contexte qu'ont été étudiés ici les procédés d'oxydation avancée Fenton et photo-Fenton, dont l'efficacité est reconnue pour éliminer la pollution organique. Plus précisément, l'objet de cette thèse est l'étude sur plusieurs cycles consécutifs de l'adsorption du phénol sur charbon actif et de la régénération in-situ de l'adsorbant par oxydation (photo)Fenton. Deux charbons actifs différents ont été étudiés : le premier à la fois micro et mésoporeux (PICA L27) et le second essentiellement microporeux (PICA S23). Deux séries d'expériences ont été ainsi réalisées : 1) d'abord en réacteur agité (adsorption et oxydation en mode batch), 2) puis dans des conditions plus proches du procédé réel, avec une adsorption continue en lit fixe, suivie de l'oxydation batch par recirculation du réactif Fenton au travers du lit saturé. Dans le premier cas, les effets de la concentration en Fe2+ et en H2O2 ont été analysés, montrant que les conditions optimales pour l'oxydation homogène du phénol (sans charbon) ne sont pas les meilleures pour la régénération du charbon saturé par le polluant : une réduction continue de la capacité d'adsorption du L27, de 100% à 23%, est observée après 3 oxydations, en raison de la consommation du charbon et de la diminution de sa surface spécifique. Par contre, une concentration plus élevée de Fe2+ et plus faible de H2O2 (2 fois la stœchiométrie) permettent de retrouver 50% de la capacité initiale d'adsorption pendant au moins 4 cycles consécutifs. Comme il a été vu dans des études précédentes utilisant l'oxydation à l'air (sous température et pression), l'efficacité de régénération est aussi bien plus faible pour le S23 (autour de 20%). Des résultats similaires ont été obtenus sur le réacteur à lit fixe avec recirculation. Durant l'oxydation, le taux de conversion du Carbone Organique Total en phase liquide a atteint à chaque fois une valeur limite, probablement du fait de la formation de complexes entre le fer et les acides carboxyliques produits. L'utilisation de l'irradiation UV, qui est connue pour décomposer ces complexes, a conduit à une minéralisation quasi-totale et a amélioré l'efficacité de régénération du charbon, jusqu'à 56% de la capacité initiale après 2 cycles (contre 40% pour l'oxydation Fenton simple)Adsorption on activated carbon (AC) is a technique extensively applied for wastewater treatment. However adsorption alone is not an ultimate solution, since the pollutants are just immobilized on the carbon surface. There is thus a need for efficient regeneration techniques. In this context, Fenton and photo-Fenton oxidations, which are promising technologies to destroy organic pollution, have been tested to regenerate the AC. The purposes of this study are the adsorption of phenol on activated carbons and the consecutive in-situ regeneration of carbon by (photo-) Fenton oxidation. Two different operations have been carried out: 1) batch procedure in order to investigate the influence of Fe2+ and H2O2 concentrations; 2) continuous fixed bed adsorption, followed by a batch circulation of the Fenton s reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (PICA L27) and an only microporous one (PICA S23). In the batch reactor the best conditions found for pollutant mineralization in the homogeneous Fenton system are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ and lower concentration of H2O2 (2 times the stoechiometry) lead to a 50% recovery of the initial adsorption capacity during at least 4 consecutive cycles for L27, while about 20% for S23. In the consecutive continuous adsorption/batch Fenton oxidation process, the regeneration efficiency reaches 30% to 40% for L27 after two cycles whatever the feed concentration and less than 10% for S23. A photo-Fenton test performed on L27 shows almost complete mineralization (contrary to dark Fenton) and further improves recovery of AC adsorption capacity although not complete (56% after two cycles)TOULOUSE-INP (315552154) / SudocSudocFranceF

Combination of adsorption by activated carbon with advanced oxidation process (AOP) for the treatment of wastewater containing phenol.

O processo de adsorção por carvão ativado é uma técnica muito aplicada para tratamento de efluentes. Porém o tratamento que envolve adsorção não é um sistema completo, pois há a necessidade da destruição dos compostos que foram imobilizados na superfície do carvão. Frente a esse problema, métodos alternativos de regeneração de carvão ativado são investigados. Os processos Fenton e foto-Fenton são considerados tecnologias promissoras de tratamento de efluentes, e foram testados para regenerar o carvão ativado. Este trabalho objetiva estudar a adsorção de fenol em carvões ativados (CAs) e a consecutiva regeneração in-situ do carvão pela oxidação de (foto-) Fenton. Duas operações diferentes foram realizadas: 1) sistema de batelada, a fim de investigar a influência das concentrações de Fe2+ e H2O2; 2) adsorção contínua em leito fixo, seguido de circulação em batelada dos reagentes de Fenton pelo leito de CA saturado, para examinar a eficiência do processo real. Foram estudados dois tipos de carvão ativado: CA L27 (meso e microporoso) e CA S23 (somente microporoso). No reator de batelada as melhores condições encontradas para a mineralização do poluente no sistema Fenton homogêneo não são as melhores para a regeneração do CA: foi observada uma redução contínua da capacidade de adsorção do L27 após 3 oxidações, devido à redução tanto da massa do CA quanto da área superficial. Uma maior concentração de Fe2+ e menor concentração de H2O2 (2 vezes a estequiometria) levou a uma recuperação de 50% da capacidade de adsorção inicial em pelo menos 4 ciclos consecutivos para o L27, enquanto que cerca de 20% para o S23. No processo consecutivo de adsorção contínua/oxidação de Fenton em batelada, a eficiência de regeneração atinge de 30% a 40% para o L27 após dois ciclos independente da concentração da alimentação e menos de 10% para o S23. O processo foto-Fenton realizado para o L27 levou à quase completa mineralização e aumentou a recuperação da capacidade de adsorção do CA (56% após dois ciclos).The adsorption process by active carbon is a technique applied extensively for wastewater treatment. However the tertiary treatment involving adsorption is not a complete system, since there is a need of destruction of the compounds that were immobilized on the carbon surface. In face of this problem, some alternative regeneration methods of active carbon are investigated. Fenton and photo-Fenton processes have been considered promising technologies for wastewater treatment and have been tested to regenerate the AC. The purposes of this study are the adsorption of phenol on activated carbons (ACs) and the consecutive in-situ regeneration of carbon by (photo-) Fenton oxidation. Two different operations have been carried out: 1) batch procedure in order to investigate the influence of Fe2+ and H2O2 concentrations; 2) continuous fixed bed adsorption, followed by a batch circulation of the Fentons reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (L27) and an only microporous one (S23). In the batch reactor the best conditions found for pollutant mineralization in the homogeneous Fenton system are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ and lower concentration of H2O2 (2 times the stoechiometry) lead to a 50% recovery of the initial adsorption capacity during at least 4 consecutive cycles for L27, while about 20% for S23. In the consecutive continuous adsorption/batch Fenton oxidation process, the regeneration efficiency reaches 30% to 40% for L27 after two cycles whatever the feed concentration and less than 10% for S23. A photo- Fenton test performed on L27 shows almost complete mineralization (contrary to dark Fenton) and further improves recovery of AC adsorption capacity although not complete (56% after two cycles)

Hybridation d'adsorption sur charbon actif et de techniques d'oxydation avancée pour le traitement des eaux

L'adsorption sur charbon actif est une technique relativement répandue de post-traitement des effluents aqueux. Cependant il ne s'agit pas d'un traitement ultime, puisque les polluants restent concentrés sur la surface solide. Des techniques de régénération doivent donc être mises en œuvre. C'est dans ce contexte qu'ont été étudiés ici les procédés d'oxydation avancée Fenton et photo-Fenton, dont l'efficacité est reconnue pour éliminer la pollution organique. Plus précisément, l'objet de cette thèse est l'étude sur plusieurs cycles consécutifs de l'adsorption du phénol sur charbon actif et de la régénération in-situ de l'adsorbant par oxydation (photo)Fenton. Deux charbons actifs différents ont été étudiés : le premier à la fois micro et mésoporeux (PICA L27) et le second essentiellement microporeux (PICA S23). Deux séries d'expériences ont été ainsi réalisées : 1) d'abord en réacteur agité (adsorption et oxydation en mode batch), 2) puis dans des conditions plus proches du procédé réel, avec une adsorption continue en lit fixe, suivie de l'oxydation batch par recirculation du réactif Fenton au travers du lit saturé. Dans le premier cas, les effets de la concentration en Fe2+ et en H2O2 ont été analysés, montrant que les conditions optimales pour l'oxydation homogène du phénol (sans charbon) ne sont pas les meilleures pour la régénération du charbon saturé par le polluant : une réduction continue de la capacité d'adsorption du L27, de 100% à 23%, est observée après 3 oxydations, en raison de la consommation du charbon et de la diminution de sa surface spécifique. Par contre, une concentration plus élevée de Fe2+ et plus faible de H2O2 (2 fois la stœchiométrie) permettent de retrouver 50% de la capacité initiale d'adsorption pendant au moins 4 cycles consécutifs. Comme il a été vu dans des études précédentes utilisant l'oxydation à l'air (sous température et pression), l'efficacité de régénération est aussi bien plus faible pour le S23 (autour de 20%). Des résultats similaires ont été obtenus sur le réacteur à lit fixe avec recirculation. Durant l'oxydation, le taux de conversion du Carbone Organique Total en phase liquide a atteint à chaque fois une valeur limite, probablement du fait de la formation de complexes entre le fer et les acides carboxyliques produits. L'utilisation de l'irradiation UV, qui est connue pour décomposer ces complexes, a conduit à une minéralisation quasi-totale et a amélioré l'efficacité de régénération du charbon, jusqu'à 56% de la capacité initiale après 2 cycles (contre 40% pour l'oxydation Fenton simple)Adsorption on activated carbon (AC) is a technique extensively applied for wastewater treatment. However adsorption alone is not an ultimate solution, since the pollutants are just immobilized on the carbon surface. There is thus a need for efficient regeneration techniques. In this context, Fenton and photo-Fenton oxidations, which are promising technologies to destroy organic pollution, have been tested to regenerate the AC. The purposes of this study are the adsorption of phenol on activated carbons and the consecutive in-situ regeneration of carbon by (photo-) Fenton oxidation. Two different operations have been carried out: 1) batch procedure in order to investigate the influence of Fe2+ and H2O2 concentrations; 2) continuous fixed bed adsorption, followed by a batch circulation of the Fenton’s reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (PICA L27) and an only microporous one (PICA S23). In the batch reactor the best conditions found for pollutant mineralization in the homogeneous Fenton system are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ and lower concentration of H2O2 (2 times the stoechiometry) lead to a 50% recovery of the initial adsorption capacity during at least 4 consecutive cycles for L27, while about 20% for S23. In the consecutive continuous adsorption/batch Fenton oxidation process, the regeneration efficiency reaches 30% to 40% for L27 after two cycles whatever the feed concentration and less than 10% for S23. A photo-Fenton test performed on L27 shows almost complete mineralization (contrary to dark Fenton) and further improves recovery of AC adsorption capacity although not complete (56% after two cycles

Treatment of wastewater containing phenol through advanced oxidation processes (AOPs).

Os Processos Oxidativos Avançados (POAs) têm sido largamente empregados para o tratamento de efluentes contendo compostos orgânicos altamente tóxicos, que por sua vez, são dificilmente degradados pelos sistemas de tratamento biológico convencional. Além disso, os tratamentos físico-químicos, como filtração, adsorção e floculação, não destroem o composto tóxico, e sim, apenas transferem-no para outra fase, causando um subseqüente problema de descarte. A principal barreira para a aplicação do POA em escala industrial é o alto custo relacionado à utilização da radiação ultravioleta (UV). Desta maneira, torna-se interessante desenvolver um reator com uma fonte artificial de radiação UV de custo reduzido. Neste trabalho, foi projetado um reator tubular fotoquímico de aço inox 304 que apresenta um conjunto de 12 lâmpadas fluorescentes como fonte de radiação UV (40W/lâmpada), posicionadas verticalmente na superfície interna do mesmo. O processo estudado foi o processo foto-Fenton, que consiste em uma combinação de íons ferrosos, peróxido de hidrogênio e radiação UV, aplicado na degradação de um efluente aquoso contendo fenol como poluente modelo (100500 mgC.L-1). Os resultados experimentais indicaram que a taxa de degradação aumenta com a radiação UV, até atingir a saturação de fótons da luz UV . Com o objetivo de verificar a influência das variáveis de processo, foi realizado um planejamento experimental, no qual possibilitou-se obter um modelo para o processo e a respectiva superfície de resposta. Neste processo foi utilizada uma combinação de Fe2+ (0,2730 mM), H2O2 (0,26 moles) e radiação UV, chegando-se a uma mineralização de 82% para 100 mgC.L-1 de fenol e 81% para 500 mgC.L-1 de fenol. Devido à complexidade apresentada pelo processo foto-Fenton, foi aplicado outro tipo de modelagem matemática, baseado na técnica de redes neurais artificiais (RNA), chegando-se a um coeficiente de determinação de 99% entre os valores experimentais e os valores calculados pelo modelo.Advanced Oxidation Processes (AOPs) have been largely used for the treatment of wastewaters containing highly toxic organic compounds, which are hardly degraded by the conventional biological systems. Besides, the physicalchemical treatments, such as filtration, adsorption and flocculation, do not destroy the target compounds, which are simply transferred to another phase, causing a subsequent problem of disposal. The main barrier for the application of the POA in industrial scale is the high cost related to the use of ultraviolet radiation (UV) sources. Therefore, it has been proposed a development of a reduced cost reactor with an artificial source of UV radiation. In the present work, a tubular photochemical reactor was developed, which is made in stainless steel and presents a row of 12 fluorescent lamps as the UV radiation source (40W/lamp), attached vertically onto the inner surface of the reactor. It has been studied the photo-Fenton process, that consists in a combination of ferrous ions, hydrogen peroxide and UV radiation, applied in the degradation of an aqueous solution containing phenol as pollutant model (100500 mgC.L-1). The experimental results indicated that the degradation rate increases as the UV irradiance increases. In order to verify the influence of the process variables in phenol degradation, an experimental design was carried out by the response surface method and the corresponding polynomial model was determined. In this process, it was used a combination of Fe2+ (0,2730 mM), H2O2 (0,26 moles) and UV radiation. The mineralisation efficiency was 82% for phenol 100 mgC.L-1 and 81% for phenol 500 mgC.L-1. Due to the complexity presented by the photo-Fenton process, another type of mathematical modelling was applied, based on the artificial neural network (ANN), obtaining 99% of coefficient of determination between the experimental values and the values calculated by the model

Regeneration of Activated Carbon by (Photo)-Fenton Oxidation

This work aims to study the adsorption of phenol on activated carbons (ACs) and the consecutive in situ regeneration of carbon by Fenton oxidation. Two different operations have been carried out: (1) a batch procedure in order to investigate the influence of Fe2+ and H2O2 concentrations; (2) continuous fixed bed adsorption, followed by a batch circulation of the Fenton’s reagent through the saturated AC bed, to examine the efficiency of the real process. Two different activated carbons have been also studied: a both micro- and mesoporous AC (L27) and an only microporous one (S23). In the batch reactor the best conditions found for pollutant mineralization in the homogeneous Fenton system are not the best for AC regeneration: a continuous reduction of adsorption capacity of L27 is observed after 3 oxidations, due to the decrease of both AC weight and surface area. Higher concentration of Fe2+ and lower concentration of H2O2 (2 times the stoichiometry) lead to a 50% recovery of the initial adsorption capacity during at least four consecutive cycles for L27, while about 20% or less for S23. In the consecutive continuous adsorption/batch Fenton oxidation process, the regeneration efficiency reaches 30−40% for L27 after two cycles whatever the feed concentration and less than 10% for S23. A photo-Fenton test performed on L27 shows almost complete mineralization (contrary to “dark” Fenton) and further improves recovery of AC adsorption capacity although not complete (56% after two cycles)