Traitement électrocinétique appliqué aux composés organiques et inorganiques dans les sédiments de dragage

Les quantités de sédiments de dragage portuaires produites chaque année se chiffrent à 50 millions m-3 en France. Par le passé, le devenir des sédiments dragués contaminés était le relargage en mer, mais ces activités sont désormais strictement réglementées; la mise en dépôt de ces matériaux dans des aires spécialement aménagées, qui arrivent à saturation, est de plus en plus couteuse. Dans cette logique, la valorisation des sédiments de dragage s'avère capitale pour un développement durable. Du fait de l’état ces sédiment qui contient des éléments trace métalliques et organiques, un traitement est nécessaire pour préparer le matériau à l’éventuelle valorisation. Le traitement par la technique électrocinétique consiste à appliquer un faible champ électrique à travers le sédiment de l’ordre de 1V/cm, qui induit la migration des espèces ionisées par électromigration et les espèces non-ionisées par électro-osmose. Les travaux présentés concernent des essais, effectués à l'échelle du laboratoire, en premier lieu sur des échantillons de sédiments modèles reconstitué est dopé par cinq métaux (cadmium, chrome, cuivre, plomb et zinc) et cinq autre type de HAP (Phénanthrène, Fluoranthène, Pyrène, Chrysène, Benzo (b) fluoranthène). En deuxième lieu on a utilisé un sédiment naturel. Nous avons évalué sous différentes conditions les performances de l’atténuation des teneurs éléments trace métallique et organique (HAP). Cette étude a mis en évidence qu’un procédé électrocinétique a permis une atténuation significative des éléments traces métalliques et organiques, que l'extraction des métaux lourds dépend frottements du pH, plus le pH est faible plus le procédé est meilleurs. L’acide nitrique et l'acide citrique ont montré les meilleurs taux d'extraction de métaux lourds. Dans toutes les expériences, le Zinc est l’élément le plus mobile. L’extraction des HAP avec un tensioactif non anionique (Tween 20) est meilleure qu’un un tensioactif anionique (SDS). Le traitement utilisant la combinaison Tween 20 et Acide citrique améliore l'extraction des HAP lourds car l’acidification du milieu améliore le flux électroosmotique donc la mobilité des polluants non-ionisés

Prétraitement de sédiments de dragage par une méthode électrocinétique

Nous avons évalué sous différentes conditions les performances de la déshydratation d'un sédiment causée sous l'effet combiné de la gravité et d'un champ électrique par rapport à celle obtenue sous l'effet gravitaire. Les résultats montrent que la déshydratation et la consolidation d'un matériau sont nettement accélérées sous l'effet d'un champ électrique, ainsi qu'un front basique qui s'installe dans l'échantillon, durant l'essai. Les effluents recueillis seront analysés afin d'évalué l'atténuation des contaminations

Contribution to the study of electrokinetic process applied to dredged sediments

Les travaux présentés dans le cadre de cette thèse portent sur la contribution à l’étude des processus électrocinétiques appliqués aux sédiments de dragage. Deux aspects ont été étudiés ; le premier est dédié à la phase de prétraitement et développe le processus d’électrodéshydratation, tandis que le second aspect traite de l’électroremédiation. L’électrodéshydratation des sédiments de dragage par la technique électrocinétique apparait comme une technique prometteuse. Dans ce cadre, des essais ont été réalisés sous différentes conditions dans le but de fournir une compréhension générale du comportement des sédiments soumis à un champ électrique seul ou combiné avec une contrainte mécanique, et d’évaluer la performance de déshydratation du sédiment, avec un accent particulier sur la détermination des paramètres physico-chimiques. Ensuite, des études sont menées afin d’évaluer l’efficacité du procédé électrocinétique sur la décontamination d’un sédiment de dragage, en utilisant des additifs aux propriétés chimiques bien définies. Afin de cibler les deux types de contaminants organiques (HAP) et inorganiques (métaux lourds), il s’est avéré intéressant de combiner les avantages de plusieurs types d’additifs. En combinant un acide avec un tensioactif, on arrive à améliorer ainsi l’efficacité du procédé d’électroremédiation. La considération énergétique du processus permet de réduire le coût par le biais de deux paramètres ; la dépense énergétique avec le traitement périodique et la concentration de l’additif. Les résultats ont montré que cette technique allie les avantages de compétitivité vis-à-vis des autres méthodes et d’efficacité de cibler les deux types de polluants.The works presented in this thesis focuse on the contribution to the study of electrokinetic processes applied to the dredged sediments. Two aspects have been studied ; the first one deals with the preprocessing phase and develops the dewatering process, while the second aspect is devoted toe electroremediation. Dewatering dredged sediments by electrokinetics appears as a promising technique. In this framework, tests were performed under various conditions to provide a general understanding of the behaviour of the sediment subjected to a single electric field or combined with a mechanical stresses, and also to assess the performance of the dehydratation with particular emphasis on the determination of physicochemical parameters. Subsequently, studies were conducted to assess the potential of the Electrokinetic process on a dredged-contaminated sediment using additives with well-defined chemical properties. In order to target the two types of organic and inorganic contaminants, it was interesting to combine the advantages of several types of additives. For example, combining an acid with a surfactant can improve the electroremediation process. The improvement of this process can also be carried regarding to the economic aspect through two parameters; energy consumption with the periodic voltage treatment and the concentration of the additive. Therefore this electroremediation technique combines the advantage of being more competitive and efficient for several elements (organic and inorganic) present in the solid matrix

Enhanced Electroremediation of Metals from Dredged Marine Sediment under Periodic Voltage Using EDDS and Citric Acid

The electrokinetic remediation (EKR) method has been extensively considered for the removal of inorganic pollutants from contaminated dredged sediment. In addition, the use of chelating agents as electrolyte solutions has been beneficial in increasing the mobility of metals. This study investigated the metals’ (Cd, Cr, Cu, Pb, and Zn) mobilities by assessing the effect of two environmentally friendly chelating agents, ethylenediaminedisuccinic acid (EDDS) and citric acid (CA), in enhancing the EKR efficiency under a periodic voltage gradient. The results showed that, for the same concentration (0.1 mol L−1), CA is more suitable for enhancing the removal of Cr (67.83%), Cu (59.77%), and Pb (32.05%) by chelating and desorbing them from the sediment matrix and concentrating them in the electrode compartments. EDDS provided efficiency to improve the Cd extraction percentage (45.87%), whereas CA and EDDS had comparable improvement removal impacts on Zn EKR (39.32% and 41.37%, respectively). From the comparison with previous results obtained with a continuous voltage, applying a periodic voltage gradient associated with a low concentration of chelating agents led to a promising result

Contribution à l étude des processus électrocinétiques appliqués aux sédiments de dragage

LE HAVRE-BU Centrale (763512101) / SudocSudocFranceF

Enhanced Electroremediation of Metals from Dredged Marine Sediment under Periodic Voltage Using EDDS and Citric Acid

International audienceThe electrokinetic remediation (EKR) method has been extensively considered for the removal of inorganic pollutants from contaminated dredged sediment. In addition, the use of chelating agents as electrolyte solutions has been beneficial in increasing the mobility of metals. This study investigated the metals’ (Cd, Cr, Cu, Pb, and Zn) mobilities by assessing the effect of two environmentally friendly chelating agents, ethylenediaminedisuccinic acid (EDDS) and citric acid (CA), in enhancing the EKR efficiency under a periodic voltage gradient. The results showed that, for the same concentration (0.1 mol L−1), CA is more suitable for enhancing the removal of Cr (67.83%), Cu (59.77%), and Pb (32.05%) by chelating and desorbing them from the sediment matrix and concentrating them in the electrode compartments. EDDS provided efficiency to improve the Cd extraction percentage (45.87%), whereas CA and EDDS had comparable improvement removal impacts on Zn EKR (39.32% and 41.37%, respectively). From the comparison with previous results obtained with a continuous voltage, applying a periodic voltage gradient associated with a low concentration of chelating agents led to a promising result

Insights into processes and consequent metal(loid) behavior in dredged estuarine sediments upon electrokinetic treatment

International audienceThe use and reuse of natural and waste materials after treatment has become increasingly crucial as a means of achieving sustainable and environmentally-friendly solutions, and is part of a broader trend towards embracing circular economy principles. This study aims to understand the behavior of different elements (metal(loid)s and non-metals) and minerals during and after electrokinetic remediation (EKR) and to develop an effective approach to monitor its progress and overcome unwanted occurrences. In this regard, estuarine sediments, collected from Tancarville (Seine River estuary, France), were electrokinetically treated using a 64 L laboratory reactor; treatment was done 8 h per day for 21 days. The physico-chemical properties (pH, electric conductivity, and oxido-reduction potential) and current were monitored during treatment. The spatial evolution of the physico-chemical, physical (grain size distribution), mineral (mainly carbonates), organic, and elemental (As, Ca, Cl, Mg, Na, Pb, Sr, Zn, and Zr) characteristics was studied to assess the treatment efficiency. The results showed that the acidic conditions in the anodic sediments caused the dissolution of carbonates (calcite, dolomite, and aragonite), resulting in a considerable reduction in As, Zn, and Pb. Additionally, Cl as well as electric conductivity were significantly reduced from most sediments, which is essential in agricultural practices. Furthermore, materials had precipitated and settled in the anolyte and catholyte chambers, which acted as sorbents for elements that were released from the sediments (mainly Zn and As). Finally, three distinct phases occurred during treatment and were mainly linked to the current intensity and electric conductivity on the one hand, and the dissolution of carbonates and metal(loid) release on the other. This approach can be used to treat sediments and other media to improve the overall efficiency of remediation processes and create an end product with desired characteristics

Influence de la taille des particules en suspension sur leur transfert dans un milieu poreux

International audienc

Electrokinetic remediation of estuarine sediments using a large reactor: spatial variation of physicochemical, mineral, and chemical properties

International audienceThe treatment and beneficial use of polluted or contaminated environmental matrices have become major issues, especially as the world strives toward a zero-waste policy. In this regard, dredged sediments need to be treated before they can be used in an environmentally safe and sustainable manner. Therefore, this work aims to treat estuarine sediments and, more importantly, use physicochemical, mineral, organic, and chemical information to understand the reactions that occur upon treatment. Dredged estuarine sediments were collected from Tancarville (Seine River estuary, France) and subjected to electrokinetic (EK) remediation using a 128 L laboratory-scale reactor. The sediments were treated 8 hrs per day for 21 days. The electric (voltage and current) and physicochemical (pH and electric conductivity) parameters were monitored during treatment. Sediments were collected from various sections in the reactor at the end of the experiment (lengthwise, widthwise, and depthwise). The spatial variation was investigated in terms of organic, mineral, and metal contents. Statistical analyses proved that the variation occurred only in the lengthwise direction. Furthermore, three main phases described the treatment, which were mainly linked to carbonate dissolution and pH variation. The results also showed that the trace elements Ni and Zn were reduced by 21% and 19%, respectively, without a direct link to pH, while Ca and Mg were only redistributed. The buffering capacity of the anodic sediment was reduced due to carbonate dissolution. The treated sediments showed reduced contents in trace metals without affecting major elements that can be useful in agriculture (i.e., Ca and Mg)

Effect of EDTA, EDDS, NTA and citric acid on electrokinetic remediation of As, Cd, Cr, Cu, Ni, Pb and Zn contaminated dredged marine sediment

(IF 2.74; Q2)International audienceIn recent years, electrokinetic (EK) remediation method has been widely considered to remove metal pollutants from contaminated dredged sediments. Chelating agents are used as electrolyte solutions to increase metal mobility. This study aims to investigate heavy metal (HM) (As, Cd, Cr, Cu, Ni, Pb and Zn) mobility by assessing the effect of different chelating agents (ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS), nitrilotriacetic acid (NTA) or citric acid (CA)) in enhancing EK remediation efficiency. The results show that, for the same concentration (0.1 mol L−1), EDTA is more suitable to enhance removal of Ni (52.8 %), Pb (60.1 %) and Zn (34.9 %). EDDS provides effectiveness to increase Cu removal efficiency (52 %), while EDTA and EDDS have a similar enhancement removal effect on As EK remediation (30.5∼31.3 %). CA is more suitable to enhance Cd removal (40.2 %). Similar Cr removal efficiency was provided by EK remediation tests (35.6∼43.5 %). In the migration of metal–chelate complexes being directed towards the anode, metals are accumulated in the middle sections of the sediment matrix for the tests performed with EDTA, NTA and CA. But, low accumulation of metal contamination in the sediment was observed in the test using EDDS