Traitement des rejets industriels liquide par électrocoagulation/électroflottation en réacteur airlift

Dans ce travail, le réacteur airlift à boucle externe est utilisé pour réaliser la flottation des colloïdes déstabilisés par électrocoagulation. L'effluent traité est un rejet de textile contaminé par deux composés aromatiques toxiques et une haute DCO. (Demande Chimique en Oxygène (250mg/L)). Ces deux composés (acide naphtoïc et le 2 naphtol) sont responsables de la coloration rouge utilisée dans un procédé de coloration de textile. L'étude a montré que la position des électrodes dans le réacteur est très importante pour avoir à la fois une bonne efficacité d'élimination des produits toxiques et une flottation des particules déstabilisées dans le même réacteur. Trois positions ont été testées. La meilleure qui a été retenue est celle où les électrodes occupaient le centre du compartiment riser. L'absence d'un système d'agitation mécanique (agitateur) ou pneumatique (injection d'air comprimé) engendre une faible consommationénergétique du système. Les expériences préliminaires ont montré que pour une meilleure efficacité du procédé, l'agitation du système doit être faite avec de très faibles débits de gaz. L'hydrogène formé au voisinage de l'anode nous permet d'atteindre une meilleure efficacité grâce à des vitesses de circulation liquide engendrées par la différence de taux de vide, assurant une agitation suffisante du système sans destruction des flocs. Les paramètres influençant la décoloration ont été étudiés : PH initial, conductivité, densité de courant, hauteur de liquide dans la zone de désengagement. L'efficacité est déterminée en analysant l'absorbance par Uvvisible et la demande chimique en oxygène (DCO). Il en résulte une efficacité avoisinant les 90% de décolorisation et 80% d'élimination de DCO après 8 minutes d'électrocoagulation avec une consommation énergétleique de 0,2 kW / L.

Defluoridation of drinking water by electrocoagulation/electroflotation in a stirred tank reactor with a comparative performance to an external-loop airlift reactor

Defluoridation using batch electrocoagulation/electroflotation (EC/EF) was carried out in two reactors for comparison purpose: a stirred tank reactor (STR) close to a conventional EC cell and an external-loop airlift reactor (ELAR) that was recently described as an innovative reactor for EC. The respective influences of current density, initial concentration and initial pH on the efficiency of defluoridation were investigated. The same trends were observed in both reactors, but the efficiency was higher in the STR at the beginning of the electrolysis, whereas similar values were usually achieved after 15 min operation. The influence of the initial pH was explained using the analyses of sludge composition and residual soluble aluminum species in the effluents, and it was related to the prevailing mechanisms of defluoridation. Fluoride removal and sludge reduction were both favored by an initial pH around 4, but this value required an additional pre-treatment for pH adjustment. Finally, electric energy consumption was similar in both reactors when current density was lower than 12 mA/cm2, but mixing and complete flotation of the pollutants were achieved without additional mechanical power in the ELAR, using only the overall liquid recirculation induced by H2 microbubbles generated by water electrolysis, which makes subsequent treatments easier to carry out

Defluoridation of Morocco drinking water by electrocoagulation/electroflottation in an electrochemical external-loop airlift reactor

An innovative application of external-loop airlift reactors as electrocoagulation/electroflotation cells with Al electrodes for defluoridation of drinking water was developed. Liquid overall recirculation and mixing were induced only by hydrogen microbubbles electrochemically generated from the cathode. This application was carried out in a 20 L external-loop air liftreactor both under semi-batch and continuous flow conditions. Results showed that liquid recirculation could be correlated to current density and gas–liquid dispersion height in the separator. Experimental data obtained at optimum conditions that favored simultaneously mixing and flotation confirmed that concentrations lower than 1.5 mg/L could be achieved when initial concentrations were between 10 and 20 mg/L. The effects of conductivity and pH agreed with the literature. Conversely, the low electrode surface vs. reactor volume ratio merged the formation of fluoroaluminum microflocs near the electrodes to fluoride adsorption on these particles in the riser and the separator sections, which differed from conventional EC cells. Consequently, defluoridation could be achieved at lower energy and electrode consumptions than in the literature. An optimum current density was defined at j = 6 mA/cm2 for pH 5, accounting simultaneously for mixing, reaction time, yield and operating costs. A promising attempt of transposition from batch to continuous process was also reported in this work, as flotation avoids the need for a downstream settling unit

DEFLUORIDATION OF DRINKING WATER BY ELECTROCOAGULATION/ELECTROFLOTATION - KINETIC STUDY

A variable order kinetic (VOK) model derived from the langmuir-freundlish equation was applied to determine the kinetics of fluoride removal reaction by electrocoagulation (EC). Synthetic solutions were employed to elucidate the effects of the initial fluoride concentration, the applied current and the initial acidity on the simulation results of the model. The proposed model successfully describes the fluoride removal in Airlift reactor in comparison with the experimental results. In this study two EC cells with the same capacity (V = 20 L) were used to carry out fluoride removal with aluminum electrodes, the first is a stirred tank reactor (STR) the second is an airlift reactor (ALR). The comparison of energy consumption demonstrates that the (ALR) is advantageous for carrying out the defluoridation removal process

UPGRADING OF MOROCCAN OLIVE MILL WASTEWATER USING ELECTROCOAGULATION: KINETIC STUDY AND PROCESS PERFORMANCE EVALUATION

Treatment of olive mill wastewater (OMW) by electrocoagulation (EC) was investigated in a stirred tank reactor (STR), the effect of dif ferent influential parameters , namely, contact time, current density and pH was determined. O ver 72 % of COD, 93 % of polyphenols and 95 % of color intensity were re moved efficiently at pH of 5.2, current density of 58.33 mA/cm 2 and a residence time of 45 min. A kinetic study of these three parameters was carried out and both COD an d dark color removal obey the first-order law model. On the other hand, the polyphen ols reduction, fits the pseudo second-order model with cu rrent- dependent parameters. A variable order kinetic (VOK) model derived fro m the Langmuir-Freundlish equati on was proposed to determine the kinetics of pollutant removal reactions with EC. Results showed that the model equations strongly fit the experimental concentrations of the three pollutants

DEFLUORIDATION OF DRINKING WATER BY ELECTROCOAGULATION/ELECTROFLOTATION: KINETIC STUDY

A variable order kinetic (VOK) model derived from the langmuir-freundlish equation was applied to determine the kinetics of fluoride removal reaction by electrocoagulation (EC). Synthetic solutions were employed to elucidate the effects of the initial fluoride concentration, the applied current and the initial acidity on the simulation results of the model. The proposed model successfully describes the fluoride removal in Airlift reactor in comparison with the experimental results. In this study two EC cells with the same capacity (V = 20 L) were used to carry out fluoride removal with aluminum electrodes, the first is a stirred tank reactor (STR) the second is an airlift reactor (ALR). The comparison of energy consumption demonstrates that the (ALR) is advantageous for carrying out the defluoridation removal process

Extraction of Oleic Acid from Moroccan Olive Mill Wastewater

The production of olive oil in Morocco has recently grown considerably for its economic and nutritional importance favored by the country’s climate. After the extraction of olive oil by pressing or centrifuging, the obtained liquid contains oil and vegetation water which is subsequently separated by decanting or centrifugation. Despite its treatment throughout the extraction process, this olive mill wastewater, OMW, still contains a very important oily residue, always regarded as a rejection. The separated oil from OMW can not be intended for food because of its high acidity of 3.397% which exceeds the international standard for human consumption defined by the standard of the Codex Alimentarius, proving its poor quality. This work gives value addition to what would normally be regarded as waste by the extraction of oleic acid as a high value product, using the technique of inclusion with urea for the elimination of saturated and unsaturated fatty acids through four successive crystallizations at 4°C and 20°C to have a final phase with oleic acid purity of 95.49%, as a biodegradable soap and a high quality glycerin will be produced by the reaction of saponification and transesterification