Adsorption et électro sorption de l’arsenic (III) sur charbon à base de noyaux de dattes activés thermiquement et chimiquement

The objective of this study is the valorization of a lignocellulosic natural residue «the date stones» and its application in elimination by adsorption of the arsenic (III) contained in water. The chronological stages of obtaining coal were: cleaning, drying, crushing and finally two types of treatments: a thermal treatment by pyrolysis at 900°C (CAP1), and a chemical pretreatment with iron oxide of the natural residue followed by a carbonization at 600°C (CAP2). The choice of iron oxide is justified by the fact that arsenic (III) has strong affinities for the hydroxide and oxide of this metal. The characterization of the carbonaceous and activated matter showed properties comparable with those of many industrially produced coals. The retention tests in static mode of arsenic (III) on the two obtained materials, gave a maximum capacity of adsorption (at 20°C, initial concentration of arsenic (III): 150 mg/g and 24 h of contact time) about 25 mg/g for the chemically activated carbon and 21 mg/g for that thermically activated. The adsorption capacity of pyrolyzed material at 600°C without preliminary pretreatment is approximately 2 mg/g. The study of the influence of the pH and temperature of the medium showed that with a neutral pH and at ambient temperature (T=20°C), the optimal adsorption of arsenic (III) suitably follows the Langmuir and Freundlich models. The kinetics of adsorption is slow, and it is of type pseudo-second order. The dynamic study of arsenic (III) on prepared coals, showed a clear improvement of adsorption in absence of applied potential; it is that ~ 86 mg/g for the activated grain carbon chemically treated (CAG2) and ~ 76 mg/g for the activated grain carbon thermically treated (CAG1). The application of negative potential (-2V) at saturation, increases the adsorption of the CAG2 at 111 mg/g and 97 mg/g for CAG1, initial concentration of arsenic (III) being of 50 mg/l.

Décontamination électrocinétique d’une boue d’eau potable contenant de l’aluminium

The electrokinetics treatment often called electromigration is an emerging technology for decontamination of soil and industrial sluges, by the application of an electric field. This technology is efficient in the decontamination of organic and metallic compounds. The methodology has required characterization of sludge issued from the classical treatment of drinking water, as well as the installation of an open electromigration cell made of glass, to simulate natural conditions. The characterization results, have showed, that the slude has no apparent toxicity, especially for heavy metals. However, very high levels of aluminum were detected (160g/kg weigh sludge). Th treatment of sludge has become so important. The optimization of the chosen treatment ‘electromigration’, has required two series of tests; the first one is with a free pH and the second one is with controlled pH respectively with acetic acid, citric acid and EDTA. The results of several parameters influences (time of treatment, applied potential etc.) on the process have showed that pH is a key parameter. In fact, a free pH limited the cathodic migration of aluminum; the sludge’s pHs near the cathode are superior to 10; they favored the precipitation phenomena of complexed negative species as well as the neutral specie Al(OH)3. However, with the controlled pH, the cathodic pH is more acid, a rate of recuperation of aluminum around 57% is reached with the acetic acid with 0.1 M. the increasing applied potential to 15 volt has improved the efficiency to 86%, in detriment of an important energy consumption which is around 1000 Kw/Kg of weigh sludge. An eventual industrial application will require finding a compromise between the applied potential, the consumed energy and of the process cost.

Caractérisation et prétraitement des eaux résiduaires de "FERPHOS" par électrocoagulation

The treatment of industrial mining wastewater (IMWW) by electrocoagulation (EC) using aluminum electrodes has been conducted with real wastewater taken from a mining industry. For reuse this water, several experiments were carried out in order to optimize the conditions of technique’s applicability. The results showed that turbidity (560 NTU) was removed reaches 99% at current density 10 mA/cm2, free pH 7.2 and temperature of wastewater ~ 20 °C. The clarification of IMWW is very quick (EC time < 10 min) and adequately described by pseudo-second-order kinetics model. Moreover under optimal conditions, all parameters of pollution measured after EC are below the standard norms of industrial discharges. The EC process can be applied 10 times without loss of efficiency, it led to a minimal volume of sludge (65-75 cm3/L), and a low cost treated effluent ~ 6 $/m3.

Décontamination électrocinétique de l'aluminium et des sulfates d'une boue de laiterie

Le succès du procédé de décontamination électrocinétique des métaux d’une boue dépend du choix des conditions expérimentales : courant ou tension appliqué, pH, réactifs ajoutés, débit du flux électro-osmotique, etc. Des conditions bien adaptées doivent permettre notamment de minimiser les phénomènes d’adsorption, d’augmenter la solubilité pour éviter la précipitation du métal dans la boue. Ces précautions, entre autres, facilitent la récupération cathodique du métal. Dans cette étude de décontamination électrocinétique de l’aluminium d’une boue provenant d’eaux résiduaires de laiterie, il a été décidé de garder un débit électro-osmotique et un potentiel constants successivement à 10 ml/h et 15 V (1 V/cm), et de faire circuler dans le réacteur un milieu basique (NaOH 0,1 M) des deux côtés des compartiments anodique et cathodique. Ce choix de pH extrême a permis d’évaluer l’électromigration de l’espèce complexe mononucléaire de l’aluminium et non de l’aluminium monomère (Al3+) qui est largement prédominant en milieu acide (pH = 4,6). Les résultats obtenus ont montré l’efficacité de cette technique d’électromigration pour récupérer l’aluminium complexe Al(OH)5 2-. En effet, à pH supérieur à 10, mesuré dans les compartiments électrolytiques, l’aluminium redevient soluble et la récupération de ce métal atteint 72 %.

Transport électrocinétique des nitrates et des phosphates dans un sol argileux

les sols argileux locaux comme tous les sols de ce type peuvent retenir les éléments métalliques et organiques pouvant engendrer des conséquences négatives pour l'agriculture. Cette étude s'est focalisée sur les éléments nitrates et phosphates constituants majeurs de la fructification des végétaux mais en même temps source de pollution des eaux en cas de surdosage. Cette étude s'est orienté vers une technique électrocinétique rapide efficace et peu énergivore à savoir l'électromigration. Les résultats obtenus après optimisation du procédé ont montré la possibilité d'étendre cette technique à grande échelle.

Prétraitement d'électrocoagulation d'eaux résiduaires de laiterie industrielle (mode dynamique)

Cette étude a pris pour objectif de comparer l’efficacité du prétraitement des eaux résiduaires d’une laiterie industrielle en employant des procédés physico-chimiques tels l’électrocoagulation (EC) en dynamique et la coagulation chimique (CC). Un échantillon réel d’eaux résiduaires d’une laiterie industrielle locale a été employé, essentiellement pour l’élimination de la composante organique ou clarification de ces eaux. Différents paramètres peuvent affecter l’efficacité de l’EC (densité du courant, débit de percolation, temps d’électrolyse etc.) ou la CC (dose de coagulant, temps d’agitation, etc.). L’influence de ces paramètres a été réalisée déjà dans une étude précédente. Les valeurs optimales de ces paramètres sont fixées préalablement pour les essais entrepris : turbidité initiale de l’eau résiduaire, pH, la dose d’aluminium utilisée dans l’EC et la CC. Pour le suivi des paramètres de qualité de l’eau, la turbidité a été choisie parmi tant d’autres paramètres, car sa mesure est simple, rapide et fiable ; elle est aussi représentative de la clarification des eaux résiduaires d’une manière générale. D’autres constituants aussi importants que la turbidité, comme la DBO5, la DCO, les graisses et le phosphore ont été contrôlés ponctuellement avant et après traitement. Une étude complémentaire de consommation énergétique et de coût a été réalisée pour mettre en valeur l’une ou l’autre de ces deux méthodes de traitement. Les résultats de l’influence des paramètres opératoires ont montré que les deux méthodes employées donnaient satisfaction en termes d’abattement de la pollution initiale, mais l’EC est plus apte à être employée technologiquement en raison du faible coût opérationnel qui avoisine les 28 DZD/m3 d’eau à traiter.

Application des tiges de dattes dans l'adsorption de polluants organiques

Les tiges de dattes sont des biomatériaux innovants de nature ligno-cellulosiques permettant grâce aux différentes caractéristiques de structure et texture d'adsorber différents composés organiques notamment les colorants alimentaires visés par cette étude. Les résultats d'optimisation ont permis d'obtenir des capacités d'adsorption intéressantes pour être testé à grande échelle.

Evaluation rapide des protéines par turbidimétrie : Application à quelques effluents agro-alimentaires avant et après un traitement de clarification

La mise en œuvre de la turbidimétrie pour évaluer les protéines des eaux résiduaires de laiterie, abattoir et céréale, s’est révélée globalement positive. Elle s’avère efficace en termes de temps d’analyses et de précision, évitant ainsi les inconvénients de l’emploi des méthodes classiques de dosage des protéines qui sont pour l’essentiel : lentes et coûteuses.

Application des tiges de dattes dans l’adsorption de métaux toxiques de l’eau

The objective of this study is to valorize a local lignocellulosic material in this case the palm stems date palm (TPAL) considered abundant natural waste and not reused up to date. The physico-chemical characterization and material surface adsorption predicted his employment and competing with frequently used activated carbon water treatment. The results of the batch adsorption tests hexavalent chromium Cr (VI) and copper Cu (II) on TPAL used raw, have confirmed the ability of this material to adsorb metals. Modeling and thermodynamic data have shown that the adsorption of metal is considered multilayer according Freundlich isotherm, endothermic for Cr (VI) and athermic for Cu (II). The kinetic adsorption follows the pseudo-second order reaction. The comparative results of the adsorption of the Cu (II) on the carbon paste electrode modified (CPE) to the (TPal) or silica (A300-5Ph8HQ) showed the possibility of using the modified EPC (TPal) as an electrochemical sensor. The rapidity and repeatability adsorption / desorption (7-8 cycles for Cu (II)) has highlighted the performance of this type of electrochemical treatment. The presence of interferents showed that calcium and copper are adsorbed on the same sites, arsenic has little effect and chromium has a synergistic effect for the detection of copper.

Contrôle de clarification des eaux résiduaires de « ferphos »avant et après au prétraitement d’électrocoagulation

The treatment of industrial mining wastewater (IMWW) by electrocoagulation (EC) using aluminum electrodes has been conducted with real wastewater taken from a mining industry. For reuse this water, several experiments were carried out in order to optimize the conditions of technique’s applicability. The results showed that turbidity (560 NTU) was removed reaches 99% at current density 10 mA/cm2, free pH 7.2 and temperature of wastewater ~ 20 °C. The clarification of IMWW is very quick (EC time < 10 min) and adequately described by pseudo-second-order kinetics model. Moreover under optimal conditions, all parameters of pollution measured after EC are below the standard norms of industrial discharges. The EC process can be applied 10 times without loss of efficiency, it led to a minimal volume of sludge (65-75 cm3/L), and a low cost treated effluent ~ 6 $/m3.

Valorisation des déchets ligno-cellulosiques (Noyaux de dattes) dans l’élimination des colorants de l’eau

The objective of this study is to valorize a local lingo-cellulosic material in this case the raw date pits (D.P) as a low cost adsorbent for the adsorption of an anionic dye Congo Red (CR) and a cationic dye Methylene Blue (MB) from an aqueous solution. The structural and textural characterization of this material has shown its ability to remove polluting substances from the aqueous solution. The application of the D.P in adsorption was carried out in batch under the following optimized conditions: initial dye concentration 100 mg/L, contact time at equilibrium 120 min, temperature 20 °C, pH 2 for CR, pH 5 for MB and concentration of D.P 1 g/L. For CR and MB respectively, the adsorption capacity corresponding to these conditions is approximately 69.81 mg/g and 93.47 mg/g and could reach 99.42 mg/g and 50 mg/g by increasing the ionic strength of the dye solution with 0.05 M CaCl2. These experimental results are well modeled in adsorption by the Freundlich isotherm and in kinetics by the pseudo-second-order and Elovich models. The adjustment of the models was confirmed by the low values of the Chi-square (χ2) test and the correlation coefficient R2 near the unity.The thermodynamic parameters indicate that the adsorption process is endothermic and not spontaneous for the temperatures studied. The tests of adsorption desorption or regeneration showed that D.P has the disadvantage of the loss of efficiency or wear, like the majority of adsorbent materials. On the basis of all these results, D.P could be used as a potentially effective adsorbent at low cost and meeting the environmental criteria of sustainable development.

Application des noyaux de dattes dans l’adsorption de métaux toxiques de l’eau

The objective of this study is to apply a natural agricultural waste, in this case the date stones, as a biosorbent to remove heavy metals (Cr (VI), Co (II) and Ni (II)) from an aqueous solution. The structural and textural characterization (FTIR, SEM, XRD and BET) of this local biomaterial used raw has shown the possibility to use it in adsorption. For all the metals studied, and under optimized conditions (initial concentration 100 mg/L, contact time 60 min, concentration of D.S 1 g/L, pH = 2 for Cr (VI) and pH = 8 (for Co (II) and Ni (II)) the adsorption results obtained are satisfactory. Indeed, the adsorption capacities of Cr (VI), Co (II) and Ni (II) are approximately 70 mg/g, 48 mg/g and 53 mg/g respectively. The experimental results of Cr (VI) and Co (II) are well adapted to the Langmuir model whereas for Ni (II): Langmuir and Temkin. For all the metals studied, the kinetic study followed the pseudo second-order model. The fit the models of adsorption and kinetics was confirmed by the Chi-square (χ2 ) and the correlation coefficient R2. The thermodynamic parameters indicated that the adsorption process is spontaneous for all metals, endothermic for Cr (VI) and Ni (II), and exothermic for Co (II). Chemical regeneration tests of D.S observed that the best eluents are NaOH for Cr (VI) and HCl for Co (II) and Ni (II).The wear of biomaterial test showed that it can be used in five cycles without replacement. Based on these results, D.S could be used as an ecological and economical biosorbent for removing of Cr (VI), Co (II) and Ni (II) from an aqueous solution.

Traitement des eaux résiduaires de Laiterie par Electrocoagulation et Couplage en mode dynamique

Wastewater from the dairy industry essentially contains organic compounds which form a considerable polluting load harmful to the environment. For this type of water, the treatments used are often biological. In this study, attempts are made to physico-chemical treatments which are simple to set up, quick and inexpensive. These treatments are chemical oxidation with H2O2 and K2S2O8 at different concentrations, EC / Fenton coupling at pH 3 and 7 with different active electrode surfaces as well as continuous EC / Adsorption coupling on GAC. The results of the optimization of each of these techniques have shown that only the coupling EC / Adsorption on CAG gives reduction rates of more than 98% for COD, BOD5, turbidity and fats in a very short treatment time (~ 15 min).In addition, the low operational cost obtained (~ $ 3 / m3 of treated water) encourages the use of this coupling as a separation technique for waste water with a high load of organic pollutants.

Décontamination de colorants alimentaires de l’eau par électrocoagulation et adsorption

The azo dyes studied, such as Red 14 acid (AR.14) and Red 27 acid (AR.27), have a negative impact on public health, the quality of surface water and groundwater. Indeed they are recognized as being persistent dyes, not very biodegradable and carcinogenic. Very little work on the treatment techniques of these dyes in aqueous solution, and even less by the electrocoagulation (EC) and adsorption methods chosen in this study, has been reported. For the EC, the experiments were carried out in a laboratory scale batch reactor with (Al) aluminum electrodes . For adsorption it was carried out with raw date stones (ND) grafted with diazonium salt (NDSD). The EC results, under the optimized conditions at current density between 50-70 mA/cm2, reaction time 60-90 min, neutral pH, temperature at ~ 20 °C, initial concentration of AR.14 and AR.27 at 50 mg/L, gave satisfactory reduction rates, namely 95% for the discoloration and 90 % for the removal of COD. For optimized adsorption results, conducted at 3g/L of raw or grafted date stones, pH of 2, equilibrium time of 60 min, temperature at ~ 20 °C, initial concentration of AR.14 and AR.27 at 50 mg/L, gave adsorption capacities of 12,7 mg/g on the raw material and 16 mg/g on the diazonium grafting. Whether for EC or adsorption, the results obtained are modeled, and the processing mechanisms are purely physical, mainly electrostatic. Based on these results, it can be concluded that EC or adsorption treatments could be applied easily, quickly and economically for the removal of the dyes studied.

Dépollution d'un effluent de laiterie par électrocoagulation et comparaison d'efficacité avec d'autres techniques de traitement

This study addressed different techniques for treating wastewater from a local dairy, namely electrocoagulation (EC), coagulation / Flocculation (CC), adsorption on OFIP (Ad), chemical oxidation (OC) and electrochemical (EC and EC/Fenton) in the presence of chemical oxidants.Experimentation with optimization of each of these techniques has shown that EC and chemical coagulation have the best reduction rates in turbidity (95-99%) and COD (75-80%).However, EC has an operational cost 10 times higher than that of CC.For the OFIP adsorption process, it could be another interesting treatment alternative to explore by studying other operating conditions, because OFIP is an abundant material in Algeria and could be used at low cost.The other oxidation and electro-oxidation techniques used in the presence of the best oxidant (NaOCl), they pose a problem of efficiency and the use of this oxidant.Taking into account the advantages and disadvantages of each technique, the choice of the application of one or the other process, requires to make a compromise in relation to the desired objectives.