Sorption Kinetics for Dye Removal From Aqueous Solution Using Natural Clay

The kinetics of the adsorption of Congo red onto natural clay has been studied in an agitation batch adsorber. The Furusawa model has been used to determine the external transfer coefficient for the system and the effect of several experimental variables have been investigated: these include agitation, initial dye concentration, clay mass and clay particle size. The mass transfer coefficient has been correlated with the system variable by the following equation:  kf = A(variable)B. Keywords: dyes, adsorption,  mass transfer, cla

Étude cinétique de l’adsorption du rouge de Congo sur une bentonite

L’avancement industriel et technologique à l'échelle mondiale a introduit des polluants de natures diverses dans l'eau. Les polluants peuvent être des contaminants organiques et des métaux lourds. Leur présence dans des effluents industriels où l'eau potable est un problème de santé publique en raison de leur absorption et, par la suite, leur accumulation dans l’organisme humain. Les règlements de pollution de l'eau exigent que les industries textiles réduisent considérablement la quantité de colorants dans leurs rejets. L'adsorption, procédé de traitement des eaux usées, exploite la capacité de quelques solides pour concentrer certaines substances sur leurs surfaces. Généralement, l’adsorbant le plus utilisé pour le traitement des effluents textiles est le charbon activé. La capacité de la bentonite pour enlever la couleur a été reconnue il y a quelque temps. Dans ce travail, nous avons étudié la cinétique d’adsorption d’un colorant acide, le rouge de Congo, en solution aqueuse sur un matériau argileux naturel (bentonite) dans un processus en lots. La concentration initiale du colorant était de 30 mg•L‑1 déterminée par une méthode spectrophotométrique. L’influence de certains paramètres, comme la vitesse d’agitation, la masse d’argile en solution, la concentration initiale du colorant et la granulométrie a été étudiée. Les résultats ont montré pour la vitesse d’adsorption : (i) une augmentation avec la vitesse d’agitation et la masse d’argile et, (ii) une décroissance avec la concentration initiale en colorant et la granulométrie. Cinq modèles de transport externe ont été étudiés et ont montré que l’ordre de grandeur du coefficient, kf, se trouve dans la gamme de 10‑5 à 10‑4•ms‑1.Industrial growth and technological advancement have led globally to the introduction of pollutants of diverse nature into water bodies. Such pollutants include dyes, organic contaminants and heavy metals. Their presence in industrial effluents or drinking water is a public health problem, due to their absorption and possible accumulation in living organisms. Water pollution regulations require textile dye industries to reduce substantially the amount of colour in their effluents. Adsorption, as a wastewater treatment process, exploits the ability of some solids to concentrate certain substances from solution onto their surface. The most commonly used adsorbent for the treatment of textile effluents is activated carbon. The ability of bentonite to remove colour was recognized some time ago. Batch adsorption experiments are used easily in the laboratory for the treatment of small volumes of effluents. Batch adsorption provides certain preliminary information such as the pH for maximum adsorption, the maximum initial dye concentration, the particle size for optimum adsorption, the mass of adsorbent, the temperature and time of the separation process. Experiments were conducted in this study using bentonite. The dye used in all experiments was Congo red. The initial dye concentration was 30 mg•L‑1 and was determined spectrophotometrically at the wavelength of maximum absorbance. The time required to reach equilibrium was about 2 h. The effect of agitation, initial dye concentration, mass of adsorbent and mean particle diameter were investigated. It appears that the rate of dye removal: (i) increased with the agitation speed and mass of adsorbent and, (ii) decreased with the initial dye concentration and the particle size. Five models for external transport were used to calculate the external mass transfer coefficient, kf, and the results showed that this coefficient is in the range of 10‑5-10‑4•ms‑1

Study of synergetic effect, catalytic poisoning and regeneration using dielectric barrier discharge and photocatalysis in a continuous reactor: Abatement of pollutants in air mixture system

International audienceIn the present work the abatement of butyraldehyde (BUTY), dimethyl disulfide (DMDS) and their mixtures in gas phase was studied in continuous reactor at three different configurations: photocatalysis (TiO2 + UV), dielectric barrier discharge (DBD) plasma and their association in the same system (DBD+ TiO2 + UV). The effect of some operating parameters such as inlet concentration of pollutant and flowrate on planar reactor performance in term of (i) BUTY removal (ii) selectivity of CO and CO2, selectivity of byproducts has been also investigated. Moreover, ozone formation has been studied to evaluate the performance of the combined process. A synergetic effect was observed by combining (DBD) plasma and photocatalysis on BUTY removal but has not been present when it was in air mixture with dimethyl disulfide (DMDS) due to the poisoning of the catalyst. Additionally, degradation was observed as a consequence of by-products accumulation on the surface of the catalyst. Moreover, the regeneration/recovery of the initial photocatalytic activity was explored in details. A significant regeneration has been occurred by combining photocatalysis and nonthermal plasma. This trend of nonthermal plasma on catalytic surface can explain the synergetic effect during the pollutant degradation time. Moreover, the catalyst was concomitant with the time required for the hydrophobic to hydrophilic transition on the catalyst surface as followed by contact angle measurement (CA). Redox catalysis was detected by X-ray Photoelectron Spectroscopy (XPS) showing Ti4+/Ti3+ switching during the degradation, poisoning and regeneration times

Photocatalytic degradation of paracetamol mediating luminous textile: Intensification of the chemical oxidation

International audienceAn innovative photoreactor was applied as an emerging advanced oxidation process (AOP) to investigate Paracetamol (PL) degradation under different operating conditions. The system consisted of a textile woven from optical fiber and textile yarn. The luminous fiber textile was coupled to UVA LED, and the photocatalytic textile fibers is impregnated with TiO2. The effectiveness of configuration I, based on a luminous textile with UV LED, was compared with that based of TiO2 immobilized on cellulosic paper (CP) with external UV irradiation (configuration 2). The specific degradation rate obtained with configuration 1 was 40 times higher than that with configuration II. Configuration I also showed efficient performance in mineralization per Watt consumed, with values reaching 81 times higher than those obtained with configuration II. Also, to achieve high removal effi-ciency of the pollutant with the new technology of luminous textiles, the effect of operating parameters, namely pollutant concentration, UV intensity, flow rate and TiO2 mass deposited were discussed. It is worth noting that the optimal conditions for a 95.7 % degradation rate of 1 mg/L of Paracetamol were obtained with 26 g/m2 mass catalyst, 5 W/m2 UV intensity and 52.2 L/h flow rate after 340 min. In addition, upon associating two luminous textiles, the degradation efficiency reached 98.76 % after only 140 min. Besides, by adding hydrogen peroxide (H2O2) in the optimal conditions with 10 mg/L of Paracetamol concentration, the degradation efficiency reached 98.81 % after 240 min. The excellent performances in terms of degradation rate, mineralization per Watt consumed, and energy consumption make luminous textiles an attractive alternative to conventional photo-catalytic reactors designed for the removal of Paracetamol in water and wastewater