Adsorption of ethyl violet dye in aqueous solution by forest wastes, wild carob

International audienceThe adsorption of basic dye (i.e. ethyl violet (EV) or basic violet 4) from aq. solns. onto the forest waste non-modified wild carob (NMWC) was carried out by varying some process parameters, such as initial concn., pH, and temp. The exptl. results showed that an increase in the pH from 2 to 7 led to a strong decrease in the adsorption capacity of the dye (EV) on NMWC, showing the predominance of the dispersion forces compared to the electrostatic interactions, owing to the cationic character of the dye and the pHpzc of the biosorbent (∼6). The adsorption process can be well described by means of a pseudo-second-order reaction model showing that boundary layer resistance was not the rate-limiting step, as confirmed by intraparticle diffusion. In addn., exptl. data were accurately expressed by the Sips equation if compared with the Langmuir and Freundlich isotherms. The high "m" values of the Sips model characterized a multilayer adsorption and the max. amt. adsorbed given by the Sips model was 100.4 mg/g at 20°C, namely close to the exptl. value and increased only weakly with the temp. The values of ΔG0 and ΔH0 confirmed that the adsorption of EV on NMWC was spontaneous and endothermic in nature. The pos. values of ΔS0 suggested an irregular increase in the randomness at the NMWC-soln. interface during the adsorption process

Adsorption of the Cationic Dye Ethyl Violet on Acid and Alkali-Treated Wild Carob Powder, A Low-Cost Adsorbent Derived from Forest Waste

International audienceThe effect of acid-alkaline treatment of lignocellulosic material (wild carob forest wastes) on Ethyl violet adsorption was investigated. It was found that surface chemistry plays an important role in Ethyl Violet (EV) adsorption. HCl treatment produces more active acidic surface groups such as carboxylic and lactone, resulting in an increase in the adsorption of EV dye. The adsorption efficiency was higher for treated lignocellulosic material with HCl (WCHCl) compared to that treated with KOH (WCKOH); maximum biosorption capacities were 170 and 130 mg/g for WCHCl and WCKOH at pH 6, respectively. It was also found that for both treated materials less than 150 min was needed to reach equilibrium. The adsorption of a basic dye (i.e. ethyl violet or basic violet 4) was carried out by varying some process parameters, such as the initial concentration and pH. The adsorption process can be well described by means of a pseudo-second-order reaction model and experimental data were accurately expressed by the Sips and Langmuir models for both WCHCl and WCKOH

The use of encapsulation as a proposed solution to avoid problems encountered with conventional materials in powder form Application in methylene blue removal from aqueous solutions

International audienceThe Ziziphus jujuba stones chemically modified with orthophosphoric acid (PZJS), then encapsulated with sodium alginate (BZJS1 and BZJS2) were used for organic dye adsorption. In this context, the basic dye methylene blue (MB) was chosen as a test molecule. The characteristics of the prepared beads were examined by different characterization techniques, such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray diffraction (EDX), X-ray fluorescence (XRF), Thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller method (BET) with nitrogen adsorption-desorption isotherm at 77 °K. In a batch system, initial pH (2−12), temperature (10, 25, 30 and 40 °C), initial concentration (50–200 mg/L), contact time, salt and organic compound effects were studied. The obtained results showed that the maximum MB adsorption amounts were 737.13 mg/g and 660.12 mg/g onto BZJS1 and BZJS2 at ambient temperature respectively, showing that the prepared materials are more efficient than most of the other adsorbents. Moreover, experimental data modeling showed that the adsorption process followed the Redlich-Peterson model. Regarding kinetics modeling, pseudo-first-order (PFO), pseudo-second-order and Pseudo-nth order models were used to correlate experimental data, demonstrating that a mass transfer equation (PFO) could describe MB adsorption. Thermodynamic parameters were also evaluated, demonstrating that the MB adsorption process was achievable, spontaneous and exothermic. The regeneration study showed that both of the beads had excellent adsorption efficiency even at the sixth cycle for the two beads, 92.01 and 82.88 for BZJS1 and BZJS2, respectively. From this and in view of a future implementation at industrial scale, encapsulation by sodium alginate polymer can be therefore promisingly proposed as a solution to avoid the problems of conventional materials in powder form, such as the difficulty of regeneration, performances and mass loss during the recovery step of the powder from the medium. © 202

Analyse des activités de modélisation des élèves en situation de résolution de problème. Étude de cas : le principe d’inertie en seconde

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A New Mg-Al-Cu-Fe-LDH Composite to Enhance the Adsorption of Acid Red 66 Dye Characterization, Kinetics and Isotherm Analysis

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Low-Cost Photo-Fenton-Like Process for the Removal of Synthetic Dye in Aqueous Solution at Circumneutral pH

International audienceFenton-like processes have been widely studied in recent years and are considered promising for organic wastewater treatment. Enhancement of wastewater treatment performance involves the development of economical and environmental aspects of the process. The present work aims to investigate the degradation and mineralization of an organic model compound, namely patent blue V (PBV) in aqueous solution. The process adopted uses the Fenton-like mode enhanced by UV light, using a low amount of reagent at natural pH, which was close to neutral. Some key parameters including UV light, H2O2 dosage, catalyst amount and initial dye concentration in the homogeneous Fenton-like processes were discussed. The complete degradation of 10 mg/L of PBV was obtained in 1 h with low reagent concentrations (0.98 mg/L and 39.1 mg/L of Fe3+ and -H2O2, respectively) at natural pH (6.4). The mineralization was justified through the determination of sulfates, nitrates and calcium formed during oxidation. The reaction obeys the pseudo-first-order and kinetic constants, namely the apparent rate constant, the half-life time and the catalytic efficiency, strongly depend on the catalyst concentration. The reutilization of the generated sludge in the photo-Fenton-like process was discussed. However, in spite of the decrease in the degradation efficiency, the possibility of recycling the catalyst Fe3+ as sludge Fe(OH)(3) makes the process photo-Fenton-like, cheaper and environment friendly

The use of a forest waste biomass, cone of Pinus brutia for the removal of an anionic azo dye Congo red from aqueous medium

International audienceCone biomass of Pinus brutia, a novel low-cost adsorbent prepared from forest waste has been utilized as an adsorbent for the removal of Congo red (CR) dye from an aqueous solution. The adsorbate concentration, pH, time, and temperature were examined in batch tests. Maximum biosorption capacity was 102.8 mg/g, showing that cone biomass of P. brutia was more efficient than most of the other adsorbents. Experimental data were analyzed by Langmuir, Freundlich, and Sips adsorption isotherms models and showed that the adsorption process followed a Sips model. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to fit experimental data, showing that the adsorption of CR could be described by a pseudo-second-order equation and that intraparticle diffusion was not the only rate-limiting mechanism for the biosorption of CR. Thermodynamic parameters such as ΔGo, ΔHo, and ΔSo were also evaluated and it was found that the sorption process was feasible, spontaneous, and endothermic in nature. These results indicated that cone biomass of P. brutia is promising as a low-cost alternative compared to other commercial adsorbents for the removal of dyes from wastewater

Integration of photocatalysis and biological treatment for azo dye removal--application to AR183.

International audienceThe feasibility of coupling photocatalysis with biological treatment to treat effluents containing azo dyes was examined in this work. With this aim, the degradation of Acid Red 183 was investigated. The very low biodegradability of AR183 was confirmed beforehand by measuring the biological oxygen demand (BOD5). Photocatalysis experiments were carried out in a closed-loop step photoreactor. The reactor walls were covered by TiO2 catalyst coated on non-woven paper, and the effluent flowed over the photocatalyst as a thin falling film. The removal of the dye was 82.7% after 4 h, and a quasi-complete decolorization (98.5%) was obtained for 10 h of irradiation (initial concentration 100 mg L(-1)). The decrease in concentration followed pseudo-first-order kinetics, with a constant k of 0.47 h(-1). Mineralization and oxidation yields were 80% and 75%, respectively, after 10 h of pretreatment. Therefore, even if target compound oxidation occurs (COD removal), indicating a modification to the chemical structure, the concomitant high mineralization was not in favour of subsequent microbial growth. The BOD5 measurement confirmed the non-biodegradability of the irradiated solution, which remained toxic since the EC50 decreased from 35 to 3 mg L(-1). The proposed integrated process appeared, therefore, to be not relevant for the treatment of AR183. However, this result should be confirmed for other azo dyes

Molecular dynamic simulation and DFT computational studies on the adsorption performances of methylene blue in aqueous solutions by orange peel-modified phosphoric acid

International audienceAdsorptive removal of methylene blue dye (MB) from aqueous medium using orange peels treated with phosphoric acid (OP-H3PO4) was examined. The OP-H3PO4 was characterized using Fourier transform Infra-red spectroscopy, X-ray diffraction, scanning electron microscopy, Energy Dispersive X-ray Spectroscopy, and thermogravimetric analysis. The effect of different process parameters, namely contact time, initial dye concentration, initial solutions pH, and temperature effect were examined. Equilibrium experimental data were fitted by Langmuir, Freundlich, Redlich-Peterson (R-P) and Sips isotherm models. For the two-parameter models, the data fitted well with the Langmuir isotherm model suggesting a monolayer adsorption of the dye onto the homogeneous adsorbent surface. However, regarding the three-parameter models, for the whole temperature range, both the sips and the Redlich-Peterson models showed high correlation factors, indicating that calculated data were close to those found experimentally and suggesting that MB adsorption occurs on both homogeneous and heterogeneous surfaces of OP-H3PO4 The present study revealed that OP-H3PO4 is an effective and efficient adsorbent for the removal of basic dyes from aqueous solution. In addition, quantum chemical calculations realized with density functional theory (DFT) method were successfully considered to correlate the experimental results. Moreover, the molecular dynamics simulations (MDS) were used to simulate the interactions between the MB molecule and the OP-H3PO4 (110) surface, indicating that the MB molecule adsorbs onto the OP-H3PO4 (110) surface in a nearby horizontal position. (C) 2019 Elsevier B.V. All rights reserved

Supported photocatalysis as a pre-treatment prior to biological degradation for the removal of some dyes from aqueous solutions; Acid Red 183, Biebrich Scarlet, Methyl Red Sodium Salt, Orange II

International audienceBACKGROUND: The aim of this study was to assess the feasibility of coupling photocatalysis and a biological treatment for the removal of azo dyes from aqueous effluents. Biological processes do not always appear relevant for dyes removal, owing to the low or total absence of biodegradability of this class of pollutants. RESULTS: During photocatalysis pre-treatment, a decrease in the chemical oxygen demand (COD) indicated oxidation of the target compound and thus a change in the chemical structure; better biodegradability or less toxicity could then be expected. However, the concomitant decrease in dissolved organic carbon (DOC), characteristic of a high mineralization yield, led to nearly constant COD:DOC ratios, which was unfavorable for an increase in biodegradability. It was confirmed by the low values found for the ratios biological oxygen demand (BOD5) to COD, which remained in the range 0.09-0.19, namely below 0.4 after photocatalytic reaction. Moreover, toxicity increased or remained at a high level after irradiation of the azo dyes for 3 h, and decreased only for Orange II, from toxic (EC50 = 53%) to moderately toxic (EC50 = 76%). CONCLUSION: An integrated process involving photocataysis and biological treatment to treat azo dyes appeared unsuitable under the conditions tested and may only be considered for Orange II among the four dyes tested. Copyright © 2010 Society of Chemical Industr