Benoît Cagnon

Contributions of hemicellulose, cellulose and lignin to the mass and the porous properties of chars and steam activated carbons from various lignocellulosic precursors.

In this study, contributions of hemicellulose, cellulose and lignin to the mass and the porous properties of chars and activated carbons from various lignocellulosic materials were studied. A predictive calculation was established using the experimental results obtained for the three components separately to evaluate the carbonization and activation yields and their respective contributions to the chars and to the subsequent activated carbons of various precursors in term of weight fraction. These equations were validated. The results showed that lignin can be considering as being the major contributor of all chars and activated carbons. Besides, the evolution of the mean pore size versus the specific porous volume showed that each component contributes to the porosity of chars and activated carbons whatever is its weight contribution.

Fractional Factorial Design Study on the Performance of GAC-Enhanced Electrocoagulation Process Involved in Color Removal from Dye Solutions

The aim of this study was to determine the effects of main factors and interactions on the color removal performance from dye solutions using the electrocoagulation process enhanced by adsorption on Granular Activated Carbon (GAC). In this study, a mathematical approach was conducted using a two-level fractional factorial design (FFD) for a given dye solution. Three textile dyes: Acid Blue 74, Basic Red 1, and Reactive Black 5 were used. Experimental factors used and their respective levels were: current density (2.73 or 27.32 A/m2), initial pH of aqueous dye solution (3 or 9), electrocoagulation time (20 or 180 min), GAC dose (0.1 or 0.5 g/L), support electrolyte (2 or 50 mM), initial dye concentration (0.05 or 0.25 g/L) and current type (Direct Current—DC or Alternative Pulsed Current—APC). GAC-enhanced electrocoagulation performance was analyzed statistically in terms of removal efficiency, electrical energy, and electrode material consumptions, using modeling polynomial equations. The statistical significance of GAC dose level on the performance of GAC enhanced electrocoagulation and the experimental conditions that favor the process operation of electrocoagulation in APC regime were determined. The local optimal experimental conditions were established using a multi-objective desirability function method.

Removal of Diethyl Phthalate from Aqueous Media by Adsorption on Different Activated Carbons: Kinetic and Isotherm Studies

The adsorption of diethyl phthalate (DEP) was studied on four activated carbons (ACs) with different chemical and microporous properties. The kinetic results showed that the non-linear form of the pseudo-second order kinetic model provided the best parameters. Results further showed that the DEP adsorption kinetics is favored by ACs which have a ratio of a specific microporous surface to a specific external surface that is relatively low. Besides, an increase in temperature induced an increase in the rate constant k 2 , but the adsorption capacity is temperature independent. Two models, (Langmuir (linear and non-linear forms) and Dubinin-Radushkevich-Kaganer (DRK)), were tested from experimental data. While the Langmuir model provided the best correlation on all the ACs studied. The surface occupied, calculated with the Langmuir parameter obtained by the non-linear form, evidenced the importance of the external surface and the mean pore size. The results show that the non-electrostatic interactions are predominant in the DEP adsorption and are essentially due to dispersion and hydrophobic interactions (for L27 and X17). In the case of F22 and S21 the DEP adsorption is only due to dispersion interaction. A comparison of the thermogravimetric analysis of the ACs washed and saturated shows that the DEP is totally desorbed between 300 and 500°C with a characteristic peak.

Comparison of the Efficiency of Adsorption, Ozonation, and Ozone/Activated Carbon Coupling for the Removal of Pharmaceuticals from Water

AbstractThe treatment by adsorption on activated carbon, ozonation, and ozone/activated carbon coupling of a solution containing six pharmaceutical compounds (metoprolol, carbamazepine, terbutaline, fluoxetine, and sulfamethoxazole) chosen among different pharmaceutical classes has been investigated. The efficiency of the processes was estimated through the removal of each target pollutant and the evolution of both toxicity (inhibition of Vibrio fisheri bioluminescence) and the total organic carbon concentration. The influence of pH, ranging from 3 to 7, on the process efficiency was also studied. In each experimental condition, the fastest removal of the pharmaceutical compounds was achieved with ozone/activated carbon coupling. Nevertheless, this process (ozonation and ozone/activated carbon coupling) leads to the formation of toxic by-products that significantly increase the toxicity of the treated effluent. Their removal would require extending the treatment time or increasing the ozone concentration,...

Multi-Objective Optimization of Indigo Carmine Removal by an Electrocoagulation/GAC Coupling Process in a Batch Reactor

A coupling process between Electrocoagulation (EC) and GAC was employed to separate dyes from aqueous solutions. The removal of an indigoid dye, namely C.I. Acid Blue 74, was tested. A novel approach for optimizing EC-based techniques is presented. In addition to maximizing removal efficiency, minimizing consumptions of energy and electrode materials were also targeted by means of multi-objective optimization in order to reduce the specific costs. A very good cost-efficiency feature of EC/GAC coupling process operated under optimal conditions to treat wastewater from dyestuff has been revealed. The independent variables considered were the current density, influent pH, contact time, granular activated carbon dose, and initial dye concentration. Simple maximization of color removal efficiency and multi-objective optimization were compared. Two different constraints were considered for each type of optimization. The determined costs outline the cheapness feature of the EC/GAC system as a potential dye wastewater treatment technology.

Diethyl Phthalate Removal by Continuous-Flow Ozonation: Response Surface Modeling and Optimization

An experimental design methodology was applied for response surface modeling and optimization of diethyl phthalate (DEP) removal from synthetic wastewater by continuous-flow ozonation. The five independent variables considered were the initial concentration of DEP, initial solution pH, liquid flow rate, gas flow rate, and ozone concentration in the inlet gas. Using the Box–Behnken design, two quadratic models were developed as a functional relationship between respectively DEP removal efficiency and ozone mass transfer and the independent variables considered. It was found that all the factors considered have a significant effect on the removal efficiency response, except for the gas flow rate which did not influence DEP removal in the ranges considered. The results show that the ozonation efficiency can be predicted and are in very good agreement with the experimental data. Optimal conditions for two different sets of constraints were determined.

Evolution of Toxicity and Mineralization during the Treatment of Diethylphthalate in Water by Ozone and Activated Carbon Coupling

Ozone/activated carbon coupling could be an efficient method to remove micropollutants, such as phthalates, that are refractory to classical treatments. However, this wastewater-treatment process can lead to the formation of oxidation by-products that may be toxic and which also need to be removed. The aim of this work was to study the evolution of the mineralization and the toxicity of the effluent during the treatment process so as to determine the efficiency of this method and the required time of treatment. Analyses (Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analyses, N2 adsorption isotherms) of the adsorbent material were performed to understand the role of activated carbon during the treatment. It is shown that depending on the activated carbon properties and the experimental conditions, a fast and complete removal of diethylphthalate, and total mineralization and detoxification of the treated solution can be obtained. Moreover, it is demonstrated that the activated carbon acts more as a reaction site than as an adsorbent, leading to an in situ renewal of the material during the process. DOI: 10.1061/(ASCE)EE.1943-7870.0000671.

Endocrine Disrupter Removal by Ozone/Activated Carbon Coupling in Continuous Flow at Pilot Scale

AbstractIn view of their toxicity, the presence of endocrine disrupters such as phthalates in surface waters requires the setup of new wastewater treatment processes. Previous studies demonstrated the efficiency of ozone (O3)/activated carbon (AC) coupling in removing micropollutants such as phthalates in batch conditions. The aim of the present work was to study the removal of diethylphthalate (DEP) from water by O3/AC coupling in continuous flow on a pilot scale. Comparison of the results obtained with O3/AC coupling (both DEP removal and ozone mass transfer) to those of conventional methods shows its great potential and the influence of experimental conditions such as pH and ozone gas concentration. The process reached a steady state with a high pollutant removal and an efficient ozone mass transfer. Moreover, it extends the AC lifetime by ensuring the in situ renewal of the adsorbent. By estimating the microporous volume occupied by the adsorbent material at different times during the treatment, it is...

Adsorption of Phthalates on Activated Carbons in Monosolute Solution and in Mix Within Complex Matrices

Phthalates are considered as dangerous priority pollutants, several effects being attributed to them: foetal deformations, cancers, and endocrine disruptions. Activated carbons are highly efficient materials for the adsorption of numerous organic molecules. Before their use, it is important first to determine both textural and chemical properties and to study kinetics and thermodynamics adsorption, to understand and to optimize the interactions between material and molecules. The aim of this work was to study the kinetics and the adsorption isotherms of three phthalates (dimethylphthalate, diethylphthalate, and diethylhexylphthalate) currently found in industrial effluents, on two different activated carbons. The co-adsorption of these molecules in a synthetic mix and in complex matrices was modeled. The kinetic study and adsorption isotherms of dimethylphthalate and diethylphthalate in monosolute and bisolute were first investigated, followed by a similar study with a mix of the three molecules in complex matrices (surface water (Loire and Loiret Rivers near Orléans city) and municipal wastewater treatment plant outflow). The pseudo-second-order kinetic model was used to determine the kinetic adsorption parameters. The Langmuir equation was used to calculate the surface occupied. Results showed that non-electrostatic interactions are predominant in phthalate adsorption in complex matrices, mainly due to dispersion forces and hydrophobic interactions.

KINETICS AND EQUILIBRIUM STUDIES OF 4-CHLOROPHENOL ADSORPTION ONTO MAGNETIC ACTIVATED CARBON COMPOSITES

Among the organic pollutants, the chlorinated phenols represent an important class of compounds having a stable world market of ca. 100 kt per year. Due to their aryl structure and presence of the chlorine atom, chlorinated phenols are exceptionally recalcitrant toward chemical reactions aimed at their reduction. Adsorption from liquid phase has received special interest due to its flexibility and simplicity in operation. Especially adsorption using activated carbon (AC) has been recognized by the US Environmental Protection Agency as one of the best available control technologies due to the high surface area, large adsorption capacities and porous structure of AC. The purpose of this study was to investigate the adsorption mechanisms of 4-chlorophenol (4-CP) from aqueous solutions on ACbased magnetic composites. Three different granular activated carbon materials (GAC), L27, S21 and X17, were selected based on their chemical surface properties to prepare magnetic composites through the co-precipitation method. Two kinds of composites, magnetic composites (M-L27, M-S21 and M-X17), and pre-oxidized magnetic composites (M-L27/HNO3, M-S21/HNO3 and MX17/HNO3) were tested. Significant lower values of surface area were obtained in case of pre-oxidized magnetic composites due to their higher hydrophilicity. L27-based adsorbents lead to the fastest kinetics of 4-CP adsorption, whereas S21-based adsorbents have the highest values of adsorption capacity. The highest Fe content of 4.41% was achieved in case of M-L27 composite.