Abdelmottaleb Ouederni

Competitive adsorption of ibuprofen and amoxicillin mixtures from aqueous solution on activated carbons

This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibuprofen (IBU) and amoxicillin (AMX), two widely consumed pharmaceuticals, on nanoporous carbons of different characteristics. Batch adsorption experiments of pure components in water and their binary mixtures were carried out to measure both adsorption equilibrium and kinetics, and dynamic tests were performed to validate the simultaneous removal of the mixtures in breakthrough experiments. The equilibrium adsorption capacities evaluated from pure component solutions were higher than those measured in dynamic conditions, and were found to depend on the porous features of the adsorbent and the nature of the specific/dispersive interactions that are controlled by the solution pH, density of surface change on the carbon and ionization of the pollutant. A marked roll-up effect was observed for AMX retention on the hydrophobic carbons, not seen for the functionalized adsorbent likely due to the lower affinity of amoxicillin towards the carbon adsorbent. Dynamic adsorption of binary mixtures from wastewater of high salinity and alkalinity showed a slight increase in IBU uptake and a reduced adsorption of AMX, demonstrating the feasibility of the simultaneous removal of both compounds from complex water matrices.

Comparative Study of Bivalent Cationic Metals Adsorption Pb(II), Cd(II), Ni(II) and Cu(II) on Olive Stones Chemically Activated Carbon

In this work the ability of olive stone activated carbon (COSAC) to remove Pb(II), Cd(II), Ni(II) and Cu(II) metal ions from aqueous solutions was evaluated. The effect of initial pH, contact time and initial concentration on metal ions adsorption was investigated. The results indicated that pH 5 is the optimum value for metal removal. Adsorption kinetic rates were found to be fast; total equilibrium was achieved after 4 hours. Kinetic experimental data fitted very well the pseudo-second order equation and the values of adsorption rate constants were calculated. The equilibrium isotherms were evaluated in terms of maximum adsorption capacity and adsorption affinity by the application of Langmuir and Freundlich equations. Results indicate that the Langmuir model fits adsorption isotherm data better than the Freundlich model. The removal efficiency of heavy metal ions by COSAC decreases in the order Pb(II) >Cd(II) > Ni(II) ≥ Cu(II).

Decomposition of Dissolved Ozone in the Presence of Activated Carbon: An Experimental Study

ABSTRACT In aqueous solutions molecular ozone (O3) decomposes rapidly into secondary radical or ionic species such as (OHo,, , …). This decomposition is enhanced by many factors, essentially the pH, the temperature, and the organic or inorganic compounds in the solution. The aim of this work is to study the effect of the addition of granular activated carbon on the rate of ozone decomposition in aqueous solutions containing promoter (P) and inhibitor (Q) mixtures. The activated carbon used is laboratory produced from olive stones. We found that the rate of decomposition of ozone in these conditions is described by a pseudo-first-order kinetic: . Experimental results show that adding 15 mg/L of the olive stones activated carbon (OSAC) enhances the rate constant of the P and Q controlled chain depletion by about a factor of two. We found that the decomposition increases linearly with the solid concentration (W): and that the kinetics are enhanced when the activated carbon specific area increases. We also conclude that the preozonation of the OSAC has no effect on its activity. We note that the temperature has a significant effect on the ozone decomposition rate even in the presence of OSAC. The value of the activation energy in the presence of the OSAC is lower than that obtained in homogeneous decomposition.

Ozone Absorption in Water: Mass Transfer and Solubility

Abstract Mass Transfer of ozone absorbed by water in a semi-comtinuous stirred reactor is studied at the lab scale. Experimental investigation using a complete factorial scheme shows a predominant effect of agitation speed and gas flow and results in a correlation for the mass transfer coefficient, k1a. Solubility of ozone in water is estimated by evaluation of an apparent Henrys law constant for different temperatures (20* and 50*C), pH values (2 and 7) and a t constant ionic strength (0.13).

Ozone decomposition on glass and silica

Abstract Ozone decomposition on glass and silica surfaces is studied by means of non‐porous particles in a fixed bed (sand, glass bead, crushed glass bead, silica). Influences of gas velocity, particle diameter and reactor volume are investigated. Ozone is produced by a silent discharge generator. A model considering the geometric characteristics of material is used so that the ozone decomposition rate per unit of surface area is identified. The decomposition reaction is represented by means of an apparent first‐order kinetic constant. The high dependency of the apparent kinetic constant on the surface area, for given flow rates, suggests that the ozone decomposition mechanism is not simple. Due to the values of the apparent first order kinetic constant, the existence of catalytic species produced by the ozone generator, as well as excited ozone and/or oxygen species, are considered, by means of several models, to explain the experimental results.

Influence of Nitric Acid Concentration on Characteristics of Olive Stone Based Activated Carbon

Abstract In this work we investigated the effect of nitric acid concentration on the pore structure, surface chemistry and liquid phase adsorption of olive stone based activated carbon prepared by mixing process using phosphoric acid and steam as activating agents. Chemicals and textural characterization show that the increase of HNO3 concentration increases considerably the total acidic groups but decreases specific surface area and pore volume. The study of adsorption in aqueous solutions of two organics, phenol and methylene blue, on raw and oxidized activated carbon indicates that the treatment of mixed activated carbon with different concentrations of nitric acid improves the adsorbent capacity for methylene blue at HNO3 concentrations less or equal to 2 mol·L−1, while it has a negative effect on phenol adsorption.

Modeling of the Dynamics Adsorption of Phenol from an Aqueous Solution on Activated Carbon Produced from Olive Stones

A continuous fixed bed study was carried out by using granular activated carbon produced from olive stone for the removal of phenol from aqueous solution. The effects of initial phenol concentration (40-250 mg/l), feed flow rate (2.2-8.4 ml/min) and activated carbon bed depth (5-20 cm) on the breakthrough characteristics of the adsorption system were determined. The obtained results showed that the adsorption capacity increases with the bed depth and the initial concentration and it decreases at higher flow rate. Three models namely Clark, Thomas, and Yoon - Nelson were employed to predict the breakthrough curves and to determine the characteristic parameters of the column useful for column design. These models fitted well the adsorption data with coefficient of correlation R2>0.9 at different conditions. The activated carbon from olive stone was shown to be suitable adsorbent for adsorption of phenol using fixed bed adsorption.

Adsorption on Activated Carbon from Olive Stones: Kinetics and Equilibrium of Phenol Removal from Aqueous Solution

Activated carbon is prepared with chemical activation of olive stones, by using H3PO4. Batch adsorption of phenol from aqueous solution was investigated. The adsorptive properties were studied in terms of pH, equilibrium time, initial concentration (C0: 25-300 mg/L) and particle sizes (0.125-1.6mm) effects. The experimental kinetic data fitted well the pseudo second order model and the equilibrium isotherm data the Langmuir model. The results indicate that chemical olive stones activated carbon is suitable to be used as an adsorbent material for adsorption of phenol from aqueous solution.

Single and binary adsorption of some heavy metal ions from aqueous solutions by activated carbon derived from olive stones

ABSTRACTIn the present work, activated carbon synthesized from olive stones was used for heavy metal ions (Cu(II), Ni(II), and Pb(II)) removal in single and binary aqueous solutions. The effect of initial solution pH was studied. The equilibrium isotherms for single systems were evaluated in terms of maximum adsorption capacity and adsorption affinity by the application of Langmuir model. Metal ions adsorption increases in the following order: Pb(II) > Ni(II) ≥ Cu(II). The examination of binary adsorption systems: Cu–Ni and Cu–Pb shows that the affinity of copper on the activated carbon surface was strongly dependent on initial concentration of nickel and lead. Copper adsorption was found to increase in the presence of nickel and to decrease in the presence of lead.

The Use of the Thermal and Electronic Effect in a Cold Plasma Reactor for Ozone Synthesis

Abstract Air or pure oxygen flowing into the discharge gap of a cold plasma reactor is the primary method for ozone production on commercial scale. The modelling of the conversion of oxygen into ozone has been set up by means of a kinetic scheme in which opposite reactions are considered. The forward reaction occurs via electronic activation, while the reverse reaction is temperature-dependent. Experimental results are in accord with this scheme, and lead to the following primary conclusions: the plasma temperature is a linear function of the applied power, while isothermal operation is the better from an economic point of view. The ozone molecule formed and destroyed in the cold plasma is suggested to be i.e., the first electronic excited state of ozone (triplet state).