Leila Khalfa

Bio: Leila Khalfa is an academic researcher from University of Gabès. The author has contributed to research in topics: Adsorption & Freundlich equation. The author has an hindex of 5, co-authored 6 publications receiving 52 citations.

Modeling of equilibrium isotherms and kinetic studies of Cr (VI) adsorption into natural and acid-activated clays

Abstract: Smectite clay has great potential for the removal of heavy metal ions from aqueous solution. This work aims to develop inexpensive, highly available, effective metal ion adsorbents from clay minerals as alternatives to existing commercial adsorbents. In particular, natural clay was modified with sulfuric acid to yield excellent adsorbent material. The adsorptive interactions of Cr (VI) ions with natural clay and their acid-activated derivative in aqueous solution are investigated in this study. The adsorption experiments were carried out under batch process with Cr (VI) concentration, pH, time, and temperature as the variables. The adsorption was strongly dependent on pH of the solution. Adsorption was very fast at low coverage, and equilibrium was approached within 35 min. The kinetic data were analyzed using different kinetic models. It was shown that the adsorption of Cr (VI) ions could be described by a pseudo-second-order equation and Elovich model. The experimental data were also analyzed using two- and three-parameter isotherm models of adsorption. Thermodynamic parameters such as ΔG0, ΔH0, and ΔS0 have been evaluated, and it has been found that the sorption process was spontaneous and exothermic. From all our data, we conclude that the treated clay by sulfuric acid investigated in this study showed good potential for Cr (VI) ions removal from aqueous solutions.

Removal of Fe(III) from synthetic wastewater into raw and modified clay: Experiments and models fitting

Abstract: Water pollution by heavy metal ions has become a serious environmental issue especially due to their toxicity and tendency to bioaccumulation. Natural smectite clay was treated using sulfuric acid ...

Multi-element modeling of heavy metals competitive removal from aqueous solution by raw and activated clay from the Aleg formation (Southern Tunisia)

Abstract: The present study has been carried out for potential use of a raw clay from Gabes district (southern Tunisia) in wastewater treatment. A representative clay sample was collected from the outcropping feature of the Aidoudi area to the west of Gabes city; it followed a simple treatment to enhance its physicochemical properties. Adsorption experiments were performed by using a simple batch technique in single- and multi-element solution (Pb2+, Cd2+, Cu2+ and Zn2+). The obtained results were fitted to different adsorption models, including extended and modified Langmuir, extended Freundlich and modified Redlich–Peterson. Our results indicated that the collected clay sample is mainly a smectite with high amounts of silica, alumina and iron. Adsorptive removal of single elements revealed encouraging efficiencies for most of the studied metals, reaching nearly 100%. Our results also indicated that lead removal reached 26.78 mg/g and 45.94 mg/g for natural and activated clay samples, respectively. Competitive adsorption showed strong dependence on the initial concentration and the metal properties, with preferential removal of lead that reached 41.71 mg/g in binary systems. In most of the mixed systems, metal removal substantially decreased in the presence of competing ions. It showed preferential removal of lead over other metals, regardless of the studied mixture. Further, the use of smectitic clay from southern Tunisia showed a good potential for metal ions removal in single and multi-element systems from aqueous solutions. Thus, it could be turned out to a viable material for the treatment of metal loaded waters.

Competitive Adsorption of Heavy Metals onto Natural and Activated Clay: Equilibrium, Kinetics and Modeling

Abstract: Abstract—The aim of this work is to present a low cost adsorbent for removing toxic heavy metals from aqueous solutions. Therefore, we are interested to investigate the efficiency of natural clay minerals collected from south Tunisia and their modified form using sulfuric acid in the removal of toxic metal ions: Zn(II) and Pb(II) from synthetic waste water solutions. The obtained results indicate that metal uptake is pH-dependent and maximum removal was detected to occur at pH 6. Adsorption equilibrium is very rapid and it was achieved after 90 min for both metal ions studied. The kinetics results show that the pseudo-second-order model describes the adsorption and the intraparticle diffusion models are the limiting step. The treatment of natural clay with sulfuric acid creates more active sites and increases the surface area, so it showed an increase of the adsorbed quantities of lead and zinc in single and binary systems. The competitive adsorption study showed that the uptake of lead was inhibited in the presence of 10 mg/L of zinc. An antagonistic binary adsorption mechanism was observed. These results revealed that clay is an effective natural material for removing lead and zinc in single and binary systems from aqueous solution.

A review on the application of clay minerals as heavy metal adsorbents for remediation purposes

Abstract: Clay minerals are affordable, abundant, naturally occurring minerals found in many parts of the world that have been used effectively for remediation of many contaminants. This review article is aimed at studies involving the use of clay minerals for the remediation of soils and water contaminated with heavy metals. All relevant scientific literature using science direct online database from the year 2000 till 2019 were evaluated. The review highlighted the properties of clay minerals which make them good adsorbents and the processes necessary for adsorption to take place. It revealed that clay minerals are quite effective for remediation purposes, confirmed that clay minerals are very affordable, reliable, and environmentally friendly remediation materials for heavy metal contaminated media. Also, several methods are available for the modification of clay minerals in order to increase their adsorption capacity. However, in order to establish the use of clay minerals as heavy metal remediation materials compared to other established methods, more investigations are required, to determine the best modification type for clay minerals as well as the standard dosage of clay minerals required for the adsorption of heavy metals.