CADMIUM IONS SORPTION FROM SYNTHETIC AQUEOUS
SOLUTIONS USING SUNFLOWER LEAVES AS A LOW-COST
MATERIAL: EQUILIBRIUM AND KINETIC STUDIES.
BENAÏSSA Houcine*, ELOUCHDI Mohamed-Amine
Laboratory of Sorbent Materials and Water Treatment,
Department of Chemistry-Faculty of Sciences, University of Tlemcen,
P.O. Box. 119
13 000 Tlemcen - ALGERIA–
Tel./Fax: 00 (213) 43 28 63 08; E-mail.: ho_benaissa @ yahoo.fr
In the field of environmental pollution, there are few subjects that, during recent years,
have been developed as rapidly as the study of toxic metals. The contamination of water by
toxic heavy metals is a world-wide environmental problem. Cadmium, in particular, has
received a great deal of attention due to its highly toxic nature and its tendency to accumulate
in the tissues of living organisms. The main sources of cadmium in streams are effluents from
industries such as electroplating, smelting, paints, plastics, battery, zinc mining and refining.
Because of its high toxicity, most countries include cadmium among the ‘’priority pollutants’’
requiring suitable treatment prior to discharge into the environment. At present, a variety of
physicochemical processes are employed to treat cadmium-containing effluents. These
processes, however, prove expensive when situations involving high volume and low metal
concentration (typically less than 100 mg/L) are encountered. Increasing awareness of the
environmental impact of metal ions in our water systems has encouraged interest in novel
sorption systems. Because plants as waste materials from agriculture are broadly available and
relatively inexpensive, an investigation of their uses as sorbent materials seems most
appropriate. Dried sunflower leaves can be used as an alternative and favourable sorbent
material for pollutants such heavy metals.
In this work, the sorption of cadmium ions from synthetic aqueous solutions by dried
sunflower leaves, in single metal solutions, was investigated. Kinetic data and equilibrium
sorption isotherm were measured in batch conditions. The influence of some parameters such
as: contact time, initial metal concentration, particle size, agitation speed, sorbent dose and
cadmium salt nature on cadmium sorption kinetics has been studied. Two simplified kinetic
models including a pseudo first-order and pseudo second-order equations were selected to
follow the sorption process. To identify the main rate controlling steps in the overall uptake
mechanism, a single external mass transfer diffusion model and intra-particle mass transfer
diffusion model were used. The sorption equilibrium data were obtained at natural pH of
solutions. In order to describe the metal sorption isotherms mathematically and to obtain
information about the maximum sorption capacity of this sorbent, the experimental sorption
equilibrium data were analysed using Langmuir and Freundlich models. Spectroscopic
techniques SEM/EDAX were used to characterize this material used, before and after
equilibration with cadmium ion, in an attempt to better understand the mechanism of the
removal. These fundamental data may contribute to a better understanding or application of
the sorption phenomena at the liquid/solid interface.