Journal of Hazardous Materials A137 (2006) 1263–1270 Adsorption of zinc on natural sediment of Tafna River (Algeria) N. Dali-youcef a,∗ , B. Ouddane a , Z. Derriche b a Universit´ e des Sciences et Technologies de Lille, Laboratoire de Chimie Analytique et Marine, UMR CNRS 8110 PBDS and FR 1818, Bˆ at. C8 2` eme ´ etage, 59655 Villeneuve d’Ascq Cedex, France b Universit´ e des Sciences et Technologies de d’Oran, Laboratoire de Physico-chimie des Mat´ eriaux, El M’Naouar, BP 1505, 31000 Oran, Algeria Received 28 July 2005; received in revised form 14 December 2005; accepted 17 March 2006 Available online 28 April 2006 Abstract The environmental impact of metal additions to sediment depends on its sorption ability. The paper presents a study of zinc adsorption using the experiment data on natural sediment of Tafna River in northwest of Algeria. The effect of various operating variables, namely initial concentration, mass of sediment, and contact time, have been studied. The optimum contact time needed to reach equilibrium is of the order of 30 min and is independent of initial concentration and mass of zinc ions. The extent of adsorption increases with increase of concentration, and with decrease of adsorbent mass. The content of carbonate in sediment increases the adsorption indicating the active support material towards zinc ions. A batch sorption model, which assumes the pseudo-second-order mechanism, is developed to predict the rate constant of the sorption, the equilibrium sorption capacity and the initial sorption rate with the effect of initial zinc ion concentration and sediment dose. Various thermodynamic parameters, such as G ◦ , H ◦ and S ◦ , have been calculated. The thermodynamics of zinc ion/sediment system indicates spontaneous, endothermic and randomness nature of the process. © 2006 Elsevier B.V. All rights reserved. Keywords: Zinc; Adsorption mechanism; Pseudo-second-order sorption kinetics; Thermodynamic; Sediment 1. Introduction Due to heavy metals, pollution remains a serious environ- mental and public problem. Chemical precipitation has been traditionally employed to remove heavy metals. However, metal removal via coagulation–precipitation is, in many cases, insuffi- cient to meet strict regulatory requirements. Adsorption has been shown to be a feasible alternative method for removing metals. The concentration and mobility of these metals in sediments has been widely studied in the last decades [1–5]. Adsorption on sediment is an important process that controls dissolved metal concentration, bioavailability, and toxicity in natural environments [6,7]. Zinc is an essential element for both man and animals and is necessary for functioning various enzyme systems where its ∗ Corresponding author at: Universit´ e de Tlemcen, Facult´ e des Sciences, Laboratoire de Valorisation des Actions de l’homme pour la protection de l’environnement et application en sant´ e publique, DFZMS, D´ epartement de Biologie, BP 119, 13000 Tlemcen, Algeria. Tel.: +213 73 45 63 68; fax: +213 43 28 63 08. E-mail address: nacera.dali@caramail.com (N. Dali-youcef). deficiency leads to growth retardation. Low intake of zinc results in retardation of growth; immaturity and anemia, condition known as ‘zinc deficiency syndrome’. Symptoms of zinc toxic- ity in human being include vomiting, dehydratation, electrolyte imbalance, abdominal pain, nausea lethargy ness, dizziness and lack of muscular coordination. Zinc imparts undesirable, bit- ter astringent taste to water at levels above 5.0 mg/L [8]. Toxic concentrations of zinc above recommended value cause adverse effect in the morphology of fish by inducing cellular breakdown of gills. Zinc deficiency in human body may also result in infan- tilism, impaired wound healing and several other diseases. A several studies are reported in this area of research. Jenne [9] discussed the role of clay sized minerals in trace element sorption by soils and sediments. Fu and Allen [10] studied the adsorption of cadmium by oxic sediments using a multisided binding model. Bajracharya et al. [11] studied the effect of zinc and ammonium ions on the adsorption of cadmium on sand and soil. They reported that the ions suppress the adsorption capacity significantly. The purpose of this work is to understand the adsorption mechanism of zinc by natural sediments samples collected from downstream Tafna River (northwest of Algeria) with a view per- 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.03.068