Thermodynamic Study on the Adsorption of Cd +2 Ions from Aqueous Solution by Seagrasses Salem M. El-Nakeib * , Ismail A. Ajaj Department of Chemistry, Al-Asmariya University, Zliten, Libya * Corresponding Author: sma7228@yahoo.com Abstract This work was to study batch biosorption of Cd (II) ions from aqueous solution by Powdered Seagrasses (PSG). The optimum conditions for the adsorption of Cd (II) ions from aqueous solution by seagrasses were investigated by considering the extent of adsorption with respect to contact time, initial metal ion concentration and temperature. The results obtained indicates that the extent of metal ions removed decreases with increasing contact adsorption equilibrium data best fitted Freundlich adsorption isotherm. Thermodynamic study indicated that the adsorption of Cd (II) ions onto seagrasses was spontaneous and endothermic in nature. Keywords: Thermodynamic; kinetics; adsorption; Cd (II); seagrasses. 1. Introduction Industrial waste water may contain some toxic met- als such as Cd +2 , Cr +2 , Ni +2 , Co +2 , Pb +2 ... etc. The release of toxic metals by electroplating, leather tanning, cement, dyeing, metal processing, textile and paint industries into the environment in quanti- ties that pose risk to human health [1]. Cadmium is among the toxic heavy metals that have been deeply studied [2],the release of toxic metals by electroplat- ing, leather tanning, cement, dyeing, metal process- ing, textile and paint industries into the environ- ment in quantities that pose risk to human health [3]. Therefore, the removal of these metal ions is necessary in order to forestall the manifestation of their toxic impact through bioaccumulation and bio magnification along the food chain [4]. The higher concentration causes harmful effects like headache dizziness, nausea, dry cough, tightness of the chest, vomiting, shortness of breath, cyanosis, chest pain and rapid respiration [5]. The aim of this study was to remove the metal ions from aqueous solution. 2. Results and Discussion 2.1. Characteristics of the Adsorbent The chemical nature and pore structure generally determines the sorption activity. The physico chem- Table 2.1: Characteristics of the Adsorbent SI. NO. Properties PSG 1 Particle size (μ) 500 2 Density (g/cc) 0.036 3 Moisture content (%) 0.2986 4 pH of aqueous solution 6.0 ical properties of the adsorbent are listed in Table (2.1). 2.2. Effect of pH The pH level of the aqueous solution is an important variable for the adsorption of metals on the adsor- bent. For above reason, in many studies, it has been pointed out that the solution pH was one of the most important parameters affecting adsorption yield. In order to know the influence of this parameter on the adsorption of Cd (II) ions by PSG, so 100 (mg.L -1 ) of PSG was contacted with 100 (mg.L -1 ) of Cd (II) ions with different pH values which varies from (1 to 10). The results of these experiments are given in Figure (2.1). As seen, removal percentage is low at strong acidic medium. Removal percentage in- creases s up to pH6 and thereafter they stay almost constant for grater pHs up to pH8. 1