Chemistry and Materials Research www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.7 No.3, 2015 84 Cactus Potential in Heavy Metal (Pb and Cd) Removal in Water Sample Collected from Rural Area around Adigrat Town Tessema Derbe * Hayelom Dargo Worku Batu Department of Chemistry, Adigrat University, P.O. Box 50, Adigrat, Ethiopia Abstract The main objective of this study is to investigate the heavy metals (Pb and Cd) removal capability of cactus powder from water sample using FAAS adsorption techniques by considering the influence of contact time, adsorbent dose and temperature on adsorption of Pb and Cd ions by cactus powder. The results revealed that adsorption of Pb and Cd ions increased as the dose of adsorbent increased at a certain limits. The heavy metal removal capability of cactus powder is affected by the present of NaCl salt. The heavy metal removal capability of cactus powder decreased from 65% up to 7% for Pb, and from 70% up to 14% for Cd as the dose of NaCl increased from 1g to 5g. The decrement in the removal of both Pb and Cd ions from water sample with increasing of NaCl is due to the formation of outer sphere complex with the NaCl salt which screening the functional group of cactus powder from heavy metals. The heavy metal removal capability of cactus powder also increased with contact time. The adsorption rate initially increased from 20% to 58 % for Pb ion, and 17% to 43% for Cd ion when the contact time increased from 30-120 min. After 120 min there was no significant change in heavy metal removal of both Pb and Cd ions. This might be due to end point at which adsorption phase reached to equilibrium. The percentage removal of Pb by cactus powder decreased from 65.05% to 29% as the temperature increased from 25 o C to150 o C. In similar condition, the percentage removal of Cd by cactus powder also decreased from 43% to 31% as the temperature increased from 25 o C to150 o C. This decrement in percentage removal of both Pb and Cd ions with increase temperature is due to the weak binding interaction between the active site of cactus powder and (Pb, Cd) ions which support physicosorption process. Keywords: Cactus Powder, Heavy Metal, Adsorbent, Adsorbate, Dose, Heavy Metal Removal and Active Site. 1. INTRODUCTION Heavy metals are the most hazardous and harmful metals even if they present as traces quantities, since they are accumulated in the tissue of living organisms[1, 2]. Heavy metals include lead, silver, mercury, copper, nickel, chromium, zinc, cadmium and tin have a detrimental health effects on human being and animals [2]. Many toxic heavy metals like Pb +2 , Cu +2 , Fe +3, and Cr +3 have been discharged into the environment as industrial wastes, causing serious soil and water pollution which leads numerous diseases and disorders [1-4]. Every day, there are many chemicals discharged directly and indirectly into water bodies without further treatment for elimination of harmful compounds (Salim et al., 2008). These heavy metals contamination in ecosystems pose a major environmental problem worldwide [2-5]. They are toxic environmental pollutants which arise from anthropogenic activities such as metallurgical process, sewage sludge treatment, warfare, military training, waste disposal sites, fertilizers and pesticides [4-6]. Migration of these contaminants into noncontaminated areas as dust or leachates through the soil and spreading of heavy metals containing sewage sludge are a few examples of events contributing towards contamination of the ecosystems [6]. Contamination and subsequent pollution of the environment by trace metals have become an issue of global level due to their sources, widespread distribution and multiple effects on the ecosystem [3, 6]. Once they inter in living organism, they inhibit transpiration and photosynthesis of plants [3, 4, 6]. They disturb carbohydrate metabolism, and they drive the secondary stresses like nutrition and oxidative stresses [2, 5, 6]. They affect the normal function of liver, cardiovascular and central nervous systems, muscle, heart and kidney [5-7]. A widespread of heavy metal such as Pb in water is hazardous to the environment and human health, and their discharge into surface water is one of the great fears throughout the world [2, 3]. Therefore, they must be removed to certain levels to meet discharge requirements [2.3]. Lead (Pb): Pb is one of the most toxic metals which are very persistent pollutant in the environment [1, 5, 7, 8]. It is found in trace amount in rock, soil, water, plant, animals and air [2, 8, 9]. Its chemical reactivity is a function of the combined properties of the metal and the associated ligands, and hence resulted in different biological effects [2, 10]. Inorganic compounds of lead such as halides, oxides, sulfites, sulfate carbonate and chromate are mostly exposed to humans being [2, 5, 11]. Lead binds to the thiol (SH – ) chemical group in the enzymes and consequently reduces the body’s ability to synthesize enzymes necessary for respiration and digestion [5, 11]. The toxicity of lead influences brain, heart, kidney, liver, central nervous system, and pancreas. Moreover, diseases like bone pain, dizziness, drowsiness, fatigue, headaches and hypertension are the signs and the symptoms of the exposure of Pb [1, 5, 6]. Cadmium (Cd): Cd (II) is the most toxic and hazardous metal ion to living organism and its allowable