Introduction
Heavy metals are regarded such elements which have atomic weights in the range of 63.5 and 200.6 and specific gravity more than 5. Rapid industrialization and urbanization has resulted in accumulation of heavy metals in the environment due to their waste disposal without any treatment. Various industries such as metallurgy, battery manufacturing, metal plating, fertilizer production, mining, textile dyeing, etc. are major contributors to enhance the concentration of heavy metals in the environment and are responsible for heavy metal contamination [1-6]. Most of the heavy metals have no known biological function in living organisms, while some of them such as Cu, Zn and Ni are thought to be essential at low concentrations for functioning of body but are toxic when increased beyond the permissible limit. Removal of heavy metals has been a severe problem for environmentalists. The elevated concentrations of heavy metals in industrial effluents ultimately contaminating soil and ground water and entering in food chain ultimately affect human beings. Contamination of water by toxic heavy metals is one of the major problems facing the world today, metals can directly or indirectly damage DNA that means an increased risk of cancer called Genotoxicity, while other adverse effects arethat these metals may enter in food chain, ingested through food and accumulated, causes health problems such as anemia, kidney disorder, failure in nervous system, high blood pressure, etc. These heavy metals not damage the human beings but also affect plant tissues [7-8]. Metals in solution may be in the form of free ions, soluble salts, associated ion with ligands or ion bound to a particulate matter. Drinking water is mainly contaminated due to the presence of toxic metal ions. Various techniques have been employed for the removal of these ions from the polluted water such as chemical precipitation [9], ion- exchange [10], Phyto-extraction [11] and biosorption [8]. Most of the methods become ineffective and uneconomical when the concentrations of heavy metals are raised 10 -100 times then the permissible limits which is mostly less than 1 mg/L. The development of procedures and protocols which can remove toxic metals from water has remained a focus for last several decades. Adsorption of heavy metals using Calcium carbonate (CaCO3) is an effective technique to remove the heavy metals from water samples. Many researchers have used natural lime stone for the removal of toxic metal ions from polluted water [12-17] and have reported that CaCO3 is an effective material for the treatment of water contaminated with heavy metal ions and have highest removal efficiency for heavy metals [18-19]. It was reported that lime stone samples containing impurities such as silica, iron/ aluminium oxide and different kinds of clay minerals demonstrated enhanced sorption capacity [1].
Introduction
Heavy metals are regarded such elements which have atomic weights in the range of 63.5 and 200.6 and specific gravity more than 5. Rapid industrialization and urbanization has resulted in accumulation of heavy metals in the environment due to their waste disposal without any treatment. Various industries such as metallurgy, battery manufacturing, metal plating, fertilizer production, mining, textile dyeing, etc. are major contributors to enhance the concentration of heavy metals in the environment and are responsible for heavy metal contamination [1-6]. Most of the heavy metals have no known biological function in living organisms, while some of them such as Cu, Zn and Ni are thought to be essential at low concentrations for functioning of body but are toxic when increased beyond the permissible limit. Removal of heavy metals has been a severe problem for environmentalists. The elevated concentrations of heavy metals in industrial effluents ultimately contaminating soil and ground water and entering in food chain ultimately affect human beings. Contamination of water by toxic heavy metals is one of the major problems facing the world today, metals can directly or indirectly damage DNA that means an increased risk of cancer called Genotoxicity, while other adverse effects arethat these metals may enter in food chain, ingested through food and accumulated, causes health problems such as anemia, kidney disorder, failure in nervous system, high blood pressure, etc. These heavy metals not damage the human beings but also affect plant tissues [7-8]. Metals in solution may be in the form of free ions, soluble salts, associated ion with ligands or ion bound to a particulate matter. Drinking water is mainly contaminated due to the presence of toxic metal ions. Various techniques have been employed for the removal of these ions from the polluted water such as chemical precipitation [9], ion- exchange [10], Phyto-extraction [11] and biosorption [8]. Most of the methods become ineffective and uneconomical when the concentrations of heavy metals are raised 10 -100 times then the permissible limits which is mostly less than 1 mg/L. The development of procedures and protocols which can remove toxic metals from water has remained a focus for last several decades. Adsorption of heavy metals using Calcium carbonate (CaCO3) is an effective technique to remove the heavy metals from water samples. Many researchers have used natural lime stone for the removal of toxic metal ions from polluted water [12-17] and have reported that CaCO3 is an effective material for the treatment of water contaminated with heavy metal ions and have highest removal efficiency for heavy metals [18-19]. It was reported that lime stone samples containing impurities such as silica, iron/ aluminium oxide and different kinds of clay minerals demonstrated enhanced sorption capacity [1].
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