Sorption thermodynamic and kinetic studies of Lead removal from aqueous solutions by nano Tricalcium phosphate

1. Introduction The adsorption procedures are introduced as a favorable way for the remediation of aquatic waste because of its efficacy, practicality and economical feasibility, as depending on the used adsorbents [1]. Lead is one of the most ubiquitous contaminants in the soil and aqueous environments. A severe environmental Pb contamination can often be found at shooting ranges where the soil Pb concentration sometimes exceeds 10000 mg kg-1 because of spent lead bullets. In Iran, many shooting ranges are generally located in mountainous regions and suffer from the degradation of natural vegetation due to Pb toxicity, which may have the potential to augment the Pb contamination via soil erosion. Therefore, development of cost-effective technologies is necessary to reduce the mobility and bioavailability of Pb in soil and water environments [2, 3]. The low cost adsorbents are the naturally occurring materials with high abundance such as aluminosilicates, clay and zeolite [4]. Calcium phosphate minerals have also been considered amongst ideal low cost adsorbents because of their high sorption capacity for metal ions, the least solubility and the highest stability in a wide range of pH, and high stability under reducing/oxidizing conditions [5]. Tricalcium phosphate (TCP) is a principal component of calcium phosphate compound and has been of interest in industry and medical fields. Its synthetic particles find many applications in bioceramic, catalysts, and powders for artific