[Application of bone char as an adsorbent for purification of water contaminated with hexavalent chromium]

Chromium is one of the most important heavy metals, which its high levels in drinking water lead to several health adverse effects. This study was performed aiming at determining the effects of primary concentration of six-valent chromium, adsorbent dosage, contact time, and pH on the adsorption of chromium from water on bone char. Bone char was prepared using electric furnace at 450°C for 2 h. Pulverizing of bone char was carried out by standard ASTM sieves with the range of 0.5-1 mm. The structural characteristics and specific surface area were determined through conventional methods. The samples' chromium concentration was measured at a wavelength of 450 nm. Adsorption isotherm of chromium was assessed by Freundlich, Langmuir, and Temkin adsorption equation models. The main component of Bone char is calcium hydroxylapatite with surface area of 100m[2]/g. In this study, adsorption reached the equilibrium at lapse of 120 min, and the increase of adsorbent dose up to 0.7g/100ml leaded to increase in the chromium adsorption. However, higher level had no effect on adsorption efficiency. The results showed optimum adsorption took place better in acidic range of pH [pH=3]. Adsorption isotherm of chromium on bone char follows the Langmuir and Temkin models, and the maximum adsorption capacity the dimensionless coefficient [RL] were 2.025 mg/g and 0.15, respectively which indicates that an appropriate adsorption of chromium on bone char. Bone char is an inexpensive adsorbent, which can be used for adsorption of chromium from water based on surface properties