Application of hydroxyapatite and cement kiln dust mixture in adsorption of lead ions from aqueous solution

This study describes the preparation of new adsorbent by hydroxyapatite and cement kiln dust as raw materials. In the first part of investigation the adsorption capacity of hydroxyapatite and dust powders were separately studied by measuring the lead concentration in the aqueous solution. Thereafter the mixed powders containing different proportions of hydroxyapatite and dust were shaped by a laboratory single screw extruder in the cylindrical form and the adsorption capacity, porosity of samples and the compressive strength were measured according to standard methods. Regardless the composition used in the purification, the solution did not remain transparent when the adsorbent was prepared with dust only and the distinguishable fine particles were suspended in the lead solution. From visual observations, the solution was clear when the same amounts of hydroxyapatite and dust were used in the preparation of porous media. In order to evaluate the mechanical reliability of extruded samples, the compressive strength data of adsorbents were statistically analyzed by Weibull theory. The results clearly indicated that Weibull modulus of porous media is not affected by hydroxyapatite but the strength increases two times compared to the bed which is manufactured by using dust only. The finding results were confirmed by the observation of the fracture surface of adsorbents with a scanning electron microscopy.