Παρασκευή και χαρακτηρισμός διφασικών φωσφορικών υλικών για την απομάκρυνση οργανικών χρωστικών από υδατικά διαλύματα

Abstract

The present study was designed for two experimental parts. The first part was constructed to synthesized phosphate materials of Ca/P atomic ratio of 1.67 and 1.33, which are stoichiometry of hydroxyapatite (HA) and octacalcium phosphate (OCP). This part also showed the effect of different concentrations of threonine and calcination effect at 900 0C on octacalcium phosphate. The second part of this study deals with the application of these synthesized phosphate materials, at which we removed azo-dye from aqueous solution. The high-energy dispersing equipment used in combination with a pH shock-wave method to synthesize HA and OCP. An 800 mL solution of 0.0538 mol of Ca(H2PO4)2.H2O and 0.1254 mol of CaCl2 with a Ca/P molar ratio of 1.67 (stoichiometry of HA) used for synthesize HA and for the synthesize of OCP, 0.0538 mol of Ca(H2PO4)2.H2O and 0.0891 mol of CaCl2 with a Ca/P molar ratio of 1.33 (stoichiometry of OCP) used. The obtained powders of HA was detected single phase in XRD analysis and the calculated lattice parameters were a= 9.427 A and c= 6.930 A (hexagonal P63/m). From XRD pattern of uncalcination samples of OCP, three phases of OCP, monetite and HA were structurally analyzed. The calculated lattice parameters for OCP were a= 10.733 A, b=13.753 A and c= 5.832 A (orthorhombic Pna-21). These values were slightly different from standard values, these differences is due to the presence of multiphase and the element content on unit cell. After calcination at 900 0C, two phases of #-TCP (monoclinic p2/c). and #-Ca2P2O7 were detected. FT-IR analysis showed all the characteristic peaks of HA, OCP and #-TCP. SEM micrograph showed the different morphology of samples. For HA, the observed particles were spherical in shape and highly agglomerated. For TH0 the shape was ununiform. After used different concentration of threonine the shape changed to needle-like for TH2, spheroidal for TH4 and spherical for TH6. The calcined samples showed the particles of botryoidal shape. The thermal transformation takes place through four consecutive steps. The first exothermic step (20-400 0C), mainly assigned removal of part of crystalline and adsorbed water. The second step is endothermic (400-750 0C) and this step OCP and monetite decompose to calcium pyrophosphate. The third exothermic step happen between temperature 750-1100 0C. The main transformation observed here