New heterogeneous synthesis of mixed Ti-Ca-Mg phosphates as efficient sorbents of 137Cs, 90Sr and 60Co radionuclides

New heterogeneous synthesis of mixed Ti-Ca-Mg phosphates was developed and investigated using DTA-TG, XRD, FT-IR and SEM-EDX techniques. The route of synthesis is based on the heterogeneous interaction between aqueous solution of titanyl-diammonium sulfate and solid precursor as phosphated dolomite Ca0.7Mg0.3HPO4 center dot 2H(2)O (PD-1) and Ca2.65Mg3(NH4)(1.3)(PO4)(4)(CO3)(0.3)center dot 6H(2)O (PD-2) composition. It has been shown that interaction of PD-1 with titanium solution is accompanied by successive dissolution of magnesium hydrogen phosphate and calcium hydrogen phosphate followed by titanium phosphate precipitation. For PD-2 solid precursor, the interaction proceeds by heterogeneous exchange reaction simultaneously with tertiary calcium, magnesium phosphates and magnesium-ammonium phosphate. It has been shown that when PD-1 is used, the final solid has surface area of 220-230 m(2).g(-1), total pore volume of 0.32-0.37 cm(3).g(-1) and average pore diameter of 5.7-6.7 nm. The solid obtained from PD-2 has lower surface properties such as 140-144 m(2) g(-1) for surface area and 0.27-0.34 cm(3) g(-1) for total pore volume. It has been shown that the samples of Ca-Mg-Ti phosphates effectively removed Cs-137, Sr-90 and Co-60 radionuclides at pH 5.0 (K-d 10(-3)-10(-5) cm(3) g(-1)) that could be used for one -stage purification of liquid radioactive wastes with complex radionuclide composition. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.