Inorganic phosphate crystal Na15−n[Al(PO4)2F2]3−n[Ti(PO4)2F2]n (0 ≤ n < 1): A novel cation exchanger with high exchange selectivity for Li+ and Pb2+ ions

A series of inorganic phosphate crystals have been hydrothermally synthesized, which have high chemical stability and can keep their crystal structure after acid/base treatments. Its cation-exchange properties have been investigated and the results show that it is an excellent ion exchanger with high exchange capacities for H+, Li+ and Pb2+ ions (12.74, 6.98 and 3.92 mequiv./g, respectively). Selective extractions of Li+ and Pb2+ from the synthetic mixtures containing (Li+, Sr+, K+, Mg2+, Ca2+ and Ba2+) and (Pb2+, Ca2+, Ba2+, Co2+, Ni2+, Zn2+ and Mg2+) have been observed. The reasons of the high exchange selection of NATP for Li+ and Pb2+ ions have been discussed.