Effects of inorganic anions on cadmium sorption behaviours on titanate nanotube surfaces

摘要

This manuscript describes the characterization of as-synthesized titanate nanotube (TNT) and its sorption behaviours on cadmium with the interactions of inorganic anions. The X-ray diffraction and transmission electron microscopy found that the nanotube is in sodium titanate crystal phase (Na_2Ti_3O_7) and the pores of TNT are bimodally distributed with nominal pore sizes of 3 and 15 run. In the binary systems between TNT and anions, the binding affinity is fluoride ＞ phosphate ＞ sulphate with sulphate being the least preferred. The order is similar to that of their first acidity constants, pK_(a1). In the presence of cadmium ions, slight decreases in fluoride and sulphate uptakes were observed. Phosphate uptake was, however, synergistically improved when cadmium was introduced. In the same ternary systems, it was found that these anions decreased the cadmium uptakes by TNT with the effect of sulphate being the most prominent.