Extractive spectrophotometric and inductively coupled plasma atomic emission spectrophotometric determination of titanium by using dibenzo-18-crown-6

Abstract

Dibenzo-18-crown-6 (DB18C6) is used for the liquid–liquid extraction, and recovery of titanium from paints, pigment, paper and pulp industries. The extraction mechanism of titanium(IV) from pH 4 medium with DB18C6 in dichloromethane was investigated. The DB18C6 concentration in organic phase, the concentration of titanium, the effect of pH and interference ions such as Mo 6+, V 5+, Nb 5+, Ta 5+, Zr 4+, Fe 3+, etc. in the aqueous phase and the temperature on the distribution coefficient for the Ti(IV) have been examined. The titanium was determined by spectrophotometric and inductively coupled plasma atomic emission spectroscopic (ICP-AES) method. Titanium forms a colourless complex with DB18C6 at pH 4.0 which is extracted with dichloromethane having molar absorptivity 1.53×10 4 l mol −1 cm −1 at 285 nm. It obeys Beer's law in the range of 0.16–3.84 ppm of titanium. The colour was developed with thiocyanate which has molar absorptivity 1.50×10 3 l mol −1 cm −1 at 425 nm. The extract is directly inserted in the plasma for ICP-AES measurement, which enhance the sensitivity several folds and the limits for estimation are 0.5–30 ng ml −1. The overall formation (log β 2K'e) and extraction ( K ex) constants calculated are 18.61±0.02 and 1.03±0.03×10 −10, respectively. The transportation of titanium has been discussed. The titanium is preconcentrated and determined in standard and environmental samples.