FTIR spectroscopy has also been applied to investigate the extraction mechanism. Two different solute solutions were extracted (1. 0.2 mol/L H3BO3 dissolved in saturated magnesium chloride; 2. 0.2 mol/L H3BO3 dissolved in deionized water), each of which had the same pH and H3BO3 concentration. Both extraction tests were carried out under the same operating conditions. The samples of organic and blank organic phases were analyzed by IR respectively, and the results were shown in Fig. 12. It is obvious that the IR spectra of two loaded organic phases are similar, indicating that the extraction complexes in the organic phase is independent of whether MgCl2 is present in the solution. Compared with the blank organic phase, the absorption bands of O-H shifted significantly from 3377 cm-1 to 3444 cm-1, but it did not disappear and the intensity had been slightly reduced, indicating the presence of TMPD that did not participate in the reaction. The new absorption peaks observed at 1416 cm-1, 1339 cm-1 and 661 cm–1 were identified to alcohol O-H, C-O and B-O bonds of the boric acid ester, respectively. We therefore conclude that the O-H groups of the alcohol are complexed with boric acid. The evidence for the extraction complex is similar to the results obtained previously by our group using 2-butyl-1-n-octanol[28]. The results will be helpful to understand the mechanism of the complexation reaction between alcohol extractants and boron.