Extraction of alkaline earths by 2,6-Di(5,6-Dipropyl-1,2,4-Triazin-3-Yl)pyridine

The extraction of Ca(II) and, to a lesser extent Sr(II), Ba(II), and Mg(II) by 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (DPTP) was studied. The extracted forms were thiocyanates, dicarbollidates, and chlorodicarbollidates. Alcohol modified mixture of branched alkanes, 1-butanol, and 4-methyl-2-pentanone (MiBK) were used as diluents. The extractability of the thiocyanates from < 0.05 M HCl decreases in the element order Ca(II) > Sr(II) similar to Mg(II) > Ba(II) and the diluent order MiBK > 1-butanol > modified alkanes > ethyl acetate. Ca(II) thiocyanate is extracted by DPTP as the complex Ca(SCN)(2) (.) 3DPTP. The Ca(II)/Sr(II) separation factor is similar to270 with the MiBK diluent, similar to380 with the modified alkane diluent and > 500 with the 1-butanol diluent. Ca(II) and Sr(II) chlorodicarbollidates are extracted more effectively than thiocyanates, namely even from less than or equal to 0.5 M solutions of mineral acids. However, the separation efficiency is lower, the Ca(II)/Sr(II) separation factor being less than or equal to 20. Very efficient is also the extraction of Sr(II) and Ba(II) dicarbollidates in nitrobenzene from 0.1 M NaOH. In this case the extractability order is Ba(II) > Sr(II) at < 0.005 M DPTP and Sr(II) > Ba(II) at > 0.005 M DPTP. The Ba(II)/Sr(II) separation factor is 9.4 at 0.001 M DPTP, and the Sr(II)/Ba(II) separation factor is 5.5 at 0.01 M DPTP. Ion-pair formation obviously proceeds between DPTP and the dicarbollide type extractants. This makes it in the scope of the work impossible to determine the composition of the extracted Ca(II)/dicarbollidate/DPTP species.