Extraction of Cd(II) from aqueous nitrate solution by thermosensitive gel crosslinked with 2,6-di(3-vinylbenzyl-1,2,4-triazol-5-yl)pyridine (BTP)

摘要

A poly-N-isopropylacrylamide (poly-NIPA) gel crosslinked with 2,6-di(3-vinylbenzyl-1,2,4-triazol-5-yl)pyridine (BTP) was prepared by the ultrasonic polymerization technique and the extraction of Cd(II) from an aqueous nitrate solution was tested.The BTP-NIPA gel showed phase transition phenomena,in which the gel was shrunken at temperature higher than the phase transition temperature (304K) and swollen at less than 304 K.The extraction capacity of Cd(II) was affected by the phase transition phenomena and was decreased by thestructural change of gelfrom the shrinking state to the swelling one.Thisis attributable to the configurational change of nitrogen donors in BTP,which occurs by the struuctural change of gel.When the exraction mechanismis assumed as the formation of a complex ion,Cd(BTP)~(2+) and its nitratecomplex,Cd(BTP)(NO_3)~+ at both the shrinking adn swelling states,the equilibrium constant for the complex formation of Cd(BTP)~(2+) at the shrinking state corresponds to about 2.5 times of that at the swelling state.These results suggest that the extractability of Cd(II) can be controlled by the configurational change of nitrogen donors with thephase transition ofBTP-NIPA gel.