Recovery of palladium by silica/polymer-based 2,6-bis(5,6,7,8-tetrahydro-5,8,9,9-tetramethyl-5,8-methano-1,2,4-benzotriazin-3-yl)pyridine adsorbents from high level liquid waste

Abstract

ABSTRACTThe adsorption properties of a porous silica-based adsorbent 2,6-bis(5,6,7,8-tetrahydro-5,8,9,9-tetramethyl-5,8-methano-1,2,4-benzotriazin-3-yl)pyridine (Me2-CA-BTP/SiO2-P) towards Pd(II) were investigated. The adsorption ability of Me2-CA-BTP/SiO2-P towards Pd(II) increased dramatically with the increase of HNO3 concentration and showed a saturated uptake of Pd(II) after the HNO3 concentration reached 3 mol/dm3. It was found that nitrate ion would participate in the adsorption reaction. Palladium adsorption kinetic and isotherm were in accordance with the pseudo-second-order rate law and Langmuir isotherm adsorption model, respectively. Thiourea could effectively elute the adsorbed palladium from Me2-CA-BTP/SiO2-P. Adsorption studies with high level liquid waste elements showed a high selectivity towards Pd(II) over other fission product elements in ≥3 mol/dm3 HNO3 solution. The stability of Me2-CA-BTP/SiO2-P against HNO3 was satisfied for the reason of the adsorption performance keeping for Pd(II) after a long-time contact with HNO3 solution. The adsorbent performed good γ-irradiation stability in dry state and low concentrations of HNO3. The presence of HNO3 enhanced the radiolysis and the adsorbent still reserved a presentable adsorption amount after γ-irradiation in 3 mol/dm3 HNO3.