Enhanced reductive removal of aqueous Hg(II) by a novel Pd-Cu-BTC catalyst

Abstract

The reusability of catalytic materials is crucial for their practical applications to environmental water treatment technologies. In this study, we synthesized a novel catalytic metal–organic framework, Pd impregnated Cu-BTC (1,3,5-benzenetricarboxylate), and investigated its performance in the reductive removal of Hg(II). Our analysis of adsorbed Hg species and valence change of metals on the catalyst surface provided valuable insights into the reaction mechanism. Experimental findings revealed that the reactivity and the transformed Hg(0) adsorbed on the catalyst surface were significantly increased following the metal order of Pd > Ru > Pt. Reduced Pd-Cu-BTC exhibited a remarkable Hg(II) removal of 99.9 % within 2.5 min, with the highest adsorption capacity (4.43 mg·g−1) and pseudo-second-order rate constant (k2 = 0.343 g·mg−1·min−1). Increasing the Pd content significantly enhanced Hg(0) adsorption, from 40 % with 1 % Pd to 96 % with 6 % Pd. Moreover, the catalyst maintained its reactivity throughout nine consecutive cycles, effectively removing all aqueous Hg species. The catalyst shows promising potential for recovery through thermal desorption due to the highest adsorbed Hg(0) from Hg(II) reduction reaction. Hence, the reduced Pd-Cu-BTC is an effective and sustainable catalyst for application in the removal of Hg(II) in water and wastewater treatment technologies, highlighting its long-term usability.