Facile pathway towards crystallinity adjustment and performance enhancement of copper selenide for vapor-phase elemental mercury sequestration

Abstract

A long-standing and predominant predicament that impedes the application of metal selenides for the elemental mercury (Hg0) sequestration from industrial flue gases is the failure to simultaneously optimize the preparation simplicity and sequestration performance of metal selenides. Based on the critical hypothesis that coordinatively unsaturated selenide ligands play a vital role in initiating the Hg0 immobilization process, this work reports the adoption of a facile precipitation method for the synthesis of the copper selenide (CuSe) sorbent. The low sample preparation temperature serves for the crystallinity adjustment, which hence enriched the copper selenide surface with coordinative non-stoichiometry and unsaturated selenide ligands. The CuSe as obtained via room-temperature precipitation thus exhibited much superior Hg0 sequestration performance than those prepared under high-temperature hydrothermal conditions, with the adsorption capacity and rate reaching 345 mg g−1 and 42.5 μg g−1 min−1. The characteristic results of fresh and Hg-laden CuSe prepared via room-temperature precipitation confirmed that the coordinatively unsaturated selenide ligands primarily accounted for the Hg0 conversion and immobilization, which provides mechanistical interpretation and theoretical guidance for further development of metal selenides with optimal Hg0 removal performance. The facile preparation logic with relatively extensive applicability can be expected for the synthesis of various metal selenides in addition to CuSe, hence marking the first attempt stepping towards the real-world application of metal selenides for the Hg0 sequestration from industrial flue gases.