Sulphidation of Cu2+, CuO and Cu2O within the matrix of carboxylic cation exchangers – compositional, morphological and thermal properties of CuxS containing composites

Abstract

The study aimed to optimize the synthesis of novel hybrid ion exchangers and evaluate the dispersion of copper sulphides within the porous polymeric phase. Cu_xS fine particles were embedded within carboxylic cation exchangers (CCEs) using different copper precursors: Cu²⁺ connected with functional groups (a), dispersed CuO particles (b), and dispersed Cu₂O particles (c). The study evaluated the impact of the CCEs' structure (gel-type or macroporous) and the copper precursor (Cu²⁺, CuO, or Cu₂O) on the quantity, chemical composition, distribution and morphology of Cu_xS. After sulphidation Cu_xS rich HIXs containing as much as 15.3–12.0 wt% Cu and 5.97–3.16 wt% S were prepared. XRD analysis indicated CuS, Cu₄S₇, Cu_1.75S, Cu_1.95S, and Cu₂S phase inside the beads, with covellite (a), (b), and chalcocite (c) as the main crystalline phase. The XPS analyses revealed the products of Cu_xS oxidation and hydrolysis: CuO, Cu(OH)₂, and CuSO₄ on the surface of the CCE grains. In the HIXs, the deposit was dispersed evenly throughout the volume of the beads. The deposit resulting from (a) and (b) was nanometric, without the formation of large agglomerates. The deposit resulting from (c) was characterized by much larger sizes exceeding several hundred nanometers. The TG/DTG curves of four HIXs obtained by the (b) and (c) transformation showed remarkable thermal stability up to a temperature of 400 °C. The obtained composites, by combining the affinity, selectivity and exceptionally high sorption capacity of Cu_xS for heavy metals (especially mercury) may be valuable in water purification processes in column flow-through systems.