Transformation of CuO and Cu2O particles into CuxS within the polymeric matrix of anion exchangers, and its structural and morphological implications

Abstract

The study demonstrates the process of anion exchanger modification in order to obtain a reactive organic polymer containing CuxS dispersed within its matrix. As starting materials, two strongly basic commercial anion exchangers were used – macroreticular and gel-type – previously modified by deposition of cuprite or tenorite within their structure. The pre-formed composites were sulphidated using an Na2S solution to obtain materials containing CuxS (5.3–6.7 wt% Cu and 4.5–6.7 wt% S), which were further studied using Raman and XPS spectroscopy, and XRD and SEM/EDS analyses. Depending on the sulphidation precursor, Cu2O or CuO, its distribution within the polymeric matrix, and the porous structure of the supporting anion exchanger, products with different CuxS content were obtained. The main sulphidation product – covellite – was accompanied by admixtures of copper-rich phases such as digenite and djurleite, but products of sulphide oxidation were also identified. The conversion of Cu2O into CuS was more efficient and selective in comparison to CuO. The sulphidation process remained within the initial distribution of the precursor particles within the polymeric matrix. The morphology of the obtained covellite particles was strongly dependent on the porous structure of the supporting anion exchanger. The conversion of the Cu2O and CuO within the macroporous matrix led respectively to spiky burr-like CuS and more densely packed elongated needle-shaped CuS particles, while the CuS particles obtained in the gel-type matrix were spherical. The spherical particles obtained from Cu2O conversion exhibited a hollow structure, which was the result of solid-state diffusion during the sulphidation, the so-called Kirkendall effect.