Construction of copper-based core-shell composite for efficient removal of xanthate from wastewater

Abstract

As the most widely used flotation agent in mineral processing, xanthate in flotation wastewater causes significant damage to the environment and is a major obstacle to the construction of green mines. It is of great urgency to develop a low-cost, easy-to-separate and high-efficient adsorbent to remove xanthate from flotation wastewater. In this study, novel copper-based core-shell adsorbents with a large particle size are prepared by the hydrothermal crystallization-surface replacement method for xanthate removal. The as-prepared adsorbents were characterized by XRD, SEM-EDS, TEM, N2 adsorption-desorption, FTIR, XPS analyses. Because of the larger specific surface area and higher Cu element content on surface, CuO-based adsorbent (CuA-2) possesses a higher adsorption capacity and faster adsorption rate of potassium ethyl xanthate (KEX) when compared with Cu4(NO3)2(OH)6-based adsorbents (CuA-1). The removal percentage of 99% KEX can be obtained by adjusting dosage and the adsorption capacity is reduced by increasing solution pH due to the electrostatic repulsion. The maximum adsorption capacity of CuA-1 and CuA-2 are 645 and 1128 mg·g−1, respectively. The adsorption kinetic can be described by the pseudo-second-order model while the Langmuir adsorption isotherm is in good agreement with experimental results. EX- anion adsorbs and precipitates on the adsorbent in the form of flakes. A strong chemisorption of EX- anion occurs on the adsorbent surface, generating the Cu-xanthate complex. Moreover, the possible adsorption mechanism of KEX is proposed. The novel copper-based core-shell adsorbents show a promising application prospect in the treatment of flotation wastewater.