Trifunctional mesoporous magnetic adsorbent-photocatalyst nanocomposite for efficient removal of potassium ethyl xanthate from mining wastewater

Abstract

Xanthates are largely used in the mining industry as mineral flotation agents, causing serious environmental problems, and therefore, removing them effectively is a significant barrier for sustainable green mining that needs to be addressed. Here, nanostructured mesoporous CoFe2O4/Co3Fe7@carbon prepared by clean and facile mechanochemical-molten salt process is employed as a trifunctional magnetic adsorbent-photocatalyst agent (M-APh) for the efficient adsorption of potassium ethyl xanthate (KEX) from its solutions in dark, and the photocatalytic degradation of the compound under LED-light irradiation. The surface- and bulk‑carbon content of M-APh is evaluated to be around 88 and 80 wt%, with the surface area of 355 m2/g and the average pore size of 3.7 nm, enabling the adsorption of 6.12 wt% KEX on its surfaces in dark. The ferromagnetic performance of M-APh, characterized by the coercivity (Hc), saturation magnetization (Ms) and remnant (Mr) values of 735 Oe, 17.9 emu/g and of 6.1 emu/g, respectively, is an asset supporting the facile separation of the agent from its suspensions. The effects of various parameters including the concentration of KEX in the solution, the dosage of M-APh, the wavelength of the LED-light, and the initial pH on the KEX removal performance of M-APh are studied. Within 5 h of LED-light irradiation of wavelengths 450, 385 and 365 nm, the KEX removal rates are recorded at 96.59, 98.61 and 99.49 %, respectively. Possible mechanisms involved in the adsorption and photocatalytic degradation of KEX are discussed.