Electrolytic production of copper from chalcopyrite

The transition to renewable energy infrastructure necessitates rapid growth in copper production, averaging at least 3.5% annually to 2050. The current smelting–converting–electrorefining route must be revisited considering these future prospects as ore grades deplete and the costs to mitigate emissions to the environment increase. Here, we investigate electrolytic alternatives, reviewing the background and recent developments for four classes of electrolytes to directly decompose the most important industrial copper mineral, chalcopyrite: aqueous solutions, ionic liquids, molten salts, and molten sulfides. These electrolytes are discussed in the framework of electrochemical engineering, as applied to the electrolytic decomposition of chalcopyrite. A vision is proposed in which an electrolytic technique, integrated with low cost and sustainable power, enables the production of unprecedented annual tonnages of copper from low-grade chalcopyrite, with valuable by-products and enhanced selectivity for impurities.     

Novel Lipophilic Fluorophores with Highly Acidity-Dependent Two-Photon Response

Lipophilic fluorophores are widely implemented in nonlinear microscopy; however, few existing membrane-specific probes combine the high brightness of two-photon excited fluorescence (2PEF) with pH sensitivity. Herein we describe four novel two-photon excited fluorophores, based on a coumarin 151 core structure, where lipophilicity is induced by a covalently attached phosphazene moiety. Changing the environmental acidity using trifluoromethanesulfonic (triflic) acid leads to profound changes in the linear fluorescence and 2PEF characteristics, due to chromophores’ switching between neutral- and protonated forms. We characterize this dependence by measuring the two-photon absorption (2PA) spectra over the region λ_2PA=550–1000 nm, observing 2PA cross sections of σ_2PA=10–20 GM, with an associated 2PEF brightness of 10–13 GM, in neutral solutions of both acetonitrile and n-octanol. Although quantum chemical modelling and NMR measurements show that, at high chromophore concentrations, protonation may be accompanied by a dimerization process, these dimers likely do not form at the lower concentrations used in optical spectroscopy.